Ishapore 2A1 headspace gauge/ Measurement

[Peter Laidler]

Let me ask a pertinent question that noone has asked yet. Given all of the trials, tests and experiments carried out at Enfield and for over 45 years - so far - with the L8 CHS, the L39 CHS and the L42 CHS then specifying that the L96 must have the same CHS specification. Then, the Sterling No4 and 5 conversions............ both of which stuck rigidly to the tried and tested specification, can any out there tell me why would the Indian ROF converting the No1 rifles would opt for anything different................... especially when the important maths, physics and metallurgy has already been done for them?

Come on lads..............! If 1.6238 go and 1.635 no-go is good enough for pretty well every other (and certainly every other Enfield.....) bolt action rifle using 7.62mm NATO ball, why would India seriously change it to anything else.

In my limited experience, and not knowing the definitive answer, then take it from me, that if these are the known spec for everything else, then it'd be a pretty safe bet that this is the spec for that other solitary bolt action 7.62mm Enfield using NATO ball.

Now come a bit closer and listen in because I don't want everyone else to know about this opinion I have........... It's about that hoary old chestnut that ALL or certainly MOST of the Indian 7.62mm SMLE's have a greater NO-GO CHS. Could it possibly be that they have already failed the REJECT 1.635 gauge at Indian Armourers shops and Ordnance and it's these rifles that they've sold off.

As an experienced rule of thumb you should take it that the CHS for this bolt action 7.62mm NATO rifle is the same as the rest of the 7.62mm bolt action rifles. No excuses now. But I'd appreciate any alternative views - but make sure that you've got your books handy!

[skiprat]

After spending (yet another) week gauging all my rifles (500 +) for cartridge headspace (CHS), and yet again finding all in order.
I find myself asking…. How far out can CHS. be before a rifle mechanically fails upon firing?

I have in the past, found weapons that have really quite excessive CHS (SA80 and GPMG) that had fired many many rounds with no dangerous consequences.

[Peter Laidler]

The simple answer to Skippy's quesation is that the weapon won't (?) fail due to excess CHS. I had a No4 that was so worn that the CHS was .018" excess at .092". However, what would happen occasionally was that there'd be a misfire. This was caused by the CHS clearance being excessive or in othger words at the HIGH end of tolerance and the percussion anvil in the cartridge being at the LOW end of its tollerance. Result. a misfire. .22" rifles are good at this too!

CHS is a wide subject but another important thing it prevents is the build up of inertia in the breech block. Think 'hammer action' for want of a better or more descriptive work. Not something that a bolt action rifle needs to worry about but think L2A1 automatic SLR. If CHS was excessive in that rifle then very quickly that action will loosen the locking shoulder in short order. Loose (and I mean loose enough to elongate the hole) locking shoulders were not a major problem with the bog standard semi auto L1A1

[pcaru1]

Out of curiosity I made a bunch of the "can" shims to see how bad this really gauges. Each slice mic'd at .004 to .0045. It took 5 shims to pass, which is approximately .022 to .0225. Added to my Field gauge of 1.638 that makes it an eye popping 1.6605. I subtracted the 7.62 Nato Max field measurement of 1.6455 and came up with .015 over. Less than Peter said one of his rifles gauged at and still was fine. If I am not mistaken, this gun has a #5 bolt head which is the biggest, correct?
I thank all of you who responded. I tried to come up with something on my own but it seemed to confuse me even more. This discussion is exactly what I was looking for. This gun looks like new, but gauges like an old tired veteran. It seems the HS on this gun is very "generous". Not one I plan on reloading for given the measurements. I just wanted to know if I can take this out and fire it without risking life or limb.

[Alan de Enfield]

Apologies for the the repetition but which NATO firearm has 1.6455 ?

As Peter Laidler has stated all of the Enfield based 7.62 Bolt Action rifles are 1.635. That would make yours 25.5 thou over max. (assuming the Indians did use the same headspace dimensions as the other Enfields)

Could Peter be correct that all of the 'sold out of service 2A's / 2A1's are BER ?

[jmoore]

US spec. field max is 1.645". I wouldn't begrudge the extra 0.0005" as it really doesn't have any functional importance. I believe the US and British reference datum planes are different, but likely they measure out the same on a real world gage.- or not!

ETA: Forster lists the 7.62 NATO max. dimension as 1.6455"-0.0003" for their gages. I've an older reference to 1.645" but no tolerancing, so it may be suspect.

[Alan de Enfield]

US spec. field max is 1.645". I wouldn't begrudge the extra 0.0005" as it really doesn't have any functional importance. I believe the US and British reference datum planes are different, but likely they measure out the same on a real world gage.- or not!

ETA: Forster lists the 7.62 NATO max. dimension as 1.6455"-0.0003" for their gages. I've an older reference to 1.645" but no tolerancing, so it may be suspect.

Ahhhhhh- that takes us back to Peter's original post on Jouster

[Thunderbox]

Could Peter be correct that all of the 'sold out of service 2A's / 2A1's are BER ?

I doubt it, because many of the rifles are/were in fairly mint condition.

I expect that India disposes of rifles in a decentralised manner - ie a regional or district police unit gets upgraded to AKs/L1A1/INSAS, and dumps their Enfields.

[Thunderbox]

As Peter Laidler has stated all of the Enfield based 7.62 Bolt Action rifles are 1.635.

Thats an assumption. The Envoy limits were actually tighter at 1.628 and 1.631, based on a datum of 0.4" at the shoulder. Why would we assume that a combat rifle - the 2A1 - should have headspace (and by implication, slower reloading) as tight as target or sniper rifles? I haven't seen the CHS figures for L8s but, as experimental rifles, I'd wager that the CHS would have been relaxed as soon as they were issued for service use - no good having stiff cartridge chambering on a combat rifle.

[Alan de Enfield]

Thats an assumption. The Envoy limits were actually tighter at 1.628 and 1.631, based on a datum of 0.4" at the shoulder. Why would we assume that a combat rifle - the 2A1 - should have headspace (and by implication, slower reloading) as tight as target or sniper rifles? I haven't seen the CHS figures for L8s but, as experimental rifles, I'd wager that the CHS would have been relaxed as soon as they were issued for service use - no good having stiff cartridge chambering on a combat rifle.

I do not have the experience, background or knowledge that Peter & yourself have but I did assume that Peter's quote was correct :

".....If 1.6238 go and 1.635 no-go is good enough for pretty well every other (and certainly every other Enfield.....) bolt action rifle using 7.62mm NATO ball....."