I wanted some jacketed bullets for my two J-Bores. Slugged the barrels and they measured .320 and .321. For some reason, even the one that slugged .321, did not like the .321 jacketed bullets. Had Lee cut me a .319 dia. bullet sizer. Using their case lube, I run Speer Hot-Cor .321 170gr bullets easily through this sizing die. Both rifles are shooting very tight groups with these bullets, they both turned in 1 hole groups at 40yds. I am going to run some 200gr. jacketed through it before long and see how they do. Have had no basal damage to the 170 grainers. I am very very happy with this little experiment.

Now, I am not relegated to only cast bullets, or very expensive jacketed. Hope this is of some use to fellow 8mm J-Bore shooters.

ogs,

I've had great results using the 170gr .321 bullets for years in all my "J" bore guns, but not all guns shoot the same.

In slugging many drillings and other combos I found that the bores are extremely uneven as you travel through the full length. This could have something to do with your results.

That sizer at .319 would be about perfect, IMO. It's a great mid point that sizes .321 and .323 bullets of many designs into appropriate bullets for your drilling.

Rates a Two-Cool!

Most "J" bore guns have .320/.321 bores.

Buffalo arms has a selection of .318 bullets from 150 gr to 200 gr.

Hawk bullets has .318's in 180 gr and 220 gr.

I've been shooting the Buffalo Arms .228 bullets in my 6.5x52R(22 Highpower) and they are very accurate for me.

I slug my rifles using the FBI method ... I use a lead bullet and a very small charge of Unique. For a shoot tube, I use a 6" PVC pipe with a Folgers can and a rag on it, placing the pipe in the grandchildren's swimming pool. Fire the rifle down the tube, the bullets come out with no deformation, and my mic gives me a good reading on bore diameter. Don't use this technique if your grandkids are in the pool !!!!!

I am using these bullets for my Kipplauf and a Mauser 98 Model M. My drilling is a 38-55. I was really happy when this brainstorm came to be. Thought I had come up with this on my own, but after searching for something else, I ran across a guy online that had used a system something like this before, his was a little more complicated, but same principle.

Think if a person needed one in .318, if you got them to cut you one .318, the bullets would come out with no deformation whatsoever. I usually use RCBS lube, but went on the recommendation from Lee, and think their lube was better for this job.

I like to push soft lead through to feel tight and loose spots as it moves along.

I am curious if you are getting any spring back. I've been thinking of getting one in .318 for my J bores.

I now do multiple slugs in my barrels. I had a 9.3 a few years ago that had .006 variation in bore diameter from the beginning of the rifling to the muzzle. I wound up using a card wad and a pea of lube to get decent hunting accuracy.
Bfly

I used two Lee dies to take some PP 175 grain BTSP bullets from .323" to .318". When I shot them in my 110+ years old Sauer & Sohn Mauser 8X57J, after bore sighting at 50 yards with my 2 1/2X Lyman Alaskan scope, it placed two shots touching low and right, and with appropriate sight corrections it placed three shots into a cloverleaf in the "X" ring of a 100 yard small bore target. Certainly good enough for a whitetail.

I have a couple of Krieghoff drillings, both the side lock Neptun model, and one of them is in the 8x57's big brother, the 8X65RS. It's too bad I didn't have it when I made my Africa trips.

That 8X65RS would be a stomper PG gun!