Need help/advice on a wandering POI problem

[gravityfan]

I have a '44 Long Branch, 2-groove, which is in excellent condition. It wears a PH5 and FS22A. It has proven to be very consistant, and with practice, I have been improving my group sizes.

Over the past couple of hundred rounds or so, it has developed a problem in that the POI drops as the barrel warms. Today I conducted a test at 100 yds, bench firing 4 strings of 5 rounds with negligible time between each, allowing the barrel to warm progressively.

The results of the 4 strings are:
- string 1 - 1", dead centre (well chuffed!)
- string 2 - 1.75", 2" low (and slightly to the left, but that was probably me)
- string 3 - 2.25", 4" low
- string 4 - 2", 6" low

Whilst details will have been affected by my use of iron sights, and my less than stellar technique, I think the trend is clear. I am very pleased with the group sizes, but that drifting downwards... It used to be very consistant vertically.

The Screw, Guard, Trigger, Front has not worked loose, and is still snug.
The Screw, Guard, Trigger, Rear is likewise.
The Butt has not loosened.
The Barrel will pass a .303 gauge, but a .304 gauge won't even start, so the barrel is not shagged out.
The muzzle has about the requisite 4 lbs of pressure, or at least it does not seem any different from when the rifle was consistant.
The Parker Hales are rock-solid.
I tried to make everything as consistant as possible from string to string.

To sum up, I can't find anything that has changed, or is loose.

I am at a loss as to what to investigate or twiddle next.

I'd really appreciate any suggestions/help/ideas/informed opinion.

Cheers.

Information

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[smellie]

Wandering zeroes or changing POI in Lee-Enfields generally is down to the bedding, given that the rifle was set-up properly in the first place (as yours doubtless was, your previous groups proving this).

Have you checked The Damned Crack? It starts right at the thinnest part of the fore-end, right where the trigger protrudes downward and there is very little wood at all and it is responsible for more lousy shooting with SMLEs and Number 4s than 3/4 of all the ropey barrels in existence.

If that is the problem, the cure is easy: spread things apart gently and squirt in a little dab of epoxy, clamp it the way you want it and leave it 24 hours. When the epoxy is completely solid, unclamp, trim away any excess and reassemble the rifle. It will NOT break here again.

I could be 'way off-base here, but that would be my first suspicion in such a case as you describe: sudden deterioration of shooting with a previously-excellent rifle.

Good luck!

[Thunderbox]

1. Check that the front handguard is not creeping forward under recoil, thus fouling the foresight assembly - this is the prime cause of vertical POI movements in a No4. This is why you often see staked front bands on a No4.

2. Apart from the "down pressure" at the muzzle, ensure that the barrel has free vertical movement inside the barrel channel. Often a "high point" inside one of the handguards is the culprit - the wood coming into contact with the barrel as the rifle heats up.

3. Check the barrel channel itself for high points - sometimes just a lump of old cosmoline. One method is to dust the channel and handgaurds with talcum powder - blow off the surplus - then reassemble the rifle with the metal parts lightly oiled. Move the barrel up and down to simulate firing shots, then dissemble the rifle to see if there are any obvious touching points.

[Peter Laidler]

And don't forget that shooters are notorious for 'chasing the zero' around the target................ Stop, have a break and then let someone else do a check shoot/zero. As Armourers, with hundreds of rifles to check for accuracy, we'd often unknowingly fall into that trap

[Edward Horton]

1. Check that the front handguard is not creeping forward under recoil, thus fouling the foresight assembly - this is the prime cause of vertical POI movements in a No4. This is why you often see staked front bands on a No4.

2. Apart from the "down pressure" at the muzzle, ensure that the barrel has free vertical movement inside the barrel channel. Often a "high point" inside one of the handguards is the culprit - the wood coming into contact with the barrel as the rifle heats up.

3. Check the barrel channel itself for high points - sometimes just a lump of old cosmoline. One method is to dust the channel and handgaurds with talcum powder - blow off the surplus - then reassemble the rifle with the metal parts lightly oiled. Move the barrel up and down to simulate firing shots, then dissemble the rifle to see if there are any obvious touching points.

Thunderbox

Is your saying "down pressure" a difference between British and American English like saying anti-clockwise and counter clockwise. In American English the fore end tip is pushing "upward" on the barrel and thus called "up pressure".





Thunderbox I mean no disrespect but I have read this from other British forum members also and it is a little confusing on this side of the pond.

As an example the American Remington 700 standard bolt action rifle has 3 to 9 pounds of "up pressure" at the fore end tip of its stock. This means the same as the above section from the 2002 Canadian No.4 manual, and the wood stock is pushing upward on the barrel.

NOTE: Before I wrote this Thunderbox I ran out to my truck and made sure the steering wheel was on the left hand side of the cab.

[newcastle]

I had a No.4 Mk2 about three years ago which did this to the point of a 4 or 5 inch drop at 50 yards. Never found ANYTHING wrong with it, I even shot it without foreend and handguards (that REALLY hurt my shoulder) and it still dropped POA as it warmed up over about 30 shots then stayed there until I left more time between shots when it started to rise again. Came to the conclusion it was a metallurgical thing.

[gravityfan]

First and foremost, thanks to you all for the input.

Smellie, very interesting about the crack, I didn't know it was so (in)famous as to have its own name! That is one for the old memory banks. I looked and looked, but can find no evidence of a crack anywhere. I definitely see your point about how that would be a big factor.

Thunderbox:
1) Unfortunately, I spaced on this one when setting about the disassembly, but I did notice when I first reassembled it that the front handguard cap was touching the foresight block (I don't have a protector because of the PH sight). I relaxed the band screws, pressed the handguard to the rear, and re-tightened. That leaves it with a small gap and its cap is now flush with the stock cap and leaves a small but noticeable gap between the caps and the sight block. The handguards are both solid, and I can't make them shift at all with the band screws snugged down. I don't think that was the problem, because the paint on the band is unmarked, but I can't be certain. Let's hope I improved things. I'll certainly keep an eye on it during shooting, in case of any forwards movement.

As for 2) and 3), all I managed with talc and oil was a mess! However, I did notice that the wood in the stock channel has only got that "incredibly smooth and blackened almost like a mirror" polished look showing an excellent silhouette of the bottom of the action at the rear, and maybe a quarter inch wide band almost a couple of inches from the front - just inside the rear of the cap. I can run a slip of paper all the way under the rest of the barrel. The rear handguard has no evidence of touching the barrel. The front handguard has a slight "polished" area just about opposite the one on the stock, about level with the rear of the cap. Would that be seen as a problem? The barrel must be contacting it on firing. Might that be it? I can't think how to change that, unless I increase the downward pressure of the barrel, or should I scrape out some of the wood on the underside of the front handguard so the barrel can, as it were, jump higher?

Captain L, thank you for the reminder. I'm pretty sure I was keeping a consistant POA, at least that was foremost in my mind during the test. However, I will pay special attention to that on my next trip.

Newcastle, please let it not be as you relate. I'd be devastated if such an accurate and reliable (and pretty) No.4 goes terminally useless. It'd just about break my heart.


I'll be most interested in any views on relieving the wood on the underside of the front handguard.

Whether or not I adjust the handguard, I'll also re-do the test at the weekend, always welcome an excuse to get some rounds downrange.

Thanks again to all, and any further guidance is sincerely welcomed.

Cheers All for the help.

[Peter Laidler]

Another small point GF. When we were doing them, we'd do it from the bench in the shoulder but if there was a problem rifle, we'd put it in the Enfield/mechanical rest to shoot it. But even here, it was always sighted in by eye. And humans err........... and human eyes lie sometimes!

[gravityfan]

Edward,

Thanks indeed for this excellent picture. In reference to it, I am pretty sure that points A, B, C & D are correct, but only the left-most 1/2 inch or so of point E. Also a similar place of contact appears on the front handguard (left-most 1/2 inch or so of point E).

I'm more worried/concerned/interested in how a really nicely performing rifle can so suddenly go bad to the point of uselessness, without at least some physical sign. Everything looks the same as it was, and the bedding points are as before, even if not quite the spec as above.

Does that seem illogical? Don't know what to do next.

Cheers.

[Edward Horton]

gravityfan

Try these two checks, you might have a little wood shrinkage which changed your bedding forces. First tighten the forward trigger guard and mark the location of the screw head.



Next take the trigger guard off and remove the forward trigger guard screw bushing or collar, remove it completely and set to the side.

Wood shrinkage effects the bushing length and bedding forces.



Now resemble the trigger guard minus the bushing and re-tighten the trigger guard screw. If the screw rotates or turns past your original marks on your trigger guard you have wood shrinkage or wood crush and the bushing is too long.



Next take a set of feeler gauges and see if one fits between the very rear of the fore stock and the receiver socket.



The rear of the stock should be touching equally on the left and right side of the socket. It does not have to be touching 100% of its area but it is very important it is touching on both sides and the bedding forces are equal.

Below the rear draws area controls the "tightness" of the rear of the stock and the forward section of the draws should "push" the very rear of the stock into contact with the receiver socket.



Below an example of only a small portion of the right touching the receiver socket. (bright shiny area)



The first thing I would do if you have any of these problems is give your wood furniture or stock a good long drink of RAW linseed oil to see if the wood will re-hydrate and swell. (re-moisturize the wood)



Let us know if you find any thing wrong.

All the information in the world is written in books, and all you have to do is read. (RTFM)