6mm Ackley Improved HELP

Plumsask

Plumsask

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Hi everyone, I recieved my new barrel chambered for 6mm AI, chamber was cut using a PT&G reamer and head space set using guages from PT&G. The reamer print shows the ackley chamber to have a .010” crush fit from the parent case which is needed when forming an ackley case. We set the head space so that the bolt would not close on the no go and so that it felt resistance closing on the “go” guage. Technically we should be set up on the tight end of the spectrum- here’s the issues- with the firing of pin and ejector, extractor removed from the bolt I feel resistance on bolt close for a crush fit on %65 of the new winchester 6mm brass as it should, the other %35 of the Brass I feel no resistance. After using a comparator to measure the cases it seems there is up to .011” difference from case head to the neck shoulder junction which is where the case is held when forming virgin brass to Ackley. Without the crush fit I’m concerned about case stretch in the web area of the case and possible brass failure due to head separation. This is on a Savage 10 action, could I tighten up the head space even more than what the go guage dictates, the savage action is easy to adjust- perhaps another .008”-.010” ive read of a lot of people saying that .010” is not enough crush fit as brass can vary this much ( and it really does ). Any opinions would be greatly appreciated.

Ave
 
Since this is your rifle and you are making ammo for it, just set the headspace so the go gauge has resistance on closing. This will put the headspace on min and the Win brass should be close enough to expand without damaging the web.

Now some brass may be really stiff to chamber so... you just need to make a decision on what headspace to use.

I would use a light pistol powder charge and cornmeal to do my first forming. this will ensure any really short cases don't get strained. So even the "undersized" brass will form without much if any strain on the web.

Plan B, neck up, then down forming a secondary shoulder, COW forming and away you go.

Jerry
 
Thanks Jerry- the plan is to do the Cream of wheat method to form, I will try a few and slowly work my way up with the proper forming charge and see from there. Thanks again for the help and the great service as always.

Ave
 
Another option would be to expand your necks up to 6.5 cal and then size all but the last little bit of the neck so you have a false shoulder to keep it tight in your chamber.
 
Thanks for the help everyone. We adjusted the headspace to bare minimum, and was able to achieve a solid crush fit on all cases. I loaded up a ladder of cream of wheat with winchester 231. I had read on a page dedicated to ackley’s to fill an empty case to the top with the powder and then weigh how much powder the case held. (40 grs. Of W231 ) then took 10% of that number as the starting charge. Started at 4.0 grs and worked up. I found nice shoulders formed at 13.5 grs. No pressure signs. And worked up .5 Gr increments. Aside from cream of wheat stinking - it was a fairly easy process. One note I made is to take a flashlight and check the chamber for any cream of wheat that may have made its way into the chamber after firing, if you fire a round in the chamber that has some cream of wheat laying in it you wil have an ugly dent in the case.

- one other bit of info- I had weight new cases with a spent primer in them and most cases held 56 Gr H2O. After fire forming I respected the process with the cases that I had numbered for direct comparison.
The cars now hold 60.8-61.0 grs H2O ( which is on par with the what I have read for 9%-10% increase).
Thanks again for all the help

Ave
 
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