DSA FAL; headspace a potential problem or not?

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islandphish

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I've been reading that DSA will often send out pretty tightly headspaced FALS.

I've heard that tighter headspace, but within specs, can help with accuracy.

So, if DSA is headspacing tightly for .308 Win does that mean that a person may see increased accuracy with a potential for decreased reliability when using 7.62x51 ammo?
 
I'll quote the Fulton Armory site, as I do a thousand times a week it seems on these .308 threads.

They are not the same, 'cause the .308 Win was released by Winchester several years before the Army standarized the T64E3 as the 7.62MM. You'll get an endless discussion of pressure specs, endless because SAAMI and the Ordnance Dep't measured pressure in different, unrelateable ways. Howver, the chamber drawings are different.

They are the same, 'cause nobody (and Clint's been looking for many years!) makes 7.62MM ammo that isn't to the .308 "headspace" dimension spec. So 7.62MM ammo fits nicely into .308 chambers, as a rule
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I've run both military surplus and commerical .308 through my FAL with no problems. It even eats soft points. I had a bad batch of South African once, but it's not picky about ammo. My FAL has a new Badger Ordnance barrel like DSA installs on their guns. The only one that might be picky is the 21" bull barrel, as that one has (I believe) a match chamber.
 
texasrifleman,

I have read that also, that Nato spec 7.62x51 ends up measuring in the .308 Win range.

Obviously I'm not a gunsmith but I'm taking a rifle in tomorrow and want to be sure I'm getting what I want for my gun.

So why then the two headspace recommendations? Does this mean that I would need to look out for older surplus ammos that follow the old 7.62x51 specs?
 
So why then the two headspace recommendations? Does this mean that I would need to look out for older surplus ammos that follow the old 7.62x51 specs?
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The 2 loadings have different MIN and MAX headspaces, but that's the rifles chamber not the ammo. The ammo is all inside the .308 specs if you believe what McKee and Kunhausen and those guys say.

I cannot imagine that DSA would ship a rifle with headspace outside of the SAAMI range, which is where you begin to have problems.

Does this mean that I would need to look out for older surplus ammos that follow the old 7.62x51 specs?
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Again, it's not the ammo it's the rifle. You won't find ammo that exceeds the .308 spec. I've read of some kind of British 7.62 that was made for some belt fed MG that had this issue but no one believes any was ever imported into the US.

If you did happen to run across some odd ammo old enough to have this problem you probably wouldn't want it anyway since it would likely have primers with corrosive compounds in them.


In my opinion the "money quote" is from Jerry Kuhnhausens book:

If you have a chamber with headspace much in excess of 1.636 (say, 1.638, SAAMI field reject), you must use only U.S. or NATO Mil Spec Ammo (always marked 7.62mm & with a cross enclosed by a circle) since the NATO mil spec calls for a far more "robust" brass case than often found in commercial (read .308 Winchester) cartridges.
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Other than that it doesn't seem to matter.
 
Ok, I think I'm getting this.

So it would be beneficial to the user to have the tighter headspace, 1.631-1.632, as any ammo fired will reliably be in spec for that and with the tighter fit you would have the accuracy bonuses?
 
So again I'll quote Clint McKee at Fulton. This is all M14 stuff but it applies to the FAL for the same reasons.

I also agree that 1.631-1.632 is a near perfect headspace for an M14/M1A or M1 Garand chambered in .308 Winchester. But I think that it also near perfect for 7.62mm NATO!

I have measured many, many types/manufacturers of commercial and NATO ammo via cartridge "headspace" gauges as well as "in rifle" checks. If anything, I have found various Nato ammo to be in much tighter headspace/chamber compliance than commercial ammo. Indeed, sometimes commercial ammo can not be chambered "by hand" in an M14/M1A with, say, 1.631 headspace (bolt will not close completely by gentle hand manipulation on a stripped bolt, although it will close & function when chambered by the force of the rifle's loading inertia), though I have never seen this with NATO spec ammo. I.e., if anything, NATO ammo seems to hold at the minimum SAAMI cartridge headspace of 1.629-1.630, better than some commercial ammo!
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hmm, this does seem to be coming back to my original question of whether there are diminishing returns with the smaller headspace.

Wouldn't it be reasonable to say that if a cartridge is chambering rather tightly in a perfectly clean rifle that it may not chamber at all in one that has picked up mud and grime in a battlefield? A question particularly important for the MBR's.

I ask only b/c I don't know and am not arguing, Fulton has an outstanding reputation. Knowledge I seek.
 
Well it seems to me that you get both if you use .631-.632. You get about as tight as you can reasonably go using surplus and commercial ammo.

1.630 is SAAMI GO so you certainly don't want to be there and .634 is NO GO and you don't want to be there til the rifle has thousands of rounds through it so there's really not much room to play with anyway.

1.631 sure seems to be the reasonable number I'd think if you want to be as tight as possible and still have smooth operation.

If you want both; to squeeze every bit of accuracy out of the rifle, and also to maintain it's usefulness as an MBR in dirty conditions I think you will find the 2 mutually exclusive.

My FAL and M14 both have 1.632 headspace, the M14 came from Fulton that way and my G1 just came from DSA the same way and I'm assuming there's a reason they set them at that number, I don't believe it's cooincidence.
 
texasrifleman,

You're gruff but you know your stuff. Thanks for the help. Tomorrow I will be that much more knowledgable when I go to the 'smith.
 
You're gruff but you know your stuff.
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Well it's hard to be nice when you got guys like in the other thread on .308 saying that you shouldn't ever use .308 and 7.72x51 NATO interchangeably or the world will end. :)


So I am curious. Would you post what your DSA rifles headspace was before you did any work on it after the gunsmith measures it?
 
I've been reading that DSA will often send out pretty tightly headspaced FALS.

I've heard that tighter headspace, but within specs, can help with accuracy
Click to expand...

I suspect DSA sends out minimum chambers, which allow for some setback. And perhaps more importantly, a FAL is a rear locker.

That means under compression the bolt stretches more than a front locker. When the bolt stretches, the case stretches. If the case stretches too much, it breaks.

If you look at Brassey's Military Small arms, a design book, the authors make the comment that the FN type of locking mechanism is not widely copied, precisely because of case break age.

I bet DSA does not want the Master Blaster crowd complaining about case head separations with Mil Surplus. Having fired and sized cases from a FAL, cases do have a short life exactly because of case stretch.

As for "tight" chambers being more accurate than "loose" chambers, well you would have to quantify that. And specify the firearm.

A bench rest rifle, the case is never sized, its dimensions don't change, and you fire single shot. One rifle I saw, no extractor. The guy used his fingernail to get the case out. And that is about the most accurate rifle around. Is that what you plan to shoot?

What about a service rifle? Things are a lot looser in a service rifle. With my FAL, I have an error source that provides more error than "loose" or "tight" chamber dimensions ever will. That is the rear sight tightness. I can grab mine and wiggle it. That provides an aiming error orders of magnitude greater than any chamber dimension issue.

For a hand held rifle the largest source of error is the human error. After that, barrels, bullets and bedding. Those are the majors.

As for a tight headspace, it is just a function problem waiting to happen. I ask my gunsmiths to give me a Go plus .002" chamber. Minimum chambers are a pain. Your sizing dies unscrews a little bit, maybe the brass is a little stiffer, and you have an oversized case for your chamber. What you end up doing is slapping down the bolt handle to get the action closed. That will really mess up a rapid fire score.
 
I prefer mine a little loose as opposed to tight, because I'm a freak for reliability. Cool thing about the FAL is you can simply buy a different-sized locking-shoulder and drive it home to adjust headspace.
 
I bet DSA does not want the Master Blaster crowd complaining about case head separations with Mil Surplus. Having fired and sized cases from a FAL, cases do have a short life exactly because of case stretch.
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Anyone have experience with the RCBX X-Series of dies?

They claim to minimize the wear on brass from case stretching with these dies, not sure exactly what they do though.
 
my gunsmith is an incompetent nincompoop. I need to order my own gauges.

which is better, clymer or forster.

also, i searched on Brownell's and didn't see pin gauges. is there a better name for them?
 
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