6mm AI from 270

[cowboybart]

I can not find any 6mm Rem brass and have just finished the parts gathering phase for a 6mm AI project. I do have several hundred 270 Win cases.
My plan is to anneal the 270 brass, push the shoulder back with a 7x57 die, neck down in a 6.5 Roberts die, then a 257 AI die then a 6 AI die. I realize that it will still require fireforming, but what other problems am I going to run into? I'm guessing that I will have to turn the outside of the necks also. Should I anneal again after all of the steps or fireform then anneal?

[EDG]

You would be better off pushing the shoulders back with a 7mm-08 die and then a 260 Rem so the shoulders are not squeezed down so far - just to blow them out again.

I would put off annealing until after any neck turning. Annealed brass is gummy to machine. It will turn with a much better finish if turned when hard.

You might measure the chamber neck of your rifle as follow:
Take a 6mm case and expand the case mouth into a funnel or bugle shape about .010 or .015 oversize at the case mouth.
Then shove the case into the chamber. The chamber will force the case mouth closed. Pull the case out and measure the diameter where the chamber neck forced the case mouth smaller. That will help you minimize any turning by identifying your chamber neck minimum diameter.

If you have an over length but FL sized case you can also measure the length of your chamber by trimming and checking until a case will chamber without hitting the end of the case neck. This will permit you to minimize trimming.
When you fire your undersize at the shoulder cases they will get shorter. The extra neck length will leave your cases closer to normal length instead of being .007 or so undersize.

Annealing might allow the shoulders to blow out better if done after turning but before fire forming.
You might try samples both way and see which you prefer.

[Artful]

might find this link useful
http://www.angelfire.com/sd/6mmackley/index.html

[Markbo]

Why dont you just start with .243 brass? Lots less workbthan too long .270

[dk17hmr]

243 is to short. Remove the expander buttons from your dies and push your shoulder back with a 308 die then neck it down that's how I did it with my 6mm ai...your going to need to ream or neck turn. Anneal when your done forming. You are going to want a crush fit also.

[roysha]

To defile 270 Winchester brass in this manner should earn you a special place in the Nether World.:bigsmyl2:

[dk17hmr]

Heres a little write up I did awhile ago on another forum.

"I recently had my 243 Super Rock Chucker set back and rechambered to 6mm AI. The
question was what to do with the LC Match brass I had formed into 243 SRC
already. After doing some measurements I took my die over to my buddies machine
shop and took .260" off the bottom of the die with one of his
lathes.

Well after some trial and error I found a method to keep my brass
from getting wrinkles in the shoulder. At first I screwed the cut off die all
the way down and had it set up to cam over on the shell holder. Well running a
piece of brass through like that would fold the shoulder up like a
sheet.

Tonight I tried a couple other dies. First set was running a piece
of 243 SRC into a 25-06 full length sizer with the decapping rod out to round
over the shoulder. Than I screwed a 308 Winchester sizer into the press about
half way again with the decapping rod out, this set the shoulder back. Next came
my cut off die which necked down the brass and set the shoulder. Than I trimmed
to length. Although its not 100% formed I think it should blow out nicely. I did
up 10 pieces to try out this weekend. If it works ok Ill work my LC Match brass
over.

http://i48.photobucket.com/albums/f208/dk17hmr/IMG_20130124_205845.jpg (http://s48.photobucket.com/user/dk17hmr/media/IMG_20130124_205845.jpg.html)

All fireformed
http://i48.photobucket.com/albums/f208/dk17hmr/IMG_20130126_164821.jpg (http://s48.photobucket.com/user/dk17hmr/media/IMG_20130126_164821.jpg.html)"

[cowboybart]

I now have dies in 7x57AI, 257 AI and 6mm AI. I'm gonna try pushing the shoulder back with the AI dies first. If that fails I'll try the 308 die then 7-08 die... . I figure if I start with the 7x57 seater die, then the FL sizer, then step it down to 6mm AI, I might not have to fire form them.

[EDG]

Which AI dies are you using? Are they 26 degrees or 40 degrees?
The smaller angle seems to work better for me when I form brass- that is why the 20 degree shoulder like the 308 family is useful. The brass is not going around such a sharp corner.


I now have dies in 7x57AI, 257 AI and 6mm AI. I'm gonna try pushing the shoulder back with the AI dies first. If that fails I'll try the 308 die then 7-08 die... . I figure if I start with the 7x57 seater die, then the FL sizer, then step it down to 6mm AI, I might not have to fire form them.

[cowboybart]

They are the 40*. Maybe the 308 die would be better to start with.

[cowboybart]

The AI dies did not work. I crushed 7 out of 8 cases. The 308 die did work on the 1 case I tried it on.
At least I won't have to fireform the 1 case that didn't crush [smilie=w:

[deepwater]

It seems to me that annealing before the forming operations would allow the brass to flow into the new dies. This would work harden the brass, if desired, before neck turning.

deepwater

[country gent]

A first step annealing sometimes helps with forming cases down into new calibers. but sometimes ut allows them to crush or wrinkle being softer. All you can do is try it on a few. I ussually try to rough set the new shoulder first then neck down and final form to finished dimensions. A final annealing can be a gig benifit for case life removing the work ardening from the sizing steps. A good lube correctly applied as to thickness and evenness is also a big plis in getting good cases and an concentric forming. To much lube you get dings and wrinkles. to little hard forming and stuck cases.