Confusing maximum 10mm charges with AA9

[Zane]

I loaded up some 10mm for the first time today. I shot them after trying some DoubleTap and some of my cartridges were....stout.

I'm using AA9 with Hornady 180gr XTP and CCI300. Hornady list the loads as 11.5gr to 14.9 gr with an OAL of 1.26.

I started at 13 gr and increased by 0.2 gr until I hit 14.8gr. 14gr seemed to be the sweet spot and by 14.4 gr there were noticeable ejection marks and the brass was really flying.

Looking at Accurate's load data, they list 13.5gr with an OAL of 1.25. Lymann doesn't have a 180 gr load with AA9, but the 175 gr Silvertip load less than 14gr. OAL is 1.25.

So can adding 0.01" really make that much difference (essentially a full grain more powder) or is that Hornady load really just off the charts? I certainly won't load above 14gr without a heavier recoil spring, at a minimum.

 

[cheygriz]

Don't obsess with OAL. 01 isn't going to make any difference.

 

[Zane]

I guess that still leaves the question about the difference in load data. They seems to use the components, but the Hornady max load is 10% higher than Accurate's.

 

[murf]

sounds like your load is off-the-charts. i would go with the accurate manual and stay below 13.5 grains. the manual says this is a compressed load already. i don't know which hornady manual you have, but mine (fourth edition) doesn't even show a listing for aa#9 with a 180gn. xtp. if you're getting ejection marks on the rim or case head, i would definitely back off on the load.

murf

 

[Glock20]

Hornady 7th Edition does show AA# 9 at 14.9gr max for 180 XTP's. It's not the first time a bullet mfg and powder mfg data are different. I've loaded #9 at close to Hornady's max and saw no signs of pressure. YMMV.

My preferred powder for 10mm is Longshot.

 

[ironhead7544]

Thats why theres a start load. Ive had revolvers lock up with the listed start load. Some guns just dont like some powders.

 

[ljnowell]

Thats why theres a start load. Ive had revolvers lock up with the listed start load. Some guns just dont like some powders.

Thats usually because they are so light the primer backs out and doesnt have enough force to reseat when it hits the breechface. This will lock one up tighter than can be.