Keyholing...Causes ????

TINCUP AL · January 14, 2009, 11:02 AM

Had a student in class the other day who was shooting a Sig 9mm with reloads. The bullets were consistantly keyholing, even at close distances. What would be some reasons for this to be happening ? Thanks

Japle · January 14, 2009, 11:06 AM

Both my 9mm Glocks, 17 & 19, shoot keyholes with 115 gr plated bullets. They're very accurate with the plated 147 gr slugs.

Why? Got me!! I figure the 115 gr bullets don't have quite enough bearing surface to stabilize them, but that's just a guess. Both loads shoot well in my BHP.

joneb · January 14, 2009, 12:26 PM

Quote:

Keyholing...Causes ????

Here's a few possibilities,
The bullets are undersized.
The bullet is too long for the barrel twist rate.
The bullet is moving to slow, not enough rotation.
The bullet is moving to fast and by-passing the rifling grooves, not enough rotation.

MASTERCAST.COM · January 15, 2009, 02:39 AM

We did some tests on 9X19mm reloads here several months ago, with 9mm cast bullets.

The groove diameter of most 9mm barrels is .355"....most 9mm cast bullets are .356"...there is not much room for error there.

You will find that the closer you can get to the maximum taper crimp diameter of .380", the better the accuracy and no leading of the barrel.

Go much below .380" with regard to taper crimp,and you can make the bullets "keyhole"....accuracy is out the window!

Get it right, and you will be rewarded with sterling accuracy!

TINCUP AL · January 15, 2009, 10:29 AM

Thanks for the info guys.

January 14, 2009, 11:02 AM	#1
TINCUP AL Senior Member Join Date: May 22, 2007 Location: COLORADO Posts: 109	Keyholing...Causes ???? Had a student in class the other day who was shooting a Sig 9mm with reloads. The bullets were consistantly keyholing, even at close distances. What would be some reasons for this to be happening ? Thanks

January 15, 2009, 02:39 AM	#4
MASTERCAST.COM Junior member Join Date: December 16, 2007 Posts: 63	Tincup Al We did some tests on 9X19mm reloads here several months ago, with 9mm cast bullets. The groove diameter of most 9mm barrels is .355"....most 9mm cast bullets are .356"...there is not much room for error there. You will find that the closer you can get to the maximum taper crimp diameter of .380", the better the accuracy and no leading of the barrel. Go much below .380" with regard to taper crimp,and you can make the bullets "keyhole"....accuracy is out the window! Get it right, and you will be rewarded with sterling accuracy!

January 14, 2009, 11:06 AM	#2
Japle Senior Member Join Date: October 12, 2004 Location: Viera, Florida Posts: 1,340	Both my 9mm Glocks, 17 & 19, shoot keyholes with 115 gr plated bullets. They're very accurate with the plated 147 gr slugs. Why? Got me!! I figure the 115 gr bullets don't have quite enough bearing surface to stabilize them, but that's just a guess. Both loads shoot well in my BHP.

January 15, 2009, 10:29 AM	#5
TINCUP AL Senior Member Join Date: May 22, 2007 Location: COLORADO Posts: 109	Thanks for the info guys.