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Ackley Headspace Gauges

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Unread 08-31-2010, 03:47 PM
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Re: Ackley Headspace Gauges

Originally Posted by fj40mojo View Post
I believe the reason for the changes is to prevent chambering of similar cartridges in the wrong gun that would result in catastrophic kabooms.
Yes that is the smarter thing to do.
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Unread 08-31-2010, 05:48 PM
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Re: Ackley Headspace Gauges

As for why the different lengths.

Different lengths certainly do help prevent the act of trying to insert cartridge "A" into gun "B".

There may be another reason though.

As we discussed earlier, the case body takes material from the neck to inflate the case and alter the shoulder angle. How much neck gets left over becomes a function of the case body diameter and length before the shoulder. Shoulder angle also plays into this. An aggressive shoulder angle is going to be shorter in length than a shallow one.

I think PO Ackley may have wanted to have his neck lengths more uniform/symetrical from one cartridge to the next. Meaning a 25-06 should look proportionally similar to a 30-06. This would be so that bullets have sufficient support along their bearing surface by the neck. That being said the case cartridge length would have to be altered to achieve this due to the larger bullet diameter. (more circumference eats more material, ='s a shorter case length)

I don't know this for sure, but it seems to make sense.

If not, you'd end up with the "Ackley/Gibbs inbread thing" I described earlier.

Chad Dixon

Last edited by NesikaChad; 08-31-2010 at 05:51 PM.
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Unread 08-31-2010, 09:22 PM
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Re: Ackley Headspace Gauges

Off topic sort of but along the same lines: i understand the mechanics of seating bullets out to the lands to hold the head firmly against the bolt face to properly fireform the case, but why have I heard that one of the benefits of the Ackley cartridges is the ability to fire factory ammo when in a pinch and end up with a fire formed case? Is this a fallacy or are all the Ackley reamers designed with the ideal throat to have factory ammo touch the lands? I don't see how that could possibly be considering all the bullet designs that were in use with factory ammo when Ackley was designing his cartridges let alone now.
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Unread 09-01-2010, 09:24 AM
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Re: Ackley Headspace Gauges

Thats what i was talking about. If you headspace the AI chamber with the parent cases headspace gauge you will be able to fireform with factory ammo and not have to worry about the forming. Fire forming can be your most accurate rounds out of your gun.
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