Bore Diameter / Bushing Question

JerrySharrett said:
Do you already have the Shilen barrel? If so go to ebay and get a set of small hole gages, you can get a set for as low as $10 and the 4 gage set will measure bores from 1/8" to 1/2". Measure the bore then order the bushing accordingly. If you do not already have the barrel, have whoever you are getting it from to measure it for bushing fit. At Shilen, Bill or Wade Hull, the owners, will be glad to measure and sell you a particular barrel.

http://cgi.ebay.com/4-SMALL-HOLE-GA...931?pt=LH_DefaultDomain_0&hash=item45edaf4c3b
or
http://cgi.ebay.com/Small-Hole-Gage...817?pt=LH_DefaultDomain_0&hash=item53de61e3c1



As is stated above, eventually you will end up buying several diameters, but for now, and your beginning, 3 sizes will suffice.

Measuring the only Shilen blank I have right now. it would take a 0.2362 bushing for reaming.

The reason for all these diameter variations is that each barrel is hand lapped and one 6mm barrel will not finish exactly the same size as another. Barrel manufacturers will label them, for example, 0.243/0.236 or 0.243/0.237 but the exact diameter will vary.
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Yes, Jerry, I have the barrel already.

So, with a set of the gauges above, and a .0001 micrometer, I can measure the bore and get probably three bushings, one in the middle, and one on either side? Or I could order the reamer with one bushing and get two others, one smaller and one larger than the reamer bushing.

I like that idea.

Thanks Jerry.

Jim
 
alinwa said:
If I remember correctly the rod you're probably referring to as a "range rod" will be called a "Grizzly Rod" at PPG. The terminology is imprecise but if you're using the Gritters method of chambering get the Grizzly rods, they're a foot or so long and parallel taper. Some of the originally termed "range rods" are tapered monstrosities that just flop around on the bushings and are designed to be used like deltronic pins, in other words you basically drive 'em in, let them hang out the end and indicate off them..... NOT at all like Gordy's method.

hth

al
Click to expand...

I know better.

What I meant to say was the Grizzly rod, not range rod.

Thanks for the clarification.

Jim
 
Thanks so much to all that have given so much helpful advice.

I really appreciate it.

Jim
 
Charles E said:
If the term "range rod" is imprecise, I mean the indicator rods as sold by Greg Tannel

http://www.gretanrifles.com/gtrtooling.asp

scroll to *Indicator rods*

They do have a taper. For all I know, this is the same thing Gordy Gritters uses, the same basic product as sold by PTG, etc.

Or not.
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Absolutely no relation to the Gritters rod. If these 'indicator rods' are the items Jerry and others have taken issue with, I'm in full agreement. These rods have no provision for eliminating (necessary) play or clearance. I would not advocate use of one of these tapered rods with a bushing on the end. For this sort of operation I'd use deltronic pins.

al
 
I gotta give back the wood?

Actually, the way Joel and I use them is to indicate in the barrel what, longitudinally? Then we use a long-stemmed dial indicator to finally indicate where the neck/bullet will reside. Then bore the chamber, finally ream. Seems to work. (If it is only luck, I'll will take that too. Let me tell you about my luck sometime . . .)
 
Charles E said:
I gotta give back the wood?

Actually, the way Joel and I use them is to indicate in the barrel what, longitudinally? Then we use a long-stemmed dial indicator to finally indicate where the neck/bullet will reside. Then bore the chamber, finally ream. Seems to work. (If it is only luck, I'll will take that too. Let me tell you about my luck sometime . . .)
Click to expand...

lemme know when you'se have got a long stemmed indicator located that'll work for the RUM or 338 Lapua case ;)

al
 
Al, I think they're available, but I don't want a mortgage on the house. Maybe Jerry knows of some

Actually, if you find one with a small body, you can drill for clearance, indicate in, then bore to true up. It's not like the whole length has to be born by the stylus. The cases you mention are over half an inch diameter, that's a pretty big hole you can drill to get the indicator inside.
 
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