AA7 in 357 Sig

[Racer377]

I was using 11.2gr AA7 under a 125 Zero FP. I had settled on this load after chrono and group testing. It was very consistent, low SD, great accuracy. However, there was a fair amount of particles left in the gun after a few hundred rounds. This past weekend, I had a failure to extract in my M&P357 towards the end of a SC match. I think the culprit was these particles fouling the already relatively snug chamber and causing the case to stick. But for that stupid FTE, I would have finished fairly well, darnit. Previously, I had been using 8.8 gr longshot, and never had the FTE issue pop up. That brings up a couple questions that I was hoping the collective wisdom here might be able answer:

1. Does this theory make sense?

2. Has anyone else had issues with AA7 leaving a lot of particulate matter in the gun? (in 357 sig or otherwise)

3. If so, is it a symptom of too little/too much pressure for AA7 to burn cleanly?

[gng4life]

I had this happen with AA5 and a .40 load a long time ago. I went to a SPM primer and that helped quite a bit. Not sure if this is your problem but when you have that much powder in a case, I would try a hotter primer.

[SLM]

Unfortunately yes, your theory makes sense. I have an Open gun that does almost the same thing with #7 but acts up feeding and won't go fully back into battery after 150 or so rounds. It has a tight chambered Schuemann barrel. I have another Open that has a more generously chambered Kart NM barrel and it runs and runs on #7. It's actually my favorite powder in that gun.

Gng4life may be on to something with trying a magnum primer.

[Racer377]

Thanks for the responses!

I'll have to pick up some Magnum primers and give that a shot. I'm using WSPs, which I'm told are generally "hotter" than the other brands' standard small pistol primers.

I'm going to try a slightly higher pressure load too. I've tested up to 11.8gr, and I had a batch of those made up for bowling pins this weekend. Hopefully those will run a bit cleaner. I've read that AA#7 burns cleanest and most consistently toward the top end of it's range. IThat seems to line up with my chrono testing, the 11.8 was the most consistent. 10.39 SD (only .7% of avg velocity) on a sample of 15 rounds. I was testing a bunch of stuff that day, so I couldn't get a good idea of how clean each was. I've got 100 ready to go, so I guess I'll get that opportunity on Saturday.

I love how consistent AA7 is and how well it meters, so I'm hoping I can find a way to make it burn a little cleaner.

The other option is to get the Apex extractor and maybe give the chamber a light polish so it'll run better even if fouled. Using 11.8, I'm getting 125gr@~1396fps, which is probably a bit much. That's a good 80fps faster than the Federal Premium defense stuff I tested.

[pbairborne]

Here's my experience with AA-7 (and others) for what it is worth.

Despite what I've read elsewhere, the issue I have had with 357 Sig has been high standard deviations. But a couple of loads seem to give reasonable results.

I have an STI open gun chambered in 357 Sig. I've done quite a bit of load development work for it. Using MG 121 IFP's and 10.8 AA-7 with COL 1.190, I got a PF of 172, but an SD of 17.6 using mixed range brass. With new Starline brass, that same load gave me a PF of 173.7 and SD = 8. The temp was 80 deg. I was using Wolf SR primers. While a bit dirty, I had no problem with the gun running for several hundred rounds.

I tried similar loads with AA-9 and mixed range brass. Using 124 MG CMJ's/13.3 AA-9/COL=1.195/0.376 crimp/Wolf SR (45 deg F), I got 170.5 PF, but the SD was horrible at 37.9. Changing bullets to 125 FMJ's and 121 IFP's gave similar results with large SD.

And then there were the couple of jugs of surplus WC-820 that I had in the basement. It appears to be similar to AA-9 and pretty dirty, but it actually doesn't run too bad. With 124 CMJ's/14.2 WC-820/1.203/Crimp=0.376/Wolf SR I got a PF of 168.6 and SD of 10.4. Probably need to bump it up 0.1 or 0.2 gr. Anyway, I've run hundreds of rounds of this load thru my gun with no fouling induced jams.

All my experience has been with small rifle primers, so perhaps these cause the powder to burn cleaner or maybe my chamber is just a bit looser than yours.

[Racer377]

Here's my experience with AA-7 (and others) for what it is worth.

Despite what I've read elsewhere, the issue I have had with 357 Sig has been high standard deviations. But a couple of loads seem to give reasonable results.

I have an STI open gun chambered in 357 Sig. I've done quite a bit of load development work for it. Using MG 121 IFP's and 10.8 AA-7 with COL 1.190, I got a PF of 172, but an SD of 17.6 using mixed range brass. With new Starline brass, that same load gave me a PF of 173.7 and SD = 8. The temp was 80 deg. I was using Wolf SR primers. While a bit dirty, I had no problem with the gun running for several hundred rounds.

I tried similar loads with AA-9 and mixed range brass. Using 124 MG CMJ's/13.3 AA-9/COL=1.195/0.376 crimp/Wolf SR (45 deg F), I got 170.5 PF, but the SD was horrible at 37.9. Changing bullets to 125 FMJ's and 121 IFP's gave similar results with large SD.

And then there were the couple of jugs of surplus WC-820 that I had in the basement. It appears to be similar to AA-9 and pretty dirty, but it actually doesn't run too bad. With 124 CMJ's/14.2 WC-820/1.203/Crimp=0.376/Wolf SR I got a PF of 168.6 and SD of 10.4. Probably need to bump it up 0.1 or 0.2 gr. Anyway, I've run hundreds of rounds of this load thru my gun with no fouling induced jams.

All my experience has been with small rifle primers, so perhaps these cause the powder to burn cleaner or maybe my chamber is just a bit looser than yours.

1.190 seems really long for 357Sig. I've never had an open gun....do they tend to like them loaded long like that? I've read that SAAMI max length is only 1.140. I load mine to 1.135, which is what most of the published data recommends.

The other interesting thing is the apparent effect of using SR primers. I'm using WSPs, and over 11gr of AA-7 and a 125, I'm only getting a PF of 157 or so, compared to 10.8/121/172PF. Well, maybe that could be due to the comp and extra barrel length too. Then again, AA-7 published data is all over the place, comparing Speer 13 to Accurate's data.

How much hotter are SR primers as compared to SPM primers?

Edited June 23, 2011 by Racer377

[pbairborne]

Loading to 1.190 may be long for some guns, but they feed and run just fine in mine. I haven't tried to load Montana Golds shorter.

Regarding how much hotter small rifle primers are in comparison to small pistol, I haven't seen anything like quantitative data out there. Certainly the cup is harder to allow for the higher pressure of rifle rounds and there are probably more differences between the two types of primers, but I just don't know what they are. Perhaps someone with technical experience in primers will chime in.

And I forgot to add another comment regarding AA7 earlier. I use AA7 in my 9mm open gun. I typically run it 1500 rounds before cleaning. My gun hasn't malf'd in many thousands of rounds. I do, however, use small rifle primers.

[Racer377]

Are you using it to make 9mm Major?

[pbairborne]

Yes I am. My load is 121 IFP/10.5 AA-7/COL 1.180/Crimp=0.376/Fiocchi SR. Gave PF=170.5 and SD=5 here at 79 degrees. At the Florida Open this year the chrono showed 175 PF (80 deg).

[RobfromME]

Good morning,

I had also noticed the residue with AA7 back in the early 90's when I was using it with 10mm loads. Regardless of powder charge, it left yellow grains of residue in the gun. I never had a problem with functioning (S&W 1006), but then again I didn't shoot nearly as much as I do now. AA9 that I now use for 357 SIG wasn't nearly as bad, but there was still a tiny bit of residue. This was noted with maximum 357 SIG loads.

Perhaps the formulation of accurate powders?

Warmest regards,

Rob

[huskerlrrp]

I don't run AA #7 in an Open Gun, but use it in 357 SIG, 9mm, and 40 S&W. It does leave some small brown spherical residue in all weapons. It's never caused a failure though.

[Racer377]

I don't run AA #7 in an Open Gun, but use it in 357 SIG, 9mm, and 40 S&W. It does leave some small brown spherical residue in all weapons. It's never caused a failure though.

What is your 357 sig recipe?

[LtDave]

I don't run AA #7 in an Open Gun, but use it in 357 SIG, 9mm, and 40 S&W. It does leave some small brown spherical residue in all weapons. It's never caused a failure though.

What is your 357 sig recipe?

I've had excellent results with 10.6 gr AA#7. 1.5" groups at 20 yds with either Zero or Montana Gold 125 gr FMJFP in my P229.

[huskerlrrp]

I don't run AA #7 in an Open Gun, but use it in 357 SIG, 9mm, and 40 S&W. It does leave some small brown spherical residue in all weapons. It's never caused a failure though.

What is your 357 sig recipe?

For higher a end load, I like 11.4gr of AA#7 behind a 125gr Gold Dot or Montana Gold FMJ. This is above some posted manuals but I've never had signs of overpressure out of a SIG P226 or P229.