tight chamber dilemma

W

woodbutcher

New member
I had a reamer made for a 300 WSM and I told the reamer maker to grind about .003 or .004 tolerance at the base. I did not send a dummy round for him to go by. After I chambered the barrel I test fired into the ground and found the primary extraction to be hard. I also had loose primer pockets and ejector marks along with the bolt click. I dismantled the gun and polished the chamber with 240 grit paper soaked in WD-40. After putting the rifle back together I still had these signs, but to a lesser degree. I was trying to use Norma brass and I got to thinking Winchester brass may be dimensionally smaller. I called a friend who gave me four pieces Saturday. I loaded up one round starting four grains under maximum load with no pressure signs and no bolt click. I worked up three rounds with a grain higher and for the most part everything went well except some of the the rounds did not spring back as much as others with a very slight bolt click and slight scratches at the web, but no ejector mark or loose primers. I really do not want to take this gun apart again. Can I alleviate this problem with custom full length sizer or what other options might I have. No more tight spec chambers for me.















W
 
I guess I don't understand your statement that you had the reamer maker grind .003-.004 tolerance at the base. A tight spec chamber doesn't necessarily mean smaller.
Butch
 
I had the reamer made to be as tight as possible in the webb area thinking the brass and primer pockets might last longer.
 
Get your reamer maker to regrind that reamer making the web area the correct size. I had a .270 Winchester reamer that was specially ground tight on the web area (to fit the lousy under size Winchester brass) and had nothing but problems... I had it reground and no more problems with the finished chambers now...
 
Kinda' hard to regrind it bigger Dennis! :)

BUT, the hard and true lesson here is simple..... YOU CANNOT CONTAIN THE CASEHEAD!!!!!

Nor can you resize it.

There is no "small base die" to fix the problem.

Your chamber is too small, you're screwed. Rechamber or polish out.

I'm still flabbergasted by the number of custom makers who believe that smaller chambers or boltfaces "make primers last longer." Pure rubbish.

al
 
alinwa said:
Kinda' hard to regrind it bigger Dennis! :)



al
Click to expand...

Not really... the reamer is tapered... they just start at the throat and regrind everything farther back on the tapered reamer... far enough that the taper is left large and then ground to the correct dimensions... :D
 
I had already talked with the reamer maker and he can regrind the reamer. I will probably polish first. This is my first experience with tight spec reamer; probably my last. I knew Alinwa had addressed this issue before so i was curious about what the response would be. Thanks for the replies.
 
I have been fighting a number of tight reamers and I think I will end up with a different reamer maker in the end. A tight reamer is okay in theory but when you can't buy a die that works it is just too tight. After looking at a number of dies from the same maker with the same specs they are nothing special either.
 
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I guess with some reamers that would work Dennis..... I stand corrected. ;)

Altho my .010/inch tapered stuff would have to be ground back perty freakin' far. I forget that most people use radically tapered cases.

I'm just glad to see people learning this stuff, but it is a hard road. I've quit using several good gunsmiths because they won't listen and want to argue. They couldn't get it through their heads that my philosophy is and will always be-- "Remember, I'm paying YOU!"


al
 
from what i have found opening the chamber only delayed the clicking but did not fix the problem which was too much pressure,if the case head went to .003-.004 over new dia it clicked but when i backed down my loads life was good again. the case heads held at .002 for 5-7 firings on my belted mags. i know this may sound wacky it really works well so far.i have opened up a few chambers now for clicking and other reasons and have pretty much made up my mind to keep doing this on all chambers from here on out if needed.what i did was with the barrel in the lathe and with the reamer in the chamber paying attention not to push inward to create more headspace but yet still all the way in, pushing sideways slightly by hand for just about 30 seconds or so has equaled about .002 in total diameter ,but i chamber at slower speeds. by this method i can basicly adjust chamber diameter to match or use it to fit the die better with the same reamer.but carefull measuring is a must.hope this helps sirs. tim in tx
 
I'll change the neck and throat dimensions of a reamer but there is nothing to be gained in changing the body dimensions of a standard case except trouble.
 
clowdis said:
I'll change the neck and throat dimensions of a reamer but there is nothing to be gained in changing the body dimensions of a standard case except trouble.
Click to expand...

I can second this from experience. There has to be enough room at the rear of the case - too little and the problem that started this thread rears its ugly head.
 
Henry,
If the base of the reamer is too small you won't be able to size the base enough to chamber the round. That is unless you make a custom die with a smaller base.
Butch
 
Butch Lambert said:
Henry,
If the base of the reamer is too small you won't be able to size the base enough to chamber the round. That is unless you make a custom die with a smaller base.
Butch
Click to expand...

Hi Butch,

That's what I'm saying. Kiff re-ground the reamer (set it all back) and that fixed it.
 
I got a reamer print and found that I had .0015 clearance at the beginning of the shoulder and .0035 clearance .200 from the base of the cartridge.
 
.0035 at the base should be OK. Tight, but not too tight. .0015 at the shoulder seems a bit tight, but should just be a bit of a nuisance.

BUT, from your original post:

After I chambered the barrel I test fired into the ground and found the primary extraction to be hard. I also had loose primer pockets and ejector marks along with the bolt click.
Click to expand...
emphasis mine.

What do you look for as signs of too-high pressure? I'd say they're all there.

See how extraction is with a load that doesn't leave ejector marks or loose primer pockets.
 
I can load 72 grains of VV N550 in a Winchester case and achieve 3765 fps with no pressure signs; brass life 3 to 4 rounds. I shot two different powder charges and two different kinds of brass for a total of three shots into a .250 hole. This combo of slow twist barrel and light bullets has worked in a number of guns reaching 4000 fps. With accuracy I am getting I will probably not have the reamer reground to do a rechamber . Groundhogs are almost extinct now because of the coyote population so the extra velocity is probably not paramount.
 
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