Home Forums Hunting & Shooting Gunsmithing What shim material to use on a Marlin 336 Leupold base

I have a 336 with a Leupold 1 piece base. I installed the base last year and have shot well with the rifle. I did notice daylight under the rear screws of said mount, and yes I put the screws on right and tightened them properly. I am thinking brass might make the best shim for this situation what say the gunsmiths?

Sound like the screws are too long. I can remember if they go all the way through on the action I don't thing they do.
If they don't your screws need to be shortened.

Actually I just took the thing apart...the base actually has a crown . I put a straight edge on it and the only areas it touches are at the rear screw and the 2 front screws. There are no marks or binding to indicate the bolt travel is hindered. There are only 2 front screws and one rear screw holding this thing on. I tried about every tightening sequence to get the "gap" to disappear but to no luck. It is still there. Other then bringing it to a machine shop to grind it flat it might be just as well to A. keep it as is B. try another brand of mount that has 4 mounting screws.

Accurglass gel.

Send it back as defective.

With the new info this is the best option.

Something's not right.

The base not fitting flush at the rear is very common with re-barreled military rifles, and even some factory rifles.

For shims, I use aluminum soft drink cans. This is easy to cut and shape to fit under the base without being noticeable. These cans are also easy to cut with scissors.

Ok since when is a Marlin 336 a military weapon??
Did you read the first post??

i have used a feeler gauge and cut from shim stock of the proper thickness. best way is to bed the rear with acra glass..

When I wrote the above post, I added 'Yes, I know the Marlin 336 is not a military rifle.'

Then, I erased it because I thought it was too smart azz, because I thought most people would realize that I knew it was a 336, and the same thing applies to most, or all rifles with bases on top of the receiver. The fix is the same, regardless.

Seems I should have left it in the post. There is always one.

If it shoots well why mess with it?
It is just as likely that the receiver is off slightly and the scope base is fine.

If it were me, I would bed the rear of the base with acraglass gel and be done with it.

The fix is not the same.

It depends on how much of a shim we are talking about. and then I'm going to want to know what is off. Is the receiver out of shape or the base?
See I don't just start shimming a scope base because it doesn't sit correctly. I want to know precisely why it's not sitting correctly on the receiver and make adjustments from there.

I understand that no off the shelf base is going to fit perfectly but it sure as hell better not require shims unless you want more elevation adjustment.

Same here. Cheap, easy to cut to size. About .001" thick.

If the base really is crowned, send it back. Scope bases should be flat. But since bases are made in mass production, they will not necessarily be a "drop in" fit or your rifle. I like to use JB weld for bedding the scope base and John McQuay at 8541 Tactical (look it up on YouTube.com) has a really well-done tutorial for the JB weld bedding method.

Receiver top is perfectly straight checked it with a straightedge

It is probably the base then. Try running it along some crocus cloth or emery paper bearing down on the front end to take a few thousands off till it lies flat. You may have to shim under the scope at the ring then, to parallel the scope to the bore....