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need some info/help/advice , taking the SAinc. parts off my new #9102ca and replacing with TRW parts , trigger group / op-rod / bolt (new) , trigger group fits great as does the op-rod , the rifle was headspaced at the fac. at 1.634 as per the tag , it is an H&R bbl , I have a foster gage for 7.62 Field , will this work to check the headspace on a new rifle / bolt , have never worn one out or needed to replace a bolt , just want a USGI M1A (as close as I can get) and like TRW's ....MOJO.... as it's been called , will I need a set of go / no-go gages ?
 

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Yes, you should get a Forster GO gauge 1.630 and NO GO gauge 1.634. If these Forster headspace gauges are like mine, they are for .308 Winchester not 7.62 NATO. Though they can be used for measuring the 7.62 NATO too, there is a difference in the lengths and headspace of the .308 Winchester and 7.62 NATO.

If the bolt does not close on the GO gauge 1.630, you have too tight a headspace. Depending on how much contact the bolt's lugs have, less than 95%, you will need to lap the bolt. If it has 95% contact, you will need to try another bolt because you cannot ream chamber on chrome lined barrels.

If it closes on the NO GO gauge 1.634, this is acceptable for shooting 7.62 NATO and 308 Winchester.

If it closes on the Field gauge 1.638, it may be acceptable for 7.62 NATO but NOT .308 Winchester! If it is a new barrel, headspace should not exceed 1.636 for 7.62 NATO.

I strongly recommend you buy a copy of Jerry Kuhnhausen's book, 'The U.S. .30 Caliber Gas Operated Service Rifles, A Shop Manual Volumes I & II'. He explains this in detail and you should read it very carefully! If you are not sure of what you are doing and "screw the pooch", your rifle can explode seriously injuring or killing you! You can purchase this book from
www.fulton-armory.com.
 
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