Thursday, April 1, 2010

Milling Scope Mount Grooves In The Crosman 180 Receiver

I decided it was time to try my hand at milling scope grooves into the receiver of the Crosman 180. Since the rifle is a beater it wouldn't hurt much if I screwed it up (and I had a backup plan).

I drew up the dovetails in CAD but being paranoid decided to test the dimensions in aluminum rod.

It's good I did as the dovetail was too deep for the mount. Notice the lack of clearance between the mount bottom and the receiver top. Every cheap cope mount is different, and there are no standards until you go with a Picatinny mount system.

So I tried less depth of cut.

Too little.

A tad more (ended up being about .050" groove width) and it looks good.

Then I had to figure out how to fixture the barrel/receiver on the mill. I decided to reference off of the loading cutout.

I finally hit on the method of using a dial depth gage to make sure the slot was horizontal. (a level would have been easier but nothing in my shop is level).

So I checked both sides, tweaked it, checked again until it was parallel to the mill table.

Starting the milling...

I used a lot of oil.

Worked like a charm!

It was a fine balance between depth of cut, position, etc.

The scope mounted right up. My only quibble is I had to make the rear mount more forward than I'd like so it would clear the bolt handle.

I think it looks good.

Just enough groove for the mounts to be solid and about .001" clearance between the mount and the receiver.


Ryan said...

Wow. I don't have a mill (yet), though I've been in tool-lust for one for quite some time now. I'm quite impressed with your workmanship Nick. Was this CNC then? Good job!

Nick Carter said...

Not CNC, just manual work. CNC would be overkill and I wouldn't have the ability to make changes on the fly.

Anonymous said...


Felice Luftschein said...

I don't do work for other people. I think Mac1 will do crosman scope grooves:

T Jay said...

Great Job Nick!

I know that you performed this task quite a while back but...

Can you please provide info on the cutter that you used? 45 or 60 degree? Carbide or tool steel? I'm thinking of machining my Crosman 400 Repeater.

Thank You!


Felice Luftschein said...

I'm reasonably sure it was a 60 degree HSS. Make it match your scope mount!