Two piece AR scope mount- bridging the gap

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BlogSarge
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Re: Two piece AR scope mount- bridging the gap

Post by BlogSarge »

Through a little work, I got the Warne mount to work with the front cross bolt in the first groove on the rear of the rail.

But, back to the original question. Has anyone who has used a two piece mount with one on the receiver and one on the rail experienced point of impact shift
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plant.one
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Re: Two piece AR scope mount- bridging the gap

Post by plant.one »

BlogSarge wrote:Hey plant!

Hope all is going well. We should meet up; I might have a ‘little’ bit of brass for ya!
i'll be down in jackson sometime this week, i think wednesday, i'll have to shoot ya a pm
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BlogSarge
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Re: Two piece AR scope mount- bridging the gap

Post by BlogSarge »

plant.one wrote:
BlogSarge wrote:Hey plant!

Hope all is going well. We should meet up; I might have a ‘little’ bit of brass for ya!
i'll be down in jackson sometime this week, i think wednesday, i'll have to shoot ya a pm
Excellent! Give me a day notice. I’m on mids and maybe we can arrange a meet on your way there.
10Driver
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Re: Two piece AR scope mount- bridging the gap

Post by 10Driver »

smustian wrote:I prefer this. Have 3 of them. Come with rounded top ring in the box as well. 1 inch and 30mm available
Burris Optics AR-P.E.P.R. Scope Mount - 1-Inch
https://www.amazon.com/Burris-AR-PEPR-S ... fkmrnull_1

My PEPR screws on the scope portion loosened after one trip to the range.

Do you guys put blue Loctite on the screws or just torque?
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bangbangping
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Re: Two piece AR scope mount- bridging the gap

Post by bangbangping »

Always loctite.
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smustian
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Re: Two piece AR scope mount- bridging the gap

Post by smustian »

10Driver wrote:
My PEPR screws on the scope portion loosened after one trip to the range.

Do you guys put blue Loctite on the screws or just torque?
Blue loctite and torque on anything scope related. Eliminates the chance of malfunctions in the future and gives me peace of mind.
rlandry6
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Re: Two piece AR scope mount- bridging the gap

Post by rlandry6 »

Blue Loctite and a torque screwdriver are your friends. I never guess at torque settings. My hands aren't calibrated. Manufacturers put out those specs for a reason.
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plant.one
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Re: Two piece AR scope mount- bridging the gap

Post by plant.one »

18-20 inch/pounds gets the job done for me on scope stuff.
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Bravo_Bravo
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Re: Two piece AR scope mount- bridging the gap

Post by Bravo_Bravo »

BlogSarge wrote:But, back to the original question. Has anyone who has used a two piece mount with one on the receiver and one on the rail experienced point of impact shift
Just don't do it.

I helped a guy several years ago that swore the zero on his scope was dead on the last time he was at the range. He kept drilling the same area next to the reactive target he was trying to hit. I called his impacts trying to guide him to the target.  He emptied 4 mags without a hit and finally gave up.  It didn't take long to figure out:

1) He wasn't too bright
And
2) He was stubborn

I looked at his rifle and his forward ring was mounted on his free float in rail and his rear was on the receiver. He had no idea that could be an issue.

Later, I stumbled across a test done on an AR with a weight pulling down on a longer free float rail to simulate someone pulling the rifle into their shoulder with a vertical grip. If I remember, it was several pounds but didn't seem unreasonable if you were under stress in a competition or similar situation. There was a measurable change in the POI which means that the stress imparted by the rail is affecting the receiver and subsequently, the barrel/receiver interface.

The upper receiver of an AR wasn't designed to deal with the amount of force that CAN be applied with a free float rail. A 15" rail is a long lever arm.  When you put your forward scope ring on the rail and the rear on your receiver the POI will likely shift with the amount of force applied to the rail. Doing so will also drive stress into your scope tube which is obviously not desirable.

I haven't built a max effort, long range AR-15. But If I do, I will consider a beefy upper such as a VLTOR or maybe go billet to minimize the affects of the above - I like to shoot prone and load the bipod
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Re: Two piece AR scope mount- bridging the gap

Post by BlogSarge »

Thanks Bravo_Bravo,

I’ve made sure all of mine are anchored solidly and solely to the upper receiver and not the rail. Even one piece mounts are now completely on the upper.

I tried the forward ring on the rail thinking that it wouldn’t make much difference at only 100yds but it seems to. Oh well, lesson learned!
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