9mm key holeing [Archive]

kennyb

06-09-2012, 07:41 PM

I bought a new CZ 75 yesterday and took it out and shot it for the first time. Accuracy was pretty good. I was shooting cast 125 SWC. But about 3 out of 16 would show to be key holeing. Any Idea where to start looking to solve this?

RobS

06-09-2012, 07:57 PM

Keyholing typically comes from undersized boolits. Have you slugged your bore? What is your sized diameter before you loaded and have you pulled a boolit to see if it is the same diameter (especially checking the very edge of the base band). Any leading in the barrel? Load may help us understand more as well.

pergoman

06-09-2012, 08:00 PM

Yup.
Bullet diameter and velocity.
Bullet may be too small and/or going too fast.
For example, .355 bullets may not keyhole under 900 fps.
The same bullet at .357 may work fine at 1100 fps.
9mm's are notorious for bore size issues.
I have at least 5 9mm pistols that greatly prefer .357 cast tips.

Shiloh

06-09-2012, 08:28 PM

So far, the 9mm's have been the most challenging for me to get running reliably and accurately.
I had key holing at 50' withthe rounds that didn't miss the target completely.

Mine run good sized at .357, better at .358.

Shiloh

RobS

06-09-2012, 08:35 PM

blikseme300

06-09-2012, 08:56 PM

I have 3 CZ 75's of different vintage. All run best with boolits at .357 minimum. The leades on mine are quite short so COL is critical to ensure proper return to battery.

In the early days I had key holing due to under sized boolits. Run them as fat as will chamber.

Bliksem

captaint

06-09-2012, 09:27 PM

I had to make my 9mm boolits at least .3575, or they leave lead behind. This, at least, with the alloy I'm running. It's currently WW's and a splash of tin. Shot them at 50 yards yesterday, just for kicks and they shot great - and no lead. enjoy Mike

MtGun44

06-09-2012, 11:38 PM

Spend a few minutes reading this:

http://castboolits.gunloads.com/showthread.php?t=121737

This should save you some time.

Bill