McMillan A5 adjustable cheek riser problem

[trental]

I have a custom 338 bedded into an older McMillan A5 that has the older style check riser adjustment system like in the attached photos. It has a pair of posts that slide into cylinders and is captured by two threaded knobs into the side acting as set screws. The knobs/bolts have pointed tips that kind of stab into the aluminum posts. Two problems with this is that it pushes up a burr on the posts and inhibits smooth sliding inside the assembly. The biggest issue though is that the set screws constantly loosen up every few shots under the recoil of the 338.

I called McMillan to see if I could get the newer style clamping system sent to me so that I could machine out the old one and bed in the new one but I was told that "wouldn't work". They did offer to send me new posts because it shouldn't be dimpling the aluminum. The never showed up though.

Anyone else have this issue and maybe have a solution? I need to be able to raise and lower the cheek rest to remove the bolt from the action. I have been trying to think of a different way of using the set screws. Maybe a different tip. I could file the tip down to more of a flat.

Thoughts?

 

[trental]

I'll take better photos of my actual rifle when I get home this evening

 

[BoydAllen]

If there is one particular height that you use all the time, perhaps you could go the other way and deepen the divots that your points make in the posts, to spread the load so that burrs will not be created when you tighten the thumb screws. Beyond that, perhaps someone makes a fastener that has has a built in locking insert that you could adapt. https://www.google.com/search?q=sel...FeawKHZfNAVsQ_AUoAnoECBAQBA&biw=1600&bih=1060

 

[Dusty Stevens]

Talk to arkco machine. He may or may not have some of the new magnetic style mechanisms in stock. Talk to matt

 

[trental]

If there is one particular height that you use all the time, perhaps you could go the other way and deepen the divots that your points make in the posts, to spread the load so that burrs will not be created when you tighten the thumb screws. Beyond that, perhaps someone makes a fastener that has has a built in locking insert that you could adapt. https://www.google.com/search?q=sel...FeawKHZfNAVsQ_AUoAnoECBAQBA&biw=1600&bih=1060

Actually, I like this idea. I could go further and machine in divits at 1/8" inch increments and make somewhat of a ladder of adjustments.

 

[watercam]

That would work. It is also possible to install a thumb wheel/threaded post in the middle and have an infinitely adjustable cheek piece. I have done this several times on match rifles. Could make a lock for the wheel so that the .338 would not knock it about. You would be able to pull the cheek piece off the gun for cleaning if you did not want to readjust the height.

 

[BigKev]

Not sure how much "downward" pressure that you're putting on the cheek piece during use but they make set screws with both brass and or nylon tips to prevent marring the posts. I would try McMaster Carr on line for these if you think they would work.

 

[skeeljc]

Bell & Carson has a bullet proof adjustable comb. It uses a clamp type lock and C-clips to retain the height setting. Very solid and quick to remove for cleaning.

 

[divingin]

Brass or aluminum pads between the screw and post? You'd need to flatten the points on the screws, though, I'd think.