Heard that the Lee-Enfield's receiver was prone to "flex" and/or "stretch" due to it's rear-locking lug design. It seemed to perform well enough in combat. Is this only a concern on older weapons?

No more so than other firearms of that vintage.
The gripe expressed about the locking was it's supposed affect on accuracy..
The only SMLE that truly was suffering from reciever flex were the experimental No4 Lightweights, and the early No5 "Jungle Carbine"..

As to hardness, ductile steels are preferable to glass hard ones. Many beautiful low serial number M-1903 Springfields are unshootable for this reason.

-Meplat

More gun shop "expert" nonsense.

All M1903 "Springfields" are shootable with US issue ammo.  Don't use hot hand loads, 7.92mm Mauser or 1917 vintage FA ammo in the older ones though as their receivers aren't as strong as the later ones.  

-- Chuck

I have an English highpower rifle shooting book (Target Rifle Shooting by Reynolds & Fulton)in which the author extols the virtues of a rear locking action and the "flex". Supposedly this affects the gun's harmonics in a positive way. The author theorized that these guns shoot better at long range than front-locking rifles because of the "flex". I think it's just British braggadocio.

I've got what I consider to be a great deal on a Longbranch No4Mk1* if anybody is looking.

Rear locking on a military bolt action rifle has many advantages.  In the case of this rifle and .303 ammo it's quite strong enough, but won't handle higher pressures as found in .30-06 and 8mm Mauser.

-- Chuck

Actually it isn't that the receiver on the Enfield which "flexes" very much but rather it is the BOLT which compresses somewhat. Receivers on Mauser type Rifles with Front locking lugs (especially those with an internal magazine) flex quite a bit.

Here is the following from another forum from an High Power Rifle competitor from Bisley:

#4 Accuracy
Accuracy keeps cropping up on this forum. I own a number of military and sporterised #4's (and a half dozen or so SMLE's) Other than the mint Irish #4 Mk2 shooting Sierra 174 match bullets, the accuracy of these rifles is fair (3" to 4" at 100 yards).
However, the #4 has been used as a target rifle. When tuned up by a master armourer who knows his trade, these rifles can be made quite accurate (under 2").
At long range the #4 rifle comes into its own. Until recently (1990) the #4 was the only rifle to use at long range, because it would "compensate". (I should point out that these rifles have all been equipped with heavy barrels in 308, but until about 1958 we shot similar rifles in 303.)
A well tuned #4 rifle would should a vertical egg-shaped group at close range, so we would use a front-locking target rifle at close range (300 to 800 yards). At long range we would change over to our long-range rifle - a #4.
Now, you might wonder how a big group (say three minutes) at 100 yards can become a one minute group at 900 yards. On the face of it, it defies logic. The key to the puzzle is barrel compensation. Suppose you are testing ammo at 100 yards, and you shoot loads with 34, 35 and 36 grains of powder. In most rifles each hotter load will print a bit higher on the target. Not so a Lee Enfield. The rear locking lug leads to a "springy" action. The muzzle of any rifle is vibrating and moving in the vertical plane when fired. In a #4 the muzzle is moving "up" as the bullet exists the muzzle. Assume ammo with some variation in velocity. A slow bullet leaves the muzzle later and the barrel has moved up more. The slow round is aimed higher. At short range it prints higher on the target than a fast bullet which exists before the muzzle has moved up as much. At long range the effect of velocity variation causes a vertical group. However, with a #4 the slow rounds were aimed higher, automatically, so they arrive on target. The faster bullets would normally printer higher, but in a #4 they were aimed lower, so they too would arrive on target.
If this strikes you as myth, wishful thinking or hokum - welcome to the club. I grew up listening to stories of "compensation' at long range and was skeptical. I served a hitch working in a ballistics lab and learned that many a theory was just an over-reaction to an anecdotal event. Only a controlled experiment can determine if an observation is statistically valid.

Eventually (I was getting tired of getting beat by #4's at long range) I built a one piece #4 and it seemed to shoot quite well, but so did my single shot front locking target rifle. So I decided to make a test. I loaded ammo with three different powder charges a half grain part. I shot them first in my #4 at 1,000 yards. All three loads group in the bull. In my front locker the middle charge grouped the bull, the hot charge shot near the top of the target and the mild charge missed. I became a believer.
Many of us built "one piece" #4's and put them into a conventional one piece target stock.
One of the problems we face on this board is that we are all reporting anecdotal information. Whether we report the rifle as "accurate" or "inaccurate" we are all correct - so far as our anecdotal information is concerned. Of course, I am referring to those who actually shoot the things as opposed to those who just read about it.
In 1990 I was Captain of the Canadian Rifle Team preparing to shoot the Palma Match at the World Championships in Raton, New Mexico. The Palma Match is shot by teams of 16 shooters shooting 20 shots each at 800, 900 and 1,000 yards.
The '92 Palma match was a landmark match in that for the first time it would be shot with high quality match ammo instead of military ball ammo. Prior to this match it would have been a given that most of us would have taken a #4 based rifle to a long range match.
To see if the better ammo negated the value of the #4's compensation, a number of our rifles were shot off a bench at 1,000 yards in a tunnel. The range is on an abandoned stretch of railway line. It is only about 50 yards wide and has tall trees down both sides - hence the "tunnel".
The match ammo grouped about 17" in our front locking target rifles at 1,000 yards. The #4's grouped around 12". The front lockers had a more dense group, but the flyers would open it up.

Here is the scary part. The best front locker had a bigger group than the worst #4. The typical front locker would be a Remington 40XB, a Musgrave (South Africa) or a Swing (Great Britain). These are $2,000 rifles. They were all beat by #4's.
We placed second in the '92 Palma, ahead of New Zealand, Australia and the Americans. The Americans were skeptical (I am being polite) of our #4's.
Jim

A #4 is tricky to bed. Bedding has a lot to do with how well it shoots and how consistantly it shoots. the #4 is not suitable for amateur bedding (unlike mausers and others). I know only a few who can do the job on a standard wood-stocked rifle. The "before" and "after" is day vs. night.
When one reads about how accurate the #4 was the results were probably based on rifles that had been set up by someone who knew what they were doing. The SMLE was the same, only trickier.
At one time each regiment would have had an amourer who knew how to tune a rifle. Very few of these men are left and I doubt that we are creating any new ones.

If you ever happen to have the chance to buy a #4 from a selection, here is one thing you can easily check. The barrel should have a few pounds of down pressure on the bottom of the muzzle forend channel. It is easy to push up on the barrel at the muzzle and see if it snaps back into place, or just wanders around.
Also, the accuracy of the rifle demands that the main action screw just forward of the magazine be tight. The tension on this sceew varies the down pressure at the muzzle.
We converted our #4 target rifles to one piece stocks so we could bed them conventionally.

The "compensation" still worked. I used a small torque wrench on mine to set the action screw to the same settign each time I used the rifle.
Those of you who enjoy shooting and handloading can easily run a simple experiment so you can see "compensation" yourself. Load ammo for a SMLE or #4 in three batches your normal load and then 1 and 2 graisn less. Do the same for a front-locking rifle like a Sagage 110, Win mod 70, rem 700 or Mauser. Shoot the groups at 100 or 200 yards using a constant elevation setting.
On your front locker the hotter ammo will print higher. On the Enfield they will print lower.
If they don't, it measn your bedding is shot and you are just shooting a big group.
Jim

Gawd, Boston! That sounds like the explanation in my Target Rifle Shooting book. Your name isn't Major E.G.B. Reynolds or Robin Fulton, is it? Do you know these guys?

Enfields are excellent bolt-action battle rifles, and can exhibit excellent accuracy with a good bore and muzzle.

BTW most Enfield collector's believe the No5MK1 wandering zero thing to be bunk. My No5 is one of the more accurate of my military bolt-actions.

Check out the Lee-Enfield collector's forum here: www.gunandknife.com/

Have fun!

Cheers,
Christopher

Enfields: I just like them thats all. I've shot all kinds of rifles. The Enfield is NOT the worlds most Accurate or powerful rifle. In fact it doesn't do any single thing better than any other rifle. But the amazing thing about them is that they do so many things so well.

The No.4 Action is perfectly capable of handling chamber pressures of over 50,000 psi. It makes a good platform for a .308 Rifle to be built upon.

Enfields do have some draw backs though. Your standard Enfield comes with a very skinny barrel that heats up and changes the point of impact. They got a zillion screws on them, and if you want to do something such as removing the stock you need to pack along a gunsmiths screw driver set.

Of course one of the wonderful things about the Enfield is that they are so cheap. You can get yourself a rifle that will cost only about $140 and yet it will have sufficient accuracy and penetration out to about 500 yards.
More accurate and powerful than a 30-30. More accurate than a standard FAL, SKS or AK.

But what about the .303 cartridge not being as powerful as the .308 ? No problem, you can build yourself a dandy .308 rifle on an Enfield Action..or....you can ream out the chamber to .303 Epps (sort of like an Ackerly Improved Cartridge) and load your own. .303 Epps is equal to or greater than the .308 in terms of performance.

I really hope the 'CHUCK from OHIO' is not proposing to shoot or chamber 7.92 mm (8 x 57) Mauser ammunition in a 1903 Springfield or a M1917 Enfield. They are chambered for the 30-06 (7.62 x 63) mm cartridges. Whether the 1903 rifles are high or low number would then be irrelevant as they would probably blow up. Jarhead Gunner.

Chuck- Go read some of the reports collected by Julian Hatcher regarding the 1903, between 1917, and 1929..

137 accidents, 68 of which were burst recievers of the old heat treating (through hardened)..

So just HOW is such amassed, and published data "Gun shop nonsense?"

Meplat-

i thought the reason the "03" receivers had problems was the grease put on the bullets by the soldiers!yep yep

Glad to see people who like decent .303's.  I took an SMLE with a severly eroded throat and grouped it at 100 yards.  Under 2" groups with lousy, corroded Mk VII ball.  Went to the 1,200 yard range and shot it.  I can empty the ten round mag just as fast as I can work the bolt and jerk the trigger, hitting well inside a 6 foot round bush every time with it.  It is an Australian FTR weapon.  Seems like even a heavily thrashed .303 can be excellent.

My minty FTR'd No. 4 Fazakerly is more accurate, and shoots just as well, at any distance.

.303 from a stock, out-of-the box turnbolt is all the power I can control *well*.  I can also stand to shoot more than 100 rounds a day, and not be bruised and shakey afterwards.  Can't do that with my 03's, 1917 Enfield or 8mm Mauser.

In actual field use, a good Enfield is better than it has(seemingly) any right to be.  Power level?  It is so close to .308 that the differences are inconsequential.

On a side note, Mk VII ball carries a lot more visual "wallop" at 1,200 yards than a 150 gr. generic .30 cal bullet going .308 Win velocities.  I have seen this with my own eyes.  Sometimes it is very nice to live in the wide open desert.