.311 vs .312 in the Arisaka 99

KEN K · February 18, 2008, 04:04 PM

Been hearing that the 7.7 shoots better groups with .312 rather than .311 bullets. Anybody load the .312s and if so what kind of speed can I get before I start to flatten primers? I've read speeds of 2700 fps with a 150 gr. sp but also noticed an 30.06 load with imr 30 31 that was 2885 fps with the 150. Any thoughts? As usual any help greatly appreciated.

"When put in command-take charge"
Norman Schwarzkopf

Sport45 · February 19, 2008, 05:18 AM

Arisaka model 99's don't all have the same bore diameter. Slug your bore to determine the best bullet diameter. (Or just try some of each.)

I slugged mine with a swaged .38 cal swc bullet. I just started in in the muzzle with a wooden mallet and pushed it the rest of the way through with the cleaning rod. A .38 cal round ball would be better, but I didn't want to buy anything to do this. Mine was .313 so I buy .312's when I can find them on sale.

KEN K · February 19, 2008, 11:13 PM

When you slug the barrel do you measure the widest diamiter or the inside of the rifling?

Sport45 · February 19, 2008, 11:36 PM

Measure the widest diameter of the slug. That will correspond to the minimum groove diameter of your bore. Make sure the bore is clean and run a patch damp with gun oil through before slugging.

(I'll wager you will find the bore to be .312 or greater.)

KEN K · February 20, 2008, 10:01 PM

Thanks Sprot45, I'll do that , I appreciate the help. Anything to make that clean sure shot.

February 18, 2008, 04:04 PM	#1
KEN K Senior Member Join Date: October 7, 2006 Location: mid west Georgia Posts: 102	.311 vs .312 in the Arisaka 99 Been hearing that the 7.7 shoots better groups with .312 rather than .311 bullets. Anybody load the .312s and if so what kind of speed can I get before I start to flatten primers? I've read speeds of 2700 fps with a 150 gr. sp but also noticed an 30.06 load with imr 30 31 that was 2885 fps with the 150. Any thoughts? As usual any help greatly appreciated. "When put in command-take charge" Norman Schwarzkopf

February 19, 2008, 05:18 AM	#2
Sport45 Senior Member Join Date: May 26, 1999 Location: Too close to Houston Posts: 4,196	Arisaka model 99's don't all have the same bore diameter. Slug your bore to determine the best bullet diameter. (Or just try some of each.) I slugged mine with a swaged .38 cal swc bullet. I just started in in the muzzle with a wooden mallet and pushed it the rest of the way through with the cleaning rod. A .38 cal round ball would be better, but I didn't want to buy anything to do this. Mine was .313 so I buy .312's when I can find them on sale. __________________ Proud member of the NRA and Texas State Rifle Association. Registered and active voter.

February 19, 2008, 11:36 PM	#4
Sport45 Senior Member Join Date: May 26, 1999 Location: Too close to Houston Posts: 4,196	Measure the widest diameter of the slug. That will correspond to the minimum groove diameter of your bore. Make sure the bore is clean and run a patch damp with gun oil through before slugging. (I'll wager you will find the bore to be .312 or greater.) __________________ Proud member of the NRA and Texas State Rifle Association. Registered and active voter.

February 19, 2008, 11:13 PM	#3
KEN K Senior Member Join Date: October 7, 2006 Location: mid west Georgia Posts: 102	When you slug the barrel do you measure the widest diamiter or the inside of the rifling?

February 20, 2008, 10:01 PM	#5
KEN K Senior Member Join Date: October 7, 2006 Location: mid west Georgia Posts: 102	Thanks Sprot45, I'll do that , I appreciate the help. Anything to make that clean sure shot.