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About Ackley improved chambers (Read 1003 times)

bullshop Full Member Offline Posts: 201 Joined: Sep 14^th, 2017	About Ackley improved chambers Aug 18^th, 2024 at 5:47pm	Print Post
	To properly rechamber a standard chamber to an Ackley improved chamber does the barrel have to be set back ? I am asking because I have a 250 Savage single shot that the barrel can not be set back on but would like for it to be a 250 Savage Ackley. With the increased shoulder angle of the imp. it seems like that would leave a small section of the original shoulder ahead of the improved shoulder. Anyone know for sure ?


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GunBum Full Member Offline Posts: 187 Location: SW Missouri Joined: Oct 30^th, 2021	Re: About Ackley improved chambers Reply #1 - Aug 18^th, 2024 at 7:46pm	Print Post
	Yes. You need to set the barrel back for the chamber to clean up.


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SBoomer Oldtimer Offline Posts: 954 Location: Michigan's Frozen North (U.P.) Joined: Jan 28^th, 2010	Re: About Ackley improved chambers Reply #2 - Aug 18^th, 2024 at 9:28pm	Print Post
	No, you do not necessarily have to set the barrel back. When you load cartridges for fireforming, load full house loads and heavy bullets with a full jam into lands. I have chambered dozens of Ackley chambers without setting barrels back and fireformed thousands of cases using the above method. Another trick is to neck the cases up to 6.5mm and then neck size back down until the bolt closes snugly on the case prior to fireforming. I would anneal the neck/shoulder before fireforming. If you have never worked with the 250AI, you are going to be very surprised at the results. Adjust sizing dies to YOUR chamber. I recommend neck sizing only.


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GunBum Full Member Offline Posts: 187 Location: SW Missouri Joined: Oct 30^th, 2021	Re: About Ackley improved chambers Reply #3 - Aug 18^th, 2024 at 10:41pm	Print Post
	If you use SBoomer’s method, you won’t have .250 Savage Ackley chamber. You’ll have something close, but with the shoulder farther forward. The reason you set back a barrel when chambering for an Ackley Improved cartridge is so you can shoot both the original cartridge and the AI cartridge. If you don’t set the barrel back, you can’t do that, and technically don’t have an AI chamber.


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Bent_Ramrod Frequent Elocutionist Offline Posts: 1457 Location: Southern Arizona Joined: Feb 8^th, 2006	Re: About Ackley improved chambers Reply #4 - Aug 19^th, 2024 at 10:38am	Print Post
	I remember the gun and sporting magazines’ Letters section in the ‘50s and ‘60s were full of complaints about “this so-called Ackley Improved gun I had made,” generally in .30-06 AI, and presumably by a local gunsmith, who simply cleaned up the original chamber with the Ackley reamer. The unhappy customer expected to fire his standard ammo, get acceptable accuracy, and pull a perfectly formed Ackley Improved shell out of the breech when he opened the bolt. But generally he got separated cases, cases that separated after a reload or two, inferior accuracy to the original .30-06 on fireforming, and disappointing velocity increases, even by the measuring methods of the day. The “Improved” cartridge was supposed to be close to the .300 H&H in performance, but few customers reported that.


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bullshop Full Member Offline Posts: 201 Joined: Sep 14^th, 2017	Re: About Ackley improved chambers Reply #5 - Aug 19^th, 2024 at 11:06am	Print Post
	All I am interested in is increased performance. I can live with the more involved fire forming process over just firing factory ammo. Necking up to create a secondary shoulder is not a problem. Having a bastard chamber that is not a true AI chamber is not a problem. The problem as I was understanding it was that without setting the barrel back there would be a short section at the junction of the original neck shoulder that would be neither shoulder or neck. Kind of a little bit like what the old Herters cyclone shoulder looked like. I think getting all the slope out of the 250 Savage case should show a substantial ballistic improvement. One final question then is would anyone here suggest where to send this TC Encore barrel to have the job done ? Mayhaps the better idea is to go with the 257 Roberts Imp and that should solve the barrel set back issue.


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frnkeore Frequent Elocutionist Offline Posts: 7271 Location: Central Point, OR 97502 Joined: Jun 16^th, 2010	Re: About Ackley improved chambers Reply #6 - Aug 20^th, 2024 at 2:30am	Print Post
	You can fire form std cases, in a Imp chamber w/o losing brass. You just have to load the bullet long, into the rifling (use starting loads) and it will form the case w/o separating. That is how Gibbs recommended doing it on his series of wild cats, based on the '06 case. His chamber moved the shoulder at least .100 forward of the std case location.

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gemihur Participating Member Offline Posts: 24 Joined: Jan 11^th, 2014	Re: About Ackley improved chambers Reply #7 - Oct 9^th, 2024 at 11:43am	Print Post
	(You need to *Login* or *Register* to view media files and links) 480 fps increase... W0W!!!


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rkba2nd Frequent Elocutionist Offline Posts: 1934 Location: earth Joined: Feb 16^th, 2009	Re: About Ackley improved chambers Reply #8 - Oct 9^th, 2024 at 3:49pm	Print Post
	Those must be Ackley's or Rocky Gibbs figures? 570 fps increase in a 25-35?

	rkba2nd
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Deadeye Bly Frequent Elocutionist Offline Posts: 1057 Location: Stephens City Joined: Feb 25^th, 2011	Re: About Ackley improved chambers Reply #9 - Oct 10^th, 2024 at 8:31am	Print Post
	Many of those numbers are extremely optimistic! Must be using magic gunpowder.


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SBoomer Oldtimer Offline Posts: 954 Location: Michigan's Frozen North (U.P.) Joined: Jan 28^th, 2010	Re: About Ackley improved chambers Reply #10 - Oct 10^th, 2024 at 9:25am	Print Post
	I am getting 2950fps with 100gr Rem/SPCL bullets out of a 23” barreled 44 1/2 in 25/35Imp. I will dig for my 117gr data. This is my “Go-To” hunting rifle.


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frnkeore Frequent Elocutionist Offline Posts: 7271 Location: Central Point, OR 97502 Joined: Jun 16^th, 2010	Re: About Ackley improved chambers Reply #11 - Oct 10^th, 2024 at 12:31pm	Print Post
	There were a few things involved in advertising velocity's in Imp chambers. They did have increased capacity so, you could get more powder in the case. Along with that, they ran higher pressure. In some cases, they ran much higher pressures!! Used 26" or longer barrels. They also, rounded up on the numbers. I don't know if Ackely did but, in the case of the Gibbs chambers, he didn't publish average velocity, he used the highest single velocity obtained when chronographing. I have a 7x57 Ackey Imp, on a nice 98 Mauser Sporter and found that I could get to Ackley's published loads, with 3031 powder, w/o blowing primers but, they were pretty flat. I didn't chrono the loads so, I don't know how accurate the velocity was but, I think it would have been pretty close, in my 24" bbl. With my Norma cases, it increased the capacity from 3.6cc to 4.0cc, or a 11% increase.

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waterman Frequent Elocutionist Offline Posts: 2835 Location: Behind the Redwood Curtain Joined: Jun 9^th, 2004	Re: About Ackley improved chambers Reply #12 - Oct 10^th, 2024 at 1:33pm	Print Post
	I played with a .25-35 AI for a couple of days. Fireforming from factory ammo, all I got were split cases. IIRC, you had to start with unfired .30-30 brass if you wanted usable cases.


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