Minimal clearance between barrel and NV bridge

[RampedRaptor]

MPA chassis with night vision rail.
Brux heavy varmint 30”

I can fit (1) one hundred dollar between barrel and bridge. 2 will not fit.

I had some unexplained results today with my ladder test and I question if the barrel is making contact with the rail before the bullet exits bore.

Hopefully will be able to run the test tomorrow depending on if the rain holds out.

Any experience with people running tolerancees that are too close and it affecting POI?


Thanks,
RR

 

[SkyScrapin]

No experience with the MPA, but my A3-5 has a tail and it’s not nearly as close as yours is to the barrel. I’m running an MTU contour with about 1/8” clearance.

 

[RampedRaptor]

I’m not sure what I’ll do if testing shows the NV bridge does influence barrel harmonics. Maybe a spacer or something.

 

[deersniper]

Probably clearance related. People have barrels hit scopes when they are that close.

 

[morganlamprecht]

Probably clearance related. People have barrels hit scopes when they are that close.

this^^ i had similar (maybe a little less) scope clearance on a new build...i didnt feel like waiting to get more rings so i took a scope/ring combo off another rifle to mount up and go shoot a match with a quick zero check...scope had visible light under it, but running a dollar bill thru was snug, i figured since it was closer to the chamber end it would be fine....it wasnt...random vertical misses throughout the match .2-.3 off POA...went back to 100 yds after the match and saw the same vertical fliers at 100 yds...took scope off and saw a small mark on the bottom of the scope bell and on top of the barrel where they were closest...got some higher rings and remounted the scope and its been spot on ever since, lesson learned

 

[RampedRaptor]

Shot with the NV bridge off this AM. Got expected results from the ladder. Disappointed that I wasted yesterday shooting with the bridge on. I may just take the dremel to the NV rail to get more clearance.

Shot at 535yds. Bipod / read bag. 7mm

 

[Sniperstud]

The result from a Dremel attack will likely be crude and imprecise. I would measure the barrel diameter where it enters the bridge, on the chamber side. If a 30mm ring lapping bar will give the desired clearance, use it with lapping compound to modify the bridge tunnel to 30mm. If you need more than 30mm for your barrel diameter, you could make a lapping bar from appropriately sized steel round stock. The result will look much more professional. Even a wooden dowel wrapped with sandpaper would produce better results than a dremel, in this application. A dremel would be faster though.

 

[Bmelt1409]

Would a proof carbon bull profile fit under it? Its a 1.20 straight no taper.

 

[RampedRaptor]

No, I don’t believe it would. I ended up selling the chassis. MPA is great, nothing against them. It just didn’t fit my needs moving forward.

 

[Terry Cross]

So you sold a stock that you liked because the barrel contour you chose interfered with the NV mount?

Would it have not made more sense to modify the barrel contour to a smaller diameter just before entering the NV mount?

Arguably, the stock is the most important aspect of a shooter being able to approach the rifle's potential when out in the field. It is THE interface between you and the barreled action. Finding one that suits your physique and shooting style is paramount.

Doing a barrel contour mod would have been quick and relatively inexpensive. In the end you would have retained the stock you carefully chose and lost maybe 3 ounces of material from your barrel.

 

[Rondogg]

Take the NV bridge off. MPA chassis (from what I read) should not be affected from removing bridge.

 

[RampedRaptor]

I wasn’t married to the chassis. Nice but I could get behind a choate stock and shoot about the same. I also wanted to try out another chassis brand that I’ve never had the opurtunity to get behind. I attempted to take the bridge off at first but was not satisfied with the amount of deflection laterally (maybe it was torsion, can’t recall how I caused it) from the chassis. May of been a non issue but I decided it was not acceptable.