Does .0001 or .0002 really

[Stoney]

make that big a difference in head space?

[richbug]

One or two ten thousandths(.0001)? No.

One or to thousandths(.001" all the closer LSs are usually measured), not to me.

[Raspeguy]

.0001 or .0002? Absolutely of no consequence and not detectable in a Fal. Incremental steps of .0005 in pin sizes are easily noticeable in the "feel" that is produced. My very accurate scoped Steyr imports run 1.633 to 1.6345, but my handloads run a little longer than norm.

[Stoney]

Hey, was never good at math, I meant .001 or .002 to big a head space

[ByronF]

On a weapon so easy to reset headspace why risk it? You can sell your short shoulder for the same price you paid for the longer one so we're really talking about time, not money, to make it right. And we're talking about 30 minutes of time. Is it fixed yet?

[Survey Punk]

I think ( ) the difference between Go and No Go is .006. Another .006 to Field Reject.
Don't think 1 or 2 thou makes much difference. There I go thinking.

JB

[richbug]

Originally posted by Survey Punk
I think ( ) the difference between Go and No Go is .006. Another .006 to Field Reject.
Don't think 1 or 2 thou makes much difference. There I go thinking.

JB

.004" for both. 1.630, 1.634, 1.638"

[kev]

.001" or .002" isn't much of an issue. If you reload and plan to get ten loadings from every case, it might be. That's the only real concern. If your headspace is on the loose side, every firing is going to stretch the case just that much to take up the slop. If you're picking up .003" of slop at every firing, pretty soon you'll use up all the stretch the case can provide and you'll end up with thickened case mouths and/or a head separation.

But for the non-reloader, a few thou isn't going to make much difference. It can have some measurable effect on accuracy, but if you're blasting milsurp and letting the casings lie as they fall, that 1/4moa isn't going to mean much to you.

[MBR29]

NO WAY

[Stoney]

I wanted to know, I always head space properly. Was thinking, that always gets me in trouble

[Powderfinger]

From the sticky in this forum:

From the British manual as cited above, the Brit L1A1's go, no go, and field reject gauge dimensions are 1.6325", 1.638", and 1.643", respectively.

That's .0105 overall, which exceeds a hundreth of an inch.

[richbug]

Originally posted by Powderfinger
From the sticky in this forum:

From the British manual as cited above, the Brit L1A1's go, no go, and field reject gauge dimensions are 1.6325", 1.638", and 1.643", respectively.

That's .0105 overall, which exceeds a hundreth of an inch.

But keep in mind the Brits like sloppy headspace. This has been the norm since the intro of the .303 round, the HS on some of them is ridiculous. Reliable function is 1st on their list. Being able to reload the fired brass didn't even make the list.

[JBHAWAII]

All I ever done was test fit and file down little by little until I got a go gauge to close, then give it a couple extra swipes and done, but I kinda like building like a cave man. I built 2 like that and they both are great. oops , my bad. The second one I never used any measuring tools, just a go and no go an a file. Am I crazy?

JB

[IRONWORKER]

Originally posted by richbug


But keep in mind the Brits like sloppy headspace. This has been the norm since the intro of the .303 round, the HS on some of them is ridiculous. Reliable function is 1st on their list. Being able to reload the fired brass didn't even make the list.

+1 - I wouldn't build a rifle with HS any longer than 1.634 - Most of mine are around 1.632, i have a CAI "Butthole" rifle that measured 1.638 when i bought it, i HATE to remove a locking shoulder so i got a like new Brit bolt & carrier from GPG & kept the Indian B&C for a Indian build, anyway the new Brit bolt brought the HS down to a loose 1.636

[Dopavash]

Originally posted by IRONWORKER

i HATE to remove a locking shoulder

Why?

[Topbanana]

Some ppl claim it causes stress on the receiver.

I think that's stupid, these things were designed to be re-barreled three to four times, with a replacement LS EACH time. I'm sure FN planned for this.

[StoneyCreekMrMauser]

Originally posted by richbug


But keep in mind the Brits like sloppy headspace. This has been the norm since the intro of the .303 round, the HS on some of them is ridiculous. Reliable function is 1st on their list. Being able to reload the fired brass didn't even make the list.

Good thing since you wouldn't want to reload some of that crap in the first place! I've had more split necks and burst cases with milsurp .303 than any other cartridge, and that was in a rifle that wouldn't take a FIELD gauge.

[Dopavash]

Originally posted by Topbanana
Some ppl claim it causes stress on the receiver.

I think that's stupid, these things were designed to be re-barreled three to four times, with a replacement LS EACH time. I'm sure FN planned for this.

I figure that the stress of a .308 round lighting off would be as much as punching a LS out, with the bolt slamming back and the spent cartridge being flung out, then ramming another one home.

I guess its stress from a different direction but its not that bad when oiled.

[richbug]

Originally posted by StoneyCreekMrMauser


Good thing since you wouldn't want to reload some of that crap in the first place! I've had more split necks and burst cases with milsurp .303 than any other cartridge, and that was in a rifle that wouldn't take a FIELD gauge.

It isn't just the length of the chamber(headspace), but also the diameter. The diameter is what gives you most of your cracks and failures, especially so with new ammo.

[Topbanana]

One other note, the LS is to be press-fit in and pressed out. Many FALsmiths do not understand the concept and pound the thing in an out which I'm sure does cause significant stress.

Do it right and LS removal is the least of your worries.

[justashooter]

phil sharpe and townsend whelen both ran thousands of rounds of 30-06 ammo thru 1919 platform guns looking for incidence of head seperation. they did this with Frankford Arsenal ammo that had been declared unserviceable on basis of brittleness. they determined that head seps generally do not occur with less than .020 excess headspace, and not reliably until about .028 excess. i remind that this is with brass that was deemed too brittle for service.

cartridge brass made for multi-purpose use, like 30-06 GI, was designed to be used in bolt, semi-auto, and machine gun. the MG criteria requires relatively hard brass to ensure reliable function. alloys and heat treatments were balanced to yeild such.

when a cartridge is fired in a gun with generous headspace it is knocked forward by the firing pin at the moment of ignition until it is stopped by the extractor. the sidewalls then balloon against the chamber walls, and the head is forced back against the bolt. the area of brass immediately in front of the "web" (solid base) of the cartridge case stretches to allow for this set-back of the case head. additionally, the shoulder is forced forward to fill chamber, and case length is stretched more in the shoulder area.

the 1919 is a gun that you can adjust headspace on by rotating barrel in it's barrel extension during set-up. you can blow head sep in a 1919 time after time, with the worst consequence that you have to bang the top cover flat again. how much the case can be knocked forward in the 1919 is dependent upon the extractor fit in the bolt. this is generally 8-12 thou slack.

if limit is 8-12, why then the separation at 20-28 thou? it appears that the case-wall grip on the chamber is not enough to keep the case walls from dragging forward as the shoulder is moved forward. in any case, seperation is routinely just in front of case web.

the value of their experiments? MG were a new phenomenon in the US Army experience during the War to End All Wars. in that conflict our boys fought with mostly french MG. it wasn't until after the first war that American designed guns became standard issue, and there were lots of issues with training and supply.

of particular interest, the 1919 was provided with spare barrels, but not with spare barrel extensions. therefore, to change a barrel the operators have to remove top cover, back plate, bolt, and barrel extension and barrel. they then have to remove the hot barrel from the extension, install a cool one, set headspace, and re-install everything.

when barrel extensions were added to the spare parts list the task of changing a hot barrel became much easier, and stoppages due to incorrect headspace were largely eliminated. sure, the MG-42 is a simpler and faster change by a mile, but "box guns is what we go, and they killed a lot of japs and germans".