View Full Version : Head space?

June 13, 2002, 09:49
Thank you for all of your help with the head space problem.

However, I just used the procedure you'all explained and for some reasin the bolt closes on the 262+ZZ guage and not the locking shoulder of the same dimmentions. But, It does close on the 260 guage just as easy (two thumbs). Could it be I found the correct head space then? This is using the go guage installed (forstner).

June 13, 2002, 11:40
It has been my experience that you must use a locking shoulder of .001" SMALLER in order to get the same fit you got with the pin gage.

i.e. closes with firm "two-thumbs" pressure on a .258 pin gage, better use a .257 locking shoulder to get the same fit.

I recommend setting HS to close with firm two-thumbs pressure using a pin gage and the .308 Winchester NO-GO gage. I think you are messing up if you try to do this with the GO gage.


If you run a search for prior posts on headspace dimensions, you will see there is much debate and disagreement over what is the "correct" headspace for a FAL. One camp says the right dimension is 1.632. The other camp says it is 1.635. Some even say 1.630 (apparently because this is the SAAMI GO-spec for .308 Winchester).

I have measured the "headspace" dimension of lots of .308 and 7.62 ammo. All of it measures under 1.630 (most of it 1.627-1.629).

Suit yourself. If you are only shooting under very clean conditions, and you like 'em tight, you can probably get by with setting it to minimum dimensions. Just, don't drop that rifle in the mud, and expect it to function.

Me, I say 1.635.

Upside Down @ 100 MPH
June 13, 2002, 11:56
Originally posted by gary.jeter

Me, I say 1.635.

I second that. For reliability reasons.

Wright Brothers Gunsmiths
June 13, 2002, 12:13
Take it to the range and shoot it. It is NOT too loose, it MAY be a little tight. If it shoots well, shoot a few rounds(say 50?) and recheck the fit. A break-in period will allow parts to seat in and tight headspace will often times result in better accuracy IMHO.

June 13, 2002, 18:11
Well , I guess FN didn't design the FAL for combat. If they actuallly thought the FAL would have been a main battle rifle, then they wouldn't have specified the minimum headspace to be an "unreliable" 1.6315". I don't commonly throw my FAL's into the mud with the actions open; but I seriuosly doubt that, if I did, that 0.003" additional headspace would make ANY difference in its ability to function (unless I was able to limit the amount of mud I chambered to around three thousanths in just the right area). I've watched the evolution of the reasons for 1.635" go from "its Nato minimum spec", "Kuhnhausen (sp.?) states 1.635" minimum for 7.62 Nato", and other such MISAPPLICATIONS of the minimum headspace spec for the M-14/M-1A to "I only shoot 7.62 Nato", to safety, to "its to tight" for reliability.

Gary, do you headspace your new build M-1A's to 1.638" or 1.639" (three or four thousanths above the minimum spec of 1.6355")?

Is there anything wrong with headspacing a new build FAL at 1.635"? No, its within field reject spec for both 7.62 and .308. Are there any disadvantages? Yes, there is a service life reduction of 37.5% for 7.62 and 50% for .308 usage before you must take the gun out of service and rehab it with another locking shoulder. Isn't it preferable to change locking shoulders as few times as possible to minimize enlargement of the receiver's locking shoulder hole to the eventual point where the receiver must be discarded? NONE of the experts or manufacturers support a minimum headspace of 1.635" for the FAL. Why should an FAL builder headspace to the minimum headspace for the M-14/M-1A?:rolleyes: :rolleyes: :rolleyes: :rolleyes:

June 14, 2002, 08:57
uh-oh here we go again:D IMHO which has changed since becoming a member of this board, it really comes down to how you are going to use your rifle. if you are going to be shooting alot then it is probably better to headspace the rifle closer to 1.632 for longevity reasons. but if you are only going to put a couple hundred rounds through it every year, then if the locking shoulder that came with the kit gives you a headspace of 1.632- 1.635 then that is what i would use.

June 14, 2002, 15:20
Ditto to that, HD99FXR3.:cool: