No.4 MkI barrel to channel contact when trigger guard tightened down.

Hello,

I have what I think is a rather odd issue and would love some advice from the brains trust.

After much searching I recently purchased a nice No.4MkI. I took it out to the range for the first time. Started at 25 metres just to see where it was at. Was absolutely chuffed to find it put 10 rounds of PPU 180gr FMJ into a ragged 1x1.25 inch hole.

The only sour note was the group was about 2 inches left of my point of aim. So I figured the stock is probably warped, drifted the sight and kept shooting. Very happy with how it shoots.

I disassembled it once I got home to check for warping and this is where the strangeness starts. To my eyes the stock is not warped. The barrel is definitely in contact on the right side in the last quarter of the forend towards the muzzle. However the forend when removed appears straight.

The even stranger part is when the tension is off the boss screw on the trigger guard the barrel returns to dead centre of the channel.

This lead me to believe the issue lay in the draws. So I did the old talcum powder test expecting to see uneven contact here. But nope, even contact on the draws, and actually really good fit in the forend on all the horizontal surfaces.

So now I'm stumped. Forend fits snugly like a glove with everything centred up. But as soon as the trigger guard is tightened down at the boss screw the barrel shifts right and contacts the channel.

I am open to any and all suggestions.

There are some ex serving armourers on this forum, but until one of them decides to chip in, I have a suggestion that you might want to look at. A long time ago I encountered a similar problem, & after a few words of advice from PL I resisted the temptation to open out the barrel channel towards the muzzle on the side that it was binding, & had a look at the routing out of the forend at the reinforce of the barrel end (chamber) ON THE OPPOSITE SIDE. If you think about it it is blindingly obvious (mind you, it wasn't to me until I'd asked!), that a high spot here will cause the barrel to push over to the opposite side progressively as you go from breech to muzzle. I'm not saying it must be this problem, but it could be, & is probably worth investigating. And the solution is simple - carefully take down the high spot a little meat at a time, until the barrel sits centrally in the barrel channel throughout its entire length, with the screws correctly tightened.

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Originally Posted by Roger Payne

There are some ex serving armourers on this forum, but until one of them decides to chip in, I have a suggestion that you might want to look at. A long time ago I encountered a similar problem, & after a few words of advice from PL I resisted the temptation to open out the barrel channel towards the muzzle on the side that it was binding, & had a look at the routing out of the forend at the reinforce of the barrel end (chamber) ON THE OPPOSITE SIDE. If you think about it it is blindingly obvious (mind you, it wasn't to me until I'd asked!), that a high spot here will cause the barrel to push over to the opposite side progressively as you go from breech to muzzle. I'm not saying it must be this problem, but it could be, & is probably worth investigating. And the solution is simple - carefully take down the high spot a little meat at a time, until the barrel sits centrally in the barrel channel throughout its entire length, with the screws correctly tightened.

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Thanks for the advice mate. I inspected this area and didn't notice any humps. However whilst I did this I did a further inspection of the interior forend surfaces and found a clue.

On the left hand draw there is the slightest indication of impact wear, whereas the right hand draw is in good condition. This indicates to me there is play there. So I went and got some proper bearing blue to do a better job at checking the fit here. I applied it to the recoil lugs (and the reinforce for good measure just to be sure) and assembled the rifle.

What do you know the right hand recoil lug left a full bold mark on the draw, while the left hand one made a patchy faint imprint on about 60% of the draw.

For posterity the reinforce left a mark indicating central contact at its base. Which is good.

So now the situation is more complicated;

- On the one hand the patchy contact and impact damage on the left hand draw is a clear indication to me that under recoil the receiver is slightly pitching left, throwing the shots left.

- On the other hand the barrel is leaning to the right, making contact with the forend. Which could cause the same thing with throwing shots left.

- On top of all this the barrel leaning right is the opposite of what you'd expect to see with a loose left hand draw when you tighten everything up. Maybe my eyes are deceiving me and the forend does have a warp?

Fun times!

My next course of action is to break out the shim stock and get a good equal bearing on the draws then see how it shoots. It should reveal whether it's the draw or the forend causing the shots to fly left at least.

I gather there is a collar in where the trigger guard screw front (Think thats the terminology PL uses) goes through as you have not mentioned it.

Lack of contact or minimal contact of the left bolt lug will cause this with a number 4.
You can eliminate the wood fit by removing it and firing the reassembled rifle, support under the magazine, you may see a change but I would certainly correct the lug contact.

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Originally Posted by CINDERS

I gather there is a collar in where the trigger guard screw front (Think thats the terminology PL uses) goes through as you have not mentioned it.

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Yes it's there, and it seems to be functioning as intended (eg. Not standing proud and the trigger guard is applying pressure to the wood not the collar).

Just to absolutely rule it out, if it's a No4 beech stock, are you sure it's not twisted.

They are susceptible to to twisting along the length unfortunately.

This can be 'so' slight, it's difficult to pick up, but enough for the barrel to make contact on one side.

I've removed a tiny amount of material before on the offending side until I could slide a piece of A4 paper up and down the channel without pinching...

The trouble is, it simply carries on twisting and it eventually made contact again....

I've also had another beech forend that had a lateral split in the barrel reinforce/ ledge, formed along an unfortunate knot in the wrong place, right were the barrel constantly knocks it like a hammer!

The only solution (for me) was to replace the forend on both occasions, the good thing about NOS No4 woodwork, is it's still available.

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Originally Posted by mrclark303

Just to absolutely rule it out, if it's a No4 beech stock, are you sure it's not twisted.

They are susceptible to to twisting along the length unfortunately.

This can be 'so' slight, it's difficult to pick up, but enough for the barrel to make contact on one side.

I've removed a tiny amount of material before on the offending side until I could slide a piece of A4 paper up and down the channel without pinching...

The trouble is, it simply carries on twisting and it eventually made contact again....

I've also had another beech forend that had a lateral split in the barrel reinforce/ ledge, formed along an unfortunate knot in the wrong place, right were the barrel constantly knocks it like a hammer!

The only solution (for me) was to replace the forend on both occasions, the good thing about NOS No4 woodwork, is it's still available.

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I checked for this initially by lying the forend upside down on a flat surface. It lay flat with no wobble. It's also not a beech stock, very dark and looks like walnut to me.

I'm convinced whatever is causing this is originating in the fit at the stock wrist collar and draws. Because as soon as I take tension off of the main screw the barrel runs true through the centre of the stock.

Quote:

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Originally Posted by muffett.2008

Lack of contact or minimal contact of the left bolt lug will cause this with a number 4.
You can eliminate the wood fit by removing it and firing the reassembled rifle, support under the magazine, you may see a change but I would certainly correct the lug contact.

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I spent an hour this evening shimming it and now have a temporary shim on the left draw. It didn't take much at all. This is giving me strong bearing on both draws.

I have also re-centred the front sight on the reference mark I made before I drifted it. I'll be able to get to the range over the weekend and see what effect this has had on the way it shoots.

The thing I'm wondering though is if this does fix the issue what's the best plan for a permanent repair?

I know the official armourers way would be to remove the proverbial gnats knacker of material from the right draw to bring the whole action back and get even contact. But I feel that this would interfere with the fit at the wrist which is very good.

I could glue the shim in. Or hell I could even use arcaglass. I have some laying around. It would literally take a drop of it to fill in.

I guess I'll worry about that after I shoot it and see.