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9/17/2020 5:59:48 PM
Posted: 12/8/2005 7:30:21 PM EDT
Ok, guys, here's the deal. I just came across a Century Imported L1A1 Sporter (FAL knockoff), with an IMBEL reciever. I don't care to hear any CAI bashing, or any of that crap, start your own thread, and let the hate grow there, I just want to know one thing-

How do I check the headspacing?

Everything else on the rifle appears to be good. Decent finish, decent function... sights... check...  I'm just concerned about the headspacing.

-I've read that in the past, century was sloppy on some L1A1 sporters, like their Cetmes can be, and I just wanted to double check and reassure myself.

Is it easy to do? Should I have a gunsmith do it. I'm fairly proficient with firearms, but I don't know if I need a special tool for this, or if I can check it with some "rule of thumb" tip.

Thanks for all the help,

Link Posted: 12/8/2005 8:00:21 PM EDT
[Last Edit: 12/8/2005 8:01:35 PM EDT by Phil1712]
See if you can get your hands on a set of headspace gauges.  Usually they come in a set, a Go Gauge and No-Go gauge.  Obviously it would close fully on the Go Gauge and not close full on the no go.

Consult your Local gunsmith, they should definitely have them or you can check Brownells of Midway for a set.  
Link Posted: 12/9/2005 5:53:35 AM EDT
FYI: headspace on a FAL can be changed by installing a different locking lug.

Low down is you drive out the old cross pin, drop a headspace gauge in, and use a test locking pin to determine the correct needed pin thinkness for the correct head space.

Real question comes down to the L1a1 being inch, and chances are the Imbel receiver is metric. So unless you can get it for a few hundred, a New DSA STG-58a can be had for around $800 is is totaly metric.
Link Posted: 12/9/2005 6:16:12 AM EDT
Yet another reason I fucking Love  AR15.COM

Phil- Thanks man, I will get ahold of those somehow.

Dano- I had heard something like that before, about the locking lug. But, it's comforting to hear it again. I did get a really sweet deal on the L1A1, and yeah, it's got a metric IMBEL up top, and inch everything else. Yeah, it would have been wonderful to snag a DSA SA-58.... may I borrow $500...?


no? ok....

Link Posted: 12/10/2005 1:39:34 PM EDT
Changing the locking shoulder (not lug) is a simple procedure.  They drive in and out of the side of the receiver.  They usually run around $15 each.

Go here for more info:


Link Posted: 12/10/2005 4:12:13 PM EDT

Changing the locking shoulder is a simple procedure

now There is good news....

I just picked it up today, it looks ok to me. Gonna go shoot it tomorrow, But, if I need to, I know what to do.

Thanks again guys, for all the help

Link Posted: 12/11/2005 4:11:38 PM EDT
[Last Edit: 12/11/2005 4:13:04 PM EDT by Teflon_Tip]

Took the rifle to the range today, after an extensive cleaning. It didn't blow up on me. Worked fine, but I had to set the gas fairly high to get it to cycle reliably (at setting 1) But, that was only with 1 type of ammo tested. I used PMC 150grn.

Another thing that I had failed to take into consideration, is that the rifle was previously owned. So, had there been any significant problems, hopefully, they would have manifested themselves in someone elses hands.

Still..... I might take it to a smith to have the spacing checked.

Thanks again for all the help guys,
Link Posted: 12/11/2005 5:02:33 PM EDT
I would strongly recommend that you have the headspace checked. If the gas setting had to be set so high it may be either leaking gas, or, may have excessive HS. Did the fired cases have any primer setback or any excessively expanded case heads? Any type of functioning problem, sluggish, etc? Charles the Gunsmith.  
Link Posted: 12/11/2005 5:53:20 PM EDT
[Last Edit: 12/11/2005 5:54:06 PM EDT by Teflon_Tip]
Damn, just when I thought I was home free.

Well, yeah, now that you mention it.

Started with gas set at 7, cases ejected completely.

Dropped it to 6, still, ok, but not feeding reliably

Dropped to 5, would fire, and feed...

After that, they started to 'stick' that's the only way I can describe it. I had to tug like Hell on the cocking knob to rack the bolt back, and eject the spend casings.

it almost seemed like the casings were swelling.

Finally, dialing it down to 1, they fed and ejected.

only fired 20 rounds of PMC. total.

-Oh, and the fired cases 'looked' OK.

Link Posted: 12/11/2005 6:48:39 PM EDT
[Last Edit: 12/11/2005 6:49:45 PM EDT by 1911builder]
Perhaps the reason they were swelling is due to the HS being off, or, the chamber being 'wallowed' out. If you get the HS checked have the gunsmith do a chamber cast using 'Cerrosafe' from Brownells. The chamber cast will give you a lot of info on the condition of the throat, rifling at throat area and the chamber geometry.

If you have access to either a micrometer, preferred, or a caliper, will be less accurate, measure the case web area of an unfired round. Then measure the same area on a fired case. If the difference is greater than 0.0015 inches you probably have excessive HS. You still need to have the HS checked with the appropriate 'GO' and 'NO GO' gauges. E-mail if any questions. Charles.  
Link Posted: 12/12/2005 5:14:14 PM EDT
The reason they are swelling is because of the heat.  If the gas regulator is set too low, the cartridge doesn't eject, retains the heat and swells in the chanber.  Doesn't have anything to do with headspace.  The Go No-Go guages are the best way to check headspace.
Link Posted: 12/12/2005 6:22:33 PM EDT
[Last Edit: 12/13/2005 8:31:06 AM EDT by 1911builder]
I have tried to be patient with some of the statements made despite the appalling lack of knowledge by some individuals on this board. But this statement from French Kat is simply absurd. If you were to follow this statement to its logical conclusion leaving a fired case in a bolt gun until it cooled off, which French Kat says it cannot do, would mean that the case would be difficult to extract at best.

Also the cases eject from the bolt face after extraction from the chamber. Do you have any idea what the hell you are talking about?

Charles the Gunsmith. Cwo-3 USMC (ret) mos 2100 small arms repair.  
Link Posted: 12/12/2005 8:22:25 PM EDT
sorry Frenchie, but I gotta go with the leatherneck on this one.

Another thing that crossed my mind, is 'Might I have the gas plug in upside down?'

I don't own a manual, and I took the gun apart using an internet guide.... Is there an Open and Closed position on the plug? Might I have re-installed it in the 'open' position?  Might that be where all my precious gas is going?

Anyway, food for thought.

P.S. - I saw 'go/no-go' gauges on bushmaster's website.... Is this something I could do myself easily, or, should I just give it over to a smith to check out?

Oh, and, Charles, thanks for all the help. I really do appreaciate it.

Link Posted: 12/13/2005 5:49:57 AM EDT
Teflon -
It will cost as much to buy the gauges as it will probably cost to have a gunsmiths' labor fees to check the HS for you. If you want to buy the gauges I will talk you through the process as best I can. Thanks for the vote of confidence. Semper fi and Merry Christmas. Charles.  
Link Posted: 12/15/2005 6:01:07 PM EDT
[Last Edit: 12/15/2005 6:05:12 PM EDT by FrenchKat]
Thanks for the constructive critism Charles, had the same problem with my STG58 on an PAC Imbel reciever.  I had a gas leak at the regulator.  Once that was fixed, no problems.  

Same symptoms, failure to fully extract and then eject, had to apply some force to the charging handle to get the brass to eject.  After firing, the bolt would only some back slightly leaving most of the brass in the chamber.  Thats where the hot brass swelled just enough to cause it to stick just enough make it hard to extract with a normal charging handle pull. Remember, the cartridge is not fully seated in the chamber as in a single shot bolt type rifle.  I believe that the brass is swelling out of its normal shape.  

Worked fine before the gas leak, and after I fixed it.  

Where does the headspace factor into that?  Enlighten me.

There are several threads over on the FAL Files on just this issue.
Link Posted: 12/15/2005 6:22:44 PM EDT
HS becomes a concern both with the length of the chamber and the width of the chamber. The length of most 7.62 NATO chambers is slightly longer than the standard for 308 Win. Also most military 7.62 barrel rifle chambers are slightly oversize in width, compared to 308 Win, to allow the rifle to function with a dirty chamber, dirty ammo, etc.

A lot of mass produced chambers are also slightly larger in diameter due to chamber reamer tolerances being what they are and because the barrel is not 'indicated in' in the lathe prior to cutting the chamber. The barrel will wobble slightly and may cut a slightly oversize chamber in width that may be OK in terms of HS length.

Also, many chamber reamers get metal chips from reaming clogging uo the reamer and this will cut gouges in the chamber. Upon firing the cartridge case will expand to fill whatever space is in the chamber and if there is a gouge, or whatever, the case will be difficult to extract.

Thanks for the inquiry. Merry Christmas. Charles.  
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