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Thread: Robb/Gotm4 inspired lightweight

  1. #11
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    Get to it Rob

    Today I shot a 150 round mix of 55gr commercial ammo. No feeding issues and was ejecting brass in a fairly consistent pattern. Recoil was sharp with the stock buffer and better with an H. This is pretty much a non issue for me, however, the muzzle jumps very quickly making quick follow-up shots difficult.

    Rob_s, you're spot on- it definitely needs a brake. I think I'm going to give the Battle Comp an audition.

    Gene
    Last edited by Warg; 06-29-10 at 18:59.

  2. #12
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    Project Featherweight with a midlength, JP LMOS carrier, CAR 3.0oz buffer and PWS FSC556 recoils like my 3gun rifle when using with 5.56mm NATO Radway Green ammo, about 15% more recoil than my 3gun rifle when using XM193 or LC M855.
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  3. #13
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    Quote Originally Posted by gfelber View Post
    Get to it Rob

    Today I shot a 150 round mix of 55gr commercial ammo. No feeding issues and was ejecting brass in a fairly consistent pattern. Recoil was sharp with the stock buffer and better with an H. This is pretty much a non issue for me, however, the muzzle jumps very quickly making quick follow-up shots difficult.

    Rob_s, you're spot on- it definitely needs a brake. I think I'm going to give the Battle Comp an audition.

    Gene
    A brake would help with the recoil impulse, correct. But if a H buffer smooths things out, doesn't that mean that it is overgassed, or to be polite well-gassed? I wish there was an adjustable gas system that was adjustable as the JP, but was a bit more robust and positive in its locking at a certain gas level.

    Impressive rifle for the weight when you consider a stainless 1911 is about 41oz empty!
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  4. #14
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    Quote Originally Posted by FromMyColdDeadHand View Post
    A brake would help with the recoil impulse, correct.
    Yes, but that's not why I would employ a brake. Perhaps compensator would be more apropos. I want to control muzzle rise since the front end is so light.

    Quote Originally Posted by FromMyColdDeadHand View Post
    But if a H buffer smooths things out, doesn't that mean that it is overgassed, or to be polite well-gassed?
    A heavier buffer is more effective at decelerating the carrier, but does not necessarily mean the rifle is over gassed. This one may be over gassed for the weight of the JP carrier, but I do not know if this is the case yet.

    When I mentioned that the rifle had a sharp recoil, this was in relative terms. It is not bothersome at all, but is a bit sharper (for lack of a better word) compared to my other three, heavier ARs. I think there are a few of variables at play here: 1. the rifle is very light (F=MA) and has less mass to react against the load. The result is a sharper perceived recoil and is the same reason my wife prefers her heavy Sig to my Glock. 2. The Colt Fiberlite stock has a smaller surface (contact) area and is unpadded. 3. The carrier is lighter as well and is probably moving faster compared to, say, an M16 carrier.

    Quote Originally Posted by FromMyColdDeadHand View Post
    I wish there was an adjustable gas system that was adjustable as the JP, but was a bit more robust and positive in its locking at a certain gas level.
    Totally agree. I had the same issue with the JP block on a 6.5 Grendel build I completed a couple of years ago. The MGI adjustable gas tube is guesswork as well.

    Quote Originally Posted by FromMyColdDeadHand View Post
    Impressive rifle for the weight when you consider a stainless 1911 is about 41oz empty!
    Indeed.

  5. #15
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    Nice Build

    I agree with the more durable and "beefier" bcg for reliability. Another thing that might help out with balance could be a different stock that adds a few oz of weight. I am sure you will still keep the weight at a minimum.
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  6. #16
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    Quote Originally Posted by FromMyColdDeadHand View Post
    A brake would help with the recoil impulse, correct. But if a H buffer smooths things out, doesn't that mean that it is overgassed, or to be polite well-gassed? I wish there was an adjustable gas system that was adjustable as the JP, but was a bit more robust and positive in its locking at a certain gas level.

    Impressive rifle for the weight when you consider a stainless 1911 is about 41oz empty!
    My wife and I took the lightweight to my uncle's place in Idaho last week and shot a few hundred rounds of ammo, milspec and commercial (55-62 gr). It cycles well and is fun as heck, but I'll concede and say that you might be correct re: 'well gassed'. Now I'm aware of the brass ejection pattern debate, but brass on this one was ejecting at about 2 o'clock with commercial ammo and standard buffer after break in. Milspec damn near threw the brass in the same direction as the targets. We had another 14.5" carbine and a 16" middy that we were using with the same ammo for comparison- no issues with those. Unfortunately, were shooting so many different guns I forgot to swap in an H or H2 buffer. BTW, I do not see any odd or excessive wear on the carrier, bolt, cam pin, upper or buffer at this point (though that's not a huge amount of rounds).

    So now I'll have to go into tuning mode and will consider some options: standard carrier, heavier buffer, XP spring, or a 14.5" middy barrel like Robb's. I'm pretty confident the carrier will solve the issue as it then becomes a regular 16" middy, but will try to stay with the lightweight spec and employ the spring and buffers first. Additionally, rather than sending the barrel to Adco for a 1.3" chop and pin, I'm going to put together a 14.5" pencil middy upper using either the forthcoming DD or BCM barrels. I plan on swapping the lightweight carrier in that one and see how it behaves.

    Oh and a BattleComp 1.0 is on the way. Even with my chunky arm grasping the end of the HG, the front end is just too light for rapid follow-up shots. As expected, my wife had a much more difficult time controlling muzzle rise than I. This is supposed to be her toy

    Any other suggestions?

    Thanks,

    Gene

    Remark: I didn't notice as much difference as I anticipated between the lightweight and the other 16" middy we were shooting other than the lighter front end of the former. The other is about 1.5-2 lbs heavier. Of course, I wasn't lugging a 70 lb. pack up and down the mountains beforehand either. On the other hand, both my wife and uncle were surprised as how light it is.
    Last edited by Warg; 07-10-10 at 01:41. Reason: Grammar

  7. #17
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    Before trying a heavier carrier try the LMOS JP with a BATTLE COMP or a PWS FSC556 like I did. That combo with an CAR buffer makes for a very soft shooting gun on a 14.5" midlength. A fullweight carrier with just a flash hider has much more recoil and muzzle lift.
    Last edited by Robb Jensen; 10-16-10 at 14:22.
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  8. #18
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    gfelber, where did you get the titanium Micor flash hider? I have looked on line and cannot find anyone selling it.

  9. #19
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    Quote Originally Posted by jp0319 View Post
    gfelber, where did you get the titanium Micor flash hider? I have looked on line and cannot find anyone selling it.
    I purchased directly from Micor. To order the Ti version, you'll have to contact them directly. Or I can sell you a slightly used one (~250 rounds) since I've changed to the BattleComp 1.0:


  10. #20
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    Awesome paint job!
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