Any tests should use new brass
7.62x54r Headspace Gauge
I am in the process of rebuilding a beatup 91/30 that I bought for about $55. Had some missing parts, cracked stock and a mis-matched bolt.
I have the entire gun stripped down, cleaned and the bolt is running smoother than my first 91/30 (which I am keeping in as issued condition).
As the bolt is mismatched, I am abit more concerend about headspace on this one than my original one.
As a crude preliminary check:
The bolt closes without issue on a previosuly fired casing.
The bolt will not close on a casing with three layers of clear packing tape on the base of the casing.
As I shouldnt be risking a bolt to the face based upon the results of a piece of tape, I figured I should do a more legitimate headspace check.
I see I can buy one at http://www.okiegauges.com/
Should I get a no-go or field?
or does have one that I can borrow to check it out?
Thanks
I have the entire gun stripped down, cleaned and the bolt is running smoother than my first 91/30 (which I am keeping in as issued condition).
As the bolt is mismatched, I am abit more concerend about headspace on this one than my original one.
As a crude preliminary check:
The bolt closes without issue on a previosuly fired casing.
The bolt will not close on a casing with three layers of clear packing tape on the base of the casing.
As I shouldnt be risking a bolt to the face based upon the results of a piece of tape, I figured I should do a more legitimate headspace check.
I see I can buy one at http://www.okiegauges.com/
Should I get a no-go or field?
or does have one that I can borrow to check it out?
Thanks
1 - 14 of 14 Posts
Why? Concerned the extractor deformed the rim? AFAIK this cartridge headspaces off the rim. And, isn't the "brass" steel?wreckhog said:Any tests should use new brass
Three layers of cheap packing tape is 6-9 thou dependng on whether you have the cheap thin stuff that looks like the brown tape or if you have 3M tape which is just shy of 3 thou per layer (3 layers will measure .0085). I don't know what the headspace is supposed to be but given the era of the rifle and its intended use I expect fairly loose tolerances. I also doubt that a commercial headspace guage is going to be less than .010 and by comparison a matchbook cardboard is about .015".
Perhaps someone on here knows what the spec tolerance is on a MN, but although I have seen numerous places selling headspacing tools, I have never seen the dimensional tolerances published. Kinda makes you wonder about those tools, doesn't it? I have also never personally heard of a MN headspace problem in spite of MANY rifles being Frankenrifles.
I bought the three gauges from okie. I will measure the three for reference, i do seem to remember the dif between go and no go being minimal.
That would be relaly helpful and I have a digital mic that reads tenths should you need it.ASSAULTFUN said:I bought the three gauges from okie. I will measure the three for reference, i do seem to remember the dif between go and no go being minimal.
The old man is a Machinist. I dont think ill need the mic, but i do appreciate the offer Captain. Ill post this evening.
Go- .063
No-Go- .070
Hope this helps 8)
No-Go- .070
Hope this helps 8)
It should close on a go gauge with no problems. It should not close on a no go gauge. If it closes on a no go gauge, you have a serious problem. If it closes on a field gauge, then the rifle has reached maximum safe head space, should be checked with a no go gauge before firing, and will likely need to be adjusted soon.
GREAT! Rim spec is .063 allowing .007 to the no-go.
OP's ideal headspace would be two pcs of (3M) tape LOL!
Cartridge spec diagram:
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Mosin 1942, I think you have field and no-go reversed- AFAIK field guage is the BIGGEST (allows most headspace). it was not posted but I'm guessing it'll allow somewhere around .010 headspace, or .073 thick. I suspest OP's gun falls within field gauge limits as is, he's gotta be somwhere ,006-.009 even with the crude "tape layers" measure (which actually is not all that bad until you have several layers of it)
OP's ideal headspace would be two pcs of (3M) tape LOL!
Cartridge spec diagram:
Mosin 1942, I think you have field and no-go reversed- AFAIK field guage is the BIGGEST (allows most headspace). it was not posted but I'm guessing it'll allow somewhere around .010 headspace, or .073 thick. I suspest OP's gun falls within field gauge limits as is, he's gotta be somwhere ,006-.009 even with the crude "tape layers" measure (which actually is not all that bad until you have several layers of it)
Mosins headspace from the rim, so even a "loose" headspace measure will be OK. I have several Mosins, and have never bothered to headspace any of them, and they shoot fine. No split cases with either brass or steel cased ammo.
This too, but it never hurts to check with a mismatched bolt/barrel combo. Personally I just try to avoid mismatched rifles so I can avoid the headache.Mad Russian said:Mosins headspace from the rim, so even a "loose" headspace measure will be OK. I have several Mosins, and have never bothered to headspace any of them, and they shoot fine. No split cases with either brass or steel cased ammo.
The only reason we purchase was to do a few builds with those heavy machine gun barrels from Classic. Still working on it, we need to turn down the barrels some for visual reasons, also just got some of the Richards Tackdriver stocks...very nice. Ill get pics up when finished.
Let me know how that barrel works. I've got a mosin that was used for parts as well, and thought about rescuing it by doing the same thing you are.
1 - 14 of 14 Posts
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