Load too hot for M&Pc/357 but not for P226?


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Baron
July 12, 2011, 09:38 PM
Hey all - I have loved shooting 13 grains of AA#9 with a Berrys 124 gr. FP out of my P226. It doesn't yield the screaming velocities I was expecting, but it's still a great load. I recently discovered that when I shoot the same load out of my M&Pc, I am unable to decap the brass afterwards. First things first: I messed up by not working up to this higher-end load when using it in a different pistol. Second, I assume that not being able to decap the brass, in addition to making my brass single-use only, is a clear sign that the load is over-pressure in the M&P. The P226 doesn't think twice about this load - does this seem normal?

Rather than give up my "flashbang" load in my 226, I might just find what the M&P likes and load separately for it.

Thanks.

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ReloaderFred
July 12, 2011, 10:36 PM
I'm not sure what you mean by not being able to decap the brass? You're using the same load I use in both of my 357 Sig pistols and I've seen no signs of pressure in either one of them.

Could it be that you're using a Dillon sizing die and Speer brass? Speer contracted with Starline to make some of it's 357 Sig brass and the flash holes are very small, while the Dillon decapping pin is the largest of the common brands. That brass has a small "s" on the headstamp.

Hope this helps.

Fred

Baron
July 13, 2011, 09:14 AM
Ah yes, I was aware of this issue with Speer brass, which lots of 357 SIG tends to be. I think you may have been one of the people that helped clarify this before. However, this issue seems independent. I'll test it again when I get home today, but I simply can't decap brass that's been fired with this load through my M&Pc. I take this as a pressure sign but I will certainly confirm and I'll also note how far it's flinging the brass to see if that corresponds.

Thanks again.

kutter
July 13, 2011, 09:54 AM
Fred would know a lot more about this than me but I always thought that primer pockets tended to loosen when you used a high pressure load. You did not mention if the cases were showing any pressure signs. I reload for 357 Sig at about 13 with a Berry's 124gr and I have never had an issue. Like you though I am shooting it out of a 226. I cannot imagine that it would that different out of the Smith.

rcmodel
July 13, 2011, 01:05 PM
but I simply can't decap brass that's been fired with this load through my M&PcCould you give a little more detail as to why you can't?

The only reason plausible is the primer punch is punching through the primer and making a hole through it.

There is no other possibility, as pressure high enough to cause primer pocket problems would cause loose primers that fall out.
Not tighten them.

rc

Baron
July 13, 2011, 03:51 PM
Everything you all are saying makes good sense - let me test again tonight/tomorrow and I'll post up.

Baron
July 14, 2011, 08:59 PM
Well isn't research wonderful.

Fired several rounds of 13.0/AA#9 and was able to decap them easily. So perhaps I'm more senile than I thought at 31. This does not bode well. Anyway, I may have gotten confused as to what wouldn't decap all those months ago.

BUT, I was re-reminded of this little phenomen: check out these primers.

http://i930.photobucket.com/albums/ad145/thetastycat/brass1.jpg

Here's a closeup of one:

http://i930.photobucket.com/albums/ad145/thetastycat/brass2.jpg

So I wondered if this, whatever this is, is a sign of overpressure, so I fired some rounds that were loaded significantly lower. I also fired one 125-gr. Gold Dot round. Here are two lower-loaded rounds with the Gold Dot case in the middle.

http://i930.photobucket.com/albums/ad145/thetastycat/brass3.jpg

Well how about that. What in the world is going on? Is this weirdness consistent with overpressure? I find it hard to believe that all three of these loads would be overpressure in this pistol - even factory Gold Dot ammo. Maybe my firing pin is strange. Any other M&P owners seen this before?

Thanks in advance for your theories!

Baron
July 14, 2011, 09:53 PM
Well, doing some research has revealed that this is a common occurrence in striker-fired pistols. As this M&P is my only striker-fired pistol, that explains why I haven't seen it until now :) In the first pic, the leftmost primer looks pretty flattened - I'll have to see if others do that as well. I will admit that when loading these rounds, the first one seated to 1.130 when it should be 1.140, and I decided to shoot it anyway, knowing full well that OAL is extremely important in this caliber. Maybe that's the corresponding brass.

Thanks for the help fellas - looks like it was much ado about nothing.

cfullgraf
July 14, 2011, 10:36 PM
Well, doing some research has revealed that this is a common occurrence in striker-fired pistols. As this M&P is my only striker-fired pistol, that explains why I haven't seen it until now :) In the first pic, the leftmost primer looks pretty flattened - I'll have to see if others do that as well. I will admit that when loading these rounds, the first one seated to 1.130 when it should be 1.140, and I decided to shoot it anyway, knowing full well that OAL is extremely important in this caliber. Maybe that's the corresponding brass.

Thanks for the help fellas - looks like it was much ado about nothing.

Fired primers in my two M&P9s and an M&P40 look similar to your pictures.

Baron
July 15, 2011, 12:09 AM
Yeah, apparently in striker-fired pistols, the slide begins to move backwards before the firing pin comes out of the primer. As the slide moves backwards, the breech end of the barrel begins to dip, and that causes the "firing pin smudge" on the primer. Makes good sense - wonder how somebody figured that out!

243winxb
July 15, 2011, 09:54 AM
"Primer wipe" is a teardrop-shaped firing pin impression, accompanied by a drag mark (scratch or gouge) following the "point" of the teardrop and leading away from the primer, sometimes into the brass. This is because the firing pin does not fully retract after the round has fired and the slide is traveling back during ejection, causing the case to drag across the firing pin as it is thrown clear. It is not in any way harmful, except sometimes to the case if the primer pocket edge is gouged. Kahr will tell you it is a normal condition for their pistols, even saying so in the owner's manual. http://i338.photobucket.com/albums/n420/joe1944usa/th_PrimerWipe.jpg (http://s338.photobucket.com/albums/n420/joe1944usa/?action=view&current=PrimerWipe.jpg)

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