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post #1 of 17 (permalink) Old 03-21-2019, 08:04 PM Thread Starter
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While researching Ackley improved chambering I find that the recommended headspace of a rimmed cartridge (ex. 30-30) is left unaffected but a rebated or rimless cartridge (ex. 35 Rem or .223) is to be shortened in chamber length by .004" to give a 'crush fit' to the cartridge in the chamber. While bolt action rifles can be turned back one thread to move chamber rearward to the bolt face to allow this, a break action barrel cannot (ex. contender). This will therefore result in a 'sloppy' chamber without the chamber set back of .004".
https://ackleyimproved.com/headspace...ed-cartridges/

How is this inability to move the datum line of headspace back accommodated in the Ackley rechambering of break action barrels.
Thank you,
Jimmy

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post #2 of 17 (permalink) Old 03-21-2019, 08:11 PM
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Cast bullet seated into the lands to control headspace is how I do it. (adjust powder charge) Right wrong or otherwise, it is MY WAY. The rest is just adjusting your sizing die to fit the brass/chamber after firing, not unlike one of the Herrett rounds really.

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post #3 of 17 (permalink) Old 03-21-2019, 08:29 PM Thread Starter
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The last paragraph of the cited article reads:
If a rimless case is rechambered using an Ackley Improved reamer without setting the barrel back the result is an undesirable wildcat. Factory ammo will have an excessive headspace condition in such a chamber. Firing factory ammo in such a chamber may result in case head separations, misfires, or at the very least short brass life. Such a chambering should be considered unsafe, as well as poor quality.

That is a bit foreboding to me.
I'm familiar with the Herrett barrel's idiosyncrasies and can handle those challenges.
I have several barrels now that are Ackley improved and they shoot great but I'm considering rechambering one myself and want to know what to expect, or should I leave well enough alone?

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post #4 of 17 (permalink) Old 03-21-2019, 08:39 PM
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I had a 7X57 Ackley that was not set back. I ate the throat out of it with some pretty mean handloads way before any of my brass gave up the ghost. You obviously know how to adjust a sizing die, so AT WORSE.....The headspace is only "wrong" once. If you are starting with fresh handloads and not factory rounds the headspace never has to be "wrong". This is a non issue to a HANDLOADER in my opinion. A RELOADER may have an issue but from what I am gathering, you will not have an issue.

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post #5 of 17 (permalink) Old 03-21-2019, 09:06 PM Thread Starter
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I appreciate your vote of confidence
... but I still have a certain degree of apprehension
I assume your 7x57 was an encore...
... or a bolt action that was not set back?

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post #6 of 17 (permalink) Old 03-22-2019, 12:27 AM
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Mine was a Mauser 98 Sporter with a reamed military barrel that had some re profiling. It now wears a run of the mill 8X57 barrel and eats only cast bullets. I bought a .270 Win for the high speed jacketed stuff and never looked back, what can I say O'Connor wasn't wrong, and once in awhile plain Jane over the counter is a nice treat in a house full of oddball rounds.


There is one other thing you can do to negate the headspace thing on the first firing but some will scoff and call me names for suggesting it. I know it works though. Load a 60-75% load with "too fast" a powder and a heavy for caliber gas checked cast bullet, and shoot the case ever so slightly oily. .004 headspace problem simply cannot happen in that environment. Such cast bullet data is not hard to find.

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post #7 of 17 (permalink) Old 03-22-2019, 08:28 AM Thread Starter
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Thanks for sharing your insights with me on the matter.
I've got a lot to consider before I start cuttting a new chamber.

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post #8 of 17 (permalink) Old 03-22-2019, 11:48 AM
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I have a couple "Improved" chambered Handi-Rifles, a 280 Improved-improved, and a 35 Whelen Improved-improved as Wayne York calls them who did the rechambers, factory ammo can't be used in them due to way too much head space, I just neck the brass up, 280 Rem to .308" and Whelen to .375", then form a false shoulder to head space on, then fire form, works great. I also have a 30-30AI that I reamed myself, rimmed chamberings requires no special treatment, will fire factory ammo just fine, but don't be surprised if you get some split necks even with factory ammo, and make sure you don't push the shoulder back too far when resizing, it still should head space on the shoulder to save the brass.

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post #9 of 17 (permalink) Old 03-22-2019, 11:56 AM
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That false shoulder advice is really good advice.

Never had to do it on a A.I, but I had to do that on a standard 35REM tender with some ancient 1X fired federal brass that was shot in something with a short short short chamber. That was before I found out about the heavy cast bullet kissing the lands thing. More than one way to skin a cat.

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post #10 of 17 (permalink) Old 03-22-2019, 01:06 PM
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Sometimes just pointing the gun straight up in the air when fire forming is enough and you don't even need the false shoulder for head spacing purposes. It varies from gun to gun but I had a Handi in 22-250 AIP that fire formed fine with a little Trail Boss/cream of wheat filler and paper wad stuffed in the end of the case. I just pointed it skyward and pulled the trigger....200 times!
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