I recently acquired a rifle which I was told was a 6mm-06. There were no markings on the barrel. I necksized a 25-06 case and fireformed it in the rifle and checked the case measurements. The result was a dia at the shoulder of .455 and it has a 20 degree shoulder. case length, etc. remained the same. I need help determining which version this is. could it possibly be the old .243 super rockchucker?

I don't have the dimensions but looking at Clymer's site it shows a 28deg shoulder on the 243 super rockchucker. The 06 case when it has been improved usually has a shoulder in the .455 range.

http://www.clymertool.com/cgi-bin/reamer.cgi

Robert:

I can't help you on determining which version your rifle is, but 20' is awful close to the 17' 30" shoulder of the standard 06 case. What I have been doing, which seems to work very well for my standard 6mm-06 is, I use new 25-06 brass, neck size them in a 6mm Rem. neck sizer and shoot. I have never full length resized any brass for this rifle. If I feel a need to full length size any brass I have found, I use what ever fl die I have handy 270, 30-06 etc. Once that is accomplished I can run them thru my 6mm neck sizer and go to it. With this system you won't have a problem with brass, or have to worry about some hard to find die.

Hope this helps.

Jerry

Hey thanks Jerry and Ramrod340. I think I can assume it is not a super rockchucker but another slightly improved version. I've found some reloading data here that will help as well. Sounds like I bought that RL25 sometime ago for a good reason now. The 6mm remington necksize work around sounds like a winner until I can get the correct dies. I was contemplating using .243 winchester dies to do the same thing since my manuals show it has almost the same shoulder diameter and same degree of shoulder. I picked up this cannon for a $127 bucks at an auction. It is a single shot built on a mauser 98 action with a gorgeous maple benchrest type stock and a 26" target barrel. Thing weighs in a 14lbs with scope. I'll have some fun with antelope this coming season.

Hey thanks again guys. I'll post my loads here as well to add to the data on the cartridge. I'm curious to see what my chronograph is going to be saying and what accuracy I can wring out of it.

Robert, I have a 6-06, in which I use RL-25. For me, that is thee powder. Previously, I had used H-1000 and 7828. Velocities picked up approx. 100fps using RL-25. If you are interested in my loads, send me a PM. Jim

jpretle I would like to see your loads for this cartridge. I haven't check the twist on the barrel yet but will be doing that today

The barrel on this rifle appears to have a 1 in 12 twist and the shoulder angle is 20 degrees.

This is an update. took the rifle out to a local benchrest shoot to see what it would do. 95gr Nosler/55 grs. RL25/ went 3/4"@ 100 (5 shots). the fired cases showed that the shoulder was pushed out to 2.054 inches with a 30 degree shoulder. My original fireforming for making up some cases didn't put enough poof I guess. So I think I am looking at a 6mm-06 improved.

Well Clymer's site shows that the 243 super rockchucker has a 28 degree shoulder but the shoulder diameter is smaller and the base to shoulder length is shorter than mine. the 6mm-06 ack improved has the right shoulder diameter but the shoulder angle is steeper and the base to shoulder length is shorter.

Well

The only factory round that could be close is 6X62 Freres

Cheers
/ JOHAN

Hey Johan thanks for the info. both the 6mm-06 Ackley improved and the 6x62 are close. The Ackley has a 40 degree shoulder and the 6x62 has a 20 degree shoulder according to clymer. I hadn't looked at the 6x62. My base to shoulder length is longer than either though. I believe I could use either set of dies until I have a set made. Right now I am necksizing with a 243 die set so I don't shove the shoulder back.

Maybe a 240 Gibbs? - dan

Hi Dan,

I checked the specs of the .240 gibbs but alas it is longer in the base to shoulder length. I had the same notion Dan