This may be a completely silly question, but if a man had a .243 and would rather it be a 6mm, is it as simple as running a chamber reamer in it, or is the difference in twist a problem?

I understand this is a low speed custom question, so I appreciate your indulgence.
CT

Twist isn't a problem, but the difference in taper of the case bodies probably is.

I see, so you would end up having to set back and rechamber.

Why wouldn't you go 243AI instead? The 6 can be a bastard in a short action, mag constraints being your main concern.

All I want to do is shoot 70 grain blitzkings and 95 grain partitions, I can't imagine that it would be a problem to run them out of a short action. I could forsee it if I wanted to shoot long matchking pills, or something like that.

I have been down the ackley road, and if I were to get squirrelly with a re-chamber it would probably be to a 6mm-284.

You would have to set the barrel back, as the 6mm case has more tapper from the base to the bottom of the shoulder than the 243 does. A 6-284 reamer would clean out the 243 chamber without setting back the barrel and would show a significant velocity gain with bullets in the 70 to 95 grain range. If you don't over-heat it, it might even last for 8,000+/- rounds.

Jeff

Those two bullets should shoot just fine out of a standard 243 Win.

erich

I had a 6mm-270 Winchester built last year,it's 1 of the most accurate rifles I own,I'm using 105 gr. Hornady AMAX'S and they worked great on deer and hogs last year.

Those two bullets do shoot just fine out of a .243, but they are beginning to be the strawberry ice cream in a gallon of neopolitan. (With a .30-06 being vanilla and a .270 being chocolate)

I just hate having the same thing everybody else has...Its a terrible sickness.

Id say do it on a long action for the 6mm or 243ai for the short.

Both cartridges can use the same twist rate, and if you want to use the 95 Partition then you'll need a 1:10" minimum. The .244 Remington (predecessor to the 6mm Remington) used a 1:12" twist and the longer 6mm bullets were marginally stable.

You'll have to set the barrel back quite a bit to clean up the chamber, this is not a "one thread" job. The 6mm-.284 is not a good candidate for a pure rechamber since at least part of the original throat of the .243 will still be there. I'd set it back ~4.5 threads if it were me. The half-thread part puts the barrel stamping under the forearm - a nice custom touch that costs nothing.


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If you did the 6Rem/243AI you have to set the barrel back not sure about doing a 6/284 other choice would be a 6RemAI and you could do that without setting the barrel back.

Well good luck

I have had a couple of 6mm's on short actions and they work great. Not sure where the idea comes from that a long or medium action is needed. A 6mm AI would be a great fit as would a 6mm/284 which I have had some play time with and really enjoyed. You do get meaningful performance upgrades going to either of the three and I agree completely that having something different is a lot of fun.

I've used a 243 somewhat and I bought my son a 6mmREM in a REM 600. No problem with any bullets as far as action length. I'd stay away from the 284 based cartidges as I would be leary of having to open up the rails. Either AI version would be wonderful especially a 6mmAI. You may want to go 243AI since you already have brass you could form.

It sounds like a fun project.

RH

Oddly enough, I've done 15+/- rebarrel or rechamber jobs to the 284 or 284 based wildcats on Remington 7, 600, 660, 700, and 722 actions without ever having to touch the guide rails. Just another proof that I live a charmed life!

Jeff

My 700 did not need any rail work, although I swapped to a SAUM follower. Feeds all 3 from the mag very well.

I have two factory 6mm Rems in short action 700's. My only complaint about being short action is that I cannot seat my bullets remotely close to the lands and still fit them in the magazine....but that's Remington's fault for too long of a throat, not that they are short action.

Just be glad its not a .30cal. You would need an H&H-length action to touch the lands if Remington chambered the barrel. Who knows what that is all about. Also have a 700 in 270win with a stupid-long throat. It takes 150's seated way out to touch the lands.

I had a 25-284 that fed smooth and flawlessly that started life as a Remington 700, 6mm. In my case I'm not so sure of the charmed life thing though.

It is called product liability and low pressures. The lawyers have been running Remington for a long time. See 8mm Rem MAg for most obvious proof. Totally took its balls away and doomed it to failure. Long throats are hard to overload for with any book spec load.

I think touching the lands is overrated anyway. Lots of accurate guns have long throats.

I agree with your second sentence, but I like having the option of hitting lands.