BUIS not jeehawing, could use some help.

[RECKON SO]

I ended up with an m4 clone type rifle- "16 barrel, flattop etc. It has a set of yankee hill flip ups on it and at 25yds it shoots approx 2 feet low. Ive got the front post all the way down and the rear doesnt have an elevation adj. Ive searched around but I am wondering is there a shorter front sight post setup available?

 

[ecdbcd]

Re: BUIS not jeehawing, could use some help.

Have you verified that the sights are properly tightened? I've had BUIS that couldn't zero worth a darn, until I found out they were completely loose. Also, have you tried your zero with multiple types of ammo?

 

[salmonaxe]

Re: BUIS not jeehawing, could use some help.

You sure you have the right front sight BUIS? Some are made for railed gasblocks and some are for mounting to a free float rail. Also, there's different ones for AR-15's vs. AR10's when it comes to the gasblock mounted version.

If you have the wrong type, it might goof you up as you say.

I've never heard of someone having a sight that was too tall. Usually it's the other way around.

 

[match308]

Re: BUIS not jeehawing, could use some help.

+1
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Salmonaxe</div><div class="ubbcode-body">You sure you have the right front sight BUIS? Some are made for railed gasblocks and some are for mounting to a free float rail. Also, there's different ones for AR-15's vs. AR10's when it comes to the gasblock mounted version.

If you have the wrong type, it might goof you up as you say.

I've never heard of someone having a sight that was too tall. Usually it's the other way around. </div></div>

 

[sobrbiker883]

Re: BUIS not jeehawing, could use some help.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Salmonaxe</div><div class="ubbcode-body">You sure you have the right front sight BUIS? Some are made for railed gasblocks and some are for mounting to a free float rail. </div></div>

What he said.

Check here for a visual to ID which you have installed (I'm guessing on your free floar rail you have a gasblock model):
http://www.yhm.net/store/sights.html

 

[RECKON SO]

Re: BUIS not jeehawing, could use some help.

The sights are tight, thats one of the first things I checked, and Im not positive but I think the ammo is 55gr, It looks to be nato of some origin, its definitely not high grade stuff. It came with the rifle in the deal. I checked Yankee hills website and found what looked to be the same sights and it said they were for std height sight plane. I dont remember it specifying if they were for an ar15 or ar10. I did find a front post on the MI site thats supposed to mount to the hand guard and they say its shorter than normal, I had thought about trying that one but I didnt want to end up with the same problem in the other direction. I put an Adams Arms piston kit on the rifle along with a DD 7.0 free float, but they all are on the same plane with the upper give or take a couple of thousandths. I wasnt sure if a std rear aperture would work with a shorter front post assembly. So I didnt want to buy one without knowing. Initially I tried it at 50yds shooting slightly down hill at the pond and it hits about 3-5 feet short of where I aimed. I cant get the post any lower in the housing, even if I could you couldnt see it cause its only sticking up about an 1/8 inch right now. Much Obliged on all the advice.

 

[sobrbiker883]

Re: BUIS not jeehawing, could use some help.

Does it impact the same spot low or all over the place low? How tight is your barrel nut?

Is the front sight mounted on a railed gasblock, the DD rail, or is it a standard FSB?

A pic (side view of rifle rear sight to front sight) would help.

If the sights are the right ones, and it is shooting that low after changing the operating system (did it shoot fine prior to the piston kit?) you may want to have someone that knows what they are doing troubleshoot the problem.......

 

[steelcomp]

Re: BUIS not jeehawing, could use some help.

For a gas block mounted flip up, the top of the sight pin (in it's proper location) should be approx. 1-5/8" above the gas block rail. If it's a rail mounted gas block (equal plane as the rear sight) it should be about 1/4" shorter, or approx. 1-3/8" above the rail. My guess is that you have a gas block sight mounted on your rail. Was your front sight originally mounted on the gas block?

 

[RECKON SO]

Re: BUIS not jeehawing, could use some help.

It seems to be holding a decent group. I didnt shoot the rifle untill I had already installed the piston system. When I installed the new barrel nut I torqued it to 60 ft/lbs, because everything I read said start from 30-50 lbs and turn it untill the gas hole lines up not to exceed 80 lbs I think it was. Not having to line up a gas hole I just went with 60lbs. I agree that the front sight post is probably the wrong one after looking at Yankee hills website and seeing that there is a shorter version available for rail mounted setups. I am going to get an MI front and rear setup for rail mount " Im getting both cause I am not super impressed with the rear sights lockup stability" and see how that works out. I am pretty confident that this will help or at least get it to where I can adjust it out. Ive got another question- The barrel did not have any markings on it except right in front of the delta ring where it was stamped "N9C". I havent run across a barrel that didnt have the caliber or nato or twist or all of the above untill this one. It looks to be a heavy barrel cause it only steps down for the gas block area and then follows that diameter all the way out. Has anybody seen this particular stamp and know the manufacturer? I appreciate all of the feedback.

 

[steelcomp]

Re: BUIS not jeehawing, could use some help.

Sounds like a Rock River code...<span style="font-weight: bold">N</span>=nato chamber <span style="font-weight: bold">9</span>=1:9 twist <span style="font-weight: bold">C</span>=chrome lined.

 

[RECKON SO]

Re: BUIS not jeehawing, could use some help.

Much obliged for all the help. Ive got a new set of sights on the way, and I think thats going to straighten it out. Thanks again for all the info.