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Posted: 1/3/2012 7:28:09 AM EDT
I am new to ARs and have been scouring the forums for a few weeks learning as much as I can. I am putting together my wish list and am trying to decide on whether to put the front BUIS on the gas block or on the rail. Is there an advantage one has over the other as far as accuracy and reliability? I think I like the look of the exposed gas block better but is it important to cover it with the rail? What I am wanting to build is a 1/2 moa 16" mid length do it all gun (although I primarily paper punch). So far I have listed as probables:

Spikes lower
Magpul AFG
Magpul UBR
YH Phantom 5C2
BCM Gunfighter
Phase 5 EBR
BADASS ambi- safety (1 son shoots lefty)
Sampson EVO handguard
YH, Troy, or ARMS BUIS

I am wanting an adjustable gas block so I can tune with my handloads and single load on the bench. I want to shoot out to 600 and past that I will build a 6.5 upper eventually. I am leaning towards a BHW barrel but that is still undecided (so many barrel makers!) Anyways, thanks for any help you guys can provide in my ""I turned 40 and am treating myself to an AR" project.
Link Posted: 1/3/2012 7:35:14 AM EDT
Probably on your gas block.

That way if you flex the barrel your iron sights will track with it.
Link Posted: 1/3/2012 7:36:24 AM EDT
Neither ... get a barrel with a pinned front sight.
Link Posted: 1/3/2012 8:13:47 AM EDT
Originally Posted By WI57:
Probably on your gas block.

That way if you flex the barrel your iron sights will track with it.


This.....
Link Posted: 1/3/2012 8:22:56 AM EDT
Originally Posted By EdgecrusherXES_45:
Originally Posted By WI57:
Probably on your gas block.

That way if you flex the barrel your iron sights will track with it.


This.....


Will not be of much help.
Link Posted: 1/3/2012 8:28:12 AM EDT
[Last Edit: 1/3/2012 8:28:19 AM EDT by EdgecrusherXES_45]
Longer sight radius.
Link Posted: 1/3/2012 8:31:38 AM EDT
Originally Posted By Gregory_K:
Originally Posted By EdgecrusherXES_45:
Originally Posted By WI57:
Probably on your gas block.

That way if you flex the barrel your iron sights will track with it.


This.....


Will not be of much help.


Based on what?
Link Posted: 1/3/2012 8:38:55 AM EDT
Either, I use the combined gas block/ front sight units, but I don’t know of any reason not to use a FF tube mounted front sight.
16” is a little short for 600 yards for my preferences.
Link Posted: 1/3/2012 8:51:49 AM EDT
Originally Posted By WI57:
Originally Posted By Gregory_K:
Originally Posted By EdgecrusherXES_45:
Originally Posted By WI57:
Probably on your gas block.

That way if you flex the barrel your iron sights will track with it.


This.....


Will not be of much help.


Based on what?


Barrel flex experienced by sling tension and shoots being off 6" or more at 100 yards. this why the service rifle (CMP rifle) has the sling mounting point removed from the barrel. introduce barrel flex into the mix and your shoots will be off no matter where your front buis is mounted.
Link Posted: 1/3/2012 8:57:54 AM EDT
Originally Posted By Gregory_K:
Originally Posted By WI57:
Originally Posted By Gregory_K:
Originally Posted By EdgecrusherXES_45:
Originally Posted By WI57:
Probably on your gas block.

That way if you flex the barrel your iron sights will track with it.


This.....


Will not be of much help.


Based on what?


Barrel flex experienced by sling tension and shoots being off 6" or more at 100 yards. this why the service rifle (CMP rifle) has the sling mounting point removed from the barrel. introduce barrel flex into the mix and your shoots will be off no matter where your front buis is mounted.


Yep.

I zeroed off a bag on the bench, shooting 1" groups at 50 yards. This zero should have me + or - 2" from 0 - 215ish yards.

When I shot prone unsupported, my POI was 6" high.
Link Posted: 1/3/2012 8:58:47 AM EDT
Originally Posted By Gregory_K:
Barrel flex experienced by sling tension and shoots being off 6" or more at 100 yards. this why the service rifle (CMP rifle) has the sling mounting point removed from the barrel. introduce barrel flex into the mix and your shoots will be off no matter where your front buis is mounted.


Yes, you are correct, I was refering to a free float handguard and the barrel being pushed against a barricade or something (3-gun style shooting).

Where the barrel may be being flexed but the sight flexes with the barrel holding somewhat better of a zero than a sight mounted on a free float rail that will not compensate for barrel flex.
Link Posted: 1/3/2012 11:56:35 AM EDT
Barrel flex and/or Hand guard flex is what I was wondering about. I will be doing a lot of long range shooting off a bi-pod which will be rail mounted to avoid pressure on the barrel. Is there any reason most people cover the gas block with the HG?
Link Posted: 1/3/2012 9:11:33 PM EDT
Originally Posted By sptfan:
Is there any reason most people cover the gas block with the HG?


Mostly just personal preference/aesthetics. Some like to have it covered to protect it from being knocked loose, but unless you're out in the sandbox and throwing the rifle around it won't be an issue. The pinned, clamp on, and set screw gas blocks are more than secure enough for range duty.
Link Posted: 1/4/2012 3:12:55 AM EDT
Originally Posted By Engel12626:
Originally Posted By sptfan:
Is there any reason most people cover the gas block with the HG?


Mostly just personal preference/aesthetics. Some like to have it covered to protect it from being knocked loose, but unless you're out in the sandbox and throwing the rifle around it won't be an issue. The pinned, clamp on, and set screw gas blocks are more than secure enough for range duty.


tests have been done where the barrel nut breaks loose, before a clamp on gas block give away.
Link Posted: 1/4/2012 3:47:08 AM EDT
[Last Edit: 1/4/2012 3:47:08 AM EDT by Lancelot]
Topic Moved
Link Posted: 1/4/2012 1:35:42 PM EDT
Ok. Thanks for the replies. I will continue to refine my build list and post for critique before I buy it all.
Link Posted: 1/5/2012 2:03:48 AM EDT
Originally Posted By Gregory_K:
Originally Posted By Engel12626:
Originally Posted By sptfan:
Is there any reason most people cover the gas block with the HG?


Mostly just personal preference/aesthetics. Some like to have it covered to protect it from being knocked loose, but unless you're out in the sandbox and throwing the rifle around it won't be an issue. The pinned, clamp on, and set screw gas blocks are more than secure enough for range duty.


tests have been done where the barrel nut breaks loose, before a clamp on gas block give away.


Exactly. Kind of annoys me when people say they'll only used pinned blocks because they don't want it coming loose lol. My clamp-on FSB hasn't moved one bit in three years. And its the barrel index pin that shears, not barrel nut.
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