Ignition, esp. primer and case web

Sure,

Well, My brother made a dieset up that goes in the punchpress here at work. It's a Minster 50 ton. You put a gagepin in the primer pocket and go around the case and when done, the primer pocket IS smaller. I use a 206 pin. I have always wanted to do an operation to make these smaller before firing to have the first work hardening be in the reducing direction, rather than expanding. It's as of the metal likes to go to where the farthest excursion has been, and since it is springing back after firing, it tends to want to go larger. Once closed back up, they last a whole lot nicer than they did when new, and I get a ton more firings from brass. Fact is, I go till the necks crack and if they still shoot, keep right on going even then. I don't think I've hit a piece of brass like that more than twice, and have always wondered if they would work even better if they got it when they came annealed (or nearly so when new)
 
I didn't wade through all of this but - - -

This wouldn't be considered any kind of scientific study but after 11 years of shooting several sized cases of 30 cal rifles and having used large and small rifle primers in three of them I will say, without any hesitation , that there is absolutely no difference in the accuracy of those chamberings between large primered and small primered cases, at least out to 300 yards. Having only won 6 - 300 yard aggs perhaps I am not qualified to say what I did but one of those aggs was the highest score of the day, including the VFS rifles and with a 6power scope and with regular large rifle Federal primers.

I cronoed various primers several years ago and I got the best crono numbers from Federal Large Rifle and Winchester small rifle.

I intended to make up some large rifle primer cases, for the 6 PPC I had, out of 7.62 X 39 brass I picked up over time at the range to compair them to the small rifle. I sold the rifle before I got to it. I am betting there is little or no difference in the way they would perform.
 
Pete, if someone were to do a study of the just the PPC, from what we're seeing from people on this tread, you'd have to ream the primer pocket of, say, a Lapua .220 Rusian to make a good test of small versus large. Using 7.62X39 cases isn't good enough.

Even then, it would take more than one rifle/barrel. Tony reported on one of his 6mm BR barrels that shot better with LR primers than with small -- But (so far) only one, his others did not show vertical using the SR primer, so he didn't test them with LRs. And besides Tony's experience, I have seen too many tests that claimed to prove one thing, where that didn't hold up universally. This is especially true for "proper" flash hole diameter, but also for primers in general. Even happened in one of my barrels.

If I were to draw any conclusions from what has been posted so far, it would be that

1. While there may well be an accuracy difference between LR and SR, in at least some chamberings, which is better depends on a particular barrel.

2. Larger cases -- with no size cutoff point established -- will do better with "hotter primers," whether that comes from a "hot" SR or "mild" LR primer. At some case size, with the powders used in them, a "hot" LR may become necessary.

3. Ignition seems to play a larger role in centerfire accuracy that many of us have believed. With respect to the primers themselves, German Salazar has argued this for some time now, but I think even he has just touched the surface. Finally, I think it will turn out that *good ignition* will involve more than just primer selection.
 
Now, this would hold true only for large rifle cases, but, I was always told a rule of thumb for selecting magnum primers was the 65 grain cutoff. In that range, you'd have a point where a magnum primer would work better than a standard. It just happens the 308 Norma, 30WSM, 300WinMag, and others in that range fall in where your load window might cross that barrier. I very very rarely ever shot a magnum primer in any case I had, and I had cases that used 82gr of 4831 or 22. Even there, I used standards, and mostly CCI BR2 and Winchester WLRs. If I did shoot a magnum primer, it was the only time I shot Federals.

I also did a ton of experimentation on primers. Even built a special primer test gun. When push came to shove, I really didn't use much of the consistency information I arrived at because I all too often had best results when I'd say "This primer worked best with this powder in these weather conditions so that's what I'm shooting today". It was basically all seat of the pants cause there were too many variables to add it up and find a "best" primer when given the test data.
 
German
I don't know if I am reading your post correctly but with the 6BR the Fed 205M is slower than the CCI 450 magnum when using Varget powder.If you try and get the velocity back with upping the powder charge you'll pierce the 205 primers but not the 450 magnums.
I think you would have to chose a lower velocity node if you went with the mildest primer available as the milder primers also seem to suffer from weak cups.
Waterboy aka Lynn
 
German, some of us have discovered another unique quality of the Wolf SRM -- a bunch of failure to fires. Maybe a paricular lot of primers, maybe certain actions, sort of moot for me.

What is the second mildest primer with a thick cup? I know it isn't Federal, they have alwys had, shall we say, a "thin" cup? (Desireable only in guns with a weak ignition system or lingerie modelled by comely young women.)

In passing, I would be willing to bore out a SR pocket to LR, but not to bush a LR pocket for SR. Just to be clear, "willing" is a long way from "wanting to" in this context.
 
107 GR. SIE HPBT Hodgdon Varget .243" 2.250" 26.0 2367 39,800 CUP 29.0C 2620 50,100 CUP


NEVER EXCEED MAXIMUM LOADS

German
Here is the book max load for the 6BR.The data is from The Hodgdon website.
What you'll find if shooting a load that mild with Varget is alot of build-up around the flashholes of soot.After 7-9 firings it gets so bad on some cases as to cause vertical stringing in your groups.I suspect the build-up is actually hindering the flame front from igniting the powder properly but this is a guess at best.
You can run a flashhole uniformer in after every 3rd firing just to make sure there is no build-up and that seems to help(again no scientific proof).Some guys went to stainless steel media to clean the inside of there cases better but I have a vibratory machine not a tumbler so cannot say if this would help.
Stepping on the powder charge seems to get rid of alot of the soot build-up and seems to shoot quite well for us.I have the Wolf SRM primers and in our guns they shoot quite well.The regular Wolf primers would pierce much worse than the Federals.
As a sidenote there was a guy who made 454 Casull pistols out of Wyoming who had some very interesting primer set-ups in regards to cup thicknesses.A shooter out here has some of these and I think they are large rifle primer in exterior size with a small rifle primer interior but may have that wrong?
I have read most of your primer work on the various sites but have you played with the funnel shaped flashholes yet?
Lynn aka Waterboy
 
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I have been looking at doing research on this subject for some time.

I have a "Universal Receiver" which I use for ballistic testing of loads and bullets. I'm looking at connecting the end of my test barrel to a close cylinder of known volume that is sealed.
Then measuring the pressure and volume of the resulting gas.
This "should" be able to give me an idea of the total combustion.

Does anyone see any value? or have any suggestions so that "data" can be collected rather then relying on "subjective" input?

Tom
 
Mtek said:
I have been looking at doing research on this subject for some time.

I have a "Universal Receiver" which I use for ballistic testing of loads and bullets. I'm looking at connecting the end of my test barrel to a close cylinder of known volume that is sealed.
Then measuring the pressure and volume of the resulting gas.
This "should" be able to give me an idea of the total combustion.

Does anyone see any value? or have any suggestions so that "data" can be collected rather then relying on "subjective" input?

Tom
Click to expand...
Tom,
It would be interesting to see a comparison of the shape of the pressure curve between primers and also the effect of temp changes between primers.
This would make a great Precision Shooting article, the magazine has been kind of lacking lately for accuracy related articles.

James
 
Tom,

Rumor only.

There was some interesting discussion about Universal receivers that used a lanyard to fire. Apparently, the force one used in pulling the lanyard gave varying results. Enough so that in one test, WLP primers were "hotter" that WLR As I remember, "hotter" here meant higher pressure/velocity. but it has been a number of years since I read the report.b

FWIW
 
Mtek said:
I have been looking at doing research on this subject for some time.

I have a "Universal Receiver" which I use for ballistic testing of loads and bullets. I'm looking at connecting the end of my test barrel to a close cylinder of known volume that is sealed.
Then measuring the pressure and volume of the resulting gas.
This "should" be able to give me an idea of the total combustion.

Does anyone see any value? or have any suggestions so that "data" can be collected rather then relying on "subjective" input?

Tom
Click to expand...

Calorimeter "bomb" testing is a pretty standardized procedure isn't it? My first google search yielded this site

http://www.ojp.usdoj.gov/nij/training/firearms-training/module05/fir_m05_t04_07.htm

I've never tried to search for info on the internet, all of my info is from books and high school chemistry, but my question is "what exactly are you trying to establish that's different from industry testing already in place?"


What am I missing?

al
 
When testing primers, don't forget that how long a burn is just as influential as how much kaboom. Some go pop, while others fizz. Which is hotter depends on what powder they're lighting.
 
Based on some of the latest posts I thought of a way to measure 1 and only 1 aspect of the primers.
The pressure that is caused by the firing of the primer should be able to be measured by simply using an old cylinder pressure gauge.
Could be used on the end of a barrel preferably a short barrel.
This should tell us the DIFFERENCE in pressures not necessarily the exact pressure because of the variances between guns but a ranking of pressure diff could be established
 
Al, The calorimeter does not simulate all the other variables ie.primer, case profile, bullet seating depth into the cartridge, the bullet going down the bore. Remember combustion is affected by all of these conditions. The testing I'm looking to do takes all that into account by firing thru the entire "system". I'm having 2 barrels made one for my comp gun and another for the universal receiver. Both made at the same time with the same reamer. Of course primer wave fronts can be looked for as well. As to the firing pin force issue my receiver is custom and uses a solenoid for repeatability and force can be controlled AND modified with solenoid current.

Tom
 
Mtek said:
Al, The calorimeter does not simulate all the other variables ie.primer, case profile, bullet seating depth into the cartridge, the bullet going down the bore. Remember combustion is affected by all of these conditions. The testing I'm looking to do takes all that into account by firing thru the entire "system". I'm having 2 barrels made one for my comp gun and another for the universal receiver. Both made at the same time with the same reamer. Of course primer wave fronts can be looked for as well. As to the firing pin force issue my receiver is custom and uses a solenoid for repeatability and force can be controlled AND modified with solenoid current.

Tom
Click to expand...

So you're going to have indicators at fixed points in/on the barrel? You're going to graph pressure/time throughout the curve?

wicked!

al
 
Al, Thats correct, as well as putting the bullet passed a chrono and into a "closed" bullet trap as a sealed system to measure for efficient powder burn.

As someone who "needs" to know why I hope to find out WHY a 6PPC and perhaps why 30BR seem to be the sweet spot in most cases for BR.
I do realize that perhaps most of this type of testing and maybe all of it may have been done before, But I sure can't find it.

As with most things, I'm sure there will be no "Silver Bullet" (pun) in the data, I bet it might stir the pot some.

Tom
 
Mtek said:
As to the firing pin force issue my receiver is custom and uses a solenoid for repeatability and force can be controlled AND modified with solenoid current.

Tom
Click to expand...
Unless you're using some very specialized/temp controlled dc solenoid, I think you'll find them to not be very repeatable. At least not nearly as much so as a mechanical system.

As far as measuring pressure goes, I built a primer test gun many years back and chrono'd gageballs that were fired from the gun using only primers. My findings were that regardless of the primer, there was a less than 10% difference in velocity across all the primers I tried, both small rifle and large rifle, standard and magnum.

If anyone cares to look, there's a whole section on primers in the Lyman reloading manual. Complete with photos and descriptions of what properties of primers do what to which powders. They talk about duration, type of flame front, size of flame front, etc. It gave me lots of ideas of things to test. Unfortunately when I was done, their pictures and text told me more than all my testing had. :D
 
Mtek, if I remember correctly there was a study done about that sweet spot you refer to.
I believe the found it to be something along the lines of powder column and bullet ratio.
I dont remember the details but you can probably find it with a search on "powder column"
 
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