Jackie Schmidt, Jerry Sharrett--chambers

L

Lucky Shooter

Guest
I have questions involving your methods of chambering----slight differences.

I have a barrel in the lathe and will follow a combination of your methods of indicating in at the throat and muzzle, pre-drilling and pre-boring and then reaming the chamber with a piloted reamer. I will push the reamer with a pusher similar to some that have been pictured on this forum----this has worked very well to prevent reaming oversize on the body diameter.

As I understand, your major difference is in the pre-boring.

One taper bores and in fact forms the shoulder angle with the front edge of the boring bar.

One does not taper bore, as I understand.

Will I get a less concentric chamber if I don't taper bore ?

Will I continue to get close to exact reamer size if I don't taper bore ?

Would appreciate opinions on this. Thanks.

A. Weldy
 
Not Jackie or Jerry, but I bore the chamber out straight without taper boring. Even with magnum calibers as long as you take out as much of the chamber as possible with the boring bar, you'll get very little runout (way under .001") with the reamer following the straight bore hole. I bore for .010" under shoulder diameter of the reamer and about .100" less than the length of the base to the shoulder of the go gage. I also will start the reamer with the rear of the reamer driven by a 60 degree center and switch to the floating holder if there's a problem with misalignment in the tailstock. Taper boring might be better, but has to be done with compound alinement and run in by hand instead of under power with the carriage feed. I checked the runout yesterday on a .284 barrel it had what appeared to be less than .0002" movement on a rotation of the chuck at the neck and rear of the chamber. Less than .0002" as you're more or less guessing how much it actually is when using a Interapid .0005" indictor with the long indicator point. One thing about taper boring as opposed to straight boring, if you happen to miss your diameter and the reamer goes in farther than it should, you probably wouldn't be hurt with a taper bored hole as long as the taper bored hole would clean up with the reamer. You have to just about cut off the complete straight bored hole if you cut it oversize and start over.
 
Thanks Mike

I decided to try a straight hole and the results were as good and probably better than I've been getting with boring a tapered hole.

The runout throughout the chamber shows very close to zero with the same
.0005" Interapid you mentioned and the reamer is a very tight fit in the hole.

This is a replacement barrel for one of a set of 223 PD rifles that can interchange neck sized brass-----not much leeway in matching the chambers.

Thanks again for the info.

A. Weldy
 
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