Which twist rate 16/24/32 for 9 Major Open

[MoNsTeR]

A friend has a Bedell shorty that got a new top-end built with an AET barrel, and brass comes out so bulged it would have to be roll-sized to make it usable again (and I don't think you even CAN roll-size 9mm since it's tapered). He called Wil Schuemann who said it's a common complaint but didn't seem to see an actual problem with the situation. I know it's a sample size of 1 but after seeing that I wouldn't use an AET.

Something isn't right there, and it sounds like an extremely hot load. Was it a fully circular bulge, just on one side, or something different? Matt2Race (I think) was having a problem with 9 Major bulging brass something terrible (don't recall the barrel brand) until he found that he was running waaaay over pressure. I can't recall if he found that the charge had increased, or saw much higher numbers on the chrono, but it was definitely a load problem that he managed to fix. Wil hasn't been there for a while now...how long ago was this? I can't see any difference between the brass that comes out of my gun with an AET and the gun that has a KKM barrel in it...they look identical, and the same is true for my .40 guns (one AET and one STI barrel). R,

Edit to add: You can definitely Case-Pro 9mm cases.

8.0 or 8.1 of 3N37, which isn't that hot as I run 7.9 in my 5.4". The bulges are full-circumference.

[trodrig]

Bringing this thread back to the top for confirmation and some additional questions. I'm getting ready to order a barrel and just wanted to confirm that for 38SC, it sounds like the majority of folks are recommending the AET barrel with the 24" 'Gain Twist' if shooting 115gr to 125gr bullets. Is that correct?

My second question(s) relate to the chamber. Schuemann doesn't list an AET 24" gain twist barrel with a .355" short chamber. They only list one with a 38 super chamber (or 9x19 but I'm building 38SC) with 24" gain. Will that chamber still require some final reaming by the smith? Is it better to go with a different twist and the short chamber?

Thanks!

[G-ManBart]

Bringing this thread back to the top for confirmation and some additional questions. I'm getting ready to order a barrel and just wanted to confirm that for 38SC, it sounds like the majority of folks are recommending the AET barrel with the 24" 'Gain Twist' if shooting 115gr to 125gr bullets. Is that correct?

My second question(s) relate to the chamber. Schuemann doesn't list an AET 24" gain twist barrel with a .355" short chamber. They only list one with a 38 super chamber (or 9x19 but I'm building 38SC) with 24" gain. Will that chamber still require some final reaming by the smith? Is it better to go with a different twist and the short chamber?

Thanks!

Having shot 115 to 124/5gr bullets out of an AET, and spoken to Mike about it a number of times, I'd get the AET. We're talking 10gr of bullet weight, which isn't the actual critical dimension. Bullet length is what drives the twist rate for proper stabilization. That's why the really long 155gr Palma style .308 bullets need the same rifling rate that people use for 175-190gr bullets. The difference in length between 115s and 125s is really very small, and the 121s are almost identical in length, so it's even less of an issue.

Your smith will need to finish ream it, along with normal fitting (hood etc). R,

[818-DVC]

I have shot both AET & Ultimatch bull, as well as an aet 6 port hybrid no holes drilled in both .38 & .40. Freestyle and rested. There really wasn't much difference. My infinty came with a .79 3 shot test group with the AET at 75 yards from SV. The problem i had was not knowing plated or moly coated bullets didn't work in AETs. I thought I bought a bunk used gun, until I loaded up some CMJ's and it shot just as good as anything. Ultimatch will shoot everything and both are more accurate than I am.

[G-ManBart]

I have shot both AET & Ultimatch bull, as well as an aet 6 port hybrid no holes drilled in both .38 & .40. Freestyle and rested. There really wasn't much difference. My infinty came with a .79 3 shot test group with the AET at 75 yards from SV. The problem i had was not knowing plated or moly coated bullets didn't work in AETs. I thought I bought a bunk used gun, until I loaded up some CMJ's and it shot just as good as anything. Ultimatch will shoot everything and both are more accurate than I am.

I hate them, but some folks have had excellent results with plated bullets in an AET....slower spin-up stresses the thin plating less (or so the thinking goes). R,

[Seth]

I have a 5" STI in .40 that has both an AET bull and an Ultimatch bushing fit to it.

The AET does leave a very slight fluting mark on the brass, but I've only had 2 come out unusable and they were BLOWN out. Wouldn't resize and were obviously compromised... Out of th the 8k rounds on it, I don't consider that to be indicative of a problem.

As for the accuracy, shooting them both side by side at 25 yards, I couldn't discern a difference. Both were 1 ragged hole. At 55 yards, I was able to hit 3 4" orange clays with the AET out of 7 shots....

I like the AET, but still went with the ultimatch in my 6" gun which was built in august.

[Resjudicata]

I have a 1:24" twist 6" AET in my Bianchi gun and have found that if my 115 grain loads run slower than about 1150 fps the group at 50 yards is about 10". But, running over 1150 fps the group is about 2-3" with me shooting prone. I haven't tested a 1:16" twist barrel to see if it will run the slower loads any better.

I realize you guys are mainly talking about running major PF but it's something to keep in mind if you decide to run some soft steel loads. Keep the velocity up close to or around 1200 fps with the 1:24" twist.

Chris

[CocoBolo]

The hour of truth will soon be upon the Schuemann 32 twist Ultimatch barrel. My smith says it will be ready tomorrow.

[Aircooled6racer]

Ron: You are a lucky guy I am still waiting for my Schumann barrel with a 1/32 twist It has been a couple of weeks and I want to get started on my next open build for next year. Tell us how it shoots. Also try some 115's again with it. I am sure it will be a tack driver. Thanks, Eric

[818-DVC]

Didn't some importer from the philipines buy out mikes stock at area 1?

[G-ManBart]

Didn't some importer from the philipines buy out mikes stock at area 1?

I don't know about that, but he has been having major electrical supply problems (brown outs, blackouts, power surges, etc) that have been causing all kinds of problems. That's put him waaay behind in production. R,