M1903A4-gery Build

[95chris]

Made some progress on the stock today. Slowly removing wood from both locations the recoil lug (carried out first) and receiver flat have made contact when fitted. As expected, the clearance between the rear tang and stock decreased so that was also worked on to maintain that ~0.0010" of relief.

With everything still tight, I checked the force needed to separate the stock and and the barrel at the muzzle. It barely took any force, I could separate the two by pushing against the barrel with my thumb while holding the barrel with my other hand. If I had to guess it probably took less and pound of force. Also used one of those luggage scales for travel and it had similar results (I'm aware they're probably inaccurate to a degree).

I decided to inlet the length of the barrel and noticed it was still making contact at the previously pictured location near the chamber, probably due to the fitting of the receiver flat. Those were relieved and by following Claven2's advice on lowering the receiver flat to increase pressure and by removing small amounts of material, I was able to achieve a pound of force on the scale to separate the two. I'll be continue this process while marking the flat and lug to ensure they remain seated.

Of course I can't make a post without asking a few questions so here goes! FYI, the bedding at the muzzle has not been touched up to this point.

From the tip of the stock, how much of the barrel is supposed to make contact with the stock to create this pressure? The number I saw online is one inch The picture on the right shows where the contact points are at this moment.

I can continue working on the flat but if too much of the forward length of the barrel is contacting, should I relieve those areas to stay within that one inch point of contact?

Cheers.

 

[purple]

About an inch of barrel/stock contact area is desirable at the forend tip.

Before removing any more wood, I'd check the fit of the upper band with the action installed and the guard screws drawn up tight. Does the top of the barrel make contact with the upper band? If there is no contact, good. If there is contact you can either remove some wood from the forend tip (but this will decrease barrel/wood pressure there), or you can grind away some of the upper band surface to get clearance between the barrel and the upper band.

As you have found, when the receiver flat is lowered further in the stock, the amount of barrel/wood pressure at the forend tip will increase. This should also tend to increase clearance between the top of the barrel and the upper band. Take note: I'd previously mentioned 5-7 lbs pressure at the forend tip, but checking my original M1903 - 03A3/A4 tech manual shows 4 lbs pressure at the forend tip. Not a huge amount of difference though.

All things being equal, if there is clearance between the upper band and the top of the barrel, the forend tip could also be shimmed to increase pressure at the forend tip. With a full length military stock, contact/pressure at the forend tip is also desirable to eliminate the possibility of the stock warping and binding aginst the barrel over time.

In fitting a number of new GI stocks I've found that minimal wood removal is required at the forend tip, but stocks can be different, and this is a commercial repro stock.

You should also verify that you are using a 03A3 front guard screw, rather than a M1903 guard screw. The 03A3 screw is 1.015 OAL while the M1903 screw is shorter (.0922 OAL). The screws are interchangeable, but the 03A3 screw allows more penetration of the receiver. The longer 03A3 screws should not be used on an M1903 receiver because they may bottom out in the blind hole for the guard screw.

 

[95chris]

About an inch of barrel/stock contact area is desirable at the forend tip.

Before removing any more wood, I'd check the fit of the upper band with the action installed and the guard screws drawn up tight. Does the top of the barrel make contact with the upper band? If there is no contact, good. If there is contact you can either remove some wood from the forend tip (but this will decrease barrel/wood pressure there), or you can grid away some of the upper band surface to get clearance between the barrel and the upper band.

All things being equal, if there is clearance between the upper band and the top of the barrel, the forend tip could also be shimmed to increase pressure at the forend tip.

I did this check with and without hand guard ring, no upper handguard (if I need to just say so) and there's a pretty good gap in both scenarios.

To be honest, I'd be happy to shim the fore end tip to achieve the required pressure. I can always come back and try it again in the future or on a proper GI stock. I'm guessing I would need to shim it just have enough to have a gap when the upper handguard is installed. A quick search online mentions 0.025" would be O.K to go with. Would feeler stock similar to the attachment be used? Can be easily cut to length and has various sizes.

You should also verify that you are using a 03A3 front guard screw, rather than a M1903 guard screw. The 03A3 screw is 1.015 OAL while the M1903 screw is shorter (.0922 OAL). The screws are interchangeable, but the 03A3 screw allows more penetration of the receiver. The longer 03A3 screws should not be used on an M1903 receiver because they may bottom out in the blind hole for the guard screw.

Looks like I have the shorter M1903 screw.

I should really find one of those tech manuals for myself.

 

[purple]

A quick check of several 03A3s and 03A4 shows .020 clearance between the top of the barrel and the upper band.

The handguard should be fitted after everything else is satisfactory.

If shimming the forend tip is necessary, different thicknesses of wooden shims can be tried until desired forend tip pressure is established. When it's right, the shim should be glued in otherwise it may dislodge from recoil. People often try shims of various thicknesses to see how a rifle shoots with different forend tip pressures.

The receiver flat can also be shimmed to check for differences in accuracy as a result of different pressures at the forend tip. The stock area behind the recoil lug acts as a fulcrum when shimming under the tang to increase forend tip pressure and/or to gain clearance between the top of the barrel and the upper band.

I have a spare 03A3 front guard screw. PM me your address if you want it. As you can see, the 03A3 guard screw hole is drilled right thru the receiver ring which allows for the longer screw.