CCI LP primer vs Magnum SPP in 45 ACP

[lugerstew]

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Due to running out of LP primers and SP primers, I did an experiment with SP magnum primers instead. I did the exact same load workup, same gun etc., I'm just not sure how the ambient temperatures compare, I didn't write down the temperature for the first load workup.

My first 45 ACP workup last year was misc. brass LP primer, Extreme 200g plated RN bullets, with CFE pistol, coal=1.250. everything was the same between last year and this year except I used CCI Magnum SP primers instead of CCI LP primers.
LP results for velocity were, 6.3g=791, 6.5g=758, 6.7g=830, 6.9g=829, 7.2=894

SP magnum primer results were, 6.3=663, 6.5=742, 6.7=662, 6.9=762, 7.2=792.
Note, 6.3, 6.5 and 6.7 had a few failures to cycle, also it was 35 deg F today.
Maybe someone here could explain why the SP magnum primers produced such odd and slower results than the LP primers? I also understand that no load data anywhere suggests using SP magnum primers. Thanks

[44 AMP]

To be clear, you are comparing Large Pistol primers against Small Pistol Magnum primers???

If so, you might be getting lower velocities from the small pistol primer cases you are using. OR you might be seeing a lower velocity because the addidional force from the magnum primer is unseating the bullet before significant powder combustion happens, which increases the volume the gas need to fill, resulting in lower velocity.

Remember with the .45ACP, you're looking at lighting off 6-8gr of medium burn rate powder or less of a fast burn rate powder, compared to 2x or 3x that amount of slow burn rate powder that happens in magnum pistol cases.

Also note that a firm crimp is recommended for those large magnum cases, for two reasons, one being the "bullet pull" of revolvers during recoil, and the other is to help retain the bullet in the case until the slow powders really get burning. The roll crimp used simply isn't the same as the taper crimp the .45acp uses, in that regard.

[lugerstew]

Thanks 44 AMP, yes that is what I am doing, I originally developed this load with large pistol primers, now I am using small primer pocket brass and Small pistol Magnum primers.
I was going to load up a batch of the 7.2g with Small pistol Magnum primers, since they seemed to do alright, no overpressure signs and I have 2000 Small pistol Magnum primers and less than a hundred of the others.
I kind of wonder though, if I'm going to get into trouble if what you're saying is true about unseating the bullet too soon, I sure don't want a Squib.

[jetinteriorguy]

I would try a heavier crimp on the SPM’s, just don’t overdo it and bulge the case.

[lugerstew]

I'm not sure that it is ok to try and put a strong crimp on a round that headspace on the front lip. I usually just crimp slightly to remove the expanded bell so that the round will feed well.

[Unclenick]

Just don't crimp below the SAAMI minimum of 0.467" at the case mouth, and you are fine for headspacing.

[jetinteriorguy]

Originally Posted by lugerstew

I'm not sure that it is ok to try and put a strong crimp on a round that headspace on the front lip. I usually just crimp slightly to remove the expanded bell so that the round will feed well.

I may be mistaken but I believe most taper crimp dies designed for cases that headspace on the mouth are designed in such a way that they won’t size a case below the proper size to headspace properly. I know Lees dies won’t undersized a taper crimped round, but they can be sized too much and bulge a case.

[44 AMP]

A heavy crimp on a plated bullet that doesn't have a crimp groove is rarely a good thing.

If you are using a pistol like a 1911A1 where the round feeds from the mag up under the extractor, and feed rounds from the magazine only, you can get away with a roll crimp (if you have to suitable bullet for that) and the pistol will "headspace" the round on the extractor. Not proper, not precise, but will "go bang".

If you have a gun that has the extractor pivot and snap over the case rim, a roll crimped round won't work well, if at all.

The OP is using plated bullets, which put their own restriction on amount of crimp so sticking with taper and not going below SAAMI specs is the best available option.

[Nick_C_S]

I'm not seeing, in this project our OP is endeavoring, why there is any need to adjust the crimp.

Are we over-thinking? Seems to me, the amount of crimp should just be business as usual.

[Unclenick]

Nick,

He's getting lower velocities and greater variation from the linear velocity vs. charge trendline with the SPM primers (R²=0.57 vs. 0.78). There is a common issue with magnum primers in small powder spaces wherein the higher-pressure primer unseats the bullet before the powder is burning enough to do it (though I don't actually know how an LP primer compares to an SPM in regard to gas volume). This results in lower and more erratic velocities because the starting powder space is a little different for each shot, and we see both here. The thinking about the tighter crimp is it could overcome the tendency of the primer to move the bullet prematurely.




Lugerstew,

A couple of things to try: Try a faster, more easily ignited powder like Bullseye or Universal and see if that mitigates the performance difference.

Another thing you can do with those relatively soft, plated bullets is to seat them long, so the round headspaces by bullet contact with the throat before the case mouths contact the end of the chamber. I use this standard with cast bullets as it improves both accuracy and ignition consistency by raising the start pressure a bit. There can be feed problems in some guns doing this, but in the 1911s, I've had no issues. I back the seating die out and gradually turn it in until a cartridge dropped into the chamber stops with the case head flush with the barrel extension (hood). As long as it feeds, it works a treat, and IME with soft, swaged lead and cast bullets, cut group size by up to 40%. It no longer makes a clear "plunk" sound, however. (Third from left, below, is what I am suggesting.)

[lugerstew]

Thanks, Unclenick, I will give both those options a try, it's just I bought 8lbs of CFE pistol about a year ago, but I do have green dot, unique, win231, be-86 etc.
I have never tried seating out to the throat in my 1911, but it does sound like it could help my situation, of course I would need to do another workup to look for pressure signs, I also am a bit concerned about how much bullet will be in the case, right now there is only about 1/4 inch of bullet seated, moving out till it is touching will of course make that even less, I will just have to see what I have at that point.
Thanks again.

[buck460XVR]

Originally Posted by Nick_C_S

I'm not seeing, in this project our OP is endeavoring, why there is any need to adjust the crimp.

Are we over-thinking? Seems to me, the amount of crimp should just be business as usual.

Originally Posted by Unclenick

Nick,

The thinking about the tighter crimp is it could overcome the tendency of the primer to move the bullet prematurely.

I'm kinda with Nick. Taper crimp does nuttin' to increase neck tension, all it does is take out the flare. Over crimping with a taper crimp, especially with plated bullets is going to do more harm than good. If anything, the OP would be better off to try and reduce the amount of flare he uses, if indeed the issue is with the bullet moving before the powder ignites.

[lugerstew]

Unclenick, I don't think having the case even with the barrel extension, (hood) is going to work for me, when I seat my bullet even with the hood and I can feel the bullet is head spacing on the bullet, then my problem is, the rounds are too long for the magazines, in my Ruger 1911 and also my Glock 21.
I'm loading up a bunch at 7.2 grains and just try my target shooting with those and see if they work ok, if not and I have issues, then I will try using a faster burning powder.
Also, from the other people's recommendations here, it doesn't sound like trying to make a tighter taper crimp is a very good idea with my plated bullets, and also since a taper crimp doesn't add any more neck tension.

[44 AMP]

Taper crimp can just remove case mouth flare, or it can be adjusted to actually crimp, IF there is someplace for it to crimp into.

I use a taper crimp loading .44 Auto Mag rounds (as well as 9mm & .45acp) but I only use bullets with crimp grooves/cannelures in the .44, and I'm a bit old fashioned, I don't use plated bullets. When I shoot lead, I shoot lead, and when I shoot jacketed, I shoot jacketed, and see no reason to mess with bullets that are neither, but that's just me.

[Unclenick]

With the soft-plated bullets, the taper can also be used to dig into the bullet a bit. Yes, it distorts the bullet, but as long as it isn't too close to the base, it doesn't seem to cause an issue.

The other thing you can do to grip the bullet harder is to paint the case around the inside of the mouth with liquid asphaltum and let it dry, then, when it is fairly hard, seat the bullet. This is how the military glued bullets in place for a long time.

Lugerstew,

If the cartridges don't feed, try seating the bullet deeper a little at a time until they do to see if you don't find a spot where they feed and still shoot better than before.

One other thing you can try with the SP primer pockets is drilling the flash holes out to about 1/8" to see if that clears the irregularity up.

[std7mag]

I have several questions.

1) Since you obviously ran these over a chrono, was there a variation in ES & SD between the LP & SMP?

2) Could part of the difference be attributed to a smaller flash hole in the SP cases?

[lugerstew]

std7mag: I'm not sure about the SD or extreme spread difference between the two, because for some reason I didn't record the SD last year of the large pistol rounds, sorry.

Although, I have done a couple comparison tests with this caliber between large pistol and small pistol regular primers, and never had the velocity differences that I am seeing here with the SP magnum primers.
When I did those tests a while back, the differences in velocity between the small pistol and large pistol regular primers was mostly the large pistol were less than 10fps faster than the small pistol rounds. Not a huge difference at all.

Is it a fact that large primer flash holes are actually larger than small primer flash holes in this 45acp caliber? or are they the same or very similar? I visually looked at them, but they appear to be the same size, and I don't have a good way of measuring the flash holes.

I erased the Magnum primer chrono data already, but I did record the SD values: 6.3=58, 6.5=53, 6.7=50, 6.9=73, 7.2=30

[44 AMP]

One way to measure flash holes is to simply use drill bits. Its not hyper precise, but its reasonably close. Find a drill bit that is a snug fit in the hole, and that size will give you the approximate diameter.

Do be aware of the possibly of English vs. Metric sizes....