is .013 safe headspace on a 7x57 Mauser

rci2950

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I used a piece of small soldier stuck to the head of a brand new brass case with solder. Closed the bolt and measured it with my callipers. it measures out to .014/.013. Would this be considered within tolerance?

Thank you
 
I looked on the SAAMI 2015 chamber drawings. From breech face to the specific reference point on the chamber shoulder slope, they call for 1.7947" minimum and 1.8047" maximum - so to be SAAMI compliant, there is 0.0100" difference minimum to maximum for SAAMI 7x57 chambers. For SAAMI compliant cartridges, the minimum is 1.7995" - minus 0.0070". The idea is supposed to be that the maximum size SAAMI cartridge will chamber into the minimum size chamber; and the minus size cartridge will fire and not rupture in the maximum size chamber. I have no clue what dimensions that European or pre-SAAMI makers used. If you truly do have .013" difference between cartridges that will chamber, then you will be above the SAAMI criteria - and Euro C.I.P. will have their published standards, which I do not have, and no doubt original German makers that were pre-SAAMI will also have their standards.

If you hand load is not an issue - you should be sizing your brass to fit your chamber - not really too concerned about anybody else's standard - is only an issue if you insist or want to use commercial made ammo from time to time - if made in North America, the ammo should (but does not have to) meet SAAMI criteria. If the ammo was made in Europe for use in a European country, it MUST meet C.I.P. criteria - most (but not all) Euro countries have that as law.

By the way - what you did or similar is done often, but is not really a measure of your rifle's headspace value - you are relying completely on whatever dimension that brass might be, and no allowance is made for anything compressing - you need to use a ground steel "GO" gauge, which will be minimum SAAMI length for the chamber that is what it was made to check - then can shim or whatever from there to find out how far you are past SAAMI dimensions, if at all. Basically same story for a C.I.P. gauge or a pre-SAAMI maker's gauging. For what you did, some people use masking tape layers or Scotch tape layers - probably a better idea to do 5 or 8 or 12 cases from more than one box of factory shells - but is all really depending on the brass maker to get it correct. The ground steel "GO" gauge is the correct way to do it - and completely strip your bolt - no internals on the bolt body, at all. Forcing the bolt closed is not really a measurement - need to "feel" when contact is made - is actually a moderately "delicate" thing to measure headspace - like one finger-tip pressure on the bolt knob when closing it.
 
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awesome. I will fire a few test shots to check for any problems signs on the brass with factory. I also ordered a neck sizing die. I handload all my ammo after i have established enough brass anyway. So wont be an issue. I am glad this will work out. It is a beautiful rifle. Zastava M70 with Timmney trigger, I refinished the stock and it turned out magnificent. I removed the terrible checkering and put a couple dozen coats of Tung oil, steel wool etc. The I replaced the entire bolt instead of trying to track down a bold shroud with a safety. I have a clapped out BRNO 21 of the same caliber as doner and it slid right in and fits perfectly. I buffed the bolt to a brilliant sheen (I didnt go anywhere near the lugs) . I couldn't be happier if this works out as i hope. I am hoping to have this as my main deer slaying rifle. The weight, balance and recoil of the 7x57 round make the perfect combination. My shots on deer are usually within 60 feet. But the rifle is topped with a Leupold VX 2 anyway. Because its not a deer rifle without a scope. You know how it is.

Thanks for the help. I really appreciate it.

Adam
 
Headspace - the Great Satan. The lengths people go to "correct" it is extreme, especially with the 303 Brit, where people search the earth for a "correct" bolthead so that the headspace is within spec, and ignore the fact that the chamber is huge and do nothing about it, just living with brass separating after two firings.

What do you mean by "safe"? If someone says it's not "safe", will you have the barrel removed, set back and rechambered? I doubt it.

You could and should do what most do - neck size or minimally F/L size your brass to fit your rifle, so as to maximize its usable lifespan. There's no danger in that.
 
OP, you did not mention it, but perhaps you want to verify that the lugs on that replacement bolt actually mate against the recesses in that receiver. Strip the guts out of that bolt body. Mark up rear faces of the bolt lugs with black jiffy marker. A couple ways to apply pressure, towards the rear, while working bolt handle up and down a few times - then remove bolt and look at the jiffy marks - some books talk about 100% even and equal contact. Maybe custom finely machined actions can get there - in my world, both lugs bearing, and about 50% or more contact on each seems pretty good. Any grinding or lapping that you do on bolt lugs to increase lug contact will just be increasing headspace dimension. The BRNO / Mauser was designed for both lugs to share the load of the cartridge being fired, I think - about worst is to have all that load taken by only one lug, and the other one does not contact it's seat.
 
OP, you did not mention it, but perhaps you want to verify that the lugs on that replacement bolt actually mate against the recesses in that receiver.

As a matter of fact, i am getting my son ready for a trip to the gun smith. He is the best in the province. About an hour and a hlaf road trip but worth it. I had already planned on letting him give it a once over. I should know what he thinks today.

update: i am back from the smith

Well, the headspace was no good. We put the original bolt back in. Changed the shroud to a standard M98 one and put a low throw safety on it. Problem solved!

and of course a picture

 
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