Gunsmithing EFR for 1.350” barrel?

[Keith Johns]

I’m wondering there is an EFR that can be put into an A5 that has a through hole of 1.350”.
1.300” might work but that wouldn’t give much clearance.

Thanks for any help.

 

[Terry Cross]

To my knowledge No.

When I was finalizing the MUNSter NV mount in SolidWorks, I absolutely wanted a larger through hole.
Reality is that you need X amount of real estate on each side to connect the upper hemisphere to the lower hemisphere. When considering that some of the units can weigh 4 pounds and cost over $20K, I wanted lugging on 2 axis as well as decent fastener size. In fact the product name came from being built to reliably handle the PVS-27 in rough conditions.

When you increase the through hole, you have to take whatever the minimal side connection width with it and arrive at a total outside width for the NV mount. If you go to a 1.350 through hole and leave any reasonable level of mating surface for the top half on each side, your final resulting part is too wide to fit in may of the stocks out there. Example is the M40/HTG and A3 forends being already quite thin on each side once inletted for the current NV mounts that only have 1.200" through holes.

When possible, I always vet potential customers looking at the MUNSter NV mount to make sure they are aware of the maximum workable barrel contour as well as publish it on the product info.

Somebody used to make a contraption that bolted onto the outside of the forend with side anchors inletted into the stock that allowed a larger barrel contour but I also heard they were terrible about loosening when actually used with NV.


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[Keith Johns]

Thanks for the info. Rifle is a big 338 Lapua that was built a while back. The EFR was an after thought.

It didn’t look too reasonable with that size barrel. I let him know.

 

[Terry Cross]

Thanks for the info. Rifle is a big 338 Lapua that was built a while back. The EFR was an after thought.

It didn’t look too reasonable with that size barrel. I let him know.

Consider doing a re-contour mod on the existing barrel.

Push in at a 45 degree angle to an O.D. of 1.050" 'ish right before the barrel enters the NV mount and keep it straight cylinder forward until merging with the existing contour taper.


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[Keith Johns]

We considered that but I have slight concerns with the whole project. Largely due to my ignorance on those rifle mounted range finders and EFRs in general.

How aligned do they have to be?

 

[Terry Cross]

Depends on the models.
I will literally hand hold a PVS27 or 30 in front of a scope (without attaching to a rail) and let a shooter fire 3 rounds as a demo for lack of POI shift when the equipment is GTG.

The better units are fine within +/- 1 degree. That spec is usually printed in the documentation that comes with each product.