Causes of Keyholing - The Firearms Forum

The_Vigilante · 06-04-2009, 11:37 PM

I am currently reloading 147g LFP 9mm and have been using VV N320-3.6g. Using COL of 1.135. A lot of my reloads are keyholing. What is the best way to troubleshoot this problem and determine the cause? Thanks

johnlives4christ · 06-04-2009, 11:42 PM

im not a reloader, but best i recall keyholing is caused by too heavy a bullet weight, heard the rifling will not stablize it and it flops like a chicken bone in a dogs gullet when it's flyin through the air. dont know if all this is true though

~john

Claude Clay · 06-05-2009, 12:54 AM

what is your target. if the paper is loose to the backing the bullet often tears the paper as it pulls it to the backing giving the appearance that it is the bullet that is tumbling.
on the other hand too heavy pushed too fast in a fast twist can lead to instability's--try lighter loads and/or 124 gr.
what model gun? what type of bullet-- hard lead, soft lead? diameter? most 9mm is .355 jacketed and .356 lead (or plated). some lead is .357 but pressure may become an issue. i dont find your powder listed but 340 is for lighter bullets and it is slower burning than 320. i have had good with bullseye for bbls 4" & under. otherwise power pistol or tightgroup.

Suwannee Tim · 06-05-2009, 03:26 PM

It is most likely that the twist of your rifling is just too slow to stabilize this boolit. Cast boolits are longer than swagged for the same weight and a longer boolit requires a faster twist. Did you cast these boolits or buy them? Why not switch to a lighter and more easily stabilized boolit?

Suwannee Tim · 06-05-2009, 03:27 PM

Quote:

Originally Posted by Claude Clay

make a fire for a man and you warm him for the nite
light him on fire and you warm him for the rest of his life

Dat's funny.

The_Vigilante · 06-05-2009, 07:07 PM

Thanks for your replies and suggestions. These are 147g bullets I purchased from Missouri Bullets. Supposed to be hard-Brinell=18 with .356 diameter. Pistol is a CZ-SP01 Phantom. Target is a cardboard IDPA target so that's not it.

Suwannee Tim · 06-05-2009, 08:43 PM

Other possible causes of keyholing, very unlikely in your case: The bullet is too small for the barrel and doesn't get spun up. Or, the bullet is so soft and the velocity so high that the rifling strips the bullet, I mean boolit and the boolit doesn't get spun up. Another possibly is the bullet, I mean boolit is of an inherently unstable shape, like a hollow base wadcutter turned backwards.

ampaterry · 06-06-2009, 07:30 AM

At the risk of stating the obvious -
Have you checked the condition of the rifling?

carver · 06-06-2009, 08:28 AM

Quote:

Originally Posted by The_Vigilante

I am currently reloading 147g LFP 9mm and have been using VV N320-3.6g. Using COL of 1.135. A lot of my reloads are keyholing. What is the best way to troubleshoot this problem and determine the cause? Thanks

Don't know anything about re-loading the 9mm, but how fast is this load supposed to moving? Too fast will lead the barrel, and then you won't get any spin on bullets fried after that.

Suwannee Tim · 06-06-2009, 08:58 AM

Quote:

Originally Posted by ampaterry

At the risk of stating the obvious -
Have you checked the condition of the rifling?

I bought a Smith and Wesson model 52, 38 special semi-auto off GB, took it to the range. The first few shots were all over the paper then I began seeing keyholes and even missing the paper. The gun was tight and in great condition. Evidently some previous owner had been OCD about cleaning and had cleaned the rifling right out of the barrel. What little rifling was left was almost invisible.

DWARREN123 · 06-06-2009, 09:01 AM

I would look at your powder for this problem this time. Sounds like it is not the right one. 147gr in 9mm should stabilize if the rifling is good and the bullet is lubed properly with the correct powder.

S&W-4me · 06-06-2009, 06:01 PM

Another factor often overlooked is the squareness of the barrel crown or chamfer in relation to the bore. If the crown is not square to the bore it allows gas to escape on one side of the bullet before the other. This causes the bullet to be unstable. This sometime only effects the longer heaver bullets because they my be borderline with the twist in your barrel. Offhand I would say the barrel twist, and charge, is not right for the bullet you are using. This is the most common cause for keyholing. regards
Ed

06-04-2009, 11:37 PM	#1
The_Vigilante V.I.P. Member Join Date: Apr 2008 Location: El Paso, Texas Posts: 123	Causes of Keyholing I am currently reloading 147g LFP 9mm and have been using VV N320-3.6g. Using COL of 1.135. A lot of my reloads are keyholing. What is the best way to troubleshoot this problem and determine the cause? Thanks __________________ The_Vigilante "Keeping the streets safe." "A man can never own enough guns." -->

06-04-2009, 11:42 PM	#2
johnlives4christ Former Guest Join Date: Apr 2008 Location: Kentucky Posts: 3,828	Re: Causes of Keyholing im not a reloader, but best i recall keyholing is caused by too heavy a bullet weight, heard the rifling will not stablize it and it flops like a chicken bone in a dogs gullet when it's flyin through the air. dont know if all this is true though ~john

06-05-2009, 12:54 AM	#3
Claude Clay V.I.P. Member Join Date: May 2009 Location: Central CT Posts: 451	Re: Causes of Keyholing what is your target. if the paper is loose to the backing the bullet often tears the paper as it pulls it to the backing giving the appearance that it is the bullet that is tumbling. on the other hand too heavy pushed too fast in a fast twist can lead to instability's--try lighter loads and/or 124 gr. what model gun? what type of bullet-- hard lead, soft lead? diameter? most 9mm is .355 jacketed and .356 lead (or plated). some lead is .357 but pressure may become an issue. i dont find your powder listed but 340 is for lighter bullets and it is slower burning than 320. i have had good with bullseye for bbls 4" & under. otherwise power pistol or tightgroup. __________________ teachers may learn you the rules; experience will teach you the exceptions. NRA Instructor Last edited by Claude Clay; 06-05-2009 at 10:56 PM..

06-05-2009, 03:26 PM	#4
Suwannee Tim Registered User Join Date: Feb 2009 Posts: 2,227	Re: Causes of Keyholing It is most likely that the twist of your rifling is just too slow to stabilize this boolit. Cast boolits are longer than swagged for the same weight and a longer boolit requires a faster twist. Did you cast these boolits or buy them? Why not switch to a lighter and more easily stabilized boolit?

06-05-2009, 07:07 PM	#6
The_Vigilante V.I.P. Member Join Date: Apr 2008 Location: El Paso, Texas Posts: 123	Re: Causes of Keyholing Thanks for your replies and suggestions. These are 147g bullets I purchased from Missouri Bullets. Supposed to be hard-Brinell=18 with .356 diameter. Pistol is a CZ-SP01 Phantom. Target is a cardboard IDPA target so that's not it. __________________ The_Vigilante "Keeping the streets safe." "A man can never own enough guns."

06-05-2009, 08:43 PM	#7
Suwannee Tim Registered User Join Date: Feb 2009 Posts: 2,227	Re: Causes of Keyholing Other possible causes of keyholing, very unlikely in your case: The bullet is too small for the barrel and doesn't get spun up. Or, the bullet is so soft and the velocity so high that the rifling strips the bullet, I mean boolit and the boolit doesn't get spun up. Another possibly is the bullet, I mean boolit is of an inherently unstable shape, like a hollow base wadcutter turned backwards.

06-06-2009, 07:30 AM	#8
ampaterry TFF Admin Staff Chaplain Join Date: Dec 2008 Location: West Tennessee Contributor Posts: 6,291	Re: Causes of Keyholing At the risk of stating the obvious - Have you checked the condition of the rifling? __________________ A woman who demands further gun control legislation is like a chicken who roots for Colonel Sanders. Larry Elder

06-06-2009, 09:01 AM	#11
DWARREN123 Senior Member Join Date: Aug 2003 Location: BETWEEN TN & KY Posts: 764	Re: Causes of Keyholing I would look at your powder for this problem this time. Sounds like it is not the right one. 147gr in 9mm should stabilize if the rifling is good and the bullet is lubed properly with the correct powder. __________________ Have a nice day!

06-06-2009, 06:01 PM	#12
S&W-4me Member Join Date: Mar 2009 Location: Connecticut, USA Posts: 46	Re: Causes of Keyholing Another factor often overlooked is the squareness of the barrel crown or chamfer in relation to the bore. If the crown is not square to the bore it allows gas to escape on one side of the bullet before the other. This causes the bullet to be unstable. This sometime only effects the longer heaver bullets because they my be borderline with the twist in your barrel. Offhand I would say the barrel twist, and charge, is not right for the bullet you are using. This is the most common cause for keyholing. regards Ed Last edited by S&W-4me; 06-06-2009 at 06:02 PM..