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Posted: 11/21/2012 9:35:02 AM EST
So I have discovered a problem with my entire supply of 9mm subsonic ammo. These were loaded with 4.2grs of WSF, CCI 500 primers, and Zero brand projectiles; in mixed commercial brass, with a 1.130 COAL. EVERY SINGLE round has been case gauged, to ensure that they will chamber. I initially worked this load up for my 5" 9mm AR, with a suppressor in 2007, and have had very good success with this recipe, up to this point. A couple of weeks ago I opened a new can of 2000rds, that I produced in 2010. I immediately noticed a loss of accuracy from my AR. Since that time I have run these through my chronograph and verified that the velocity is where it is supposed to be, and that my standard deviation is also within tolerance; so that has ruled out bad powder or primers. I have also purchased some factory AE 147gr rounds, and run those through my AR, which produced excellent results; thus ruling out a bad barrel or poor shooting on my part. The bullets all measure .355, they all weigh ~146grs, and measure .376 at the mouth after being loaded. I have come to the conclusion that for whatever reason my AR no longer likes the Zero brand bullets. Not sure if it is composition, or design, or what; but at 50yds, I can barely keep 20rds inside a 10" circle. So what the hell? Mathematically, everything is where it is supposed to be; yet my results are completely unacceptable. The only thing that could have changed, and I know this is a stretch; is possibly the amount of buildup in my suppressor. Could this possibly be causing some kind of turbulence inside the can, resulting in an unstable flight path with the round nose bullets; vs. the flat nose factory loads? I'm at my wits end. Please help...

R/,
Matthew A. Roddy


––
Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
Link Posted: 11/21/2012 10:12:41 AM EST
.355 is pretty small. Maybe you got an undersized lot of bullets? Have you slugged your bore? Did you measure the diameter of the AE bullets?
Link Posted: 11/21/2012 7:02:33 PM EST
Sounds like undersized bullets to me.

I experienced this exact problem many years ago with Ranier plated 9m/m bullets. The problem then was undersized bullets.
I literally couldn't hold a group any smaller than a playing card at 7 yards with a pistol.
Link Posted: 11/21/2012 7:57:29 PM EST
When accuracy starts going to hell in my 1911s one of two things has occured.

1.) Barrel is fouled. I know there's a crowd who suscribes to a dirty barrel is an accurate barrel theory. I used to be one of those guys until shown different and my groups started making clover leaf groups instead of fist sized groups at 15 yards.

2.) Recoil springs weaken or not calibrated to my handloads. I've proven this to everyone who's ever challenged the issue. Could it be your buffer has weakened ? Gas tube partially plugged or as you've mentions suppressor dirty ? I've got an AR and two uppers for it and capable of assembling one. Just not very high speed on trouble shooting since mines never had issues yet. 1911s, that's a different story.

Could be your gas, buffer and buffer springs are set for 147 accuracy and off for lighter bullets. Just throwing stuff out to get to this point. When problems occur, think back to what change could have occured to throw off what you know has worked before.
Link Posted: 11/22/2012 5:23:16 AM EST
Originally Posted By jonthear15guy:
.355 is pretty small. Maybe you got an undersized lot of bullets? Have you slugged your bore? Did you measure the diameter of the AE bullets?


I don't know if I missed it but are these cast or jacketed? .355" would be fine for a jacketed bullet but for cast I like to go .002" or .003" over groove diameter.
Link Posted: 11/22/2012 5:42:16 AM EST
Full metal jackets, thanks...

R/,
MR
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