6mm-06AI ?

[bigtime9]

I have a 243 I am considering rechambering to 6mm-06AI does anyone use one of these? It only has a 22" barrel is that to short? It has 1-9 twist. I am just looking for a little different round to shoot and I have a ton of 3006 brass laying around. Just in the thought process right now so any input would be appreciated.

 

[1sniper]

I have one in a pistol with a 15-7/8" length barrel. I shoot H4831sc with a Berger 105 vld and I'm getting around 2800 fps out of that short of a barrel. I have shot 3/4" three shot groups at 300 yards and 1" five shot groups at 300 yards. My barrel has a 1/8 twist.

 

[Bart B]

I knew a guy some years ago who had a 6mm-06 made up; just a .30-06 necked down to 24 caliber. His barrel lasted about 600 rounds before severe throat erosion prevented decent accuracy. Therefore, I think a 6mm-06AI's greater powder capacity will get about 500 rounds of good (that's no worse than 1/2 MOA at a hundred) accuracy. That's a way overbore cartridge to begin with.

 

[Shumba]

I have had a few 243 Catbirds. The Catbird is a 270 case necked to 243 and improved. My opinion is that you are not going to gain much in that short of a barrel. As Bart B said they are hard on barrels as well. Not nearly as bad as his expectation of 500 rounds but if you don't have a barrel just for fire forming brass it's not the best choice. Barrel life for top accuracy is in the 1200 round range depending on how you shot it, i have one with 1900 rounds and it will still shoot 1/2 MOA. Accuracy is typically great. Making brass from 30-06 cases is not a simple process either. I use a form die with 270 cases to step the neck down and make a false shoulder. With the 30-06 it will be more involved. I have had 4 catbirds and 26" is the shortest barrel I have put on one, 28" is much better. Hope this helps.

 

[shortgrass]

IMO, the 6mm AI is about max as far as 6mm cartridges go. You won't do a thing but shorten barrel life with any case larger. Very forgiving, accuracy wise, during fire forming and at its' peak with 100g. + weight bullets. If you're thinking of re-chambering a factory barrel, I have to ask, Why Bother? You've got to realize, it's not just throats that wear, but the full length of the barrel that does, starting at the throat. 95%+ of the barrels I see that the owner wants me to re-chamber are long past that point of improvment. Much of what it's seen on the forums these days has been tried, some of it long ago. If it hasn't "caught on", there's a reason.

 

[bigtime9]

Thanks for the replies.

Shumba, I already neck down for 2506 so I figured I would start with that and then go on down to 6mm? I'm thinking it would work alright.

Shortgrass, This is on a basically brand new rifle I have, I bought it sighted it in and it has sat in the safe the last 3 years. I have a couple other 243s and just want something different to play with.

 

[Shumba]

You will see quite a bit of improvement in velocity with a 26"-28" barrel over the 6mm AI. 4000 with 70 g bullets and 3550-3600 with 107 smk, but with the 22" barrel I think it would be a waste to chamber this cartridge, just not enough barrel to take advantage of it.

 

[bigtime9]

I looked at going to 6mmai but decided on the 06 because I already have brass laying around. Besides once I shoot this barrel out I am all set up to put a 28" on and get real seriousgun)

 

[Trickymissfit]

Ackley stated that the plain jane 6x57 was about all the 6mm bore could handle, and we see this with a look in the reloading manuals as it's only good for about 150 fps more velocity than the .243. The Ackley version of the 6mm is about another hundred feet persecond at the most, but has an even better neck & shoulder design. Now you compair the 6/.284 to the 6mmAI and you don't gain a thing but new barrels. The 6-06 ought to be even worse yet!

Probably the best would be a 6mmAI reamer ran into the barrel with a .243AI headspace. Or better yet a 6.5AI headspace. This would allow you to use the 57mm case length to form cases and yet have enough to allow for case shrinkage on fireforming.
gary