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Discussion Starter #1
The neck gets too short and subsequent firings form the shoulder better, but the neck stays short.
 

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The Hog Whisperer (Administrator)
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Don't worry about it, it will eventually 'grow' back out to the correct length. How much short of the minimum trim length is it?
 

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The Troll Whisperer (Moderator)
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YUP, like Mike says -

You'll be ok - as long as you have a bullet diameter length on the neck (.257") the bullet will be seated fine. If shorter, just be careful to have the bullet aligned with center of cartridge. I seat bullets in stages, turning the case in 1/4 increments to assure proper alignment. Don't own a runout gauge - that's next on my wish list!
 

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If the neck wasn't shorter, you'd have an incipient case head seperation. That shoulder brass has got to come from somewhere.

If you're not getting fully formed shoulders, worry more about headspace. If you don't have a cartridge headspace gauge of some kind, you might be forming cases as much as .050" under chamber headspace, and not know it.
 

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As to the question of fireforming, you already know how to do that. A mistake some people make it to use reduced loads when fireforming the AI rounds. You should use a factory loaded round or a round that is loaded to, or very near, factory velocity and pressure. There is no reason not to do this unless you're trying to form a bunch of chases on the cheap. In the 5 calibers I've worked with that involved fireforming brass, the accuracy was quite good with the UNFORMED cases. You should start with new or once fired brass for a project like this.

As far as headspace goes, that is a viable concern. The short neck you discuss could be caused by an excess headspace situation. You should have the chamber checked with an appropriate guage. The upside is that the AI cartridges are supposed to use standard headspace guages.

Take a full length sized casing that has been formed previously and compare it to a fireformed casing that has not been sized. If you you have a headspace problem it will likely be visible when the two cartridges are set side by side on a level surface.

The shoulder brass typically comes form the shorter shoulder itself. Ackley Imporved cartridges are not intended to be shorter than the predeccesor. They are the same lngth typically and often have a LONGER neck than the original. Some cases change the body length of the casing, these are not improved, they are called wildcats. The thing that would cause a short neck in my opinion would be a long chamber, which woud cause you to have excess headspace in relation to your cartridges, as was mentioned by Hangfirew8.

If you want, I have a book that shows every measurement for your casing at it different points and I can send you the info.
 

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kciH said:
The upside is that the AI cartridges are supposed to use standard headspace guages.
No. A lot of people think that because an AI chamber can accept and fire factory cartridges, it has the "same headspace", and can use the same gauges. This is not the case.

A proper (not Bubba) AI chamber should have .003"-.004" of crush at the neck/shoulder junction for a factory case. As a result a standard GO gauge will not quite fit. As a fireformed AI case will headspace normally mid-shoulder, instead of at the neck/shoulder junction, it shares neither headspace datum with the factory cartridge.

Bubba-ized quasi-Ackley Improved chambers are simply reamed-out factory chambers without the barrel being set back. These need to be treated like the wildcats they are. To properly case-form these safely, one needs to neck-up the cartridge neck to the next largest caliber, then size the neck only far enough to get it to chamber. This provides the neck/shoulder engagement that Mr. Ackley intended for factory cartridges.

kciH said:
Take a full length sized casing that has been formed previously and compare it to a fireformed casing that has not been sized. If you you have a headspace problem it will likely be visible when the two cartridges are set side by side on a level surface.
No. Headspace differences of as little as .020" are dangerous and not readily apparent to the human eye. Compounding the problem is the difficulties of visually compairing compound angles side by side. We do not want to deal with the dangers of 60,000 PSI gas blowing out on the next firing.

In order to see if a formed case has proper headspace, one needs a proper tool to measure it, such as those made by RCBS or Stoney Point.

An improvised cartridge headspace can be made out of a squared-off cut tubing with an inner diameter aproximately the same diameter as the midpoint of the cartridge shoulder, slipped over the top of the cartridge and the whole measured with dial calipers. However any such measurements cannot be reasonably compared with anyone else's.

kciH said:
The shoulder brass typically comes form the shorter shoulder itself. Ackley Imporved cartridges are not intended to be shorter than the predeccesor. They are the same lngth typically and often have a LONGER neck than the original.
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I really don't know what you are talking about here. The mid-shoulder headspace point of an AI formed cartridge is higher than that of a factory parent cartridge. The neck/shoulder junction is nearly the same, usually shorter by the crush difference of .003"-.004".

When an AI case is fireformed, the shouler brass has gotta come from SOMEWHERE. If the neck slips down to fill the shoulders, the case OAL is shorter (no harm) and the case is fine and usable. If the neck stays put and the case body stretches to allow shoulder fill... the brass is now thinner at the point just above the web. This condition can be measured with a gage like the RCBS Case Master, and is not always noticable with a bent paper clip scraping. Such a condition is called INCIPIENT CASE HEAD SEPERATION and is a DANGEROUS CONDITION.

kciH said:
The thing that would cause a short neck in my opinion would be a long chamber, which woud cause you to have excess headspace in relation to your cartridges, as was mentioned by Hangfirew8.
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Possibly. Or, it could be the result of proper fireforming in a good AI chamber, where the brass that fills the shoulder is drawn down from the neck, not up from the body above the web. Either way, you don't know if it is a good fireformed case until:

a.) you check the mid-point shoulder headspace with a cartridge headspace comparator, and

b.) you check for brass thinning (reverse taper) above the web.

These two checks should be done on EVERY Ackley Improved fireformed case.
 

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Discussion Starter #7
I headspaced the chamber with a Win 257 Roberts case right out of the bag.

I reamed the chamber until, when I torqued the reciever on, the bolt just closed with 5 pounds of force. I normally go for about an extra 2 ounces of bolt closing, and I thought that was enough.

Now I get .004" more headspace on formed cases without oil.

I should have chambered the rifle tighter, like 20 pounds to close the bolt

The next time the reamer was used, on my brother's rifle, he tried to use one of my cases as a chamber guage, but the reamer must have worn down, becuase the case would not fit. He wound up cutting much brass off the forme case to get it to go in his chamber.
 

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hangfire,
I understand that excess headspace does not have to be visual to be dangerous. Looking at cartridge drawings for different AI cartridges show that the neck length is as long or longer than the parent case in many situations. I understand that the actual formed case may not end up being what the actual drawing represents. In the example of the cartridge in question, the body length of the case is actually shorter than the parent case. The shoulder is shorter than the parent case and the neck is longer. I may be mistaken, but it seems to me that the additional brass needed comes form the shoulder and not the neck. The shorter shoulder and body would provide the brass needed to reduce the body taper. If the oal is the same, which it is very close, and the body is shorter, and the shoulder shorter, it would make sense that the neck would be as long or longer. The drawings I'm looking at are from the Handloader's Manual of Cartridge Conversions and may be in error, but this seem to be consistent with other rimless improved cartridges, even in those without a great deal of reduction in body taper. From what I can see, as a general case with rimless cartridges, the powder capacity is gained through reduction in body taper, which is accomodated by shortening the shoulder (sharper angle), and not increasing the actual body length of the case.

I was wrong to think that the standard cartridge headspace guage was the correct tool to use. I've been told it many times and actually know better. In the latest improved cartridge I've played with, the 35 Whelen, was a fresh chamber job and not a rechamber. By looking at the drawing for this cartridge it seems as though a rechamber would be feasible, but the drawing for the .257 Roberts does not make it seem this would be possible based what I have for measurements. I understand the principal is to be able to rechamber a factory rifle, but the .257 measurements just don't look right unless, as you mentioned, the barrel is set back before rechambering.
 

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I see your point. There is the design intention, and then there is what actually happens in the chamber. We've all seen different fireforming results with different brands of brass or different speed powders used.

I have found that fireforming dry cases with full pressure loads exhibit the usual behavior of case/chamber stiction at the neck, and the case does its usual stretch back towards the bolt to accomodate excess headspace, and in an AI chamber, the shoulders get filled out too, providing enough pressure is there. I have also found that many cases formed as such exhibit case wall thinning through the body near the web. I've discarded all these cases.

On the other hand... no matter what the design intentions where... if I oil the neck and shoulder, I get no reverse taper/thinning through the case body, a shorter neck, and a more uniformly formed case. It might be .02" to .03" shorter but I have every confidence in its integrity.
 
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