AR-MPR: Accurizing the Upper Receiver – Test Results

In the following posts:

I’ve documented an experiment in accurizing the upper receiver of the AR-MPR rifle. It was a bit painful to file away hard anodizing, followed by drilling, welding, milling, and finally epoxy bedding. The whole point was to remove slop between the upper and lower receivers on the AR-MPR rifle.

I finally had a chance to test out the rifle with the modifications in place. I did a quick sight-in on the paper at 25 yards, then dialed it in at 100 yards. From a bipod and rigged up rear rest, the first 5-shot group measured just .604″ (.577 MOA) – well within the .5-.75 MOA goal for the project.

The first 100 yard 5-shot group with the accurized AR-MPR rifle - Image Copyright 2011 Ultimate Reloader

Next, I’m looking forward to shooting off a proper rest, and experimenting with different loads to see how good this rifle can get.

I’m confident that this rifle will continue to turn in more great groups. Stay tuned, because there’s another related project coming up!

-Gavin

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6 thoughts on “AR-MPR: Accurizing the Upper Receiver – Test Results”

  1. Gavin,

    Noticed that you are using 52Gr. bullet. What is the twist rate of the Sabre Defense barrel. Tried to look up but could not find. I know my JP shoots 1 in. with factory 52Gr Hornady and I get .5 in. to .75 in at 200 yds. with my handloaded 69 gr. Sierra and 24.3 Gr. Varget. The twist rate is 1:8.

      1. I suppose that’s a fair reply.

        I actually didn’t pay attention to the shot counts and made the incorrect assumption they were consistent between the tests.

        I know there are forums I visit where 3 shot groups are scoffed at as evidence of accuracy, even though they seem to be the industry norm’, and 5 shot groups are held in much higher regard.

        And a 0.6″ group is nothing to sneeze at whether 3 shots or 5.

        Thanks for entertaining the question, I’m looking forward to the progress on the AR-308 project.

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