“Pin Your Tikka”, or “Void Your Scope Base Warranty”

[Low_Sky]

Got some new Hawkins Tikka Hybrids. Cleaned and degreased everything. Torqued to spec with a Fat Max. Some spicy 7mm Rem Mag reloads rattled the base screws loose from the receiver on the first range trip. Let the cutting and grinding commence!

Drilled, pinned and epoxy bedded. So far so good.

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[Oldffemt]

Looks like you did a nice clean job of it. I’ve been considering doing this with the Talley lw’s I just got.

 

[Low_Sky]

Looks like you did a nice clean job of it. I’ve been considering doing this with the Talley lw’s I just got.

I did mine by making a jig first. Took some trial and error to get the jig right, but now I can do this modification on demand. If I ever wear this jig out I’ll have a machine shop make the next one. Getting this one right with a drill press and basic layout tools was an iterative process. Luckily I had a Warne Mountain Tech base I didn’t care about to practice with so I could get it 100% before making chips on the Hawkins.


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[ericF]

This makes me feel better about going with a separate Murphy Base and Rings.

 

[Newtosavage]

Factory rings have a pin, and also an easy way to make a 2nd pin if you just shave down the head of the proper sized screw. I never once had an issue with factory rings when pinned that way, and it requires no mod to the rifle.

 

[16Bore]

Loctite works too.

 

[fightthenoise]

What about the pin keeps your screws from coming loose?

 

[Low_Sky]

What about the pin keeps your screws from coming loose?

The pin carries the shear forces between the base and receiver instead of relying solely on friction from the clamping force of the screws. Without the pin, if forces from recoil exceed the friction, the bases will slide relative to the receiver until the screws themselves carry the shear load.

Tikkas have four short 6-40 bolts. They're good for a clamp load of 640 lbs each, 2560 lbs total. The coefficient of friction between hard anodized aluminum and steel is 0.22, so the shear force that the mounts can withstand before slipping and transferring that shear to the screws themselves is about 563 lbs. I did some napkin math on the force to accelerate my scope during recoil and came up with 472 lbs. This is all rough calculation, but the numbers come out way too close to each other for my comfort, and having the scope shoot loose once was all the encouragement I needed.

 

[Low_Sky]

Loctite works too.

The screws have loctite now, but I wanted to try without it first. Loctite may have kept the screws from loosening, but it wouldn't have stopped the bases from slipping and transferring the shear load to the screws themselves. The mounting screws that came out of the Warne base when I removed it from this rifle were deformed, so they were being shear loaded too. Same size screws, same torque, with loctite.

 

[Ndbowhunter]

I don’t have a tikka in front of me but doesn’t it have 5 screw holes?

 

[Low_Sky]

I don’t have a tikka in front of me but doesn’t it have 5 screw holes?

There are five threaded holes on top of the receiver. I’ve never seen a one- or two-piece mount that uses all of them.


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[idig4au]

I’ve had issues with Talley ULW’s well in past. i moved away from using them but tried them again on my last two builds as their weight is so attractive. I had them pinned and have had zero issues with them so confidence is back.

 

[CD0311B4]

I’m late to this one, but…. Low, you offering this service ?