[Firemanpete]

Like the subject says, I'm having massive issues zero'ing in my magpul gen2 MBUS I'm certain they're NOT the pts ones but it seems I can't hit the broad side of a barn at 50 yards with these things, I've had the front sight pin all the way up, down and every spot in between. The rear sight all the way left and right as well as every spot in between, and maybe get about 1-2 shots in about a 5" group before the sights need to be re-adjusted up/down, left/right....Anyone have any ideas on how to get this squared away? or should I just toss those and get a pair of something like Troy iron sights??.....

specs of rifle for clarifications sake:
dpms lower
rock river arms upper
Blackhawk tactical quad rails on the fore end.
((I have noticed that the blackhawk quad rail fore end sits maybe a couple milimeters lower than being straight inline with the rail on the upper, could that really through it off that much that often?))

please help, it's annoying the hell out of me, to the point where I might just take them off for good and keep my vortex strikefire on there alone..... thank you.

-- Pete

 

[sr20sean]

I have a feeling it's probably that quad rail. I noticed they weren't really designed for normal use. More of an aesthetic thing.

 

[llink78]

did you buy these new or used? could you of possibly picked up the cheaper air soft versions?

 

[Firemanpete]

sr20Sean---> I was unaware of that, do you really think that they're designed more for aesthetics?? I think it's rather solidly built it holds my vert. grip and a tac light with no problems...not even the slightest bit of wobble((then again those aren't really important to the accuracy of the weapon huh? lol

llink78---> I bout the sights and rail both brand new from the same shop I go to alllllll the time for any of my needs/wants/desires. Anything is possible regarding that he might have gotten a botched shipment but from what I remember the box did NOT say anything with pts on it. The only thing that was bought used was the weapon itself, I bought it from a friend of mine who has built about 2 dozen AR's and never had a problem.

 

[cgrutt]

I know this will only give a short LOR but did you try putting the front sight on the upper receiver to see if it holds zero there? Sounds to me like it could be the front rail. Is there any noticable play in it?

 

[Camper4lyfe]

Dumb question but is everything tight?

 

[llink78]

here is a good one. are your MBUS facing the right way? a buddy of mine had his on backwards and they shot off, they should be flipping up forward. so it looks like your looking at the bottom when they are in use

 

[Dieter122]

The PTS ones are actually made the same , just of a cheaper plastic.
Ive put some side by side and it's literally impossible to tell the difference.
I think there may be a lack of a certain marking or something minor , aside from that though...

 

[DirgeNYS]

If you use a rail mounted front sight on a non free-float handguard, your shots are going to be off every time. A non free-float handguard will vibrate with each shot, since the handguard is making contact with the retaining cap, which in turn is making contact with the barrel. It's even worse when the top rail is not perfectly level and aligned with the receiver's flattop. It may not look like much to you, but any offset is magnified over several yards. The further out your target is, the worse it will become.

You have three options:
1.) Have a smith install a standard FSB.
2.) Install a drop-in, two-piece free float handguard like a Daniel Defense Omega.
3.) Forego a front sight entirely by using a quality optic and cowitnessing it with a quality rear sight.

 

[Firemanpete]

here is a good one. are your MBUS facing the right way? a buddy of mine had his on backwards and they shot off, they should be flipping up forward. so it looks like your looking at the bottom when they are in use

--Yes they are.

Dumb question but is everything tight?

--Yeah they are all tight as they should be, BLUE loctite and all lol.

The PTS ones are actually made the same , just of a cheaper plastic.
Ive put some side by side and it's literally impossible to tell the difference.
I think there may be a lack of a certain marking or something minor , aside from that though...

--Good to know thanks.

If you use a rail mounted front sight on a non free-float handguard, your shots are going to be off every time. A non free-float handguard will vibrate with each shot, since the handguard is making contact with the retaining cap, which in turn is making contact with the barrel. It's even worse when the top rail is not perfectly level and aligned with the receiver's flattop. It may not look like much to you, but any offset is magnified over several yards. The further out your target is, the worse it will become.

You have three options:
1.) Have a smith install a standard FSB.
2.) Install a drop-in, two-piece free float handguard like a Daniel Defense Omega.
3.) Forego a front sight entirely by using a quality optic and cowitnessing it with a quality rear sight.

-- Interesting bit of info here, thank you. I am not 100% sure if it's freefloated or not, my friend who built it(as he has done many others with no problems) originally had the M4 fore end on it, and installed the quad rail for me, the front of the quad rail does sit into the retaining cap ((opposite end from the delta ring going towards the muzzle end.)) with a railed gas block with a UTG front sight post (obviously gas block height) I removed that flip up sight when I got the MBUS' and the quad rail.
With all that do you think my best option would be to have a smith install a normal AR front sight gas block like the A2 front sight post gas block type thing? or just put the UTG front sight back on with the magpul rear sight?.....I am so frigging lost on this lol. my last AR was so much simpler lol...

---Thank you all for the insight and help in my dilema.

-- Pete

 

[evileyeswatchin]

Got a pic?

 

[DirgeNYS]

-- Interesting bit of info here, thank you. I am not 100% sure if it's freefloated or not, my friend who built it(as he has done many others with no problems) originally had the M4 fore end on it, and installed the quad rail for me, the front of the quad rail does sit into the retaining cap ((opposite end from the delta ring going towards the muzzle end.)) with a railed gas block with a UTG front sight post (obviously gas block height) I removed that flip up sight when I got the MBUS' and the quad rail.
With all that do you think my best option would be to have a smith install a normal AR front sight gas block like the A2 front sight post gas block type thing? or just put the UTG front sight back on with the magpul rear sight?.....I am so frigging lost on this lol. my last AR was so much simpler lol...

Ah, so the front sight is mounted on a railed gas block. For some reason I thought the front sight was mounted on the handguard.

Anyway, yes, I think having a standard A2 FSB would be your best option at this point. I hate those railed gas blocks; I never saw what the point of them were. My father had one on his build and it gave us nothing but grief, as we couldn't mount a flip-up sight to it and putting on a fixed sight rendered it pointless. An A2 will be the most accurate front sight option you can get because it will be pinned to your barrel. It'd also be the most inexpensive option, compared to getting a whole new handguard or a $400+ optic.

If you don't have a professional smith or armorer near you, I highly recommend ADCO. Steve is a GOD among smiths, has great prices, and will do just about anything to make your gun compliant and/or tailored to your demands. He's my go-to guy.

 

[Camper4lyfe]

MBUS shouldn't be used on the FGB. Even Magpul says this.

 

[sdb3023]

Sounds like you dont have the sights in the same horizontal plane. Post a pic of ur current set up. I think it could be an easy fix.

 

[Dieter122]

MBUS shouldn't be used on the FGB. Even Magpul says this.

yep. Great way to melt the BUIS to the gun.

 

[LDD]

Your list of options isn't great at this point.

First, if you're using the blackhawk two-piece no-mod-to-the-upper rails, then your rails are quad-rail, non-free floated. These are useless for mounting any sort of fine aiming apparatus on, so that is a no-go.

Second, the MBUS are not designed to work on gas blocks. 1) the front MBUS is not tall enough; 2) the MBUS will melt as the gas block absorbs a lot of heat from discharge and has much less surface area than a barrel (with which to dissipate that heat).

YHM makes a front sight that is gas-block-height, but it isn't pretty:

[deleted link because it is apparently suspect]

(yes, the website plays annoying "olde tyme" music, no idea why)

Once you get your front sight issues squared away, your problems with the rear MBUS should disappear.

Going with the Vortex alone is actually a viable solution and the one I would suggest since you already have it (but not the complete solution). I would save for a new low-pro gas block and a good free float foreend system that matches the receiver in height (Troy, Knights, Samson, etc, lots to chose from here). Ultimately, you will want to get rid of the non-free-floated handguards. Just because they have rails on them (and sometimes because they have rails) does not mean they will do what you want them to do.

Edited to add: Try this link (it's not the weird music Yankee Hill site)

https://www.primaryarms.com/Yankee_Hill_Machine_Gas_Block_Mounted_Front_F_p/yhm-9584.htm

 

[Trekmtbr89]

(yes, the website plays annoying "olde tyme" music, no idea why)

Wow that is obnoxious!

 

[Sponty]

Gas Block Mounted Front Flip Sight [YHM-9584] - $90.50 : YHM, Yankee Hill Machine Co., Inc. | Makers of High Quality Firearms, Accessories & Sound Suppressors, Makers of High Quality Firearms, Accessories & Sound Suppressors

I just clicked the link and AVG gave me a threat blocked notification. You guys might want to scan your pc with a good anti-virus program. The music and threat came from bfantastic.com. No clue what it is but I blocked it with ABP and all is well.

 

[cgrutt]

Wow that is obnoxious!

Lol, with all the mud slung around these parts, that's what you find offensive ? Carry on gents.

 

[Trekmtbr89]

Lol, with all the mud slung around these parts, that's what you find offensive ? Carry on gents.

I develop Websites for a living, so yes I take personal offense to being forced to listen to that music