Home Forums Hunting & Shooting Custom Rifles & Wildcats 6mm build quandry - 6 CM, 6x284, 6mm AI or plane old .243?

Yes I know these sort of questions get old. But just about to pull the trigger on one and can't decide between chambers.

This rifle will primarily be used for deer and hogs and the occasional coyote. I seldom shoot past 300 yards but I would like the maximum potential to that range or slightly beyond.

I have a Bartlein 0 contour 1 in 8 twist 5r barrel so should be good for most 6mm bullets. I have a Borden stock. I was going to use a Rem. CDL short action I already have but decided against dismantling this one.

What I am leaning towards is either a straight .243 or the 6x284 even though I really feel the 6mm AI is the best of the bunch but in a longer action. I am considering the Stiller or Pierce medium actions so a little more room than a Remington is possible. The Creedmore is a good one but brass and die availability is a consideration. As a hunting rifle only barrel life is a secondary consideration. Bullet choice will be 95-107 grains mostly.

I know there are no wrong choices.

I would run straight 243, but I like to keep things simple. It would be easy to get brass, and at that range it will do everything you need.

Want the most? 6-284. I have had three at one time in the last few years. A 28" heavy, and two sporter weight versions.

Barrel life IS short at approximately 1000 BUT you get a hot rod.

Here are some of the results:

28" barrel 105 Berger 3475 fps
24" barrel 95 gr Berger classic hunter 3465 fps
24" " 55 gr nosler bt 4175 fps

Brass is always available, something you can't say for the 6mm Rem.

I used 6.5-284 Lapua brass. Necking down was easy. Reamer was made with a no turn neck. The heavy barreled rifle was still using the original brass when I retired it, with 12 firings with primer pockets still tight.

RL-33, RL-22, Retumbo worked with the heavy rig and 105s-107s
Used RL-17 with the lighter bullets in the 24" barrels.

I would go no other way than a 243 for what you mention.
Plenty of good brass available and it fits fine in a 700 action with any bullet you like if throated properly.

If you want a little more speed and don't mind fireforming and additional die cost, do a 243 AI. you will be rewarded with more speed, little case stretch and a little longer throat life

I have shot a 6-284 for almost 20 years. Shoot sierra 70 grain blitz right at 3800fps. It has about 1800 rds down it and still shoot .6 moa. Lilja barrel, 12 twist ,mcmillan, nightforce and jewell trigger. Using wincester brass which can be scarce. Lapua 6.5 is a better choice and more available. Definitely a 243 on steroids. Does not stretch like a 243.

You might try googling 6mm Competition Match, it uses .243 Win brass, but is supposed to significantly increase barrel life. Though the 6mm CM doesn't give up much to either.

Just went through same thing - decided to go with another .243 - I don't hand load so was the obvious choice for me. Plus already have one and its my favorite rifle so figured another could be a good thing. Parts will be off to the smith tomorrow.

The 6x284 is tempting but the barrel is already crowned at 24" so not ideal for a hot rod. Also this will be a light weight so not ideal for a dedicated long range rifle either.
Even at a barrel life of 1000 - 1500 I may not shoot one out in my lifetime with hunting use only

Probably ammo for this one wouldn't interchange well with the other .243s but it might. Throated for 105 Amax's probably be too long for the factory chambers.

The .243AI is really popular enough so that off the shelf dies are available. Doe's it really add up to 250 fps over the original?

"The .243AI is really popular enough so that off the shelf dies are available. Doe's it really add up to 250 fps over the original?"

-Not in a 24" barrel

FWIW, I spoke with a guy at GAP last week... he said 6 creed brass would be available within a month. He also mentioned Hornady was picking up the 6 Creed this year. I would expect brass to be more readily available when this happens.

If brass availability is high in your criteria list, I would count on spotty availability of any brass other than the ubiquitous 243-308-30/06-7mag/etc for the foreseeable future. Remington seems to have given up on the component market and the others can't seem to keep up either. Figure on doing a little leg work to feed the beast.

+2 ...

+ 1 on the 6-284

+ 1 on the 6-284.

6mm rem brass is impossible to find.

I've got a 6 creed and 7 twist 243. Next barrel will probably be a 243AI. 115 dtacs are a lot of fun.

243 SLR--best of all worlds

Don't rule out that 24" barrel length. When I first got my lathe and the 6mm-284 reamer the first barrel I did was a 20” 243 which got rechambered to 6mm-284. Sounds ridiculous to even try this huge 6mm with such a short barrel. I wanted to make a fireforming barrel. I was surprised that I got an accurate 3375 fps with the 87 gr hornady and 2985 fps with a 105 Berger.

I tried, can't come up with a reason to go 6mm/284.

For the tasks you stated I would go with the plain old .243.

Agree with .243, unless you like making things more challenging.

6x47 Lapua can offer you all the advantages of 6CM as far as fitting long bullets in the magazine AND readily available, awesome brass. Just a thought...