HW scope stop pin hole deformations.

[nced]

A pet peeve I have had for a long tome is the fact that the stop pins of the UTG, Leapers, Sports Match scope mounts have the ends of the threaded stop pins machined to a rather small diameter. The combination of small diameter stop pin end in a relatively large stop pin hole always deform the stop pin holes in the receiver, especially with heavy scopes. While the stop pins do arrest most scope mount movement with recoil, there is obviously enough movement to deform the holes in the receiver tubes.
Here's a pic of the end of a UTG type stop pin........
Uploaded at Snapagogo.com

Here is a pic of the stop pin hole damage due to the stop pin deforming the metal with recoil.......
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com

Tonight I decided to make a steel "sacrificial bushing" to use as a buffer between the stop pin and the stop pin hole and here are a couple pics......
Bushing in the last stop pin hole..........
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com

Stop pin and bushing.......
Uploaded at Snapagogo.com
http://www.snapagogo.com/uploads/source/1092016/1461034592_1753775245_ScopeStopBushing3.JPG

I did learn that I needed to bore out the hole in the bushing to make the hole both concentric with the outside and to add more slop between the stop pin and bushing ID simply so the stop pin could be inserted into the bushing with the fixed scope mount "claw" in the dovetail that was milled into the receiver. Took some fiddling around but now the mount is clamped to the receiver dovetail and the stop pin is in the bushing which is in the receiver tube.

As a side note, I made a tiny boring bar from a ground masonry nail that was hardened and quenched in oil. The boring bar holder was made from an old bolt that was split on one side to hold the "boring bar" when clamped in the tool post holder...........
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com

[Yogi]

Ed,

You do great work!

What is the ID of the insert?  Would aluminium work too?  I figure it would "deform" to fit perfectly.

Great work,

-Y

[Charles Outdoors]

Glad I'm not the only one that bugs. I was going to make a bushing just like that for the HW90.

[nced]

Ed,

You do great work!

What is the ID of the insert?  Would aluminium work too?  I figure it would "deform" to fit perfectly.

Great work,

-Y

The "sacrificial ring" for the HW95 is .18 id x .23 od x .10 high.
I initially made the ring a closer fit to the .129 od stop pin and the .24 id receiver stop pin hole but a close slip fit wouldn't allow me to position the fixed mount claw into the dovetail groove. Even with the "sloppier fit" I had to place the "sacrificial ring" into the receiver stop pin first, position the mount stop pin thread directly over the hole in the ring, snug the base clamp a bit, screw the stop pin into the ring making sure that the stop pin pilot was in the ring, tighten the base clamp by torquing the horizontal screws to 35 inch pounds, screw the stop pin so the tip bottoms out on the receiver end plug, then mount the scope in the base saddles and attach the top straps. LOL....even with the sloppier ring fit the base can't be removed from the dovetail unless the scope is removed and the stop pin is retracted.

As far as the ring height is concerned the .10 hight allowed me just enough clearance to slide the base over the ring projection. The R9 receiver tube wall thickness is .088 so a bit less height could be used if necessary.

I suppose aluminum would work but judging by the amount of deformation to the STEEL receiver tube I do wonder if aluminum would be hard enough. Before installing the "sacrificial ring" I took time to file away the "upset metal" at the back of the stop pin hole because the "upset metal" was displaced both inside and outside the tube wall. I made my sleeve from an old socket head cap screw (about grade 12.5) and then further hardened the ring by heating red hot and then quenching it in oil.

Hope this helps some!

[nced]

Glad I'm not the only one that bugs. I was going to make a bushing just like that for the HW90.

A while back I took another approach to solving this issue by making a sacrificial ring that was a press fit to the stop pin projection like this.........
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com
Uploaded at Snapagogo.com
It worked OK and I was going to do the same this time but thought that a separate ring with slop to both the pin projection and stop pin hole in the receiver would make attaching the mount to the receiver less problematic.

Still...either approach worked well if not a bit tedious to mount the base.