[CaptMax]

I posted this on the FALFILES website but am waiting for an answer there and thought I would try here as well. This is my first FAL build so I really want to get it right. Here is the question: I'm using a 1.63 Forster "GO" pin gauge in the freshly cleaned chamber. I found that a 2.62 pin gauge would allow the bolt to close tight under a little "two" thumbs pressure and it would no way close on the "No-Go" gauge. This was as high a number pin gauge that I could use and still get the bolt to close & then checked it again with the No-Go gauge in there where it would not close.
If I add +.001 to this to allow for "set-back" after break in that would mean I need a 2.63 locking shoulder, correct? I think my original locking shoulder that came with the kit is this. I will confirm what it is with my dial calipers.
Does this look correct to you or should I add +.002 as someone previously told me? Just trying to confirm before I press a locking shoulder in place. Thanks for the help guys, CaptMax

 

[IMBLITZVT]

Its not a for sure thing. I had little set back but you do not want the bolt to need pressure to lock. Remember the specs are pretty great and you will want it to work for 7.62 and 308. I would think you would be looking more at a 2.61 because the 2.62 was a little tight from what it sounds. Then if you get .001 set back you should still be fine... I think. Maybe just go with a 2.62 but I do not think adding to it is a good idea because if its to tight, thats will give you an out of battery were if it to loose you will just split the brass... however its been 2.5 years since I did mine...

I would suggest gunthings.com for the locking shoulder... they let me return one after it was installed and tighten my headspace up a bit. You can not get better service!

 

[TARGSHOOT]

best head space for .308/7.62 is 1.634 to 1.636 you can fire either at that headspace. minimum headspace .308 commercial is 1.630.

 

[CaptMax]

Thanks for the replies. It didn't take "alot" of pressure to close but it was "kinda" tight with the 2.62 pin gauge on the "GO". I may just take a break until morning and see what the gurus at falfiles have to say. I'm anxious a ever to get this completed and try it out. This proves to me John Brownings design is alot simpler!!!
CaptMax

 

[IMBLITZVT]

Yeah man, do not do quick when you are setting off explosions a few inches from your head! Thats good advise. Take your time and make triple sure you do it right. The guys on FAL files will get it perfect... I think I looked at every thread on that forum when I did my FAL.

 

[CaptMax]

Yeah I will be positive I have it correct before I fire it. One of the guys over there has been a real help. He sold me two DSA receivers at a great price and then loaned me all his build tools for it too. I hope he decides to build a 1919 so I can return the favor!!! I will post a pic when I get it done. The next question is what do I build next? So far AK's, 1919's, and soon STG58's, so what's next???
CaptMax

 

[fal_specialist]

If it locks snug w/a .262, go w/ that. I "used" to headspace them that way and still do if a fellow is building a bench rifle.

If h-spaced tight on a .308 gauge, expect a lot of break in before random nato will chamber easily. I sometimes had to strip the same nato rnd twice out of the mag to get it squished enough to chamber.

Actually the FAL headspacing system is of superior design to many rifles. If the receiver stretches, merely pull the shoulder re-gauge and install a new one.

I did a routine maintenance check on a guys factory SAR-48 and a no-go gauge chambered easily. The rifle shot fine too.
Overall mileage was un-known though.

It's always good to start out snug, but many service grade military weapons are not built with super tight tolerances.

Larry

 

[gska3873]

Typical rule of thumb is once you have the proper gage pin selected with the "light"pressure required to close you should subtract .002" to get to the nominal headspace size then add .001" for set back (basically just subtract .001" from the gage pin). Remember to make sure you are doing this with the extractor removed from the bolt.

 

[CaptMax]

Got it, thanks guys!!!
CaptMax

 

[shortround]

gska3873 has it right. Look at it like this: When you find the pin size that will allow the bolt to close on a Go gage with minimum pressure, your headspace will be at minimum of 1.630. Ideally, you want to be at 1.632 which would put you around the center of .308 headspace (1.630-1.634). (1.632 is a tight enough chamber for .308 and I have yet to find 7.62 that won't chamber.) To get there you want to subtract .002 from your locking shoulder size. Making it smaller gives more "play", so longer headspace. If you account for "setback", which is probably just the process of everything settling in, you want to add back .001", because setback makes the headspace longer.

So, bottom line, figure your pin guage size and subtract .001". Leave the Nogo out of the picture until you check your headspace after locking shoulder installation (it will just confuse you).

 

[CaptMax]

Got it installed, now just to get that damn extractor back in and go fire some test rounds. Thanks again to all who helped out.
CaptMax

 

[Joey2tone]

I'm learning how to build a FAL now with the kit I picked up from hochimin. I found an inexpensive receiver wrench and barrel vice and pulled the stub off. Now it's time to determine which headspace gauge set to get. Over on the FAL files I've read through some of the threads on headspacing for both calibers and it gets confusing fast. With some other builds I've done it's reccomended to have a tight headspace but not on the FAL? What gives?

 

[gska3873]

If you go with the Forster gages and the light thumb pressure -.002"+.001" you should be fine. If you want it to run a little looser for piece of mind then just the -.002".

 

[Abominog]

I always like to note that if you mic a FAL locking shoulder it most likely won't be consistent, but will exhibit up to .003 in variance. Based on this, I tend not to worry so much about absolute precision. Whatever size you elect to use, always check with go/ no go AFTER you install the locking shoulder, and make sure the extractor is removed from the bolt.