A question

J

Jim Kobe

New member
Kinda off the wall here but am curious. Chambered up a new barrel for a client in 223 ackley, can't get his loaded ammo to chamber. I had done the previous barrel a while ago using the same reamer. Problem is, the difference between the old barrel and the new shoulder diameter differ by .006". the newer one is tighter. Headspace is correct, go on the AI gauge, no go on the 223 go. Same reamer, same lathe same, same. What he H gives.

Jim
 
perhaps a bit of wobble or a tad off center on the old when chamberd? or some chattering on the new. Has the reamer been sharpened? or how many other chamberings on the same reamer between the 2- like any tooling some wear takes place. then we get into tail stocks and all the variables that entails depending on your choice of methods. So what I am saying is we need a lot more information for more accurate guesses.
 
Was the loaded round that you tried full length sized with a correct 223 Ackley Sizing Die.

At first glance, I would think the first chamber, for some reason, got wallowed out when it was chambered.

Once brass is fired in a grossly oversized chamber, ( I would call .006 grossly oversized), it is difficult to size it down to fit in a correct chamber.
 
I'm not sure it would even be possible to woller out the shoulder diameter .006" without the neck and entire body being out also. I could see the ass end opening up with a misaligned rigid reamer holder but I'd think there would be enough flex in the reamer to keep the front inline with the bushing and bore. What shoulder diameter are you measuring? Brass or the chamber?
 
I've seen commercial floating reamer holders cut a chamber oversize. Given the diameter of a .223 though .006" is a lot oversize.
 
I think I found the problem. I made a chamber cast of the original and the new barrel, New barrel .006" under the dimension of the old barrel at the neck/body junction. I ordered a print from PTG, got it and compared. Guess what, the new barrel is undersize by .006" at the neck/shoulder according to the print, old barrel right on. Now, how did the old barrel become oversize compared to the new one. I was certain I used the same reamer on both! Maybe I had rented a reamer for the old one. Anyway, new, in spec reamer on order. Hope this clears this up.

Thanks for all the replies.

Jim
 
Rubicon Prec. said:
Oversized at the shoulder or the rear?
Click to expand...
Not sure. I cut it off and rechambered it. There was enough slop in the chamber that you could see the reamer wiggle in the chamber. I've tried two different commercial reamer holders and tried each of them one time only. One had two screws that held the front part of the reamer holder against the rear part of the holder in a oversized holes. When the reamer started cutting it torqued against the screws and pushed to the side making the reamer cut oversize. The other one was made a little different but did about the same thing if allowed to float. I haven't found a method yet that works better than an aligned dead center for most of the chamber and then finishing the chamber with a floating pusher. When fired brass from two different rifles will interchange before resizing, then you've either done a good job or are at least consistent from one to the next. I'll be the first to say though lots of ways to get to your goal and doesn't mean that because someone gets there by a different method that they are wrong and I'm right or vice versa, just different.
 
Mike,
A friend has found the same thing. Push the reamer with a center for most of the chamber and then finish with a pusher. The reamer will probably be held off center just slightly by the center, and if you finish that way it will be true but progressively larger toward the back, but by stopping short enough for that enlargement to be cleaned up as you finish, you get a true reamer sized chamber, and the support provided by the partial depth chamber keeps the reamer aligned while cutting the rest of the chamber. This is truly an instance where experimenting and thinking out of the box pays off.
 
Boyd, I found that out when chambering two barrels with the same reamer for my two Bats. One barrel was chambered by pushing the reamer with the dead center for the whole chamber. The other with the floating pusher, both after drilling out and bore no most of the chamber. I couldn't feel any slop with the reamer in either chamber. However fired brass from the barrel chambered with the pusher would fit in the barrel chambered with the dead center, but not vice versa. After that I went to chambering most of the chamber with the dead center as it gives the reamer better support at the rear and then finishing the last .100 to .150" of depth with the pusher. I've found that if the bushing on the reamer is undersize of what just fits that you'll get a smaller neck diameter normally than if you use a tight fitting pilot bushing when checking the neck diameterxwith pin gages. Whether any of this actually makes any difference on how the barrel shoots, I highly doubt it. But does make you feel good when you can take fired brass from one gun and put it in another. Since we use full length bushing dies to size, that interchangeability of fired brass actually doesn't make any difference. But, does make you feel like you're doing your part with the gunsmithing.
 
I have several barrels that were done by a smith that has an adjustable dead center mount on the saddle of his lathe. I am not sure if it is the tool post or what. In any case he puts a magnetic base and indicator on his chuck and dials in the dead center so that it is perfectly centered on the spindle's axis of rotation, and does the whole chambering job using the center. Brass from those barrels can be interchanged.
 
^^^
I've seen centers that adjust along the x axis as a substitute for setting over the tailstock- but never one that could compensate vertically as well.
Sure would like to see such an animal.
 
BG Gunworks said:
^^^
I've seen centers that adjust along the x axis as a substitute for setting over the tailstock- but never one that could compensate vertically as well.
Sure would like to see such an animal.
Click to expand...

BG,

I built what you're describing, and what Boyd provided a link to, a couple of years ago for use whilst truing actions. There is a picture of it here:

http://benchrest.com/showthread.php?91625-Action-Truing-Justin-Style&highlight=

Even with such a tool, you're at the mercy of your tailstock ram travelling to and fro in a straight line.

Variables...there is no end to them, it seems.

Justin
 
Zebra13 said:
BG,

I built what you're describing, and what Boyd provided a link to, a couple of years ago for use whilst truing actions. There is a picture of it here:

http://benchrest.com/showthread.php?91625-Action-Truing-Justin-Style&highlight=

Even with such a tool, you're at the mercy of your tailstock ram travelling to and fro in a straight line.

Variables...there is no end to them, it seems.

Justin
Click to expand...

And you are at the mercy of the lathe foundation moving, and it will. A vertical movement of the concrete foundation of just 0.001" vertically, where the dead center is sitting and where a reamer is fixed, as in a dead center, will make the chamber base 0.002" oversize.

We used a $250,000 laser alignment tool to set a new lathe, on a 48" thick reinforced pad. In just a few hours the lathe would move a few thousands. Then, sometimes, move back. This was a Monarch 48" lathe with 228" centers.


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.
 
Don't forget temperature change. As the head of the lathe warms up while running the center line of the spindle to the bed distance changes. That amount times two is the amount the rear of you chamber will be oversize.
 
Last edited:
Gappmast said:
Don't forget temperature change. As the head of the lathe warms up while running the center line of the spindle to the bed distance changes. That amount times two is the amount the rear of you chamber will be oversize.
Click to expand...

What is the workaround to prevent oversized chamber rear due to temperature change?
 
I hold the reamer in a gimbal to take the torque and for alignment. This method has always made the rear of the chamber the same size as the reamer
 
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