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ab_bentley
09-24-2015, 01:06 PM
Recently on 6mmBR.com I posted a 40x that I salvaged by taking a long action bolt and fitting it to the action. Then modifying the bolt body to take savage heads. In the thread I mentioned that the firing pin only have .125" of travel and .032" protrusion, I got a few responses that has made me curious. Most of the responses mentioned that the short lock time, even with constant ignition, wouldn't necessarily create uniform ignition, which would result in fliers. Even with the short pin fall, I have shot several small groups including one right at an inch at 400yds. I got so curious I made another firing pin for the rifle, with .200" pin travel and .052" protrusion to see if it made any difference.

I guess I am asking what does the consensus here say about pin fall and protrusion? Do primer ignite in a uniform manner regardless the pin fall and protrusion?

** I can see excessive headspace playing a large role in this, but my cases are bumped back .002", not really allowing my case to run from the pin.

adamsgt
09-24-2015, 01:42 PM
At a gun nut lunch meeting last Friday there was some discussion about firing pin travel and spring force. The firing pin spring can also be a factor in consistent ignition.

B.Larson
09-24-2015, 01:46 PM
didn't the pin with .052" protrusion pierce primers...???

Boyd Allen
09-24-2015, 03:18 PM
Why would it? It is within the range considered normal. BTW I believe the usual consensus is that the primer stops the pin, not the pin shoulder, so protrusion should have nothing to do with piercing primers.

B.Larson
09-24-2015, 03:59 PM
Why would it? It is within the range considered normal. BTW I believe the usual consensus is that the primer stops the pin, not the pin shoulder, so protrusion should have nothing to do with piercing primers.

Interesting.... so... for the sake of discussion... a pin protrusion of 1/8" would be o.k.....................?????........in theory....????

Tim Singleton
09-24-2015, 04:16 PM
I was reading about pin fall a few days ago. Found a pretty old thread where Joe Krupa was talking about pin fall. If I remember right he felt like .220" was what worked well for him. He changed triggers around until he found a combination that fit this parameter.

I'll see if I saved a link to it.

Found it about half way down http://benchrest.com/archive/index.php/t-84430.html

afrench
09-24-2015, 04:20 PM
all of my guns are setup with protrusion of 50 to 60 thou. and FP fall somewhere in the .200 range.

20-22lbs measured spring force.

i'm sure you'll get replies from guys far more successful than myself, but i'd be willing to bet that this is the generally accepted norm.

mwezell
09-24-2015, 04:28 PM
Fwiw. ..I fought an accuracy issue for a whil, a few years back on a custom. Replaced spring, shot like a new barrel.

Boyd Allen
09-24-2015, 04:37 PM
If you extend the tip of the firing pin and keep everything else the same, you decrease the firing pin fall, which may or may not be a problem, depending on what you started with, and how much you extend the tip. If you fire a primer, and measure the depth of the dent in the primer, from the case head (It would be best to use a tight fired case to do this.), you are very likely to come up with a number that is less than the protrusion of the pin from the bolt face...by a significant amount. Unlike most other actions, Savages have adjustable pin protrusion. Bob Greenleaf, retired from Savage where he worked as an engineer for many years, wrote that he set his at .035, well under what is considered "normal".

ab_bentley
09-24-2015, 05:41 PM
On this pin I shortened the OAL and the collar, this pin is fluted and i used a new spring. It'll be interesting to see the differance.

Adam

jackie schmidt
09-24-2015, 06:31 PM
This is based solely on anecdotal evidence from my own experience. I think that in actions that have a firing pin similar to a Remington's, anything less than .200 travel is a detriment.

I also think you need a minimum 20 lbs of static spring tension. All of my Benchrest Rifles are at about 23 lbs.


Protrusion? .045 seems about optimal.

Butch Lambert
09-24-2015, 06:43 PM
I just asked an honest question......

Mr Larson,
Will your rifle pull your firing pin .125?

alinwa
09-24-2015, 09:52 PM
didn't the pin with .052" protrusion pierce primers...???

Can someone just tell this man that firing pins aren't "pierced"......EVER???

They're "blanked,"

you can't "pierce" a primer cup with a firing pin.

Even with 1/8" of fall.

Turds in the catbox is one thing but this is just WRONG and takes from a good discussion.

CMaier
09-24-2015, 10:43 PM
gawd i love it when al wakes up!

ebb
09-24-2015, 11:17 PM
I had a guy build a Remington 700 in 7 rum. He talked me into using a PGT bolt that was real close to the dia. of the raceway. It all sounded good, but he didn't check the protrusion of the firing pin. I shoot like crap and it took me a while to figure it out. I was sitting at the bench and decided to watch the bolt instead of the scope. I could watch the firing pin drop and decided to try it with another rifle as it seemed to me you shouldn't be able to see it hit the primer. I couldn't see it on the other rifle, it all happened too fast and recoil interrupted the eye sight. Greg Tannel fixed it and it shoots good now. Would a bunch of shots through the chronograph tell you if you have a problem? A short firing pin (at least in my gun) caused a hang fire. I don't know if your situation is the same, but I am sure the chrono would tell if you had a hang fire. Maybe also just inconsistent ignition?

ab_bentley
09-24-2015, 11:34 PM
All of my chrony work didn't indicate an issue. Infact i was readily obtaining single digit ES and very uniform speed.

Adam

B.Larson
09-25-2015, 08:18 AM
Mr Larson,
Will your rifle pull your firing pin .125?

Mr.Lambert.... the question as stated was in theory.......

B.Larson
09-25-2015, 08:22 AM
Can someone just tell this man that firing pins aren't "pierced"......EVER???

They're "blanked,"

you can't "pierce" a primer cup with a firing pin.

Even with 1/8" of fall.

Turds in the catbox is one thing but this is just WRONG and takes from a good discussion.

Thanks al....for your kind reply...... reminds me of others who no longer post on this site...... stool and mikeinco

Lee Martin
09-25-2015, 11:35 AM
I'm no expert on the subject but we make our actions with 0.200" free travel and 0.050" protrusion. Spring force is typically 22 lbs. Seems to work well on the 20+ we've built.

-Lee
www.singleactions.com

alinwa
09-25-2015, 01:53 PM
Thanks al....for your kind reply...... reminds me of others who no longer post on this site...... stool and mikeinco

Sorry Blarson but stool and mikeinco are not "others," they're names used by one person who had to change names because guys like you thought he was "mean."

If you'd really searched and understood this subject you'd know that no firing pin has ever poked a hole in no primer.......EVER..... even if you can find opinions to the contrary. Unfounded opinions, un-TESTED opinions, but knee-jerk opinions nonetheless.

In simple fact, the reason I no longer post much here is because people like yourself find this "diversity of opinion" to be more interesting and more "fair" than tested facts.

And more important than safety.


sad

easy, the liberal way is ever filled with support......mob mentality is The New World Order.... garner enough supporting "friends" and you must, by fiat be "right," right?

but sad

Facts aren't up for vote, thankfully! (Although "support" is, sadly. And few care to differentiate)

Go freaking TEST IT before spouting opinions here!!! I'll know you're telling the truth when you tell us how you killed the primers used in the testing regimen.

The op asks a good question, relevant, it needn't be clouded by digressions into banality. Experts across the world, REAL experts, shooters and builders, have documented differences in ignition due to firing pin fall variation. I know of several people who get paid to address this very real issue for shooters in the BR community, and not ONE of them has ever "pierced" a primer. I've spoken with the authors of some of the best books and articles ever written on the subject of accuracy regarding the effect of the firing pin fall/protrusion/diameter/spring weight on accuracy. I know of several systems purposely DESIGNED and built to address this specific topic.......

And none of THEM has ever poked a hole in a primer either...


al

JerrySharrett
09-25-2015, 04:22 PM
Known facts from several sources tests, you are going to need AT LEAST 0.200" fall, AT LEAST 0.045" extension, and AT LEAST 18# of spring to get CONSISTENT ignition with today's small rifle primers!



.

ab_bentley
09-25-2015, 04:23 PM
At times like this I miss Steven Perry.

I choked on pop reading that.

Adam

B.Larson
09-25-2015, 04:25 PM
Sorry Blarson but stool and mikeinco are not "others," they're names used by one person who had to change names because guys like you thought he was "mean."

If you'd really searched and understood this subject you'd know that no firing pin has ever poked a hole in no primer.......EVER..... even if you can find opinions to the contrary. Unfounded opinions, un-TESTED opinions, but knee-jerk opinions nonetheless.

In simple fact, the reason I no longer post much here is because people like yourself find this "diversity of opinion" to be more interesting and more "fair" than tested facts.

And more important than safety.


sad

easy, the liberal way is ever filled with support......mob mentality is The New World Order.... garner enough supporting "friends" and you must, by fiat be "right," right?

but sad

Facts aren't up for vote, thankfully! (Although "support" is, sadly. And few care to differentiate)

Go freaking TEST IT before spouting opinions here!!! I'll know you're telling the truth when you tell us how you killed the primers used in the testing regimen.

The op asks a good question, relevant, it needn't be clouded by digressions into banality. Experts across the world, REAL experts, shooters and builders, have documented differences in ignition due to firing pin fall variation. I know of several people who get paid to address this very real issue for shooters in the BR community, and not ONE of them has ever "pierced" a primer. I've spoken with the authors of some of the best books and articles ever written on the subject of accuracy regarding the effect of the firing pin fall/protrusion/diameter/spring weight on accuracy. I know of several systems purposely DESIGNED and built to address this specific topic.......

And none of THEM has ever poked a hole in a primer either...


al

GEEZ AL............. I`m sorry you feel that way..... did you search and read prior discussions on this site pertaining to piercing primers on this site......?????..... seems others have had firing pins put holes in primers......?????

Butch Lambert
09-25-2015, 07:05 PM
Chuckle chuckle!!

ebb
09-25-2015, 09:06 PM
AlinWA could you link us to some material that backs up your statements. I would like to read about this at length. Ive had some very inconsistent ignition problems and now is as good a time as any to learn. thank you sir

Boyd Allen
09-25-2015, 11:03 PM
While you are waiting on Al's answer, while almost any firing pin assembly will set off primers, getting one right for the highest level of accuracy can require a bit more. In fact, it seems that a whole cottage industry has sprung up to improve the most popular actions in short range benchrest. BATs. Such things as spring rate, spring drag on the firing pin, cocking piece drag, and pin weight have all been modified. Beyond the modifications that are common to that brand of action, others may feature firing pins that are supported by their pin tip holes throughout their range of travel during cocking and firing, so that they do not have to find their way into that hole as they move forward during firing. Some have this feature. Others may have their bolt faces bushed to create it. There is also the matter of firing pin tip diameter, and how spring weight relates to that variable. Then we get to shroud fit in the bolt, which can affect accuracy. One thing to keep in mind is that vibrations that originate in the striker assembly influence accuracy. Inconsistencies show up on the target. One more thing, how solidly the cocking piece stays indexed in a vertical plane can be a factor. If it is not, it can hit trigger side plates which can have a negative impact (pun intended) on accuracy. As you can see, there can be a lot more to obtaining consistent fine accuracy than a fresh spring. Some time back, after I had answered a question, the fellow asked if I had any documentation. After I stopped laughing, I told him that I do not document my hobby, I enjoy it, and that most of the really good stuff, that is not in books was shared by friends, and remembered.

Andy Cross
09-25-2015, 11:40 PM
Many moons ago back in the early eighties I used high speed film not video to capture the rotation pattern the cross hairs made in a scope when the rifle was dry fired. After looking at a few rifles I soon realized the rifles whose cross hairs did a rotation using a different path each time and or did not come back to the same point it started from usually didn't shoot very well. Those that crossed over at some point were the worst shooters. For want of a term I called it the return to battery effect of the cross hairs...... and yes any likelihood it was the scope was ruled out. In two cases just changing the spring helped the situation.
Andy.

ab_bentley
09-26-2015, 12:21 AM
http://i396.photobucket.com/albums/pp46/ab_bentley/Mobile%20Uploads/20150925_213137_zpshra5utmb.jpg

http://i396.photobucket.com/albums/pp46/ab_bentley/Mobile%20Uploads/20150925_194042_zpsru5uqxbl.jpg
I tried several different loads and depths, but figured out the pin does have an effect on the group. I was using 450s in every group that has a distinct flyer to the right. I switched to Fed GMM primers and presto, the flyer disappears.

So here's my theory, the harder cups on the 450s are creating inconsistent ignition, resulting a flyer. The wolf standards would blank at this pressure range (wherever that is) so i didn't get to compare the GMM primers against another "soft" cup primer.

Yet it's clear that the primers or primer/ pin combo has more to do with the groups than I really gave credit to.

Adam

Boyd Allen
09-26-2015, 12:42 AM
There is one more thing that you may want to consider. A hotter primer may produce more velocity...and if tune is as Jim Borden puts it "velocity specific" then perhaps adjustments to powder charge are in order so that primers can be compared at the same velocity.

As far as dry fired cross hair movement goes, another variable that I have found affects this is the rear sand bag. Some time back I did a comparison using the same rifle and two different rear bags.

Speaking of dry firing, a friend was having trouble progressing beyond the low twos, with excellent equipment. On one occasion he had packed up his shooting and loading equipment and gone to the range, but found it too windy to work on loads, so I suggested ( I had called him to see how his practice was coming.)some dry fire practice (He shoots free recoil.) That turned out to be very worthwhile. Initially he was able to see some cross hair movement that he did not like, and trace it down to his trigger technique, which he was able to remedy by trial and error, and on a more favorable day get into the ones. In position shooting dry fire practice is well established as a good technique for improving performance, but in benchrest, I find that shooters typically want to hear and feel something go bang. Dry firing, you can see things that get lost in the noise and recoil.

Kevin Gullette
09-26-2015, 01:30 AM
This pic, from a few years ago, may be of some interest.

Yes......the primer did not blank.....it pierced.

The 40XBR 17 Javelina had it's bolt bushed by Greg Tannel, and FP turned to 0.060" with a 0.045" protrusion. The old Wolff 32lb. spring had been left in........putting the factory 24lb. spring back in cured the "problem".

Primer.....Fed 205M

Hope this helps.

Kevin
click on pic to see VERY small pinhole.
16848

JerrySharrett
09-26-2015, 07:55 AM
So here's my theory, the harder cups on the 450s are creating inconsistent ignition, resulting a flyer. The wolf standards would blank at this pressure range (wherever that is) so i didn't get to compare the GMM primers against another "soft" cup primer.

Yet it's clear that the primers or primer/ pin combo has more to do with the groups than I really gave credit to.

Adam

Adam on the CCI450 vs 205GM/s if you are shooting some of the high pressure loads we shoot in 6 BR and Dashers the 205's will not hold the pressure. Contrary to some beliefs magnum primers are not necessarily hotter but they will withstand higher pressures.

Your inconsistent ignition may be because you need a firing pin spring changeout. At Kelblys and Brownells new Wolf springs are in the $20-25 price range.


.

AMMASHOOTA
09-26-2015, 11:18 AM
Adam on the CCI450 vs 205GM/s if you are shooting some of the high pressure loads we shoot in 6 BR and Dashers the 205's will not hold the pressure. Contrary to some beliefs magnum primers are not necessarily hotter but they will withstand higher pressures.

Your inconsistent ignition may be because you need a firing pin spring changeout. At Kelblys and Brownells new Wolf springs are in the $20-25 price range.


.

Hoping this is not comparing apples to oranges: I have found a 5% difference in muzzle velocity between std. and magnum primers (in handguns). If this is not due to the primer being 'hotter', what is the basis for the difference?

JerrySharrett
09-26-2015, 11:35 AM
Hoping this is not comparing apples to oranges: I have found a 5% difference in muzzle velocity between std. and magnum primers (in handguns). If this is not due to the primer being 'hotter', what is the basis for the difference?

What chrono are you using that you can tell 5% difference in velocity. I would question your chrono's accuracy and inquire to your sample size.

I have Oehler 35 and a 43's and they are not that accurate even with the verify screens. Now if I were to space the screens 20 feet apart and change the clock pulse rate, going to probably a 100 or so sample size might tell us something.

Some where on there are photos of primer spark but that is not an indication of pop!


.

AMMASHOOTA
09-26-2015, 12:09 PM
What chrono are you using that you can tell 5% difference in velocity. I would question your chrono's accuracy and inquire to your sample size.

I have Oehler 35 and a 43's and they are not that accurate even with the verify screens. Now if I were to space the screens 20 feet apart and change the clock pulse rate, going to probably a 100 or so sample size might tell us something.

Some where on there are photos of primer spark but that is not an indication of pop!


.

I am not sure why the brand of the chrono matters. If I shoot the same load with two different primers (std. and magnum) during the same session and see a 5% difference in muzzle velocity, that is good enough for me. 10 rounds of each.

In pistol competition, we use Federal primers almost exclusively, due to its softer cup (consistent ignition with lighter firing pin / striker springs). I have done this test with a variety of chronographs over the last 5 or so years and they have always shown the 5% variation.

Greg Langelius
09-27-2015, 11:09 AM
I wonder if the springs that needed replacement were on rifles that were stored cocked?

Greg

Dick Grosbier
09-27-2015, 11:46 AM
At times like this I miss Steven Perry.

You been hanging around with Pete and gone off your meds Francis?
Dick

Dick Grosbier
09-27-2015, 09:35 PM
it went downhill like a skier.

Just yanking yer chain FB

Rflshootr
09-28-2015, 08:02 AM
All this discussion on pin fall, protrusion, spring weight, consistency and blanking.....and no thought of the shape of the firing pin tip?

Gene Beggs
09-28-2015, 01:28 PM
All this discussion on pin fall, protrusion, spring weight, consistency and blanking.....and no thought of the shape of the firing pin tip?


Riflshootr, you 'hit-the-nail-on-the-head' so to speak.

It was only after several years in benchrest that I came to appreciate the importance of firing pin tip shape.

Tony Boyer, in his, "Book of Rifle Accuracy" describes perfectly and in great detail the best shape for the firing pin tip. If you do not have a copy of this book, make it priority one to get one as soon as possible.

In chapter 7, "The Action" Tony goes into great detail on firing pins, springs, triggers and other related subjects. There is a perfect illustration of firing pin shape on page 57.

Later,

Gene Beggs

JerrySharrett
09-28-2015, 03:01 PM
All this discussion on pin fall, protrusion, spring weight, consistency and blanking.....and no thought of the shape of the firing pin tip?

The tip shape, generally accepted to be spherical is probably a minor factor, IMO.

.

mwezell
09-28-2015, 04:06 PM
The tip shape, generally accepted to be spherical is probably a minor factor, IMO.

.

I agree, Jerry. But a smooth, spherical tip is likely to be less stressful on the primer cup. A sharp or rough tip is more likely to end up with a blanked primer...Not pierced, mind you. :D

JerrySharrett
09-28-2015, 08:05 PM
I agree, Jerry. But a smooth, spherical tip is likely to be less stressful on the primer cup. A sharp or rough tip is more likely to end up with a blanked primer...Not pierced, mind you. :D

Oh I'm sure there could be tip designs that would puncture the primer. Someone in a book I read from discussed tip design and IIRC spherical was not the optimum.

(Remember, primers are never pierced!)

.

mwezell
09-28-2015, 08:49 PM
Oh I'm sure there could be tip designs that would puncture the primer. Someone in a book I read from discussed tip design and IIRC spherical was not the optimum.

(Remember, primers are never pierced!)

.
May well be....I do remember an unnamed but well respected custom action maker using a flat tip. It was clear to the eye and plain as day on a fired primer. I can't say with certainty that it mattered but I also can't imagine how or why it would help. Good ignition, in my feeble mind anyway, is much like breaking a piece of glass. Other than the stress put on the cup, I can't see how a tip that isn't smooth and round would be of benefit. Primer compound should be quickly "shattered", for lack of a better term, for best ignition...fast like striking a match.

I use the match analogy after talking with Allan Hall about RF ignition. He claimed that a hard, fast, but shallow hit of only .002" depth was sufficient for good ignition. I understand there are differences between rf and cf, but the priming compound is similar.

For this reason, my problem with the op's post is not as much about fp protrusion as it is about total energy with that amount of fall and spring energy/fp weight.

Boyd Allen
09-29-2015, 12:14 AM
I just got out a factory Remington firing pin and examined it with good light, in front of a white background, using my low power binocular magnifier. The tip appeared to be spherical, but you could see it turn the corner where it transitions to the cylindrical part. I think that this means that the radius of of the sphere is greater than that of the cylinder behind it. IMO this is to reduce the incidence of cratering because the hole if fully filled at slightly less protrusion.

JerrySharrett
09-29-2015, 06:49 AM
I just got out a factory Remington firing pin and examined it with good light, in front of a white background, using my low power binocular magnifier. The tip appeared to be spherical, but you could see it turn the corner where it transitions to the cylindrical part. I think that this means that the radius of of the sphere is greater than that of the cylinder behind it. IMO this is to reduce the incidence of cratering because the hole if fully filled at slightly less protrusion.

Mathematically speaking what you see is a truncated sphere or a spherical cap as opposed to a hemisphere.


.

WSnyder
09-29-2015, 01:16 PM
More firing pin minutia:

In geometry, a spherical cap or spherical dome is a portion of a sphere cut off by a plane. If the plane passes through the center of the sphere, so that the height of the cap is equal to the radius of the sphere, the spherical cap is called a hemisphere.

So it seems that under the above stated conditions a "spherical cap" can also be a "hemisphere".

JerrySharrett
09-29-2015, 02:51 PM
More firing pin minutia:

In geometry, a spherical cap or spherical dome is a portion of a sphere cut off by a plane. If the plane passes through the center of the sphere, so that the height of the cap is equal to the radius of the sphere, the spherical cap is called a hemisphere.

So it seems that under the above stated conditions a "spherical cap" can also be a "hemisphere".

Certainly would be if the altitude of the cap is the same as the radius of the sphere. Redundantly we say!!!


,

B.Larson
09-29-2015, 03:55 PM
Oh I'm sure there could be tip designs that would puncture the primer. Someone in a book I read from discussed tip design and IIRC spherical was not the optimum.

(Remember, primers are never pierced!)

.

from our archives......

--------------------------------------------------------------------------------



Mike Bryant

11-08-2010, 07:59 PM

A blanked primer is the "technical" or correct name for a pierced primer. The cartridge fires with too high pressure resulting in a hole in the primer. Gas shoots out the hole in the primer, blowing the small disk that came out of the primer back through the firing pin hole. The gas then blows the cocking piece back farther than it should and then the firing pin spring drives the cocking piece forward hitting the top bar on the trigger. You might get by with it once, twice or more times, but more than likely it's going to break something in the trigger eventually. The cocking piece driving forward has the same effect as hitting the trigger with a small hammer. I've seen the top bar and a few other of the levers inside Jewell trigger break all caused by blanked primers.

B.Larson
09-29-2015, 03:58 PM
from 6 br forums........


Posts: 429
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Holes in my primers
on: 10:20 AM, 06/15/12
ReplyQuote
Ok, pretty sure I know the answer, but here goes. 30 BR @ 34.2 gr. of 4198. I use Rem brass for my 30 BR repeater and use it for Yotes. I think, the large hole in the primer pocket is the cause for holes in the primers. It doesn't do it when using the same load in my other 30 BR for benchrest. Same Barrel (Kreiger), same gunsmith (DD), same reciever, same chamber (.330), different brass (Lapua) with small primer holes. The only difference is the brass. It shoost very well, just pokes holes in the primer. This reciever was a 22-250 prior to a 30 BR. Do you think the firing pin difference between large and small primer is the culprit, or the size of the hole in the primer pocket? Do you think Mag primers will solve the problem? It pokes holes in the primers with CCI, Wolf, and Tula SR primers.

Tom
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B.Larson
09-29-2015, 04:05 PM
Hoping this will solve some misunderstanding of what the term "blanking" actually means.... and I believe the word is taken from tool and die work and applied to us shooters.....of whom many are tool and die/machinists....

Blanking: A blanking die produces a flat piece of material by cutting the desired shape in one operation. The finish part is referred to as a blank. Generally a blanking die may only cut the outside contour of a part, often used for parts with no internal features.
Three benefits to die blanking are:
Accuracy. A properly sharpened die, with the correct amount of clearance between the punch and die, will produce a part that holds close dimensional tolerances in relationship to the parts edges.
Appearance. Since the part is blanked in one operation, the finish edges of the part produces a uniform appearance as opposed to varying degrees of burnishing from multiple operations.
Flatness. Due to the even compression of the blanking process, the end result is a flat part that may retain a specific level of flatness for additional manufacturing operations.

Kevin Gullette
09-29-2015, 04:16 PM
Didn't Jerry Stiller write an in-depth "Blanking" article in Precision Shooting, some years ago?

Kevin

JerrySharrett
09-29-2015, 05:04 PM
It is quite common for pressure behind that blanked disk to push the firing pin back far enough for the blank to end up inside the bolt and stop the firing pin from ignighting the next shot. Many times I have taken my bolt disassembly tool to the bench when I had loads that were really hot.

Having standard 0.078" pins reduced to 0.068" or 0.062" is common. Greg Tannel keeps busy doing that. Hard to blow a primer with a 0.062" pin.....but I have!



.

mwezell
09-29-2015, 07:37 PM
It is quite common for pressure behind that blanked disk to push the firing pin back far enough for the blank to end up inside the bolt and stop the firing pin from ignighting the next shot. Many times I have taken my bolt disassembly tool to the bench when I had loads that were really hot.

Having standard 0.078" pins reduced to 0.068" or 0.062" is common. Greg Tannel keeps busy doing that. Hard to blow a primer with a 0.062" pin.....but I have!



.

Not hard at all, Jerry. Put your .062 pin in a bolt with a fp hole for a .078 pin and you'll see how easy it is.:p

JerrySharrett
09-29-2015, 07:57 PM
Not hard at all, Jerry. Put your .062 pin in a bolt with a fp hole for a .078 pin and you'll see how easy it is.:p p



Why in the 'ell would I do that?


.

Boyd Allen
09-29-2015, 09:57 PM
It is my impression that when one gets a round hole in a fired primer that is about the size of the pin hole in the bolt face, that what has happened is that the pressure on the front side of the primer became great enough to overcome the inertia of the striker assembly and the force of the spring, and back the pin up far enough so that the primer was pushed into the pin hole, shearing the cup material. Heavier springs, and firing pins help mitigate this, as do smaller diameter firing pins. The reason for the latter is that the amount of pressure exerted on the firing pin tip is its cross sectional area multiplied by the pressure in pounds per square inch. If we pick .072 and .062 as our tip diameters, a little calculation will show that the area of the larger one is about 1/3 greater than the smaller, or putting it another way, the smaller 75% of the larger. These percentages also show the difference in pin "backup force" at a given chamber pressure.

Perhaps 30 years ago, I made a reloading error that opened up the primer pocket of an '06 case to the point where the primer fell out when the bolt was opened. The pocket looked like it would take a shotgun primer. The rifle was a Springfield with a double heat treat receiver, and a Remington bolt ( a parts gun shooter) The firing pin spring had been replaced with the heaviest one that two strong hands could assemble onto the two piece pin, and the pin hole in the bolt face was a good fit on the pin, and had a sharp corner. As you may know the striker weight of those rifles is among the highest, as is the pin fall. Curious, I examined the primer, it had a perfectly formed indentation, and no sign of a crater.

I have seen several kinds of primer failure. I have seen them crack (which I thought to be the result of a cup material problem), which flame cut the firing pin tip, and sharply increased the number of similar problems after that, until the cut tip was fixed. I have see the so called blanking mentioned above, and I have seen leaks around the perimeters of primers that pitted bolt faces. Then there have been reloader failures that resulted in problems in the area of the primer, like the example with the Springfield.

JerrySharrett
09-30-2015, 07:01 AM
The reasoning for using the truncated sphere or cap as opposed to the full hemisphere is to eliminate the wedging effect of where the full hemisphere approaches the vertical (cylindrical) surface of the firing pin body.

.

Wilbur
10-01-2015, 11:15 AM
I was shooting a fairly hot load at the nationals and was doing pretty good - good enough not to change anything. Every now and then I'd have a hole in the primer and didn't think much of it as, again, I was shooting pretty darn good. I looked at my bolt face and realized that the firing pin hole was plugged with a piece of primer so I took it apart to clean it. Turns out, there was a whole bunch of pieces all about - two or three in the firing pin hole. I cleaned the pieces out and proceeded to shoot poorly for the remainder of the nationals. I've often wondered what actually happened there!! Well, I say often, but I've tried to block that incident out as much as possible.

JerrySharrett
10-01-2015, 12:34 PM
I was shooting a fairly hot load at the nationals and was doing pretty good - good enough not to change anything. Every now and then I'd have a hole in the primer and didn't think much of it as, again, I was shooting pretty darn good. I looked at my bolt face and realized that the firing pin hole was plugged with a piece of primer so I took it apart to clean it. Turns out, there was a whole bunch of pieces all about - two or three in the firing pin hole. I cleaned the pieces out and proceeded to shoot poorly for the remainder of the nationals. I've often wondered what actually happened there!! Well, I say often, but I've tried to block that incident out as much as possible.


What happened? you molested some primers.

You did not puncture them, never happens.

Still looking for HFV a pup.

Can unhousetrained pups ride in your Cadillac?


.

Joe Salt
10-01-2015, 02:30 PM
Wilbur You were Lucky, My buddy pierced a primer with his 6 Dasher. We were wondering why the rest did not have any pressure signs, He ended up winning his relay but in the shoot off the thing wouldn't fire, I was in the pits so I didn't see what happened. Took the bolt apart and sure enough piece of the primer. So I'd say if that happens take the bolt apart and clean it.

Joe Salt

Kevin Gullette
10-01-2015, 03:06 PM
Click on my previous post pic........to see......VERY small hole.

Kevin
Is this any better?
http://i49.tinypic.com/6gzq6b.jpg

alinwa
10-02-2015, 04:51 AM
I dare say Mr Kevin Gullette seems to show an image of a truly pierced primer :) or at least not the typical blanked primer.

I'll not go into what may have occurred to produce such an effect but will state with fair certainty that it had nothing to do with "excess protrusion"

That said, thank you Kevin, you've broadened my horizon this day........this has absolutely no bearing on what's 99.99% of the time referred to as a "pierced primer" (every other instance in this or any other thread on BRC refers to blanking) but that thar shore appears to be a punctured primer, and without any sort of description I'm guessing Kevin that this rifle has somehow been modified (hacked) to produce this effect? Or was it a one-off? A weak spot in the primer cup...a fluke?

I don't see a previous post.

al

alinwa
10-02-2015, 04:59 AM
Oooops, Kevin I found the previous post.... sorry, I just don't keep a comprehensive overview of this site anymore.

My bad

al

alinwa
10-02-2015, 05:03 AM
I was shooting a fairly hot load at the nationals and was doing pretty good - good enough not to change anything. Every now and then I'd have a hole in the primer and didn't think much of it as, again, I was shooting pretty darn good. I looked at my bolt face and realized that the firing pin hole was plugged with a piece of primer so I took it apart to clean it. Turns out, there was a whole bunch of pieces all about - two or three in the firing pin hole. I cleaned the pieces out and proceeded to shoot poorly for the remainder of the nationals. I've often wondered what actually happened there!! Well, I say often, but I've tried to block that incident out as much as possible.

Classic blanking, the pieces in the bolt are simple proof that you were over-loaded. They're sheared by the fp hole and blown into the bolt by the excess pressure. "What happened here" is running near unto max with thrown charges. Some threw heavy ....... "POP".....

Joe Salt
10-02-2015, 10:13 AM
Al sorry to disagree but my buddys rifle had no signs of pressure, and hasn't had a problem since. It's just a bad primer like you mentioned! Oh there CCI primers. Never had a federal do that and I've run some hot loads over the years.

Joe Salt

DSM
10-02-2015, 10:30 AM
I had an incident that happened at a large long range match that I blew numerous primers over the weekend...ruined about 60 pieces(primer pockets) of fresh fire formed Dasher brass. So bad, that I opened the bolt and the primer fell out in the load port! One actually made it into the the lug recess that I did not know about and fired 10 record rounds! All this in a custom action that was running the same tried and true load. Nothing changed other than a few degrees warmer. I thought too that it was a pressure issue. Spent weeks trying to trouble shoot from buying a borescope to testing several lots of powder, chronographing, testing other bullets, charges, barrels....etc. Finally hit me...maybe I should install that new firing pin spring that I had in my box. Evidently, I was saving it for a rainy day, LOL. Like a light switch, problem totally solved. In the end, turns out that it was NOT a pressure problem, but ignition. If it goes bang, does not mean that you have strong consistent ignition. This is one of the most over looked issues that guys aren't aware of and can create many problems that are misdiagnosed. Since then, I have upgraded my ignition system and will keep a fresh spring on hand at all times, LOL. Edit added: Would also like to add, the gun shot well....so well it took the 2 gun group agg for the weekend! So, even though it shoots good, does not mean there isn't a problem.

ab_bentley
10-03-2015, 06:27 PM
Well, I'll admit that a fresh spring doesn't hurt. Changed mine to a new one. It didn't hurt/ help my groups, but it did solve some primer flow. Also for those that are interested, 29.9gr of IMR4166 and a 105gr Amax is a killer combo. Adam