reloading and the 7.62 No.4

[ireload2]

>>>The circular stamp near the charger guide on the left hand side receiver wall is a type of proof stamp, indicating that the action has been "crack tested".<<<

What type of testing was done?
Liquid penetrant or magnetic particle?
What area of the receiver were they checking for cracks?
Were they looking for charger guide cracking or cracking of the load bearing rails?

[Maxwell Smart]

What type of testing was done?
Liquid penetrant or magnetic particle?
What area of the receiver were they checking for cracks?
Were they looking for charger guide cracking or cracking of the load bearing rails?

To paraphrase "Oddball" (Donald Sutherland, "Kelly's Heroes" movie)

"I only shoot them, I dunno what makes them work...."

Have no information about the details of the No 4 crack testing work.

[Alfred]

Well to confuse the matter further, as usual, while running down information on a posted warning at Bisley against use of bullets weighing over 144 grains in converted Enfields I found that an arbitrary retained energy ruling meant to prevent use of 338 magnum rifles at some ranges were bullets could endanger populated areas if they escaped the range had also included .308 match loads of 155 grain and higher. Whether any ban is in effect I haven't found out yet.

British target shooters seldom handloaded in earlier times, but modern day UK shooters seem to do a lot more handloading, or hire others to work up loads for them.

Heres the post that started me looking

I was in the NRA office at Bisley on Saturday and on the notice board in large print Do Not use any heavier projectile than 144gn Nato round in No4 conversions damage will result. I think that advice would extend to the Indian 2a, 2a1 as well. That Indian proof load test is the same as the current proof test used in the UK test. One dry @+ 25% one oiled @ + 25%

[ireload2]

I can understand range limitations being connected to bullet weight but I cannot understand bullet weight being connected to breech pressure.

[Alfred]

I can understand range limitations being connected to bullet weight but I cannot understand bullet weight being connected to breech pressure.

There is only so much room in the case below the neck.
If both .303 and .308 cases have the same volume in the powder space, and both are loaded with bullets that do not extend into the powder space, then using the same charge both will generate very nearly the same pressure levels.

The Over All Length of the .308 is shorter than that of the .303 and set to a limit. the neck is short compared with many in this class. Bullets of 144 grains don't extend below the case neck much if any.
To seat bullets heavier than 144 grains the base of the bullet will usually extend into the powder space effectively reducing case capacity.

When bullets of 175 grains are loaded in a .308 to the same velocity levels the case capacity is reduced so its like loading in a smaller case.
The .303 was designed for longer and heavier bullets of first 215 and later 175 grains and its OAL reflects that. To use 150 grain bullets to best effect in the .303 I seat them further out than intended to reduce jump to OR, at the same OAL as the standard .303 Ball.

How much difference a 150-155 grain bullet makes in pressure I couldn't say, probably not that much.

If the throat would accept a bullet seated further out, past the standard .308 OAL, the rifle being used as a single shot, then the two rounds could be loaded to basically the same pressures.

When .308 sporting ammunition is loaded using 200-220 grain bullets these extend even further into the case and greatly decrease powder space.

The 7.62 was designed to produce ballistics as near as possible to the WW1 era .30/06 150 grain Ball at circa 2700-2800 FPS, using more highly developed powders to allow this power to come in a package no larger than less powerful rounds like the 7.65X53 or the .303.
Converted WW2 era rifles were intended to use the standard Ball round with a safety margin. More recent Heavy Ball rounds were not designed to cater to this sort of converted rifle, they were meant for use in the most modern and strongest of designs, including updated Sporting Rifle designs of proven strength modified for use as Long Range Sniping Rifles.
Theres no ballistic advange to using .308 as a sniper round in these rifles, the .30/06 performs better at lower pressures, but the sniper rifles must be able to use available 7.62 Ball or delinked MG ammo in emergencies.

There was such a problem not long ago. A screw up by JAG caused open point ammo to be withdrawn, and snipers had to make do with whatever 7.62 they could find including de-linked long range MG ammo till the mix up was straightened out.

Another issue that came up in the UK was use of solid bronze or Copper bullets. These were found to be unpredictable as to ricochet and such.

[ireload2]

My comment about bullet weight and breech pressure was based on the possibility maximum breech pressure can be reached with any bullet weight given a powder that is fast enough burning.
The US military specifications do not specify the powder charge or the powder to be used. Only the performance characteristics are governed.
Those include maximum average breach pressure and variability of velocity and pressure.

[whiterider]

Ok that little stamp put on the left side of the action usually under the charger guide was put on by the Lithgow small arms factory after 'crack testing' the action before installing a 7.62 barrel and proofing.

As far as I am aware (and I stand corrected if a 'real' expert comes along) I recall hearing that it was a 'dye penetrant' examination of locking lug recess and shoulder...but I'm unsure if it encompased the whole action as such.

A few years ago much 'hoo hah' was put about by our National Rifle Association here in Australia about 'certain ex-military actions being not strong enough for commercial loads' of the 7.62 cartridge... Among those listed were the No.4 Lee Enfield and the M 98 Mauser.... Apparently the NRA put out this advice after information from a gunsmsith of some renown...

The advice went to say that 'only military ammunition or its equivalent and CERTAINLY NOT COMMERCIAL LOADED 308 ammo should be used in 'conversions'...

Now it should be fairly obvious to most reloaders that it takes more than just BULLET WEIGHT to constitute pressure...barrel internal dimensions, chamber cut and of course POWDER TYPE AND WEIGHT OF CHARGE all need to be taken into account. So limiting No. 4 conversions to a bullet weight of 144 grains WITHOUT ANY OTHER INFORMATION seems a bit ridiculous.

Now the strength of the No.4 action has been and will probably continue to be the subject of much argument. AS FAR AS I AM AWARE the only No.4 rifles known and documented to have suffered failure in service have been those 'cadet' rifles in the UK...and they suffered a barrel split not a failure of the action...

So make up your own minds about the safety of the No.4 action...I've put my eyes and head where my mouth is and have used them without a problem for many many years. I dont use hot loads in them and (by measurement of the fired case in a case guage) I keep a close watch on headspace, stretching of the action and any battering of the locking lugs or recesses.

Perhaps the learned engineer Mr. Horton could advise us further on the Lithgow crack testing process. I say this with sincerity and not sarcasm.

[srjg3432]

Here are the loads I use
Its a No4 MK2 with a 26inch target barrel on it, so it looks like an enforcer, and has a scope on it.

I use 45.5 grains of 2208 (varget) with 155 HPBT projectiles in Winchester cases.
I also load ADI cases, and because they are heaver, I use 44.5 grains.

Rifle has a harris bipod on it, and last time I shot it in 2 X 1000 yard 15 round matches, it did 66 and 70 out of 75, (with a 12mph crosswind)

[Alfred]

I dont use hot loads in them and (by measurement of the fired case in a case guage) I keep a close watch on headspace, stretching of the action and any battering of the locking lugs or recesses.

Thats as it should be.

The advice went to say that 'only military ammunition or its equivalent and CERTAINLY NOT COMMERCIAL LOADED 308 ammo should be used in 'conversions'...

While there are commercial loadings of the .308 that should be safe enough theres seldom anything on the box to gaurantee to what pressure these are loaded, or whether the bullet profile is suited to any particular indiveidual chambering.
A military throat may be a fairly loose fit to the Ball or equivalent bullet, but no telling if a Match rifle chamber would be cut too tight for a much heavier bullet with a different profile.

Military Ball powders seem to allow a lower pressure level for the same velocity in lighter bullet loads, but the pressure advantage seems not to extend to full power loads using heavier bullets.

The 7.62 Match Cartridges loaded with 4895 single base gave about two hundred FPS increase over the .303 at aprox the same bullet weight, but presures were a hair under ten percent higher.
The long Range Special Ball uses a Double base propellant with slight velocity advantage but at even higher pressures.

Theres only so much elasticity to any steel alloy, and metal fatigue will take its toll sooner or later, the more stress applied the sooner the frame reaches the limit of its durability.

Another thing to take into account is the maximum deviation in pressure of M118 LRSB, the working pressure is 52,000 CUP but its Max SD is 57,000 CUP. More than a few rounds like that fired in an action already stressed past design expectations by repeated use of a higher than expected pressure level and things could go south unexpectedly.

If the warning about wet chambers is correct, that a wet .303 case can crack the action body of an SMLE, then a M118 LRSB cartridge or sporting round of the same pressure range accidentally getting wet on the range or in the field could probably do the same to a No.4 receiver despite its heavier construction. Keeping your weapon and ammo dry may be no big deal on the range but every place I've ever hunted has been rained on with big drops of water splashing down from the trees for hours after the rain stops, and moving through wet brush can have you soaked to the bone even with rain gear. Snow is another way of getting wet. I've fired Sub MOA groups in driving sleet just to see if I could, range 185 yards in twilight.

Contrary to popular belief no one gives a rats patoot about whether we have accidents with milsurp rifles unless someone gets killed by their own rifle or a bystander gets injured, and even then its not going to get past the Hooterville World Guardian unless the victim is someone of note.
Gunshot wounds must be reported to the police, but injuries from a breech failure or blown cartridge base do not.
When legal action may result the facts may never be known outside of the jury box, records sealed as part of the settlement.
I've seen enough badly damaged Enfields , both No.1 and No.4, sitting in rows of trash barrels priced at 6.95 each to be stripped for spares that I have no illusions about there never being a blown Enfield action, and since these were straight from the arms dumps of some third world pesthole they weren't likely to have been blown up by someones pet reload getting double charged.

Ive seen dozens of damaged Enfields and I've never seen a blown up Spanish 93 Mauser, but I have no doubt that a Spanish Mauser can be blown up by an unsuitable cartridge.
I've never seen a 1888 Commision rifle blown up by 7.92X57S but I have no doubt that it can happen, and that there are WW2 heavy MG loadings that would damage most Model 98 rifles if very many rounds were fired.

If an accident happens to the average shooter the most you'd see would be a couple of lines on page twelve saying, old rifle blows up, no details except perhaps the alcohol level of the victims blood. No newsbreaks with hourly updates or banners running across the bottom of the screen during the state of the union address.

Those "Crack Tests" were done for good reasons, not every rifle made it through fifty to one hundred years without time and harsh conditions taking its toll.

[ireload2]

I have Rockwell tested a number of actions and bolts most of them M98 Mausers. The recommended receiver ring hardness for a Mauser is in the low 30RC range. I have tested mostly 1909 Argentine Mausers that Bockwelled B 80 which is the approximate equivalent of rockwell C0 (zero). Early metallurgy could be all over the map.