Sizing die dimensions vs reamer dimesions

W

Wm Cook

Member
I'm setting up a .308 for F/TR competition. I'm using a Type S Redding bushing die and the Krieger barrel that was chambered by a trusted gunsmith.

Cases that are fire-formed measure .4561 at the shoulder. Saami specifications for the .308 Winchester looks to be .4539. After forcing the case into and out of the die the die I get approximately .4532 at the shoulder which means the shoulders were squeezed back .0029".

So I assume the die is correct. At least the SAAMI spec of .4539 and the Redding die producing a sized case at .4532 seems reasonable. After initial fire-forming I've resized about 50 cases and though none stuck in the die they sure as heck were harder to get in and out (using Hornady one shot and I also tried sizing die wax) than I expected.

So after the range visit I took three cases and averaged the shoulder width change and the shoulder bump back.
- The shoulder was pushed in an average of .0036" with the Redding die
- The shoulder was bumped back (using Redding competition shell holders) to where I had a snug closure of the stripped bolt that averaged .0021.

As a heads up I gotta tell you I'm spoiled. As a short range PPC benchrest shooter all we have to do it send some fired cases to Harrell and he sends us the die we need to match our cylinder. So this is the first production sizing die that I've used for quite a while. And I'm somewhat handicapped as I am using a dusty old RCBS Partner press that I used on all of the small calibers I shot back in the 90's. So maybe the .0036 resizing at the shoulder is within industry standards? And I just need a beefier sizing press??

So here are the questions:
- Is it normal for a sizing die to push the shoulders in as much as .0036" in order to yield .4532 within industry standard of a SAAMI spec of .4539.
- Is the chamber that produces a fire-formed case (measured at the shoulder) .4568 (versus the SAAMI cartridge speck of the .4539) oversized?
- What options are there for a .308 Winchester custom die.

On a positive note the last group I shot with this rig yesterday was a nice .250 @ 100 yards so I see light at the end of the tunnel. Just gotta get the sizing die thing sorted out.

Thanks for listening. Bill.
 
No die from ANY manufacturer will ever fit ANY chamber of any sort, custom or factory except by pure luck.

ALL rifles need to be fitter per chamber just like a PPC for them to work properly.

The brand, "quality" or size of the press has no effect either positive or negative.


opinionby





al
 
And BTW there are blessed few people on this planet who can get two chambers the same diameter using the same reamer.

Same "headspace" pretty much any hack can hit, "same headspace" though is a non-issue.

It's SIZE that matters.
 
Bill - Look at it in another perspective for a moment. If you can live with the die you have and continue to shoot a quarter inch at 100 yds...then you're good to go. If for some reason you can't live with the way it is now. you can have a die made to any specs you wish. Forget those SAAMI specs...just don't oversize the cases in fear of premature failure.
 
My concern is about over sizing. pushing the shoulders back +.003 seems a lot to me and I would rather have the faith in a Harrell sizing die that pushes pack to chamber dimensions +/- .001. I'm just getting to anal about this. Maybe I should just buy a heavier sizing press and slam the cases back to the .003 that the die is cast for. Shoot them and replace brass as necessary. I'm just a nit picker. Benchrest competitions does that to a guy.
 
Alinwa is right

The chances of an off-the-shelf sizing die matching any chamber cut by the finest gunsmith in the world is about as close to zero as it gets.:rolleyes: The only answer is standardization and I don't mean SAMMI specs, which are better than nothing but nowhere near what is necessary for benchrest or F class accuracy. I believe it's the gunsmith's responsibility to know all dimensions of his chamber reamer and to see that the shooter has a sizing die that is perfectly compatible with that chamber.

On page 99 of his book, "Extreme Rifle Accuracy" Mike Ratigan states, "Proper full length resizing is the single hardest mechanical thing we do."

If you have not read Ratigan's book, I highly recommend you do so. I regard it as the most useful information a benchrester or F class shooter can have in his library.

This area of precision shooting and extreme rifle accuracy is my main pet peeve developed over thirty years in benchrest.
It's downright disgraceful the way many rifles handle. Loaded rounds should chamber as smooth as butter and the fired cases should extract effortlessly with no click-at-the-top. If a rifle is built and set up correctly, this can be accomplished even if a shooter is known for shooting in the upper load window. Your gunsmith is the one to consult about this. He should know.

FWIW

Gene Beggs
 
Why not try to set the sizing by chambering a sized case with firing pin and extractor removed from the bolt. When the bolt handle just drops freely, you have all the sizing you need.


Only If this doesn't work, should you look for a new die.
 
i disagree.
if his cases are as big as he says they are( and his loads are safe and reasonable), he needs to go back to the gunsmith and fix the PROBLEM.
AND QUIT WORKING ON THE SYMPTOMS.

powderbrake said:
Why not try to set the sizing by chambering a sized case with firing pin and extractor removed from the bolt. When the bolt handle just drops freely, you have all the sizing you need.


Only If this doesn't work, should you look for a new die.
Click to expand...
 
just an idea

Bill, going back to your first sentence about the barrel was chambered by a good gunsmith. Why don't you go back to him and have him prepare a custom sizing die to match the chamber he produced? Provide 3 fired cases fired three times.
He buys the die you want, maybe a reamer and presto You have your Harrells set up?
Just my 2 cents worth.
Centerfire
 
I believe you're right Centerfire. Buying a reamer for a sizing die to size the cases to match the bore is the only practical solution. I have two fresh barrels chambered with this reamer so its economically practical for me to go that way.

Seriously, I'm just concerned about working the brass back +.003 at the shoulder when using the stock die from Redding. I'm trying to contact Redding to ask the simple question as to how much shoulder push back (.0015 vs .0032) is a realistic target. In fact I'll call Harrell tomorrow and probably learn a lot with that conversation. I am still amazed that he answers his own phone and is always on the production floor.

Till then I have a heavy duty press coming in tomorrow that will make it easier to mash the brass into the dimensions of the Redding die so I can at least keep shooting.

As a side note. One .250" group means nothing. The Redding competition sizing shell holders patches up some of the problem but short of buying a reamer to fit our chamber the .308 and other calibers have no precision sizing die that we can count on.

We dwell on that one .250" group just because we're frustrated and we need something to think positive about.

I might be wrong but brass is the number one thing you have to have right for consistent sub .250" groups. We all know powder needs to go up or down pending temperature and humidity. But the right powder, a quality bullet and properly prepared brass is the underlying basis for accuracy.

Assuming optimum bench shooting protocol is followed.

Thanks for the help.
 
msalm said:
I’ve read about, but not tried yet, lapping out your sizing die to provide the proper amount of sizing. There is an excellent gunsmith book out there by William Hambly-Clark that has a whole chapter on refitting factory dies for a specific chamber. The book is excellent in its entirety.

https://www.amazon.com/Centerfire-Rifle-Accuracy-William-Hambly-Clark/dp/0990568733
Click to expand...

This is a great book. I have a sizing reamer spec'd from my chambering reamer. Remember, if your brass is old or used enough that it has no spring back, chunk them. Mine is .003 smaller at the shoulder and .002 smaller at the base. Works great for me.
 
Thanks for that. Lapping compound and the same shell holder we use to turn brass did cross my mind but not knowing how to approach the difference in the metal hardness had me stymied. I have most accuracy geek gun books the most recent being Mike Ratigan and Boyer's book. But I don't have William Hambly-Clark's book. Yet. But after internet skimming Boyd's suggestion of Whidden, Hornady, and Jones could be taking the path of least resistance. Maybe a couple of calls in the morning is in order. Thanks for all of the help. I'll let you know how things turn out. Bill.
 
And no matter how well you match the die to the chamber as the hardness and spring back of the brass change the size of the shell will vary.

Even if everything else is the same.
 
brickeyee said:
And no matter how well you match the die to the chamber as the hardness and spring back of the brass change the size of the shell will vary.

Even if everything else is the same.
Click to expand...

That is time to $hitcan your brass.

Have a friend that built a 30BR for his brother. After a bit brother needed another barrel. Head space exactly the same as the old barrel, same reamer and so on. He had a very hare time extracting the brass. He sent me a sample of the brass fired in each chamber-unsized. It was also unmarked so I wouldn't let it alter my thoughts. Ball mic showed the necks were the same, head space within .0002, shoulder diameter the same, diameter above the extractor groove the same, and over all length the same. The problem was solved when new brass was used. It had about 30 firings on each round.
 
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