Rechamber job

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kevin barrett

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Hello: I have been asked to rechamber a Thompson-Center
Pro hunter.

The customer wants the 7mmRem mag opened up to7mm STW.

In the past I have usually set these barrels back somewhat before
rechambering,about 1/8 inch or so.

My concern with this single shot is,will the shoulder/neck area

"clean up" when reaming to STW,I would hate to leave a ring in
the chamber.

Trying a new STW case in the 7mm Rem chamber hints that this
MAY be an issue.Calculations show me that case taper is within .0001
per inch .I am worried that lengthening the chamber by .349 will not
remove all traces of the original shoulder.

Does the collective wisdom here have an answer ?

Thanks in advance
 
On the two I've done/had done, if you didn't set the barrel back you ended up with the ring. I know the design of the STW was supposed to clean up the 7 RM chamber, according to Layne Simpson. That hasn't been my experience though, probably because of the variance between assorted 7 RM chambers, if I had to guess. - dan
 
I have had to set the barrel back or I got a ring... it is cosmetic, it does not hurt anything... tell the customer up front about it and let him decide... unless he has a 28 inch barrel he is wasting his money anyway..

...not increasing the headspace is important too...
 
Just to further comment on this issue.
The barrel in question is 28 inches long
stainless steel.

I am just a little concerned about potential
extraction problems,also leaving a cosmetic
flaw in the fired cases is all bad in my opinion.

Also the calibre marking is a problem because
the existing 7MM REM Mag would ideally need
to be milled off and 7MM STW stamped in.

I see SAMMI specs showing the STW running
at slightly higher pressures,but likely not an
issue.

As I have used a 7MM Rem for many years I know
this load will perform well in the rifle,especially in
a 28 inch tube.Not as fast as an STW ,however
in my hunting experience the Remington is a good
killer even at extended range.

I appreciate the comments so far,even though I am
giving up the potential earnings it is not really worth
the trouble to do this .

If there are any more insights I welcome them

Thanks Again:)
 
There's been quite a few pictures of folks blowing those guns up when they were rechambered to something bigger, the last one i saw was a .257 STW.
 
tell him to go buy the 7mm stw barrel??????? He can virtually go to any store that sells these barrels and trade it for a very small fee instead of paying for a whole new barrel...Just doesn't make sense.
 
I would like to thank the responders to my question.
After weighing the pros and cons I decided to go
ahead and do it,learn something new every day I guess.

The shoulder area in the new chamber looks great
I needn't have worried about it "that much"

as well my milling off of the REM marking and stamping STW
and bead blasting looks pretty good as well.

I used a new STW case as a headspace gauge because
I wanted to be sure I didn't increase the headspace,
it actually did look as if the STW reamer didn't QUITE
cut to the original belt line.

I left the case head .001 proud of the face ? problem?
it chambers beautifully I might add .

I feel this is the proper technique, especially for handloaders.

Again Thanks to all ,feel free to add
 
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