Finish Reamer Chambering Short......Go gage doesn't close

[mdoerner]

Hi All,

Well, I got one of those fancy Brownells reamers that are supposed to ream down to the min head space so the bolt closes on the go gage and doesn't on the no-go gage. Well, it doesn't.

I'd say I'm about 0.002" to 0.003" short. The bolt almost closes on the go gage, but the bolt is fully closed when the finish reamer is inserted (I got no more "bite" when I turn the reamer.) Do I just use a strip of tape on the back of the bearing to get me to close on the go gage? Or is there something else I'm missing here? Thanks.....

Mike D

[Dave Waits]

I'm not real familiar with the particular Finish-reamer you're using but I'll assume it's a pull-thru Mike. If it is then you supply the cutting pressure for the reamer. Pull slightly and give it a few turns, don't count on the bolt to supply the correct pressure. That should give you enough to headspace on min. Then send it back to Brownell's with a note stating it's undersized. That's one of the reasons I use PTG reamers.

[mdoerner]

I suppose I can do it like that. I'd fear I'd crank it too much and have a 7.62 NATO chamber.....not that it would be a bad thing, just makes the brass a bit stretchy......

Mike D

PS Yes, it's a pull-thru reamer.

[Dave Waits]

Just put a little, light constant pull on the crank and give it a couple turns and check. Use plenty of cutting oil Mike.

[1mark]

Is the bolt stripped down? What brand gauges are you using?

[Dean-DGR]

The pull through reamer should have a thrush bushing on the end that rest up against the bolt face. The thickness of the bushing will determine how deep the reamer will cut. The bushing can be anywhere from .251 to .255 and still work. I like the .251 bushings for most of my work.

Also, I have only had this happen once and this is why I lap the bolt face...but I had a bolt that had a very slight ring around the inside that caught the headspace gauge but not the reamer. Once the ring was lapped down the headspace was correct.

Oh and of course...Forster Go gauge will measure a slight different from a Clymer gauge.

Dean-DGR
www.dgrguns.com

[mdoerner]

Clymer headspace gages and pull-thru reamer. You'd think they'd have gotten the tolerance stack correct. Tried it with the WRA bolt I am going to use and also with a spare SA bolt I have lying around, but gave the same result.

Measuring the depth of the thrust bushing it is a hair over 0.249". Looks like that's where my issue lies......I'll see about shim material today.

Mike D

[Dean-DGR]

I cannot recommend enought that you just ordering another thrush bushing. Messing with shims just sounds risking. I use Manson reamers and bushing and I believe .253 is their standard length. I have never had a problem with the bushings being interchangeable with manufactures. Manson can be reached at 810-953-0732. I just ordered and received two finish reamers from them. Good people.

Thanks, Dean-DGR
www.dgrguns.com

[Dave Waits]

Dean's right Mike, your thrust-bushing is probably the problem. Clymer makes good stuff, they'll take care of you. Get ahold of Ken and tell him what's going on. ken@clymertools.com

[mdoerner]

I'll call 'em sometime next week. In the interim, problem fixed....a 0.004" brass shim between the bolt face and thrust bushing has taken care of the problem. Closes on GO and does not close on NO GO. Dunno if it would spin freely with the shim, but the point was to get enough bite to get the GO gage to close, and the NO GO to not close.

I've enlarged the gas port to 0.104" with a #37 drill bit (for .308 Winchester), so on to final assembly. I can go bigger later if I need to, the spec I think is 0.105" +0.0015" off the top of my head. I will re-park parts once the weather here in NE Ohio warms up a bit. Maybe a photo op for all the different colors (Olive-Park, Dark Gray Park, Greek Black Park, Winchester Browned Park, etc...) may be in order for people to help distinguish what's "new" parkerization vs. what's "old" parkerization, since I've got the colors of the freakin' rainbow goin' on right now.

Thanks for all your help everyone, I'm sure I'll be back with a ".308 Win Garand shoots high and to the right at 100 yrds, but low and to the left at 600 yrds" once I get some boolits down the tube....

PS Thanks for the contact at Clymer. I've emailed him, we'll see what they have to say.....

Mike D