Head Space and the 1917

[milboltnut]

forgot about full length sizing that Hatcher didn't include sorry all

[fjruple]

If the headspace is too tight, the last thing you want to do is removing material from the bolt lugs especially if the bolt is fitted to the reciever. when the military was using the M1917 they would just look for a bolt that properly headspaced to the barrel. Now a days we do have those luxuries of the endless supply of bolts. A finishing chamber reamer should be used to clock in the final headspace. A pull through chamber reamer is better yet.

[lyman]

I'm not sure what you are commenting on,,

headspace is a measurement from the bolt face to a datum line on the shoulder for the 1917, (in 30.06),
too tight and the round will not chamber,or will have to be forced to close, too loose and brass will stretch ,

at no time would anyone grind on the bolt lugs or face to fix headspace, just simply ream the chamber correctly (yes, pull thru works best) until it headspaces with the correct guages,


it's not rocket science, but can be difficult at first to wade thru the chaff to get to the wheat,,,

the pics shown are of a 308 fired in a 3006 chamber, not really dangerous, but also not really relevant to headspace issues

[milboltnut]

Chambers are cut to spec or slightly beyond in this case of military rifles.... and bolts are fitted to cut chambers.

I never said I would grind bolt lugs. Hatcher was saying that's what would increase HS, if bolt lugs were ground. Cutting chamber further down the barrel would not effect HS.

the 308/30-06 was an example to reinforce what Hatcher was saying, that's all. After reading his notes, I see how HS really works. Always wondered, but not fully knowing what increases HS... and it has nothing to do with the chamber.

Noted was HS 1.950 or more was due for an overhaul.

Reamed to 1.955.. "with excellent grouping at 100 yards"

Reamed to 1.960.. "larger group"

Reamed to 1.965.. "group was better.. but not as good as the first, but don't put too much store in group size.... got no reaction whatsoever and the cases themselves showed only a very slight indication stretching and were nowhere near a rupture"

Below show no sign of incipient case head separation

https://i.imgur.com/TeYqYFV.jpg

[lyman]

thanks for editing your post,

I am not sure (been a while since I have read Hatcher) if US Rifles were headspaced to a standard, the bolts fitted,,,

seems counter productive, esp when replacements are all short chambered and finish reamed using the bolt that is with the rifle,

1903 armors or some level were issues Test Bolts , I am not sure one was used on the 1917,

[milboltnut]

I'm sure setting back the barrel was done if need be.... if the original bolt was used.

He was just proving a point that chamber dimensions doesn't really effect case head separation. Case in point .308 case fired in a .30-06 chamber.

If the case is... #1 fully supported by the bolt and lugs locked against the recesses with minimal clearance #2 held by the extractor #3 expands and grips the chamber walls.... the case expansion is very minimal at the head.

But..... if the clearance isn't minimal, and excess movement is present between the lugs and recesses... then the case thrusts rear ward while the case thrusts forward. The old saying goes....for every action there is an equal and opposite reaction.

http://www.qrg.northwestern.edu/proj...basketball.gif

so the lock up.. lugs and recess prevents separation, but the roller skates is lugs a bit worn or more.

[lyman]

I'm sure setting back the barrel was done if need be.... if the original bolt was used.

He was just proving a point that chamber dimensions doesn't really effect case head separation. Case in point .308 case fired in a .30-06 chamber.

If the case is... #1 fully supported by the bolt and lugs locked against the recesses with minimal clearance #2 held by the extractor #3 expands and grips the chamber walls.... the case expansion is very minimal at the head.

But..... if the clearance isn't minimal, and excess movement is present between the lugs and recesses... then the case thrusts rear ward while the case thrusts forward. The old saying goes....for every action there is an equal and opposite reaction.

http://www.qrg.northwestern.edu/proj...basketball.gif

so the lock up.. lugs and recess prevents separation, but the roller skates is lugs a bit worn or more.

.gov did not set barrels back,

if headspace or bore warranted a replacement, it was replaced, old tossed,

civilian gunsmiths will set back, .gov is not set up that way

[milboltnut]

I hear ya

[fguffey]

it is almost impossible for reloaders to be able to keep up' and then it gets worst when they read Hatcher's Notebook. Hatcher was before the Internet, it would seem he had his hands full, he head the 03 rifle and he had to answer questions about head space. Hatcher increased the length of the chamber from the shoulder to the bolt face .065"+ thinking that would be enough to cause case head separation; problem, nothing has changed. They did not know or understand what happen between pulling the trigger and the bullet leaving the barrel (nothing has changed, they still don't)

For years I have shared information on my M1917, when I fire a factory, over the counter new full length sized/minimum length ammo in that rifle I have .016" clearance. My chamber is .002" longer than a field reject length gage; reloaders do not understand or know what effect the chamber has on the case when fired.

ME? I form 280 Remington cases to 30/06 cases by adding .014" to the length of the case from the shoulder back to the head of the cases. I off set the length of the chamber with the length of the cases and like magic I have .002" clearance between the shoulder of the chamber and shoulder of the case. And my shoulder does not move, I can not bump it back, I can not move it back with a die that has full body support.

F. Guffey

[fguffey]

I doubt very much, I doubt very much if we would get a rupture this way, no matter how much we reamed the headspace. We would just move the shoulder further and further forward.

The first team shooter that took himself too seriously claimed the firing pin struck the primer and then drove the case, power and bullet to the front of the chamber. That cute little saying put reloader into a rut; I could not get him to consider other options, instead he made up another one of those cute little sayings. He claimed the case had head space, for years and years and years I have never seen anything from SAAMI that suggested the case had head space. He called SAAMI and tried to convince them they were wrong, they were not as easy to convince as reloaders, anyhow my cases do not have head space.

MOVE THE SHOULDER FORWARD? And now you are back to the team shooter that claimed the firing pin drove the case, powder and bullet to the front of the chamber; anyhow, I suggested he think about it but he had so much time invested in getting it wrong he had to convince others they were wrong.

F. Guffey