Schrodinger's headspace - a problem that isn't?

[Griff557]

When I got my Mark 3 Enfield I was worried about headspace after reading all the horror stories about case separations then I read about guys using either small o-orings or hair tie rubber bands slid down the case against the rim and either form fired with a light charge or just fired with a live round. Doing this will take up any slop in headspace and push the case neck out so it now headspaces on the case neck-now you just necksize for that rifle. Ive got 7-8 reloads on some of my .303 cases and havent had a case separation yet.

I didnt do this with my Krag but I do fire form my cases and neck size only and havent had any case issues with several reloadings

Disclaimer: I didnt invent the technique and your results may vary...use your own judgment.... ;)

[butlersrangers]

'Ignoramus Rex' - For shooting purposes, You would probably sleep easier with a NOS Bolt, which is pretty cheap insurance at $55.

By all means, clean your present bolt and at your leisure do the testing, you are considering, and share what you determine.
IMHO - We can all learn from this one, if cracks or flaws are found.

[butlersrangers]

'Griff557' - I use to have a S.M.L.E. Mk III rifle, that was a "Destroyer of Brass".

Ironically, it was a rifle that was rebuilt and re-barreled by B.S.A. and marked "FTR -1953" (Factory Thorough Repair).

All serial numbers matched and the new barrel had the B.S.A. trademark on its 'knoxform'. New wood and metal re-finish were part of the military rebuild program.

This rifle's Head-Space was correct and the bolt was fitted properly. However, brand new quality commercial brass, neck-sized and loaded with a 'Lee-Loader', showed incipient and complete head separations on the second firing of the brass!

A virtue of the .303" cartridge is that the rim prevented high pressure gases from blowing back into the action. The only evidence of my case 'failures' was the failed brass.

This rifle ruined all my .303 brass. The experience killed my interest in reloading and shooting .303 British.

My understanding is that the problem was not head-space, but, British military chambers. Dimensions were generous for reliability and military brass was heavier than commercial brass. The British Military did not reload the once fired Berdan brass.

My generous FTR chamber allowed the cartridge case body to be stretched to the side-walls and forward toward the chamber-neck.

This movement of brass, ballooning to the side and stretching to the front, likely caused my .303 brass to fail at the web area of the case wall.

(Suffice it to say, I have not had this experience with the U.S. Krag and the .30-40 cartridge).

[Parashooter]

. . . My generous FTR chamber allowed the cartridge case body to be stretched to the side-walls and forward toward the chamber-neck.

This movement of brass, ballooning to the side and stretching to the front, likely caused my .303 brass to fail at the web area of the case wall. . .
It's fairly easy to demonstrate that cases actually do not stretch forward on firing. Photo attached below shows this. .303's loaded to stiff normal pressure in neck-sized cases can fail at the head because of the rear-locking action's flexibility, allowing some rearward movement of the bolt face on firing at full pressure. This allows the case head/wall junction to stretch, thin, and fail.

[butlersrangers]

My .303 British loads were: W-W cases, Winchester large rifle primer, 35 grains IMR-3031 (each charge weighed), and Speer 150 grain spitzer, (.311 diameter).

Ammo was loaded with .303 British 'Lee-Loader'.

Accuracy was good with a new BSA barrel.

Case life was shockingly short!

I hadn't had reloaded brass problems and head separations with a 1943 Long Branch #4 rifle or 1947 Fazackerly #5 rifle.

A 1953 - FTR rifle with a generous chamber for Korean War conditions???

[FredC]

. . . My generous FTR chamber allowed the cartridge case body to be stretched to the side-walls and forward toward the chamber-neck.

This movement of brass, ballooning to the side and stretching to the front, likely caused my .303 brass to fail at the web area of the case wall. . .

.303's loaded to stiff normal pressure in neck-sized cases can fail at the head because of the rear-locking action's flexibility, allowing some rearward movement of the bolt face on firing at full pressure. This allows the case head/wall junction to stretch, thin, and fail.

Flexibility was going to be my first guess also. I have not worked with any 303 actions but I sort of remember a reputation. Maybe during the rebuild a mismatch in the locking lug/lugs happened that made it even more flexible.

Parashooter,
The demo with the scribed lines on the case is comforting, when fire forming cases it is good to know that you are not stretching the case contributing to head separations.

[butlersrangers]

Parashooter's graphic is quite educational. I always appreciate his input, knowledge, illustrations and observations.

It is interesting how 'fire forming' re-located the .303 case shoulder and shortened the overall case length.

I wish, I still had some of my wrecked .303 brass, to see what the case diameter measured just above the 'incipient separation ring'.

I may be very mistaken, but, I can envision a cartridge case failing by being overly stretched 'sideways'.

This might happen if the chamber is generously large radially and not adequately restricting expansion of the case wall at its juncture with the solid case web.???

(p.s. - I am not arguing or debating, just trying to better understand my experience).

[FredC]

BR,
I think the head and rim are still moving after the forward brass expanded and sealed. Head space and flexing of the receiver or bolt most likely.

Looked at you gauge photos again, it does have a recess to clear the firing pin. With your gauge, firing pin damage is a non issue.

KCA is an informative place you just keep learning things here.

[butlersrangers]

Yes, whoever made my 'knock-off' head-space gauge thought things through.

Actually, it can be easily 'hooked' under the extractor, to retain it against the bolt-face, and be feed smoothly into the chamber. (No wear or tear and convenient at gun shows).

But, as we both have said, it is best to strip the bolt and focus on 'feel' of gauge.

[FredC]

.

Actually, it can be easily 'hooked' under the extractor, to retain it against the bolt-face, and be feed smoothly into the chamber. (No wear or tear and convenient at gun shows).

Had not even thought of that, to quote Paladin "have gauge, will travel"