Lee Enfield headspace question..

Keller

Keller

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My situation: I have two No4 Mk1* Long Branch rifles, a 1943 and 1944.

The 1943 has a matching bolt with a #2 bolt head and has been confirmed to have good headspace.

The 1944 came without a bolt, and before I could obtain one I had a gunsmith confirm the headspace was ok to use the bolt from the 1943 rifle. (I was excited to shoot the gun before I got a bolt for it).

I have since obtained a Long Branch bolt that came with a #1 bolt head. My question is, if I can obtain a #2 bolt head can I safely assume that the bolt will be good to go, or do I really need to get it checked with gauges?
 
No you cannot. Bolt heads were ground down by armorers when fitted to rifles. The number on the bolt head was a starting dimension.

If you measure the bolt head from the bearing surface to the bolt head, you would need to confirm your new bolt head is the same dimension.

Or just invest in gauges like serious collectors do.
 
Canadian source? Original military gauges do turn up from time to time - .064 and .074. GO and FIELD. Try a WTB ad in the EE, watch the auctions.
There was someone making disc type gauges. Basically just washers of known thicknesses.
Making rimmed gauges on a lathe is quite doable.
Any of the reamer makers will have gauges for sale but you'll likely have to import them. Commercial gauges might include a .064 GO, .068 NO GO and .074 Field.
 
An FYI - I do not do enough barrels to warrant buying full sets - so most here are GO gauges - that is, ground to SAAMI minimum spec. Then I bought a cheap (at the time) feeler gauge set at Canadian Tire, and punched out circles to head stamp size - I think I have .002 to .020" done - I slip those between the bolt face and a GO gauge to create a headspace gauge whatever length that I want - a dab of grease will work like glue to hold them together for fussing to close the bolt. Specifically for .303 British, during wartime, both Canada and Australia relaxed the Maximum headspace dimension - so be careful which gauge set that you rely on - i do not think the militaries particularly cared what SAAMI had to say about it.

I can not find in SAAMI documents where they spec how a NOGO gauge is done - it is longer than minimum, but it is shorter than maximum - I think a NOGO gauge might be a gauge maker or barrel maker invention - not a SAAMI spec. SAAMI does specify a Minimum (GO) and maximum (FIELD) headspace dimension for most every cartridge they list for, but I have not found where they list a NOGO dimension.
 
Use a known thickness shim on the back of a fully sized case. Measure the rim thickness then add shims to make it between 0.064 and 0.068 then try closing the bolt on it. Upto 0.074 thickness would still be fine just a little harder on the brass if you full size it, if you neck size the brass you don't need to worry about head space being 0.074

Ideally you would remove the extractor so it doesn't add any resistance or cut that part of the rim off the case

I've made little coin like pieces with a cutout for the extractor at the go, no-go and field thickness for checking
 
If using a cartridge case as a starting point, I'd pick a new one. Measure the rim thickness very carefully. Then add shims. But the rim thickness must be accurately measured to start.
Here is another quick and dirty method. Take an empty case. Accurately measure rim thickness. Seat a primer, and fire it. The fired primer will protrude. Measure the protrusion. Add to the rim thickness. Total measurement tells you the gap between barrel face and bolt face.
The catch with using cartridge cases is that rim thickness varies, so this must be determined accurately.
 
tiriaq said:
If using a cartridge case as a starting point, I'd pick a new one. Measure the rim thickness very carefully. Then add shims. But the rim thickness must be accurately measured to start.
Here is another quick and dirty method. Take an empty case. Accurately measure rim thickness. Seat a primer, and fire it. The fired primer will protrude. Measure the protrusion. Add to the rim thickness. Total measurement tells you the gap between barrel face and bolt face.
The catch with using cartridge cases is that rim thickness varies, so this must be determined accurately.
Click to expand...
I can't believe I forgot about this method in my post. It's the simplest and I use it probably more often then shims or gauges. It's simple to get head space with a few extra thou for clearance or tolerance of brass thickness when you have 30 bolt heads lol
 
I use the protruding primer as my gauge. Next test is my regular cast bullet loads, 10 or 15. Checking for any abnormalities. That is probably 75% Pressure of my hunting loads. If everything looks fine I shoot the hunting loads. Those are inspected. I take them home and inspect again. I have had a rifle that I knew had excessive headspace and corrected before firing. With a case in the chamber the bolt shouldn’t move forward and back. This one did. I changed the bolt head out fixing the issue. Helps to have extra parts around.
 
Snider shooter said:
I use the protruding primer as my gauge. Next test is my regular cast bullet loads, 10 or 15. Checking for any abnormalities. That is probably 75% Pressure of my hunting loads. If everything looks fine I shoot the hunting loads. Those are inspected. I take them home and inspect again. I have had a rifle that I knew had excessive headspace and corrected before firing. With a case in the chamber the bolt shouldn’t move forward and back. This one did. I changed the bolt head out fixing the issue. Helps to have extra parts around.
Click to expand...
The only fly in that ointment would be the "thickness of the rim" on the cartridge case you're using.

303 British cases are notorious for having different thicknesses.
 
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