LE Tight Headspace

I

I Dont Care About You

CGN Ultra frequent flyer
Rating - 100%
3   0   0
Any reasons why I shouldn't shoot a No4 Enfield with slightly tight headspace?

As the headspace is based off the rim thickness, the length of the case to the shoulder is irrelevant and thus should not cause any overpressure issues. As long as the bolt closes completely there should be no issues ..... right.
 
You should have that correct. I have never seen the military drawings, but staring at SAAMI drawings - a Maximum cartridge (thickest allowed rim) is supposed to chamber in a Minimum head-spaced chamber. If your bolt/chamber is less that Minimum, will still work fine if the cartridge rim is also less than it's maximum. As you say - cartridge body length and its conformity to the chamber have nothing to do with "head-space" on a rimmed cartridge like 303 British.

At the moment, is not real clear to me how excess headspace in any cartridge can lead to "over-pressure" - I can see that with bullets pushed tight against lands before the cartridge fires? Excess head space is maybe more likely to lead to miss-fire - the case pushed forward too far by the firing pin strike - pushing it too far, before the firing pin can crush and fire the primer? Not being exact, but many SAAMI standards seem to have circa 0.008" and 0.010" difference from Min to Max headspace - I think is more common to have circa 0.030" to 0.020" "jump" before the bullet hits the lands - so I don't think excess headspace can cause "over-pressure" in a otherwise compliant rifle. Split cases, venting powder gases and so on, in that case, are not a result of "over-pressure"?
 
Last edited:
Are you using a headspace gauge or do you happen to have a batch of brass with rims that are a few thou thicker than spec.
 
bearhunter said:
Are you using a headspace gauge or do you happen to have a batch of brass with rims that are a few thou thicker than spec.
Click to expand...

I have a headspace gauge.

I have 4 or 5 different types of brass. I have not measured any rim thicknesses yet. Just tried a couple of Hornady cases and the bolt fully closes with just a bit of pressure.

IMO as long as the bolt fully closes without a ton of effort, it'll be fine.
 
I Dont Care About You said:
I have a headspace gauge.

I have 4 or 5 different types of brass. I have not measured any rim thicknesses yet. Just tried a couple of Hornady cases and the bolt fully closes with just a bit of pressure.

IMO as long as the bolt fully closes without a ton of effort, it'll be fine.
Click to expand...

As long as it's the head space or lack of, causing the resistance.

if it's the case mouth or bullet into the lands you could get problems. Although that's easy to test by dropping the round in the chamber with the rifle pointed at the floor. If it stays loose in the chamber it's not the case mouth or bullet. If it wedges it self in you may want to look more into that.

If the shoulder isn't pushed back enough it can cause that resistance same as the lack of head space but will be perfectly safe still.
 
Evanguy makes several good points in Post #8 - there is actually a technique used to prevent "incipient head separation" with the 303 British - for reloading that case, which was never an original consideration in the military design of the rifle or the round. So, a reloader can transfer the "end play" stop from rim to shoulder - that 303 British has enough shoulder to do that dependably - is a 300 H&H here that does not - so you end up not really caring what is the "head space" gauging - within reason - going to make that case to fit snug between bolt face and the chamber shoulder when it is fired - minimal to no "end play" - end up with that brass sized to that chamber, more or less exactly. That can not repair a previously fired brass case that already has the expansion groove formed inside - is usually something to be done with a new, unfired case.
 
I Dont Care About You said:
I have a headspace gauge.

I have 4 or 5 different types of brass. I have not measured any rim thicknesses yet. Just tried a couple of Hornady cases and the bolt fully closes with just a bit of pressure.

IMO as long as the bolt fully closes without a ton of effort, it'll be fine.
Click to expand...

I believe as you do. In fact, I really like it when the bolt closes tight on the rim because it's holding the cartridge in the center of the chamber, which means the bullet should feed true to the axis of the bore into the leade when fired.

If all else is good, such as proper bullet diameter for the bore, that shoud be a very accurate rifle.
 
Not a bad thing if the bolt closes with a bit of pressure on the rim. The cartridge is uniformly positioned, and the risk of incipient separation is reduced. The case body is going to fireform to the chamber. Minimal resizing when reloading should enhance case life.
 
tiriaq said:
Not a bad thing if the bolt closes with a bit of pressure on the rim. The cartridge is uniformly positioned, and the risk of incipient separation is reduced. The case body is going to fireform to the chamber. Minimal resizing when reloading should enhance case life.
Click to expand...

Agreed on all counts.

One thing I noticed when the headspace was within spec, or maybe slightly loose, was that fired cases come out of the chamber with a slight bulge on one side. That makes me think the cartridge is lying down in the chamber slightly? This makes some logical sense as the military chamber is quite big to allow for reliable function. I will have a look at the cases when using the tighter headspace bolt and see if the one sided "bulge" is more consistent around the case.
 
bearhunter said:
I believe as you do. In fact, I really like it when the bolt closes tight on the rim because it's holding the cartridge in the center of the chamber, which means the bullet should feed true to the axis of the bore into the leade when fired.

If all else is good, such as proper bullet diameter for the bore, that shoud be a very accurate rifle.
Click to expand...

Thats the plan. :)

What I didn't really explain, for simplicity sake, in the OP is that I have two bolts for this rifle. The OEM bolt just barely closes (with a wee bit of pressure) on a NoGo gauge. The second bolt, just barely closes (with a wee bit of pressure) on a Go gauge. With these two bolts I have the ability to "tune" the headspace for differing rim thicknesses.

Once I've got a good load, I should shoot groups with each bolt and see if there is an accuracy improvement or difference. That'd be an interesting piece of information to know.



I will need to measure some rim thicknesses for various brands of cases so as to ensure I maintain a reasonable case rim to headspace combination.
 
You must log in or register to reply here.
Back
Top Bottom