View Full Version : Headspace check

June 23, 2002, 08:17
Okay, it's a grade 1 Imbel, on an Imbel NGL. Assembly went pretty smooth. Had to take the barrel shoulder down a little to torque to TDC. I am using GO/NOGO gauges from Forrester. Here's the question. It takes a little pressure to close on the GO and it definitely will not close on a NOGO. The LS is .260. Am I too tight or is she okay? I did not use pin gages to set headspace with. I just put in the LS that came with the kit, could'nt wait for anything else in the mail. I got caught up in the moment. I'd like to thank all you guys/girls for your infinite knowledge and wisdom as it made this project relatively easy. This is the first build and now I hear the G1 talking to me.

June 23, 2002, 09:25
The last three kits (2 G1, one STG) I bought came with .260'" locking shoulders.

My last rebuild came out at .266" while "common sizes" run from .254 to .272" depending on the source.

Sounds like you're okay. Go shoot.:)

June 23, 2002, 12:16
Closing on 1.630" Forster go gauge with "light" pressure (as opposed to firm two thumb/finger pressur) indicates that your headspace is approximately 1.6305" to 1.631" before initial firing and any setback of the locking shoulder. Accounting for the nominal 0.001" setback allowance upon initial firing, your should have a headspace of 1.6315 to 1.632" after initial firing which is right at FN's minimum headspace spec of 1.6315". You are good to go

You don't want to start out shooting out of spec (loaded in excess of 1.630") mil surp with high primers as there is the chance for an out of battery ignition and serious injury of death. Port, Hirt, and SA all seem well within spec (loaded to below 1.630" headspace), but you should check for high primers and discard any ammo found with high primers (good advice whether your gun is at minimum headspace or not).

June 23, 2002, 12:43
Thanks guys, now it looks like I'll have to polish the receiver feed rails. It won't chamber from the left side of the mag and does the bolt over, round half in-half out thing. The brass is being gouged pretty good. So we'll use a little 400 grit sandpaper to break the edge.

June 24, 2002, 01:46
Try polishing the contact surfaces on the bolt itself- not the reciever. The two lugs on the side of the bolt can be rounded a bit for better cycling. Also try a rat tail file on the barrel itself to add a feed ramp on the barrel. If you change the dimensions of the feed ramp on the reciever you may have worse problems.