Another dumb question

[243LPR]

Ok,so if a parent case can be fired in an Ackley chamber,what does the parent case headspace on if the Ackley shoulder is pushed farther up and a different angle? Seems to me that it would be a loose fit. :-[

[gotcha]

No such thing as a dumb question. ..... Lets just hope this isn't a dumb answer ;D On the Ackely Improved cases designed by P.O. himself, the measurement from base to shoulder/neck junction remains the same. This allows parent case cartridges to be readily fired in the improved chamber.........So the parent cartridge is actually headspacing on the small rounded transition from the neck to the shoulder. Beware of so-called A.I. cartridges that don't share this design feature. Using a properly reamed chamber (head spaced correctly) you should feel a slight resistance to bolt closing as compared to an empty chamber when using factory parent case ammo.... Could the fit be slightly loose?------ YES. All factory ammo is not created the same dimensionaly. However, I've used this method in both of my AI's with no problems. Keep in mind that a portion of pressure needed to form the case will also be absorbed by the case upon fire forming. Expect lower velocities when fire forming. Hope this helps. If this was a dumb answer we'll hear about it ;D

[bootsmcguire]

I think you covered it, except that the neck/shoulder junction is .004" closer to the cartridge base on the Ackley Version. That is what gives you the "slight resistance" you feel and is actually crushing the case that tiny bit to take up the slop. As you stated though, in a properly cut and headspaced chamber.

[gotcha]

Thanks for the input Boots ! I've heard about the .004" variation but have never found any concrete evidence to verify. My Hornady #7 shows a cartridge drawing for both the 257 Robts & the RCBS version of the "improved" cartridge ( 28 degree). These drawings show the improved version being .005" shorter from base to shoulder/neck........... I probably need to get a copy of P.O. Ackleys' book for future reference. Your point is well taken. Dale

[Eric in NC]

This is why the parent "go" gauge becomes a "no-go" in an Ackley chamber. The Ackley chamber is shorter to support the unformed brass when it is fired for the first time.

[243LPR]

Thank you men,that answers my question.Ordered a 6mmAI on the Gun Shack group buy.It's about time I added a wildcat (sorta) to my arsenal. Now time to start getting things together for the new arrival.

[gotcha]

Sounds like a winner to me! If you need some fire formed cases for head spacing just drop me a PM. Dale

[243LPR]

I can't use a FLS 6mm to headspace?

[bootsmcguire]

It can be done, but better with a formed case and best with gauges. My first Ackley was headspaced with a sized parent case. I set it to where I could feel that slight crush. If you have a chance to get a formed case or two, I would opt for that if not gauges.

[243LPR]

Even if its from a different chamber? I will probably be shooting 75 gr and up. What powders do you guys have the best luck with? I've read alot about H4831 and R19. My barrel will be 1:8 twist.

[Eric in NC]

Best to use the AI GO gauge. No questions then as to what a "slight crush" is...

[bootsmcguire]

Best to use the AI GO gauge. No questions then as to what a "slight crush" is...

I agree, if there is any question in your mind definitely get the go gauges and set. Best with a set of gauges.

It can be done, but better with a formed case and best with gauges. My first Ackley was .....

[gotcha]

No doubt a steel go-gauge would give more reliable "feel" than a soft brass case. A friend and I (Gacop) recently chambered rifles in same cartridge using CBI bbls, Lapua brass. He HD spaced to unfired brass, I HD spaced w/ gauge. There was less then .001" difference between our F/F cases. .0006" to be exact. He, however, has MUCH more experience than I when it comes to HD spacing. For me, the gauge gave me piece of mind & well worth the $25.00 cost. As to powders my 6AI was set up w/ 12 twst expressly for 70/75 gr. bullets driven @ high velocity. RL-19 gave me better results than H4350 or H4831. Best velocity & excellent accy. Haven't tried any of the newer powders appropriate to this case capacity or bullet wgt. A shoulder hit on a yote inside 350 yds will knock'em off their feet. Yur gonna love this cartridge. Good luck to ya :)