Inherent Weakness ?

[Alfred]

Now put your thinking cap on, how many times have you heard ANYONE saying that shooting fire formed cases that were neck sized only and fit the chamber perfectly caused increased or excess bolt thrust?

How many times did you hear bench rest shooters complaining about bolt thrust and their perfectly fire formed cases in their super accurate bench rest rifles.

You've made my point for me, whatever reduction in bolt thrust there might be from a completely dry chamber, which isn't feasible under field conditions any way, is of no significance. The rifles are designed to stand up to the full chamber pressure, not some undefined reduced pressure effect resulting from the case gripping the chamber walls.

A certain amount of locking lug spring back was counted on for reliable extraction of fired cases from the bolt action designs that had poor primary extraction, the LE included. The bolt bounced back driving the tapered case back into the chamber slightly resizing it so it didn't stay stuck in the chamber. You can probably find that information in the books I've linked to earlier, it was a recognized factor from the begining of the use of brass casings for cartridges, and is still factored into action designs.
The more bolt thrust applied to the bolt face the more energy there is for the lugs and locking surfaces of the receiver to apply in loosening the case in the chamber and breaking any grip on the chamber wall from fouling and other contaminants before extraction.

PS

After chamber pressure becomes sufficient to initiate case wall stretching, the case head soon hits the bolt. As pressure progressively increases, it pushes the case head progressively harder against the bolt. Hence, the bolt will progressively compress and the action will progressively stretch until chamber pressure peaks. (Actually, owing to inertia, the case head will continue to push against the bolt, as the bolt continues to retreat, for some time after chamber pressure has peaked.)

Eventually, the bolt will exert more force against the case head than chamber pressure exerts against the case head. At that instant, the bolt will begin to slow, eventually to stop, and then to reverse direction. As chamber pressure continues to plummet, the energy stored in the bolt and receiver will drive the bolt back toward the resting position. In practice, the bolt will hammer the case into the chamber with considerable force; often sufficient to set the case shoulder back enough to assure that case headspace length is shorter than chamber headspace length. As a result, the action will open freely.

While all of this is happening, the chamber also is stretching in both length and diameter. This contributes some to case stretching; it also supplies the energy that allows the chamber to hammer back against the case body, so that it is reduced in diameter enough to assure free extraction.

Depending upon case shape (body taper, shoulder width, shoulder angle), case construction (hardness, thickness, etc.), load variables (pressure peak and duration), action design and barrel design (over the chamber), many results are possible. First, the action can open freely and the case can extract freely. Second, the bolt can turn freely (because case headspace is shorter than chamber headspace) but the case can hang up in the chamber (because relaxed case body diameter is slightly larger than relaxed chamber diameter (the case is an interference fit). Third, the bolt can turn hard (because case headspace length is longer than chamber headspace length) but the case can extract easily (because case body diameter is smaller than chamber diameter).

This partly explains why various chamber and gun designs show different symptoms with loads at similar peak pressure. The classic comparison is the 22-250 versus the 22-250 Ackley Improved (AI). With the former, this rebounding bolt can easily drive the case into the chamber far enough to move the shoulder and solidly wedge the case; with the latter, the shoulder is many times more resistant to being moved and driving the case into the chamber the same distance accounts for many times less increase in case diameter at any given location. Hence, pressure that causes sticky extraction with the 22-250 will show perfectly free extraction in the AI version.

THE GUN
How much the case head moves the bolt face rearward depends upon the following factors:
Shape of pressure curve — a wider curve means more movement (owing to inertia, the case head never has time to move as far as it would if the same peak pressure were applied in a static situation. Therefore, the longer the pressure stays close to the peak, the more the bolt will compress — the farther the head will move);
Peak chamber pressure — force and movement are directly proportional;
Distance between bolt face and locking surface — distance and movement are directly proportional;
Cross-sectional area of bolt — area and movement are inversely proportional; and,
Cross-sectional area of receiver — area and movement are inversely proportional.

http://www.longrangehunting.com/arti...fire-gun-1.php

[Edward Horton]

Dimitri

I find this thread or posting very laughable, two American armed with insufficient and spotty information and a computer program that tells him estimated pressures and force generated by fired cartridges have determined the Enfield rifle is junk and should not be chambered in 7.62 NATO.

If they think old Enfield barrels look bad they should look at newer Yugo 59/66 SKS with an un-chromed barrel, they should look at old beat up mosins and their barrels or they should look at my T-53 (Chinese M-44 clone) that was a Viet Nam bring back and then talk about “inherent weak design”.

I have nine Enfield Rifles and they are my favorite rifles in my small collection, I conceder myself very lucky, I have an un-issued No.4 and a un-issued 1953 FTR No.1 to compare my other Enfields to and NONE of my Enfields are second class citizens in my collection.

What they both need is better reading material

[Alfred]

Ed already caught it but the P14 is the No. 3 Enfield, you may be thinking about the "Mark 3" which is the No. 1 Enfield.

L8 Battle Rifles, L39 Target Rifles, Envoy's, Enforcers, L42 Sniper Rifles, DCRA and private gunsmith built conversions all using the basic No4 action that was used in the war, with the conversions done on surplus rifles or with over stock new receivers that were left unassembled after the war have held up just fine, while the Indians instead of adopting the No4 action decided to change the material to make the old No1 Mk 3 action to be usable for the NATO round being in service for many years now.

Dimitri

The best No.4 receiver with the best quality bolt body converted to 7.62 NATO held up okay but was never subjected to the stresses of a Battle Rifle to the extent that the rifles of WW1 and WW2 were.

The 50,000 PSI of the 7.82 NATO exceeds the maximum allowable pressure for .303 ammunition by 2,000 psi, so it exceeds the safety limitations of the Enfields for extended use under expected harsh conditions of the field as opposed to the range and casual use with regular cleaning after relatively few rounds at any one time.
No.1 Mk III* rifles were found unsuitable for the 7.62 for good reason, insufficient margin of safety.

7.62 conversion kits were available at reasonable prices in the 90's, I considered getting one at the time. The reason these kits were available is that wide spread conversion of No.4 rifles was not considered to be a good idea in the long run.
Had I converted a No.4 I'd have used only handloads that generated pressures no higher than those of the .303 handloads I already used.

Whether the modifications made in producing the A10 clone of the No.4 are entirely necessary or not is a question of individual rifles and the quality of available ammunition. Dangerous 7.62 NATO shows up now and then even today, with pressures far higher than a No.4 should be subjected to.

The Indian rifles vary greatly in quality and condition, and I'd expect that the worst examples had been scrapped long ago and never made it to the surplus market. Any obviously defective Indian rifles should have been broken down for spares by dealers to avoid accidents to their customers.

If a No.4 or No.5 receiver can be spread by hard use firing .303 ammunition then how much worse might the situation have been when the ammunition generates higher pressures as a matter of course.

[Dimitri]

The reason these kits were available is that wide spread conversion of No.4 rifles was not considered to be a good idea in the long run.

No the reason they were available is because they were parts originally made for a contract of L8 rifles for India before the contract being canceled (due to the British not selling Sterling SMGs at the same time). Once the last of the 7.62x51mm NATO No4 rifles went out of service there was little need for the British to hold onto their spare parts.

Considering the L42 Sniper rifles were in service till 1992 and the target rifle conversions probably fired more rounds the Enfields used in the war (with some competitors shooting a couple thousand rounds a year or more through them), I doubt there is much if anything to worry about.

Dimitri

[Alfred]

No the reason they were available is because they were parts originally made for a contract of L8 rifles for India before the contract being canceled (due to the British not selling Sterling SMGs at the same time). Once the last of the 7.62x51mm NATO No4 rifles went out of service there was little need for the British to hold onto their spare parts.

Considering the L42 Sniper rifles were in service till 1992 and the target rifle conversions probably fired more rounds the Enfields used in the war (with some competitors shooting a couple thousand rounds a year or more through them), I doubt there is much if anything to worry about.

Dimitri

Well a quick look around and postings by L8 owners indicates that the L8 rifles suffered from inaccuracy problems that were attributed to the barrel profile or bedding. One owner saying he might get two inch groups one day and five inch groups the next.
The L42 used a heavy profile Hammer forged barrel of the highest quality. I suspect that the mass of that barrel dampened the harmonics and offset bullet throw from the weaker right side of the receiver. A barrel that heavy would not have been usable for the standard infantry rifle version.
Years ago I read a field test of surplus L42 rifles, the fellow that ran the test had less luck with heavy bullet target loads than he had expected, and said the rifles were intended for the 144 grain infantry loading.

Wartime use of any rifle can be varied with some rifles firing few rounds while others may fire hundreds of rounds per day for weeks on end with little or no cleaning, and certainly no through detail cleaning to remove metal fouling build up in the field. Instructions were for Infantrymen to never try to remove metal fouling themselves but rather to turn the rifle over to their non coms to be cleaned using potentially damaging copper or nickel solvents.
No target shooter would have allowed the sort of fouling build up I've found on almost every surplus rifle I've examined, with Enfields leading the pack when it came to hard set up carbon and metal fouling.

Near as I can tell accurate L8 rifles were few and far between. Those that are still around were probably the best of the bunch, but the average results were disapointing enough that the British decided it wasn't worth the effort to convert any more.

In any event the NATO cartridge exceeds the max SAAMI pressure of the .303, so I don't consider converting a .303 to 7.62 NATO wise in the long run. I don't consider the 93 actioned Spanish Mauser conversions to be any better. Both actions should be left in original chambering, and if rebarreled or rechambered only chamberings that generate the same max pressures or less would be advisable.

[Edward Horton]

Alfred from now on you and ireload2 are going to be called the dynamic duo, able to leap tall gun articles you have read in a single bound, the only problem is you both don’t know what you are talking about.

"The more bolt thrust applied to the bolt face the more energy there is for the lugs and locking surfaces of the receiver to apply in loosening the case in the chamber and breaking any grip on the chamber wall from fouling and other contaminants before extraction."

Let me explain excessive bolt thrust to you, you stand in front of me and let me hit you as hard as I can over the head with a hammer and see how well you spring back and function.

This hammer test will discover any inherent weakness you may have and I will write about them here in this forum.

Alfred I have NEVER in my life heard more BS than what I have heard from you and ireload2 in these forums and I wouldn’t let either of you near any of my firearms. Neither one of you understands WHY you should have a dry oil free chamber nor what excess bolt thrust is or does.





Now tell me again how the more bolt thrust applied to the bolt face helps eject the cartridge case on the Enfield Rifle.

Now excuse me this is my last post in this thread, I’m going to join the French Foreign Legion and get as far away from the “Dynamic Duo” as possible.

[louthepou]

Ed with French soldiers... I HAVE to see that!

[Dimitri]

In any event the NATO cartridge exceeds the max SAAMI pressure of the .303, so I don't consider converting a .303 to 7.62 NATO wise in the long run.

Because American Arms manufacturers know best that, is why they load the 8mm Mauser to comparable levels to the 30-30 WCF.

Dimitri

[ireload2]

Because American Arms manufacturers know best that, is why they load the 8mm Mauser to comparable levels to the 30-30 WCF.

Dimitri

I am sure that you would not load it at all considering the smorgasbord of land and groove diameters that is the goat roping called the 7.92X57.

[Alfred]

Because American Arms manufacturers know best that, is why they load the 8mm Mauser to comparable levels to the 30-30 WCF.

Dimitri

When the Mauser 8mm rifles first began showing up in the US in significant numbers they were often rebuilt WW1 actions and often of much poorer quality than you'd expect from the examples that survive today.
I've read reprints of articles on the Mauser sporters available during those days, and from what was written then its not at all unlikely that downloading the cartridge for sporters prevented many accidents.
The .318 and .321 bores were as common as the .323 bores, and metalurgy ranged from excellent to abysimal. Wood work and finish on the otherhand was almost always exceptional. But a pretty face can hide an evil mind.
The obsolete 1888 Commision rifle was not considered safe with WW1 era 7.92 ammunition so why expect US sporting ammunition manufacturers to supply ammunition known to be of unsafe pressure levels when it would fit the chambers of rifles that could easily be blown out by it.


To repeat since some apparently didn't understand it earlier.

After chamber pressure becomes sufficient to initiate case wall stretching, the case head soon hits the bolt. As pressure progressively increases, it pushes the case head progressively harder against the bolt. Hence, the bolt will progressively compress and the action will progressively stretch until chamber pressure peaks. (Actually, owing to inertia, the case head will continue to push against the bolt, as the bolt continues to retreat, for some time after chamber pressure has peaked.)

Eventually, the bolt will exert more force against the case head than chamber pressure exerts against the case head. At that instant, the bolt will begin to slow, eventually to stop, and then to reverse direction. As chamber pressure continues to plummet, the energy stored in the bolt and receiver will drive the bolt back toward the resting position. In practice, the bolt will hammer the case into the chamber with considerable force; often sufficient to set the case shoulder back enough to assure that case headspace length is shorter than chamber headspace length. As a result, the action will open freely.

While all of this is happening, the chamber also is stretching in both length and diameter. This contributes some to case stretching; it also supplies the energy that allows the chamber to hammer back against the case body, so that it is reduced in diameter enough to assure free extraction.

Depending upon case shape (body taper, shoulder width, shoulder angle), case construction (hardness, thickness, etc.), load variables (pressure peak and duration), action design and barrel design (over the chamber), many results are possible. First, the action can open freely and the case can extract freely. Second, the bolt can turn freely (because case headspace is shorter than chamber headspace) but the case can hang up in the chamber (because relaxed case body diameter is slightly larger than relaxed chamber diameter (the case is an interference fit). Third, the bolt can turn hard (because case headspace length is longer than chamber headspace length) but the case can extract easily (because case body diameter is smaller than chamber diameter).

This partly explains why various chamber and gun designs show different symptoms with loads at similar peak pressure. The classic comparison is the 22-250 versus the 22-250 Ackley Improved (AI). With the former, this rebounding bolt can easily drive the case into the chamber far enough to move the shoulder and solidly wedge the case; with the latter, the shoulder is many times more resistant to being moved and driving the case into the chamber the same distance accounts for many times less increase in case diameter at any given location. Hence, pressure that causes sticky extraction with the 22-250 will show perfectly free extraction in the AI version.

THE GUN
How much the case head moves the bolt face rearward depends upon the following factors:
Shape of pressure curve — a wider curve means more movement (owing to inertia, the case head never has time to move as far as it would if the same peak pressure were applied in a static situation. Therefore, the longer the pressure stays close to the peak, the more the bolt will compress — the farther the head will move);
Peak chamber pressure — force and movement are directly proportional;
Distance between bolt face and locking surface — distance and movement are directly proportional;
Cross-sectional area of bolt — area and movement are inversely proportional; and,
Cross-sectional area of receiver — area and movement are inversely proportional.

Without bolt and lug compression and resulting recovery actions with poor primary extraction would have a difficult time extracting the fired case. Its a basic principle known since the bolt action rifles first appeared on the scene.
The taper of the .303 case body was likely meant to take advantage of this, since theres not that much of a shoulder there even after fire forming.
The Enfields have a far less effective camming action than other turn bolt rifles of the day. Theres so little primary extraction that a cock on opening conversion isn't likely to work. the cock on closing action allowed easier opening.

It occurred to me that some might not realize just why a non rotating bolthead of the Enfield and Mannlicher designs or the non rotating extractor of the mauser style and Krag designs is necessary for turn bolt actions of high powered rifles.
The fired casings are firmly pressed into the chamber and seldom can be turned in the chamber by the bolt. Without primary extraction the case would be extremely difficult to extract under the best circumstances, and without the spring back of the compressed lugs or bolt body to break the adherence of the case to the chamber walls turning the bolt to engage the camming surface would also be very difficult. Both the non rotating extractor claw and camming surface are necessary, the case isn't going to just jump out of the chamber by itself. If nothing breaks the grip of the case to chamber adhesion then turning the bolt would be several times more difficult.
The springyness of the Enfield action in this way greatly makes up for its relatively weak primary extraction.