Why Does Just #9 Powder Work In MY Kimber?

[K10]

It seems that the only accurate loads I can get in my Kimber target II is with #9 powder. I have tried longshot, AA#7, and power pistol. I would like to use some other powders, that did not take as much powder as #9. Any ideas?

[sqlbullet]

What is the disparity in accuracy between the loads?  Are we talking 2" vs 3" or 2" vs 3'?

[cwall64]

Interesting, I have definitely found AA #9 to be the most accurate in my Glock 20, but Longshot is pretty darn close, with BE-86 just a tad behind Longshot.  All of my loads have been close to book maxes (or should I say manufacturer website maxes) with Hornady 180 grain HAPs.  I have worked up loads for 800X, but didn't really pay attention to the paper results while chronographing!  My bad, I just was too excited getting all the chronograph data (new toy)!  I have some AA #7, but haven't done any 10mm loads with it yet.

[sqlbullet]

Traditional wisdom that a full case is more accurate would give the nod to #9 in most cases.  But I wouldn't expect the other powders to have "bad" accuracy.  That is why I would kinda like to know what the delta is in accuracy between the loads.

[K10]

The #9 loads are about 2" and the others are about 3". It could just be me. Old eyes. I want to try Power Pistol some more with the 155 XTP's. My gun does seem to like the XTP's better than the Noslers.

[The_Shadow]

About the XTP vs. Nosler 
Measured XTP's 0.4000" - 0.4005" and Nosler 0.3995" - 0.4000" (many have been 0.3995")

About the powders, your Kimber may like the AA#9 because it is slower...WHY?  Your slide may unlock slightly later keeping the barrel on target.  Consider you recoil setup.  What is your recoil spring weight?  Is it maintaining a good lock up?  Slower powders also hold the casing against the chamber walls for a duration of time, which can add to the dwell time.

Have you measured to see how much pull it takes to move the slide from the in battery position?  I used a digital fish scale and a small "C" clamp with heavy card stock to cushion the clamp to the slide so it would not mark the finish.  While not scientific it showed differences on both ends.

When I measured my Glocks there was a difference between the factory RSA and the Wolff non captive RSA
Glock 20Sf Factory spring test - Full retraction at 18lb 0oz at lock open.
It takes 5lb 3oz to start the slide to move from the locked position.

Glock 20SF spring test Wolff Gun Springs 22lb RSA installed.
It takes 6lb 4oz to start the slide to move from the locked position.
22-Slightly over a pound difference 1lb 1oz to start the slide to move from the locked position.
Full retraction at 22lb 9oz at lock open.

Glock 20SF spring test Wolff Gun Springs 24lb RSA installed.
It takes 7lb 6oz to start the slide to move from the locked position.
24-Slightly over a pound difference 2lb 3oz to start the slide to move from the locked position.
Full retraction at 24lb 1oz at lock open.