Please list the case capacities of: 243 Win, 243 AI, 6 mm Rem and 6mm AI. It would be best if the same method of measuring is used. Please state the method used. Thanks

Rick,

These are approximate water capacities with a typical lead-core 100-grain bullet seated:

.243--50 grains
6mm--52 grains
6mm AI--56 grains

The 6mm AI is from .257 Roberts AI info. Have never measured a .243 AI but would expect it to be grain or so more than the 6mm.

243AI has 57gr capacity according to QL, but have never measured, it. It lists the 6mm as 54.40, 243 as 50gr. I did not see the 6mmAI listed, but 257AI was listed as 63gr.

240 WBY is listed as 64 and the 6x284 is listed as 67grs.

Thanks guys. I am ordering a NULA in some sort of a 6mm on Monday and can't decide on the ctg. Normally detest wildcat's but could live with a 6mmAI, maybe. Just can't get too excited about a 243 and the 6-06 seems a bit too much. Sorry Dober. So it is either a 6mm Rem or the AI version in a M24, yes M24 action.

What about a 6-284? Wouldn't require any fire forming...

The only capacities I'd be looking at here would be was did I have a short action or a long.

If short, then 243 Ai is the way I'd go. If long, then 6/06 is the way I'd go.

Dober

Three Winchester .243 cases with water to the neck and shoulder junction held 53, 52.3 and 52.7 grains of water.

Three Winchester .243 AI cases (same lot) held 54.7, 54.6 and 55 grains of water.

Note the regular .243 cases had been once fired and neck sized so their internal capacity was a tad more than if they had been FL sized down to factory ammo specs.

+1

I think the M20 has a 3 inch magazine which would be a very good fit for the 6mm AI--can't see any advantage in the M24 if you're going to use either the 6mm AI or the 243 AI--just carrying around more weight...

Melvin Forbes at one time had a short necked version of the 6AI that still had a longer neck than the 243. I assume you could form them from .257 brass in one pass then fire form so not much more effort than the 6AI. It would come closer to splitting the difference between the 6mm and 6/284.

Sort of a 240 short Gibbs.

I have never wanted short actions around cause I develop a habit of short stroking the longer actions. In addition I like a lot of magazine. If I dont like a ctg then I can rebarrel. Also, I like to seat the bullet out. Have found it adds about as much as "improving" a chamber. Mule Deer suggested a 240 but the brass, although great, is about a buck sixty each! Have had two 6-284's but that was before there was brass for the 6.5-284 and I had issues sizing the 284 cases to 6mm despite using multiple steps. So am back to 6-06 as the easiest choice. It has lots of horsepower, so I don't need to run it at the max and yet will outrun most everything. Kind of like my automobile come to think of it. OK Hello Dober (was the pic of your 6-06?)

I may have coloured glasses on... But there seems to be something wrong with this picture....

A guy who's spending 3K for a rifle is COMPLAINING about the price of brass? Now that just makes no sense at all!

Depends on how much you shoot and how many times you reuse brass. I never shoot more than three shots from any piece of brass. Just me but I try to have 500 cases for each rifle which is why I have a fewer rifles now than in my past. I have 4-5 at any one time. More than that and one goes. BUT they all get used.

Then why not just get a .25-06? Or is that not loony enough?

You could go with the 6mm Stuver (6mm-6.5x55 Ackley Improved). It's what all the cool kids are running these days.

And a really cool cartridge it is!

If I built a 6mm other than a BR or 243, I would seriously look at a 6/6.5x47 Lapua. Great brass - similar speed - stellar accuracy, reasonable bbl life, forget trimming like a 243, and it feeds as is w/o mods like a BR might need.

It's what my 'smith' shoots, and sub 2" at 600 yds gets my attention!

All you do is bump the 6.5 brass down to 6mm, load and go. Simple.

That said, brass and die cost will be more expensive, but nor forming.

A 6mm XC would also be of interest to me.

Having owned several custom 6mmBRs, and seeing how accurate they are, pleasant to shoot, and deadly thru deer to 400 yds, I am sold on the value of a ctg. that has a proven track record of accuracy as it's SOOO easy to load VERY accurate ammo for and get anywhere from .1-.5 moa....all day long w/many bullet combos, esp. assuming you use an 8" twist.

Do a little research on the above rounds if inclined.

In the end, for a sporter rifle - esp. ULA a 243 likely will shoot as good as you can, but I would defintely use an 8" twist in whatever you build. Properly built and loaded, I like all 6mm's thru 6AI, but would stop there before getting a bbl burner like a 6/284.

That's just my thoughts. Good luck.

I want a 6mm because of the bullet selection. I grew up shooting a 25-06. I shot a lot of deer antelope and many many jackrabbits. With the heavier bullets it gets pretty close to 270 Win recoil. It is really good but I live in coyote country and I want something less like my 270's.

I would go 6XC or 6mm Remington.....fast twist in either one....but that's just me.....

Each to his own, but I wonder why one would want to use cases only three times, even if pretty heavily loaded? It would seem that if they only last for three uses before the pockets get loose, one might be well above 60,000 psi. I shoot a .223 using Lapua cases pushing 40 grainers 3780. I have four hundred cases and haven't lost or discarded even one after eleven loadings. (Your experience may vary.)

There isn't enough difference between the three to write home to mamma about when it comes to hunting. If you want the fast 6mm then get the 240 Wby or 6mm-06

I am a very lazy fellow when it comes to loading ammo. Ask BobinNH. I have lost a lot of enthusiasm for it having done it for 50 years now. Mostly I hunt big game and I like the safety margin built into new or once fired brass. This is the first time in a long time that I have had a varmint rifle so am out of the habit of using brass for multiple loadings. Example, recently I gave a buddy about 600 rounds of twice fired 270 Win cases.

OK a 6mm Rem (6mm Roberts-26 degree) it is. I may do an improved if I can convince myself it is worth the effort.

Good choice - the 6 Rem to me has a few feature that to me, puts it close/at a 243 AI, yet w/ready made brass, dies, ammo w/o going custom.

Good choice IMHO. Even though none would be a poor one

65BR I have had trouble understanding the love of the 243 AI given that 6mm Rem brass is available from Winchester and that it has the same capacity as the 243 AI and that the dies are cheap and that it has a nice long neck. Perhaps it would have more sex appeal if it was called the 6x7x57 or the 6mm Roberts etc. The 270/280/30-06 like body taper makes it a slick feeding deal. It also has a reasonably sharp shoulder (26 or 27 or 28 degrees, can't remember). Anyway thanks for the comment.

No doubt, if it were called a 'cult wildcat' name - it might garner more attention. I truly believe many rounds thrive or nosedive in a good part just to how well received the name on the headstamp is perceived.

Think about how much effort/research pharmaceutical companies, car mfg. etc. put into the name of their new babies.

Heard it before and my experience mirrors, but some of my past Sako's were SLICK feeding, and those older 579 and AII in 243 w/mild shoulder fed great. A nice sidenote as I'd get frustrated with any round that gave any 'bobbles' in a hunting rifle.

I think you will be taking a good liking to your new ULA/NULA, as I hear nothing but good things about them.

Correct on that - 26 deg.

It is a good design IMHO - as many marketing made Winchester's 243 more commercially successful - the '244 Rem' was not properly launched w/12" twist IIRC - so the 243s w/10 and 9 twisted bbls shot better w/heavier 100gr. Later 244s i.e. 6 Rem as you probably know have proper twists for all standard bullet weights.

Enjoy your new rifle - look forward to range reports.

Use a long action and a 1 in 8 twist to take full advantage of the 6 mm or 6 AI chambering and heavier bullets. I have had all four and prefer the 6 mm AI as described.

If it was me I would do the 240 Hawk.
Neck size a 280 and presto your done.
Will do just under 4000 fps out of a decent tube.
Combine that case with a premium mono bullet like the Nosler 90 gr E-tip.

With a 300yd zero you still only drop 16.5" @ 500yds (3,900fps @ muzzle)!
Go big or go home, LOL.

What barrel life with that chambering?

Pick your build around Lapua brass and you may have to re-think the only 3 reloads from one piece of brass mindset.

I have 20 firings on my first set of 6br cases.

Good choice the "6mm slightly improved Rigby". Or 6x275 Rigby if you will.