Different size primers

[charlie b]

I have inadvertently entered into an interesting test series with my .308Win.

I have always use Hornady or Lapua brass for jacketed and cast loads. Almost all were fired using CCI BR-2 or Fed GMM primers. I drilled out the primer pockets early on and used them that way for all my cast loads as well as jacketed loads. Never ran into any problems and have a LOT of load data and targets that show me what has worked and what has not. For cast I normally use IMR4198 but have had good luck with IMR3031, IMR4166, Accurate 4064 and even Varget. My favorite load is the XCB bullet (165gn) and 21.2 gn 4198 at 1850fps. It groups less that 1 1/2MOA out to 300yd and frequently goes less than 1MOA. All of the bullets are seated to firmly engage the lands when chambered.

The problem. Due to the primer shortage I bought some Peterson brass with SR primer pockets. I have 50 with the original 0.050" flash hole (the small size also used by the 6BR). Another 50 I enlarged the flash holes with a #38 drill. All of the brass was first fired with a jacketed load (155gn ELD Match bullets) to fire form them. The ones with the smaller flash holes I have used for all of my jacketed loads with no issues.

The ones with enlarged flash holes I used for my cast loads. I started seeing rounds fail to fire and hangfires. About 1 in 5 would not fire properly. At first I thought it was a firing pin issue, but, the jacketed loads didn't have any problem. I replaced the firing pin spring(s) anyway but the problem persisted. I was using CCI BR-4 primers. I suspected the primers (even though they worked in the jacketed loads). So, I got some Federal match AR primers. Those worked a little better. Most recently I tried CCI SR magnum primers and they were even worse.

The thing that surprised me came when pulling down the failed rounds. There was still powder in them so I figured the primer had not gone off. That was up until this last session. One round I pulled still had pressure in it from the primer firing, just not igniting the powder. There was a small 'clump' of powder at the bottom of the case that looked like it had been 'melted' together a bit. I check the primers in the other failed cases and they had also all gone off, just did not ignite the powder. Two others also had a small 'clump' of powder at the base.

So....my theory is the smaller initial flame front of the SR primers and the low density load of the 4198 (about 55% load density) results in a failure to ignite the rest of the powder due to too low a pressure.

Any other theories?

FWIW, the loads that did fire properly grouped very well.

PS when I load the rounds I load them after tipping the nose up and slowly chambering them. I have not had good luck with dacron, but, this method seems to work well. My LRP loads are usually less than 40es and 15sd. Of the SRP loads that have fired properly they have had the same consistency and vel is within 20fps of the LRP loads using the same powder charge.

[Winger Ed.]

It may not make any difference for what you have going on, but I'd read here and there that some guys
trying for that last little molecule of performance and consistency would take their ammo out of the press after seating,
and stand/store it in a ammo box with the bullet facing down.

I don't know if that's a solution for a problem that doesn't exist,
or they were trying to avoid a clumping kind of something in, or on the flash hole.

[45_Colt]

In the Mar/Apr '89 Handloader (#138) there is an article that a reader (Steve Gash) submitted about the same thing. He used LC-63 '06 brass for the 6.5-06 cartridge. Used primer pocket bushings to fit SR primers in place.

Found the same as you, many misfires, and some hangfires with most brand of primers. The ones that did light off the powder did show better accuracy. Note that the powder was H-4350 (50 gr), and a Speer 120 gr spitzer.

He found that the only SR primer that reliably set off the powder was the Remington 7-1/2. The cartridge fired normally every time.

For the ones that didn't light off, every primer fired, just didn't fully ignite the powder. The powder was the same as you found it. Mostly caked with fine soot.

Unfortunately he didn't have an answer to the issue, so no help there.

45_Colt

[charlie b]

Well, at least I'm not alone :)

The nose down thing I have seen before. I use what I have heard referred to as the 'SAAMI twist'. Pick up a cartridge and twist the wrist a few times to 'mix up' the powder in the case. Then tilt bullet up and carefully lay the cartridge in the rifle.

Next up I will use a different powder, 3 different primers (Rem 7 1/2, BR-4 and Fed AR match) and a 'control load' using LRP brass (Win LRP) with the same load.

[Larry Gibson]

"So....my theory is the smaller initial flame front of the SR primers and the low density load of the 4198 (about 55% load density) results in a failure to ignite the rest of the powder due to too low a pressure."

Put a dacron filler in the case to hold the powder back against the primer. If the misfires go away your theory is correct.

[charlie b]

That was something else I was going to try in this batch.

[Gobeyond]

My theory FWIW. Maybe it’s the drilled out flash hole and the powder is getting too close to the small primer and getting an incomplete burm. I tried to do that in an 06 with red dot but it had big flakes. The small granules maybe snuffing out the fire causing the clumps. Are those all stick powders? Then maybe one or two all the way down on the primer. Or three. The flash hole is the only thing different from the others.

[charlie b]

Short answer, turns out Larry and I were correct. My previous loading technique had gotten sloppy, which led to the hang fires. Sloppy loading with a low density charge of powder can result in incomplete or no ignition of the powder using small rifle powders.

Three ways to fix. 1) use a filler. 2) use very careful loading to make sure powder does not move away from the primer. 3) after chambering a round tilt barrel up near vertical, then carefully lower to aim.

Size of flash hole had no bearing on the ignition failures. Size of powder granules, slightly higher charge density, size of powder granules, brand/type of primer had no bearing on the failures.

--------------------------------------
Details:

Batches tested were all with Peterson SRP brass. The original brass had 0.050" flash holes, smaller than what is 'normal' for flash holes. The larger flash holes were enlarged with a #38 drill. Almost 100 rounds were fired. Chronograph is a Labradar.

Small flash holes:
167gn (XCB) std lube: Fed AR Match primers: 21.2gn IMR4198, 24.0gn IMR4198, 27.0gn AA4064

Larger flash holes:
167gn (XCB) std lube, Rem 7 1/2BR primers, 21.2gn IMR4198
167gn (XCB) powder coated, Rem 7 1/2BR primers, 21.2gn IMR4198
167gn (XCB) powder coated, Fed AR Match primers, 21.2gn IMR4198
167gn (XCB) powder coated, Fed AR Match primers, 21.2gn IMR4198, 0.5gn dacron fill

I did this as carefully as I could. Except as noted I would pick up a cartridge, shake it a few times, tip it bullet up and CAREFULLY lay it in the action. Then SLOWLY slide bolt forward, chambering the round. Carefully aim and fire. Forward rest and rear bag so the rifle was not moved except for fine aimpoint adjustment.

I fired in order above from a clean, cold barrel. I only stopped shooting once to change targets (between small flash hole and large flash hole batches). Range was 100yd. Wind was at 45deg, 10-15mph. I won't go through all of it in detail simply because I got my answer in the first 20 rounds, 167gn (XCB) std lube: Fed AR Match primers: 21.2gn IMR4198

First group, extremely careful loading
167gn (XCB) std lube: Fed AR Match primers: 21.2gn IMR4198
1.5" 1798fps avg, 33es
no misfires or hang fires

Second group, 'sloppy' loading
167gn (XCB) std lube: Fed AR Match primers: 21.2gn IMR4198
1.2" 1835avg 30es
Tested process with this batch. Let round 'drop' into action, and slid bolt with some force.
One failure to fire (same 'clump' remaining) and 3 hang fires.
The group size and consistent velocity surprised me.

Remaining groups were all done very carefully and consistently. If the rifle was moved or chambering process not smooth, I redid it. I had no other hang fires or misfires.

The exception was the batch with the filler. I intentionally tipped them bullet down and loaded by quickly cycling the bolt. No misfire, no hang fire.

Notes:
1) The loads with the enlarged flash holes were not as accurate as the ones with the small flash holes, but, most of those were powder coated bullets. Previously the PC and lubed bullets performed similarly.
2) The loads with the filler had over 70fps es, consistent with previous experience with fillers (which is also why I don't normally use them).
3) The higher vel load (24.0gn 4198) had a higher es (41) and 2" group, which also tracks previous performance with this load.
4) The 4064 powder load produced good groups (1.5" and 0.7") but had horrible extreme spread (80fps).
5) The most consistent velocity was the PC bullets with the Rem 7 1/2BR primers, 1811fps, 21es, 7sd but not great group (15rnd, 2.2").
6) Quality control on the bullets was not what I would call match level. Group size was not the important part of this test so the bullets were sorted by weight, but, not for overall quality. No conclusions should be drawn considering accuracy of the loads.

Thanks for watching :)

[Kestrel4k]

Thanks for posting your experiences, I always find this particular topic very interesting indeed.

Does IMR4198 have any sort of reputation in this regard ? I have never loaded with it, but I have a pound or two and always like knowing as much as possible about my inventory.

[charlie b]

I had never had much trouble with it before when using large rifle primers. Which was probably why my technique got sloppy. I could induce a problem by tipping the bullet down or up before loading. The 'SAAMI twist' described above usually worked fine. The SRP situation just made it more critical.

I've used 4198, 3031, 4166, 4895, Varget and AA 4064 and low density loads (<60%). Funny that the Varget, 4166 and 4198 have been my 'best' powders. Quite a range in burn rate that all seem to work well for me.

[Larry Gibson]

My M70 Match 308W rifle with the 30 XCB loaded over 2400 with no filler. Loading technique was my variation of the SAAMI twist; hold cartridge vertical between thumb and fingers, tap lightly a couple times on bench, twist cast a couple times, insert case into action laying it gently on the magazine flooer plate and close bolt gently. Sounds a lot more complicated to do than it is.

CBA score targets were at 100 yards. Botton left target was sighters/foulers. Was a wind out of 3 o'clock so I was holding for that shooting for score not group.
Bottom right target has two 5 shot strings on it. First is pretty much centered over the 10 ring as I was holding for the wind. Second string is the 5 shot cluster at 9 o'clock as I shot straight away w/o holding for the wind.

320218

320219

[charlie b]

Larry, I always appreciate seeing your shooting. FWIW, if I can get anywhere near as good I'll be happy :)

Here are some of my targets from yesterday. 1" squares. The circles match CBA 200yd targets.
320226320227320228

First one was the 'very careful' sequence. Second was the 'sloppy' one, note the S and H to designate 'slight' or 'heavy' hang fire. The 'heavy' is about half a second. The true hang fires have had an added benefit. I get to see if I properly follow through on my shots. :)

The third was just the best group of the day. That was also one where I think the Labradar had a bad reading. Doesn't happen often but when a vel comes in that far off and the bullet is that close to the group it makes me wonder.

PS Larry, how much 2400 do you load and what vel are you shooting at?

[Larry Gibson]

I'm using 16.5 gr Alliant 2400 [no filler] in match prepped fire formed LC Match cases which have the necks reamed [Lee target Loader] and the flash holes drilled. Necks are sized with Lee collet die to give .002-.003" tension. Velocity runs 1788 fps [15' from muzzle] out of the Winchester 12" twist 26" barrel. Last chronographed test with Oehler M35P of 10 shots gave an ES of 18 fps with an SD of 6 fps.

BTW; You're shooting pretty darn good also. Nice to see the consistency of several groups you post other than the usual one cherry picked "group" we see most often.

[charlie b]

Thanks Larry. I try. Now days it is trying to figure out things like this powder position issue or causes of fliers. Little steps. I think the position issue might be why some of my groups have been a bit inconsistent lately. I already found my seating depth got messed up, which led to some poor groups. It has been a long process. I also like the Lee collet neck die. I already 'fixed' the Lee seat die to produce less runout.

I am considering another powder. While I like 4198 I am not getting SD's below 10 consistently. If 2400 were more available I'd try some. Have you tried 296/110?