Oversize jacketed bullets? 312 in a 310 barrel safe?

MuscleGarunt · June 9, 2009, 02:02 AM

Can it be done safely, we are talking about .002 here. Will it accelerate barrel wear?

Edward429451 · June 9, 2009, 08:03 AM

Probably not but it will save on powder.

Start light

**Unclenick** · June 9, 2009, 09:51 AM

Not really an issue. I have a little MAB in .32 ACP. The bullets are .311" and the bore is .309". No problems. Consider that in .30 caliber rifles the GI bore spec is 0.3065-0.395" and that some .30 caliber bullets are .309" rather than .308", with many match bullets made at .3085", and you can see it is easy to get a 0.002" difference even in high power rifle rounds.

Every once in awhile you hear of someone shooting a .308" bullet through a 7 mm (.284") gun by mistake and the gun survives undamaged. That 0.024" difference in bullet diameter is definitely not safe, and there are many guns that would not survive that without at least blowing the case out and damaging the magazine and splintering the stock. A couple of the Springfield failures that Hatcher investigated between the World Wars proved to have been damaged by firing 8 mm German rounds in the gun, which is only a 0.015" diameter difference. So don't try it on purpose. Those Springfields may have been weak low-numbered receivers, but my point is not to count on that sort of immunity with any particular gun. I mention it only to give you some sense that the safety margins built into most guns will allow for several thousandths in bullet over bore diameter difference if the load is not at maximum.

MuscleGarunt · June 9, 2009, 12:25 PM

Thank you for the informative response.

June 9, 2009, 02:02 AM	#1
MuscleGarunt Member Join Date: May 20, 2009 Posts: 75	Oversize jacketed bullets? 312 in a 310 barrel safe? Can it be done safely, we are talking about .002 here. Will it accelerate barrel wear?

June 9, 2009, 09:51 AM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Not really an issue. I have a little MAB in .32 ACP. The bullets are .311" and the bore is .309". No problems. Consider that in .30 caliber rifles the GI bore spec is 0.3065-0.395" and that some .30 caliber bullets are .309" rather than .308", with many match bullets made at .3085", and you can see it is easy to get a 0.002" difference even in high power rifle rounds. Every once in awhile you hear of someone shooting a .308" bullet through a 7 mm (.284") gun by mistake and the gun survives undamaged. That 0.024" difference in bullet diameter is definitely not safe, and there are many guns that would not survive that without at least blowing the case out and damaging the magazine and splintering the stock. A couple of the Springfield failures that Hatcher investigated between the World Wars proved to have been damaged by firing 8 mm German rounds in the gun, which is only a 0.015" diameter difference. So don't try it on purpose. Those Springfields may have been weak low-numbered receivers, but my point is not to count on that sort of immunity with any particular gun. I mention it only to give you some sense that the safety margins built into most guns will allow for several thousandths in bullet over bore diameter difference if the load is not at maximum. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; June 9, 2009 at 09:58 AM.

June 9, 2009, 08:03 AM	#2
Edward429451 Junior member Join Date: November 12, 2000 Location: Colorado Springs, Colorado Posts: 9,494	Probably not but it will save on powder. Start light

June 9, 2009, 12:25 PM	#4
MuscleGarunt Member Join Date: May 20, 2009 Posts: 75	Thank you for the informative response.