Ignition, esp. primer and case web

[Charles E]

Let's give the BRX thread back to Lynn and Robert Whitley. One of the interesting things in its many digressions was Al's statement that cases using small primers would come to rule the long-range benchrest world.

Why is that?

Does it have to do with the "power" of the primer? The (usually) smaller flash hole? The more meat in the case head from the smaller hole for the primer?

Things I think I know:

• The less the chemical power of the primer that will still give adequate ignition, the better.

• Adequate ignition is hard to define. It is usually mentioned when something was done to "increase" ignition, and a problem (usually vertical dispersion) goes away.

• If the striker spring is weak, there will be more vertical dispersion

• Some chamberings, such as the Dasher, seem to work better with hotter primers.

• flash holes can be uniformed, either by drilling (always larger), or by swaging (can be made some smaller)

• The flash hole is a metering device. Aside from circumference, length and shape may play a role. Length is determined by the case web, and can't easily be altered.

• The case head is unsupported in the chamber, to allow for extraction How much of the case head is unsupported depends on the arrangement/design of the locking lugs and extractor. With a rimless case and locking lugs at the front of the bolt, it is typically completely unsupported

• If you really, really want to, you can make up steel head cases

• Front and center ignition has been tried multiple times with small-arms cases; there has been no demonstrable advantage

There is probably more, but you get the drift.

So just what problems/issues do small primers address?

 

[mikecr]

I think the idea is that additional pocket brass allows higher pressures for a given brass life, allowing faster powder, with a higher efficiency burn.
I picture it as putting your tune well into an extreme. Then all you need do is stay into extreme (tolerance).
I doubt most reloaders could get away with it. But for the advanced, shooting small capacity cartridges & light bullets, it obviously works.

Now we get the 6.5mighty mouse(6.5x47L) to attempt this feat out to 600yds. Might work there, but not enough gas, even in extremes, for consistant performance at 1Kyd against bigger guns/bullets.
With any challenge to a LR course, it is still a high BC that most often wins, and you can't run extremes with heaviest per cal bullets.

 

[gonehunting378]

actually mike, the most accurate, and centered wins, the target could care less what the b.c. was, or how they got there.... why can the 6.5x47 not work? if it can push 130 vld's up to 2960-70, it then is equal to my dasher in the wind...of course assuming both were fired at the same exact time, on the same line, and both shooters wearing blinders and holding center all 10. maybe i am not understanding "light bullets"?
tom

 

[Charles E]

If you guys want a "light bullet" thread, start one. It is easy. I wanna talk about ignition & small primers.

 

[Boyd Allen]

Charles,

To address the large vs. small primer issue, could one start with one or more of the larger cases that are available with a small primer and flash hole, tune to peak accuracy, and then enlarge the primer pockets and retest using the same rifle and bullets?

One more thing, that I remember reading about years ago in PS, was a fellow who cut a bevel on the inside end of his flash holes. I think that it was a fairly large included angle , and he found a way to control the depth. The author claimed lower SDs, I believe. The thought was that the shape of the primer's flame was altered in a way that improved the consistency of ignition. If he wasn't fudging his data, perhaps this might be an additional area for inquiry. Do you know of anyone that has tried this?

Boyd

 

[mikecr]

the most accurate, and centered wins, the target could care less what the b.c. was, or how they got there....

Well the most 'accurate' at 1Kyd these days rarely breaks 1/2moa. Any cartidge on earth is capable of this... And although every anomoly has had it's day, still the biggest 30cals win most often.
They produce better in the wind, and only need 1/2moa to win.

why can the 6.5x47 not work? if it can push 130 vld's up to 2960-70, it then is equal to my dasher in the wind...

But conceding to a 260AI releasing 140vlds, or a 6xc releasing 105vlds, or many other cartridges that have been options for a long time now.. And again, shoot around 1/2moa at 1kyd, and you're having a good day. Do it in tougher conditions and you might run with 30cals. But that won't be the norm.

My point is that smaller primer advantages in small cartridges, fade to none against winning capacities at windy 1kyd. Of course there will be anomolies, and I recognize that you like the new mighty mouse.
But..
You're re-inventing a light bulb for a 'new' bulb, that you brag -matches what we already have(with enough effort), and anyone has to reason 'why'.

 

[mikecr]

I wanna talk about ignition & small primers.

I'm sorry, I thought you wanted to discuss advantages to small primers, that Al had been referring to.

 

[Charles E]

I'm trying to figure out where this notion came from. Aside form Al, that is. I hope we'll hear from Al, in a less abbreviated manner as this is the central point of the thread.

So, Mike, if your point was that small primers work best with light bullets, you certainly belong in this thread. Keep right on going, say why, my mistake. (I would note that at 1K, often enough the winning light gun group in IBS is under .5 MOA. Sadly, it is getting to the point they are in the high .3s)

* * *

Boyd, Dave Tooley , one of the developers of the 6mm American, has done some comparisons of case size, primers, and ignition. There was at least one lot of full-size .30.30 during the 6mm American development. Well, sample size one test. He has said, ceteris paribus, that anything bigger than the 6 BR was on the edge of poor ignition with small primers. He has also done the taped flash hole test -- by accident, "oops" when deburring PPC cases. "Best set of cases I ever had." Hardly a controlled study. Joel Pendergraft and I have done this on the big .30s as well. Just one more "seemed to help" without any real proof.

* * *

To give you some notion on just how far I'd range with this topic, consider this:

Norma brass is suppose to be the best, except for being "soft" (e.g., loosening) primer pockets. OK, consider the 7x65R case. Depending on how you arrange extraction, the case can be supported all the way up to the rim. Headspace can be *exactly* controlled by rim thicknes. Look at what Michael Turned has achieved with his .30-30.

If this solves problems, we have a whole other set of cases --rimmed ones -- where primer pocket size disappears as a problem. They might be better in some other regards, as well.

Or -- the 6.5x54 Mannlicher-Schoenaur has an exceeding long web. Now, I think Al would say, "Doesn't matter. The only thing that counts is the diameter of the flash hole, that's what allows pressure back in the primer pocket." I've actually make a 6mm wildcat on that case, a 2-inch PPC. Problem is, it has it's best accuracy with 105 grain bullets if I don't push it too hard, so primer pockets don't open anyway.

* * *

First job is to determine the problem, if any. Al is right a lot, and sometimes wrong. So, "are (rimless) cases using large primers at a disadvantage to cases using small primer?" If so, then (1) why, and (2) can we make some progress, aside from just being stuck with a few SP cases?

 

[mikecr]

Well, I believe I got it right with a view of Al's notions relating to case life -at very high pressures seen as needed to be competitive. If so, I think Al is absolutely right, but not w/respect to long range cartridges, or competition.

David Tubb tested large & small primers with his 6XC, and found that small primers produced inconsistent ignition beyond a certain capacity. This limit was below his 6XC, so he went large(he made the call).
Also, I know of no basis, or evidence, of small primers producing any better ignition than large primers. Does anyone here?

The reason bullets come into it, is the same reason bullets come into everything shooting. It's ALL based on the bullet.
Just like tires in racing, ALL the dots connect back to them.
There are short range BR bullets, and there are long range BR bullets. Exceptional use is so extremely rare that it provides no debate. And successful LR BR shooters are using heavy per cal bullets not for accuracy, but for BC. In fact, these long range bullets cannot be as accurate as short range bullets. Doesn't matter in long range, else everyone would be shooting 6PPCs with very accurate bullets at 1kyd.

Long range bullets are heavy to buck wind(it's uncertainty), and you can't push heavier bullets with higher peak pressures. Instead, the greater power needed is extended in duration(slower powder, longer barrel). This lowers safe pressure limits because the pressure peak(although lower) is applied over a greater length/area of bore.
It would do no good to hit a 140vld at 80kpsi from extreme undercapacity(like a PPC or BR). This is why LR shooters must and do increase their capacity.

Now, I don't compete. But I can review results/equipment from nearly all the IBS 1kyd matches. What I see are few small primer cartridges, and few shooters within 1/2moa. So 'accuracy' obtained with high pressure, lighter bullet cartridges, has yet to appear beyond pipe dream.
They only small primers I see(the 6x47), have been adjusted for use of heaviest per cal bullets by necking down to 6mm. They dropped light/cal 130vlds for heavy/cal 105s, and it wasn't for accuracy...

 

[4Mesh]

Does it have to do with the "power" of the primer? The (usually) smaller flash hole? The more meat in the case head from the smaller hole for the primer?

The aggregate material in there does vary quite a bit from one primer type / brand to the next. Also, the amount of it in there is very inconsistent.

Hotter is a difficult thing to define. There are several things to consider which is why we spend so much time fiddling with primers to begin with. Well, some do. Does hotter mean, faster burn, more material to burn, or longer burn. Each does something different to different powders, and each is greatly affected by ambient temp.

Things I think I know:

The less the chemical power of the primer that will still give adequate ignition, the better.

I think you are looking for consistency and I'd prefer more power and more consistent. Unfortunately, in the manufacture of these things, those two seem mutually exclusive (in my testing)

Adequate ignition is hard to define. It is usually mentioned when something was done to "increase" ignition, and a problem (usually vertical dispersion) goes away.

I've actually walked away from the firing line and said to people, "that ignition really felt crisp today", then had a smokin target. It's like the good ignition is something you can feel. A difference in ignition delay as low as a couple milliseconds, but, you can fee the difference between 1 and 4ms.

If the striker spring is weak, there will be more vertical dispersion

In my experience, that was not true, but, if the fall stays the same, you probably have a good point.

Some chamberings, such as the Dasher, seem to work better with hotter primers.

I think they all work better with hotter primers, but, each has a different condition / ignition needs, that makes it "hot".

flash holes can be uniformed, either by drilling (always larger), or by swaging (can be made some smaller).

The flash hole is a metering device. Aside from circumference, length and shape may play a role. Length is determined by the case web, and can't easily be altered.

They are very easy to alter, but, like all uniforming operations, you are always headed in one direction. Shorter.

The case head is unsupported in the chamber, to allow for extraction How much of the case head is unsupported depends on the arrangement/design of the locking lugs and extractor. With a rimless case and locking lugs at the front of the bolt, it is typically completely unsupported

Most are partially unsupported. Usually the entire primer depth is unsupported if that's where you're headed with that.

If you really, really want to, you can make up steel head cases

You'd have to really want to.

Front and center ignition has been tried multiple times with small-arms cases; there has been no demonstrable advantage

Is fun to read about tho.

There is probably more, but you get the drift.

So just what problems/issues do small primers address?

They fit in smaller cases.

Sorry Charles, but, I'm not real agreeable on these points.

 

[Charles E]

Where I'm headed Phil, is trying to open up Al's statement that cases using small rifle primers will (eventually) take over. Now he hasn't chimned in yet, so this is a little premature.

But what I'm aiming at is to open things up from "this case" versus "that case." Really open it up, so that if the objection is the meat of the brass around the pocket, we could look at rimmed cases without an extractor groove, which would let a (physically) large primer have as much support as a (physically) small primer.

Or, if changing the characteristics of the flash hole seems an advantage, that could be done.

Pretty much, I'm trying to get away from "bolt part A to part B" type thinking.

BTW, I think you'll get considerable argument against hotter is always better. I don't know, so I'll not say. But it is conventional wisdom, coming out of NRA/American Rifleman testing -- and German Salazar.

We're still waiting on Al - he writes late a night.

PS Damn, this wireless keyboard is nice. But with it floating around on my lap, I make more typos.

 

[4Mesh]

Ok, I see what you're getting at.

BTW, I think you'll get considerable argument against hotter is always better. I don't know, so I'll not say. But it is conventional wisdom, coming out of NRA/American Rifleman testing -- and German Salazar.

When it comes to the faster powders not generally used in 1K, that's probably true. At 600, lots of people are using powders generally found in varmint cartridges and those definitely are not hard to light. If you were to cut off somewhere in the range of R15/19 or 4350/4895, there and above my statements are probably pretty accurate. Varget, 380, 322, 3031, R12/10/7, etc, those are small enough extrusions (balls) to light without a lot of help.

I think when Al finally weighs in, he'll confess that it may not be so much the primer itself, but the cases that use the small primers that are to "rule". Bout that time a cousin to a 30Br will show up and re-write history.

PS Damn, this wireless keyboard is nice. But with it floating around on my lap, I make more typos.

 

[gonehunting378]

If you guys want a "light bullet" thread, start one. It is easy. I wanna talk about ignition & small primers.

sorry charles, you'll hafta wait for al

 

[alinwa]

OK, some of my thoughts FWIW

This may well raise some points for discussion if nothing else....

FIRST.... to accept my hypothesis/prediction one must be comfortable with the idea that the PPC/BR family of cases does and will continue to rule shortrange BR.

SECOND, one must accept the idea that the reason why this is true is due to the elevated pressures employed by the shortrange BR crowd.

THIRDLY, one must be convinced that the reason we can run these elevated pressures is directly connected to the small primers.

And FOURTH one must be convinced that inherent accuracy is an important part of today's longrange game.

And FIFTH, one must be convinced that dragging SR BR techniques into longrange can be beneficial to achieving this level of accuracy.

I'm convinced.



When I first claimed 1/4moa groups with the 6BR and 105 VLD's "Yo" from over on 6MMBR.com called me at home to see if I was lying. 6MMBR.com was in it's infancy but "Yo" even at that time had a healthy grasp of reality.....I appreciated his skepticism, it's all good. Time and improvements in systems has proven that true 1/4 minute guns are a reality. (Remember all you'se Olde-Timers to this board that there useta' be LOTS of threads about groups 'shrinking w/distance' and how guns that shotgunned at 100 were still winning plenty wood..... AIN'T the case now. Bughole@100 or Lose, end of story.)

IMO


And now we get to WHY I think the hyper-accurate 6MM's are the thing to watch.....



600yd Light Gun

Does this need explanation? I mean, if you choose to shoot a 300WSM w/187's or 210's then more power to ya' but WOW! that hurts....... almost hard to remain "fun."

600yd Heavy

In the little shooting I've done one thing has become apparent. Unless it's a trigger-pull the winner here will mos' gener'ly have the closest thing to a return-to-battery setup. I see 40-80lb 6BR's and "Dasher" variants, and now we have two new larger cases....

1000yd Light gun

And now we have two new larger cases.... cases which easily reach 1K.

1000yd Heavy

Ditto..... add return-to-battery.


return-to-battery


I'm playing with a 300WSM that weighs 50+lb. Really shoots well. Equal to my 17lb 6X47L even.

HUHH????

For maybe .050 "BC points?" Maybe even .100 IF I can get the 210's to really shoot which I haven't yet? At 50plus pound it's just like shooting my 17lb 6mm........

Manalive I wish I could rewind the clock........ it could have been a 50lb 6BR, or now a 45mm+6mm, without having to bush the boltface etc etc......

Last match my little 17lb 6-banger was shooting like a machine. I mean, I took it from Light straight-on into Heavy, DROPPED a shot clear to the bottom of the rings because I bumped my trigger on reset, (shot a 10"er,) ADDED an eleventh shot just because..... nearly got DQ'd ..... and still managed a 3rd in Grand Agg, the only score I really care about......but, Kurt Mendenhall flat cleaned my clock in Heavy shooting his "heavy metal 300WSM." Afterwords I looked over and ????














and he smiled and said.......







"6BR"


(or Dasher or something similiar...)

He'd redone it to the 6MM.... it WEREN'T no 300WSM no more....

pop-slide-pop-slide-pop....



And regarding the small primer (30X47L variant or .308 Palma variant) in HBR, the pure game..... I mean this is a no-brainer. Steenkin' SHOOT one They shoot "like a 30BR" the undersized bastard round which spawned a whole new comp.... I don't think anyone will even question the fact that the small primer cases in 47mm and 52mm lengths completely reset the meter for HBR legal cartridges.

But that's another subject.

So yeahhh, in short, I feel that the PPC/BR type cartridges rule the intrinsic accuracy fields.... due IMO primarily to the fact that they'll take the higher pressures (required??? test it yourself) used in short-range BR.

And yeahhh, I've proven to my own satisfaction that the WSM case will also take some nice pressure, will shoot really well, BUT.......... it's also a mule-kicking sonofagun!

Now, does it follow that Ol' Anilwaugh thinks we need small primer BIG cases????

NO!

But we do need to do whatever it takes to make our loaded rounds capable of the high-pressure, clean-burn, low ES and hyper-accuracy required in today's comp.

And then we've got to make the unit tractable so's we can get back on target when the blueball's showing air all-round.........

I'm sure I missed a bunch of stuff....

But there's some of my thoughts

ramblings

LOL

al

 

[alinwa]

And now, on a completely different note........ I feel that the single biggest favor one can do for oneself when shooting VLD's is to break some of the rules of short-range BR.

Shoot VLD's seated clear down to the neck/shoulder junction or beyond. Shoot minimal clearance, like .001 to .0015 and ZERO FREEBORE.......

Make your cartridge case to allow this with your chosen powder charge.

Learn to make really GOOD necks and use them for the primary guiding means of the base of the bullet.


Looks funny but YOWsahhhhhhh!!


i better shut up


al

 

[alinwa]

(I've never actually shared this last one... but this is what really got me to my first 1/4moa aggs with VLD's.)

Throats wear out, necks don't.

and if they do, YOU CAN MAKE NEW ONES!



al

 

[alinwa]

i dunno why i said that!

weakness i guess

 

[alinwa]

Ohhh, and Charles. You're right, IMO there are several items:

-primer pocket expansion
-primers popping
-the next limiter is brass extruding into the ejector hole.
-and then, the flashhole also controls flash characteristics.....

The rimmed cases should help support against expansion, and you can eliminate the extractor several ways, and Stiller's firing pin diameter is crucial to eliminating blanking.....

The small flashhole does meter less gas back IMO, but equally importantly it is the "nozzle" which allows the small primer flash to effectively penetrate the long powder column..,,, heavy bullets here....slower powders.

al

 

[Charles E]

A TIME OUT POST

FIRST.... to accept my hypothesis/prediction one must be comfortable with the idea that the PPC/BR family of cases does and will continue to rule shortrange BR.

SECOND, one must accept the idea that the reason why this is true is due to the elevated pressures employed by the shortrange BR crowd.

THIRDLY, one must be convinced that the reason we can run these elevated pressures is directly connected to the small primers.

And FOURTH one must be convinced that inherent accuracy is an important part of today's longrange game.

And FIFTH, one must be convinced that dragging SR BR techniques into longrange can be beneficial to achieving this level of accuracy.

OK Al, I think I understand better. This helps a lot. I don't agree with two through five, (so, I suppose, I don't really agree with one -- I think there is a different reason).

But Phil didn't agree with my "think I knows," an after some back and forth, we started getting at useful examples.

I'm going to digest & think about what you've posted before replying. If we can keep at it, we might get a really good thread. Both examples purporting to show one thing, but maybe showing something else, and some good generalities. In spite of the beating "generalities" take from college sophomores, I have found them quite useful in life, as long as one remember they have exceptions.

We're not going to change the sport on an internet forum, or compete with the data they get at Aberdeen. But we might shake out some ideas & debunk some myths; an aid to those who are interested in understanding what's happening and trying to develop useful stuff.

I need some time to think a bit. Other, perhaps younger minds may be ready to go, if so, have at it.

 

[gonehunting378]

charles,how do you not agree with number 4? i agree with all 5, exept we then can't explain the 300 wsm, so maybe number 4 is the ONE...

al, why do you need 1/4 moa? mike allready said 1/2 moa is good enough.
tom