Improving chambers (Ackley Improved)

J

Jay Cutright

New member
Do you really need to set em back a thread to make the chamber come out right?
I have a couple of chambers to do on Savage rifles and I will set them both back a thread just to see the factory chamber get cleaned up, but, what's the problem with just running the reamer in to a "go" and shooting it?
Will the case heads separate when factory ammo is fired without the "crush" fit?
 
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Jay,

I'm fairly new to this whole deal but, I have done a few Ackley's. I think you should set them back a thread. I have a friend of mine that also does a little gun work, and I know in speaking with some of his clientele that they have had case head separations when fire forming because he does not set the barrel back on an Ackley. I have never done one without a setback so I don't know personally since I set all mine back, and would recommend it from my standpoint. Maybe some of the pro's will chime in. Just my opinion, take it for what you paid for it.

Hope this helps,
Med.
 
An Ackley Improved go gauge is shorter than the standard go gauge... to correctly set the headspace the barrel needs to come back some.
 
An Improved chamber is supposed to be safe to use with standard ammunition. That's why it's called Improved rather than a wildcat. If you chamber one without setting the barrel back you'll find that a standard no-go gauge will be accepted which means you have excessive headspace. There are all sorts of ways to fireform brass to avoid this situation. But, think about the next guy who will own that rifle and not know that it's not a proper chamber. Maybe that next guy will be your grandson. Think about that.

JMHO

Ray
 
"come out right" Well that depends on what your idea of that is. If I had the barrel in my lathe I suspect it would take about 1/2" or so to make a new chamber. Picking up the threads and cutting some more is no big deal. Refacing the breech end is super simple because its flat. The case spec is .125" protrusion.

Since the case protrusion of .125" has some tolerance, it is highly probable you could turn the barrel in another .004" without hitting the bolt head. So yeah, its possible.

If someone asked me to do it I would say my way or the highway. My definition of coming out right would be to start with a new barrel.
 
If you are working on a Savage with the barrel nut you would not have to set back as long as you can get a tight feel on the go gage. If you have a shouldered barrel you would set back as the go gage is probably not a tight fit to begin with. That is the beauty of the barrel nut system. If I was doing an Ackley on a lightly used barrel I would set back at least the length of the neck so if neck diameters did not match you would not have a step in the neck and have a fresh throat.
BV
 
Dennis hit the nail on the head.

Not to change the subject, but I'm curious.
I've read of lots of people doing imp chambering jobs on single shot actions like the tompson centers or H&R style, which are impossible to 'set back'
I could understand this imp chambering with rimmed cartridges, since they head space on the rim regardless of chamber shape.
But how are they doing rimless imp chambering jobs and producing a chamber thats safe with standard ammo ?
 
Before a case is fire formed, the only place that it is restrained, longitudinally, at the front of the chamber, is at the neck shoulder junction. Factory ammo, and unfired cases are shorter at this point than a minimum headspace chamber, and in fact may be under SAAMI ammunition minimum spec. This can lead to excessive case stretch on first firing, and may cause ignition problems as well. Some time ago, a friend had an 22-250 AI that would fire one brand of factory ammunition, but would not reliably fire another. This was a new barrel chambering, on a custom action. As I remember it, one should use a standard GO gauge as the NO GO gauge (corrected after Jim Borden pointed out my mistake) when setting the headspace for an Ackley. As to how things are done when chambering a TC barrel, if a false shoulder is not formed on the case to be formed, (negating the intended advantage of an AI design) then I would say that there is a very good chance of cases being weakened by excessive stretching near the web. I have seen all sorts of things done that should not be copied. Generally, I find people have a tendency to rationalize in order to save money. Many times it is better not to do a thing, if it cannot be done correctly.
 
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[QUOTE/

Not to change the subject, but I'm curious.
I've read of lots of people doing imp chambering jobs on single shot actions like the tompson centers or H&R style, which are impossible to 'set back'
I could understand this imp chambering with rimmed cartridges, since they head space on the rim regardless of chamber shape.
But how are they doing rimless imp chambering jobs and producing a chamber thats safe with standard ammo ?[/QUOTE]

They are not safe with standard ammo, and cannot be called Ackley improved, They can be called improved but should be made with new brass not by fireforming a parent cartridge.
I used to Stub T/C and H&R barrels that let me properly set the barrels back for an Ackley improved chamber. I have also built a few new barrels by welding lugs on and they can be set up as ackley improved.
Kim
 
Boyd

Definitely do NOT use a no-go as the standard gauge for teh Ackley. The standard go becomes a no go for Ackley. Ackley Standard chambers are usually .004 to .006 crush on std go.
Reason is so that factory brass has shoulder/neck interference in chamber and case is held against boltface

Jim
 
Jim,
Thanks for the catch. Obviously, a NO GO is longer than a GO. what is needed is something shorter. I will edit my post.
 
Jay, I remember years ago when I wanted a 30-06 Ackley Improved. At that time I was shooting a Sako Delux and did not want to set the barrel back. The only way I could satisfactorly fire form was to neck the brass up to 8 mm and then size most of the neck back down to 30. I think you need an interference fit to properly fire form rimless cases.

Don Carper
 
I've read of lots of people doing imp chambering jobs on single shot actions like the tompson centers
Click to expand...

Almost all of these Improved TC barrels are with rimmed cartridges. A rimmed cartridge which headspaces on the rim is very easy to Acklerize..........Just run the reamer in..........
 
One thred seams like a lot as corse as barle threds are . How much Is one thred on a Remington? Thanks Max
 
I believe the 308 and the 260 use the same headspace gauge. But check with Dave to be sure....

I have a friend of mine that also does a little gun work, and I know in speaking with some of his clientele that they have had case head separations when fire forming because he does not set the barrel back on an Ackley.
Click to expand...

Please let me know if someone with one of these guns sets up on the bench next to me............God help us!
 
My point being it doesn't say "308 AI" or similar. I am to believe this is a standard 308 Winchester go gage. I already have one of those!
 
The 308 go gauge becomes the 260ackley no go gauge .
You still in a 260 ackley improved go gauge unless it is a 308 ackley improved go gauge,which is interchangeable as the 260 ackley go gauge .

Chris
 
In 2002 I built a 257 Roberts Ackley Improved on a VZ24 action with a Lothar Walther light varmint CM barrel blank. I cut the threads and the chamber.
I used a piece of 257 Roberts brass new out of the bag as a go gauge.

I was never able to form in one step. The case would separate .1" behind the shoulder.

What was happening was the firing pin would push the case forward. The angle of the chamber shoulder was different the the angle of the case shoulder, so the only point of contact was a ring of contact at the base of the neck of the case. That sharp ring would cut into the case .004" before the primer went off.

I learned to form a partial shoulder with 10 gr pistol powder and the rest of the case filled with Cream of Wheat. Then on the next firing I used a bullet and got a full shoulder formed.

Other rifles I subsequently built with that reamer, I set the head space .004" tighter, and they form a case on the first firing with no case stretching separations.
 
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