SCAR with 40 grain loads

Discuss the FN lineup of tactical rifles; the FS2000, SCAR, and the venerable FAL.
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Wollychop
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Posts: 5447
Joined: 20 Aug 2008, 09:09
Location: MN

SCAR with 40 grain loads

Post by Wollychop » 21 Jul 2009, 18:41

Just a quick report.

It appears that the SCAR will not reliably cycle with 40 grain loads, particularly 40 grain loads on top of 25 grains of Hodgdon 322.

The rounds fire fine, but the rifle constantly appears to short stroke and fail to load the next round properly. I think this might be due to the heavier moving parts group. If you've taken your SCAR apart, you probably notice just how much larger the SCAR's assembly is than an AR15 or SIG 556.

Loads I tested cycled fine in a SIG 556 (again, the bolt carrier group on the sig 556 is not nearly as large) and AR-15, however suffered about a 25% failure rate to cycle on the SCAR.

Piston in the second stage only marginally improved performance. I think there is just not quite enough pressure to operate the action reliably.

25 grains of H322 is close to the max, so I don't think I will push much further to test these. I might load another twenty with an extra half grain, but 55 grain and 62 grain loads using published data had no issues.

If anyone has any experience that would contradict this, please let me know. I think it's just a function of the weight of the moving parts vs. the pressure produced by the lighter loads.

Accuracy was fine though (about 2" at 100 yards with pulled 40 gr V Max and assorted brass using 556 primers).

SSBiggun
Junior Member
Posts: 215
Joined: 27 Aug 2008, 14:03
Location: Salt Lake City Utah

Re: SCAR with 40 grain loads

Post by SSBiggun » 21 Jul 2009, 18:58

Wolly ,you might want to try a slower powder like 335 . It will give a longer duration of port pressure before bullet exit. Looking in my Sierra V it lists 25.3 at max for H322 and only 3200 fps. With H335 you can go up to 28 and close in on 3500 fps.
Last edited by SSBiggun on 21 Jul 2009, 19:00, edited 1 time in total.

Wollychop
Senior Member
Posts: 5447
Joined: 20 Aug 2008, 09:09
Location: MN

Re: SCAR with 40 grain loads

Post by Wollychop » 21 Jul 2009, 18:59

:ponder: Good suggestion!

H322 was the only powder I had available. Might load up a magazine's worth using 335 if I can get my hands on some.

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