243 Ackley and 6mm Ackley

[Curmudgeon]

Good Morning, if someone could help me understand the difference between the 243 improved and the 6mm improved I would appreciate. I will begin shooting the 243 improved tomorrow and hope to improve my long distance shooting. It is my first 6mm so am anticipating the greater availability of lead free bullets over the 6.5 I now shoot.I have been comparing load data between the two and even though they appear similar I need to ask. Thanks for looking

 

[coford]

The 243 improved is based on the 243 Winchester and the 6mm improved is based on the 6mm Remington. The improved means that the shoulder is blown out - usually to 40 degrees and the body taper reduced. The 6mm has a little larger case capacity and a little longer neck so in theory it should be faster - like around 50 to 100 fps. The 6mm also has a little longer neck which tends to be easier on throats. They are very similar but the 6mm improved comes out a little on top - at least on paper.

 

[tiny68]

5% increase in water capacity in 6ackley over 243 ackley.

http://www.angelfire.com/nd/243ackleyimproved/casecap.html

I personally have a couple of 6 ackleys. I mine are fast twist to shoot the 107s. I can drive them harder than they like. Better accuracy if I keep them at 3200 fps or lower. I think the 243ai could do that. Better brass available for the 243. It ended up making my brass from 7x57 RWS parent brass. I was wrenching RP brass after 2-3 hot firings. I can hammer the RWS and it says happy.

Problem is that both are probably a little overbore and the 6ai even more so. However, buy your reamer and keep a gunsmith in business with a couple of set backs to cleanup the neck.

I am a big fan of the 95 Berger VLD. Running them at 3450 fps makes me look like a much better wind reader than I am at 300-500 yards.

Luck in your choice, Tim

 

[bsekf]

Parent case for the 243 is 308. Parent case for the 6mm is 7x57. Side by side the 6mm is a bigger case. When you Ackley improved any case you simply blow the shoulder angle out to 40~ and take the taper out of the case, datum line remains the same. If the chamber is cut to a true AI, you can safely shoot a standard 243 in a 243AI chamber but not vice-versa. That's fireforming. The ackley case doesn't get you much more performance but it gets better case life, they don't stretch as much.

 

[ShootDots]

+1 What bsekf stated, with one item added.. I had a 6mmRem A.I. that I used for deer hunting. With 95gr. "Combined Tech Silvertips" I was shooting 3400+f.p.s. and that was not a "pushing the envelope" load... It does give about 175-225f.p.s. increase in velocity depending on the powder used and barrel length. I was using H1000 in a 27" barrel...

 

[M4Punisher]

Best info I ever found from a smith who has built a ton of 6mm AI guns... I am planning on building a 6mm AI in the future just because I have read this and I have a good friend who owns one. I think it is the King of varmint calibers...
My 2 cents...
Here is the article...
http://www.6mmbr.com/gunweek042.html

 

[Catfur]

I've been kicking around the idea, when my 6mm Rem is shot out, of having a 57mm 6XC style chambering done, with the same long, 6mm Rem, neck.

 

[Curmudgeon]

Thanks for the replies. Since my post I have been looking and found some info that helped. The 6 mm has a little more capacity and a longer neck that was suggested allowed a wider variety of bullets. I shot today and ran a powder charge in 1/2 grain increments from 43 to 46 grains of 7828. My testing was at 300 yards with speeds at 3150 with 95 grain bullets shooting best. I also formed some cases with factory Prvi ammo that came out beautiful. I have a 30 inch Shilen barrel with a fast twist so I will try some heavier bullets next. Thanks to all who replied, the round was comfortable to shoot without a brake and after I add a little weight in the stock it should get better. Thanks again.

 

[ShootDots]

There are cartridges cases that lend themselves to "Acklyizing" better than others. Two (2) of the best are the .250 Savage and the 7mm Mauser cases. The 7mm Mauser case is also the parent case of the 6mm Remington. The 6mm Remington case, with it's L-O-N-G neck and relatively "sloping body" is a prime candidate for "Acklyizing".. Improving that case is tantamount to making a "magnum" as it were, to the 6mm caliber. Once "Acklyized" the 6mm Remington comes within a hairsbreath of a .240 Weatherby, however the case design is better. There are precious few cases that can benefit more from "Acklyizing" than the cases derived from the old 7mm Mauser case. The 6mm Rem A.I. .257 A.I. and the 7mm Mauser A.I. all make substantial increases in case capacity as well as the added benefit of a better case after fireforming. Many, if not most, of the "improved cases" benefit from a better case but do not increase case capacity as the .250 Savage and the 7mm Mauser cases do. The other case that really does make a difference from "improving" are the cases based off the old 30-06 design. Having said all that, the 6mm Rem A.I. is one of the "better" if not one of the "best" cases to improve.

 

[Gary in MD]

My 6mm AI groundhog gun. It puts the "big hurt" on varmints! I shoot 70 -75 grain varmint bullets out at between 3700 - 3800 fps depending on the load. 28" Krieger, 1-12" twist. Necked down and neck turned 7x57 brass works really well.
Gary

 

[stacy]

I HAVE 2 243 ACKLEYS ONE IS A 8 TWIST OHTER IS A 14 TWIST I REALLY LIKE THIS CARTRIDGE I HAVE VERY GOOD BRASS LIFE W/LAUPA OTHER THAN TURNING NECKS THAT IT SOMETIME AFTER SHOOTING THE BRASS OVER AND OVER YOU FORM A DOUNUT INSIDE I JUST PUSH IT TO THE OUTSIDE W/A 6MM NECK DIE AND TRIM THE NECK AGAIN YOUR READY AGAIN