View Full Version : Headspace to tight?
September 22, 2001, 18:45
I'm aware that a heapspace that is tight will cause failure to extract.
My problem, I set that headspace (without the extractor) at 1.630, the bolt will drop right on a Foster Go-Gause without the slightest force. After one mag, the bolt will not move, I can't pull it back because it appears the fired case get stuck in the chamber. I have to pry it back with a screwdriver. A new round will close fine.
With case stickin/swelling in the camber, should I headspace to 1.632 or to 1.634?
Is that what happens (cases get stuck in the chamber and cannot pull the bolt back) when the headspace it tight?
Is 1.630 tight?
thanks for resonding.
September 22, 2001, 20:10
It is a bit on the tight side.
It is generally accepted that 1.632 is the "correct" headspace for 7.62 NATO
However, see http://www.l1a1.com/cgi-bin/forums/ultimatebb.cgi?ubb=get_topic&f=3&t=003177
for comparative headspace dimensions
September 22, 2001, 20:12
For what its worth, I put together one recently that measured right at 1.631" on the Forster gages.
It eats everything.
September 22, 2001, 20:16
Have you tried different ammo to see if it is what you are using, I dont know what you are using but if it is the steel cased stuff that is your problem right there. I also headspace mine to 1.632 and have never had a problem with it taking ammo. Have you checked the inside of your chamber is it rough?
September 22, 2001, 20:41
Ammo is South African, which is all I have. The rifle is a R1 on an Imbell. The chamber seems to be smooth.
A spent case will not even begin to chamber. Is that right?
[ September 22, 2001: Message edited by: Hammerhead ]
Upside Down @ 100 MPH
September 22, 2001, 20:52
If the bolt closes easily on an unfired round it ain't the headspace. But 1.630" is tight, probably too tight for the FAL. I like 1.632" better.
Try some different ammo. It sounds like you might have some that is hot.
September 22, 2001, 23:01
"...the bolt will drop right on a Foster Go-Gause without the slightest force."
The generally accepted measurement practice calls for "two thumbs pressure" in seating the bolt. This is a moderate to firm push. It sounds like your headspace is certainly at least 1.630" and possibly closer to 1.631"; a little on the tight side but not a federal case. (Note that gary's rifle is set to that figure and runs like a Swiss watch.) Headspace will naturally open up over time; in your case, a little more time than in others. I wouldn't worry about it.
I very much doubt the ammunition is the problem. South African is perfectly good shootin' stuff and is not usually "hot." I wouldn't worry about it.
"A spent case will not even begin to chamber. Is that right?"
Posted by gary.jeter: "Sounds like this failure to extract was more likely a failure to eject that resulted in the non-ejected casing being rammed back into the chamber." "Spent cases should not be re-inserted in the chamber without resizing. They are bigger (fatter) than the chamber. The bolt slams with enough force to drive them into the chamber so tightly that it really takes excessive force to extract them."
Topic: chamber fouling question
This sounds to me like a classic case of insufficient gas pressure to properly cycle the action, as per your descriptions and gary's explanations above. I'd try to open up the gas regulator all the way for maximum pressure and see if the rifle cycles; then start trouble-shooting all the other systems like gas piston, gas tube and pin, mag fitment, carrier rails and receiver channels, dented dust cover, recoil spring etc. This subject gets thrashed regularly so you'll find a wealth of information in Gunsmithing archives as well as the FAQ. Good luck.
September 22, 2001, 23:33
Just a heads up. A while ago a friend had some trouble with the SA which I reported in an ammo thread.. It case miced at 1.633. We dusted his LS to give a HS at 1.633 and it now works fine. You can crush feed a little, but .003 is too much.
September 23, 2001, 00:58
Consider also that many austrian barrels have what I consider a tight throught. This is not detectable on a headspace gauge as its forward of the .400" datum line. But insering a pull through finishing reamer with the headspace set at minimum will still shave a tiny bit of material off the shoulder and throat forward of the .400 datum.
September 23, 2001, 02:57
Radio - the gun ran for the first 25 rounds fine with the gas setting on 4. Then the problems started. After the problems started, I shut off the gas by turning the plug to garnade. AFter firing, charging handle will only pull back about an inch, just enough to pull the carrier off the bolt. But the bolt will not move because the case is stuck in the chamber, this leads me to believe the gas system is not the cause of the problem. However, let the gun cool down completely and it will be fine until it again gets a little hot. BTW - the barrel is 16.5 inches before the muzzle brake with the gas port enlarged to .116.
Back to the headspacing, I toyed around with it for about an hour with the go, no-go, and field gauges, even with the ammo. I believe I set it as Mark exlained in his video. Also, I have another FAL that was assembled by Mark of ARS. I have inserted the go-gauge and bolt (without removing the extractor)into the ARS rifle just to compare. The headspace seems to be just as it is on the ARS rilfe. The ARS rifle will run fine with the same SA ammo throwing the cases about 12 feet way.
Mark, this is leading me believe what you said to consider, the throught being tight. But being this was a R1 kit with what I condisered to have been fire quite a bit, is it still possible to have a tight throught?
So, I'll start with opening up the head space. The rifle assembled with a .261 LS which set the head space probably close to a 1.631. I have and a .259 LS, this should set it to .263 and still not close on a no-go.
I'll post the outcome.
A big thanks to everyone that replied.
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