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Old May 16, 2018, 08:47 PM   #1
Bartholomew Roberts
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NSWC Crane Determines Midlength ARs Run Better

http://soldiersystems.net/2018/05/14...d-performance/

Synopsis:
Midlengths pick up an average of 32-40fps on velocity
Midlength cyclic rate about 60rpm lower
Midlength had 2800 MRBF at 160F, 1993.8 MRBF at ambient temp, and 562.5 MRBF at -60F.
Crane is planning to put 34,000 rounds of M855A1 through each upper. At 12,000, they still haven’t noted a degradation in accuracy in the midlengths (twice the barrel life M4A1 averages).
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Old May 16, 2018, 11:02 PM   #2
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Interesting.
While my own preference is for mid-length gas on barrels shorter than 18", I can't say that I've done enough testing to really show any difference other than a 'smoother' recoil impulse than carbine gas.
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Old May 17, 2018, 07:45 AM   #3
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Great. I recently bought a mid upper, thought it was fugly, was gonna sell it this afternoon. Now you've got me wondering if I should hang onto it.
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Old May 17, 2018, 08:49 AM   #4
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The part I find curious is I can’t think of any reason the gas system would have an effect on barrel life, especially such a dramatic one (twice the average and still going). Something about that seems off to me.
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Old May 17, 2018, 01:49 PM   #5
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I think the barrel life claims are questionable, as well.
My assumption is just that it's a good lot of barrels, and/or a manifestation of a good lot of ammunition.
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Old May 17, 2018, 02:57 PM   #6
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It would be nice to have the actual report from the Navy instead of just the reporter's take on its findings.
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Old May 18, 2018, 06:55 AM   #7
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That’s from last week’s 2018 NDIA conference in Indianapolis. They take forever to publish the conference materials; but they’ll publish most of the presentation materials eventually. I think they are up to March 2018 right now.

If you actually attend the conference, you get copies of the presentations plus you get access to a lot of info that never makes it to the DTIC.mil website.
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Old May 18, 2018, 12:21 PM   #8
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Would increased Barrel life come from decreased gas port erosion? Would a mid length have less gas port erosion?
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Old May 18, 2018, 01:40 PM   #9
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I was wondering the same...

Gas port errosion would play a factor is barrel life and accuracy long term.

A midlength should see less errosion than carbine length.


Now my question is... Are the rifles 16in barreled or 14.5in barreled with midlength?
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Old May 18, 2018, 02:22 PM   #10
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The article says 14.5”
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Old May 18, 2018, 02:40 PM   #11
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Thanks for clarifying... I didn't have time to read the article earlier.
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Old May 18, 2018, 02:55 PM   #12
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Sorry, posted (and deleted) response.
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Old May 18, 2018, 11:22 PM   #13
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Edit: Disregard.
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