Sighting in new BCM 14.5 middy with LaRue BUIS...is this a problem? [Archive]

JohnnyNumbers

04-22-12, 16:21

Hey guys. I rarely post here as I'm basically a lurker taking in as much information as I can and learning as I go along, but I ran into an unusual situation today at the range and I'm curious to know if this is something to be concerned with or not.

Before I get into the issue...A while back I purchased a Magpul MBUS for my LE6920 as I had removed the carry handle in order to mount a RDS. Zero the MBUS at 50yds with the base of the front sight post flush with the top of the FSB. A couple windage adjustments and I was dead on without having to make any elevation changes. GTG.

A week ago...I got in a new BCM 14.5 mid-length upper. Now what I don't want to do, is move my red dot and MBUS from the Colt over to BCM since the 6920 is zero'd.

A year or so ago, I picked up a LaRue BUIS that I never really used...so I figured I would mount the LaRue to the BCM, zero it...and then whenever I can pickup another lower, I'll have another AR build to play with.

Here is the LaRue BUIS I'm referring too...
http://i53.photobucket.com/albums/g52/MH353/IMG_0374.jpg

Ok...start out with base of the front post flush with the FSB, rear aperture (small) centered. Take 5 shots at 50 yds. In the picture you can see the first group at the top right...then you can see the adjustments as I walked in my rounds to the center of the target.

http://i53.photobucket.com/albums/g52/MH353/IMG_0368.jpg
http://i53.photobucket.com/albums/g52/MH353/IMG_0367.jpg

Now...this is what has me at pause...

http://i53.photobucket.com/albums/g52/MH353/IMG_0372.jpg

My question is...is it normal for the front sight post to be this elevated after a 50 yd zero depending on what rear BUIS may be used? I was under the impression that rear sights be they folding or not...were supposed to be pretty close to the same height off the upper receiver...but I may be wrong. IDK.

Remember...the front post on my Colt needed no adjustment at all. It's still flush with the FSB and it's dead on at that same range.

What I may do, is mount the carry handle off the Colt onto the BCM and re-zero to see if there is a change.

Failure2Stop

04-22-12, 16:50

No, that is not normal.
Something is off somewhere.
Easy answer is to get a taller front sight post.

JohnnyNumbers

04-22-12, 17:07

No, that is not normal.
Something is off somewhere.
Easy answer is to get a taller front sight post.

I thought of that as well, but if it needs a taller front sight post, then I would think BCM would make that the standard.

I think I'll test out the carry handle and maybe even pull the MBUS off the Colt if I have too. If I still have the same problem, then I know it's the front site. If not...then the LaRue is screwed up.

sewvacman

04-22-12, 17:11

JohnnyNumbers

04-22-12, 17:20

Looks like the sight post is above the ears though.
I have the same LaRue buis on one of my rifles and several other brands as well (DD, Troy). None have the sight post that high, most are flush w/ the top of the FSB or lower. Try the carry handle, that should narrow it down to the sight or the upper.

Yeah that's where the sight post ended up after I got it sighted in. I started off with the front post flush with the FSB.

When my first group was like 6" high at 50 yards... I knew something wasn't right.

Failure2Stop

04-22-12, 17:24

I thought of that as well, but if it needs a taller front sight post, then I would think BCM would make that the standard.

I think I'll test out the carry handle and maybe even pull the MBUS off the Colt if I have too. If I still have the same problem, then I know it's the front site. If not...then the LaRue is screwed up.

Is the FSB "F" marked?
Usually BCMs are good to go, but sometimes things fall through the cracks even with good companies.

I also misspoke, the "easiest" answer is to swap rear sights if you have one available.

JohnnyNumbers

04-22-12, 17:34

Is the FSB "F" marked?
Usually BCMs are good to go, but sometimes things fall through the cracks even with good companies.

I also misspoke, the "easiest" answer is to swap rear sights if you have one available.

Yes...the FSB is most definitely "F" marked.

I'll get back to the range as soon as I can.

Cowtown556

04-22-12, 18:54

try another rear sight,my troy lets my front post set two clicks lower than my LMT or GGG rear sight.

JohnnyNumbers

04-24-12, 15:54

Update...

Ok...back to the range today with carry handle off my Colt mounted on the BCM upper.
http://i53.photobucket.com/albums/g52/MH353/IMG_0381.jpg

FSP reset to flush and the rear sight set to 6/3 and centered. Range is 50 yards...

http://i53.photobucket.com/albums/g52/MH353/IMG_0376.jpg
http://i53.photobucket.com/albums/g52/MH353/IMG_0377.jpg

Now from what I have read using M193 w/14.5" barrel and hitting about an inch high at 50 yards...should put me right on at 100yds. At least thats what I thought I read somewhere on this forum... I may be wrong.

Move to the 100 yard range...thinking I should be hitting around the general vicinity of the 10x with my grouping, granted my fundamentals are in check.

Fire a 5 shot group...

http://i53.photobucket.com/albums/g52/MH353/IMG_0379.jpg

That first group is roughly 5" high from center. :confused:

Make a 1 click FSP adjustment and lower my POA to where I have it marked on the target (at least that's where it appeared looking thru the aperture at that distance and my eyes aren't as good as they used to be) which still has me printing 2" high from center of the 10x.

I could make further adjustments raising the FSP to bring my POI lower...but here we are getting back to raising my FSP up to a point to where it's as high or higher than the ears of the front sight base, which to me isn't right...and the whole purpose of this thread.

Here is where the FSP is set as of now...

http://i53.photobucket.com/albums/g52/MH353/IMG_0380.jpg

So again I ask...do you guys think this a unusual? I could just remember that I'm hitting 3" high at 100 yards :rolleyes: or just go ahead and see about getting a taller FSP. It just seems to me that if a taller post is needed...BCM should make that a standard.

tsconver

04-24-12, 16:07

Doc Safari

04-24-12, 16:53

Something is out of spec.

Another bad BCM upper?

I used one of the improved battlesight zero's on my BCM carbine. I zeroed at 50 yards and the front sight post's flange was just above the sight base hole, but not as bad as yours. A taller Bushmaster front sight post fixed my issue. It may fix yours but I suspect you will still have part of the front sight flange showing above the edge of the front sight base hole.

I'm not an expert on this but I'm wondering if your gun just shoots unnaturally high.

Tweak

04-24-12, 16:56

Is your BUIS seated into a slot in the upper?

ETA: a 100 yd zero will be low all the way out.

If the BUIS is properly seated then contact BCM.

JohnnyNumbers

04-24-12, 17:05

Why not set it at 300 yards like that carry handle is designed for? Zero at 25 and you should be about 6 high at 100 and zero at 300. Once set at 25 verify at 300 and fine tune your zero.

Sent from my DROID RAZR using Tapatalk 2

That might be possible if I had access to a 300 yard range...but I don't. 100 yards is all I have to work with.

I'm grouping 4" high at 50 yards with FSP set flush and rear sight set at 6/3. I can only guess where I would be printing at 25....5" maybe 6" high? I can only imagine where my front post would be elevated after I zero'd at 25 yards.

Something is out of spec.

Another bad BCM upper?

I used one of the improved battlesight zero's on my BCM carbine. I zeroed at 50 yards and the front sight post's flange was just above the sight base hole, but not as bad as yours. A taller Bushmaster front sight post fixed my issue. It may fix yours but I suspect you will still have part of the front sight flange showing above the edge of the front sight base hole.

I'm not an expert on this but I'm wondering if your gun just shoots unnaturally high.

I'm thinking that I may go ahead and get a taller post because something isn't right. I'm also going to send BCM an email and ask their opinion as well.

Is your BUIS seated into a slot in the upper?

I used the carry handle today. If you look at the picture posted, you can see it's mounted properly.

Canonshooter

04-24-12, 17:13

I'm also going to send BCM an email and ask their opinion as well.

^^^THIS^^^

I also have a relatively new BCM 14.5 Midlength (LW) with a FSB and the same LaRue rear sight, and it sighted-in fine. The top of the post base about flush.

Something is amiss, IMO.....

Tweak

04-24-12, 17:29

I used the carry handle today. If you look at the picture posted, you can see it's mounted properly.

I saw that, I've also seen people who don't know how to mount their sights and if they do it with one they can do it with another. The only thing to check is the rear sight, either construction or installation. If both of those are good then it's on the manufacturer and the innumerable variables that can lead to mis-alinement.

JohnnyNumbers

04-24-12, 17:30

^^^THIS^^^

I also have a relatively new BCM 14.5 Midlength (LW) with a FSB and the same LaRue rear sight, and it sighted-in fine. The top of the post base about flush.

Something is amiss, IMO.....

When I sighted in my 6920, all I had to do was make a couple windage adjustments and I was dead on at 50 yards. That's why this whole episode seems so strange.

I hate to go thru the hassle of having to send this thing back if need be...but for the money spent and my OCD (LOL) I don't see another option.

JohnnyNumbers

04-24-12, 17:35

I saw that, I've also seen people who don't know how to mount their sights and if they do it with one they can do it with another. The only thing to check is the rear sight, either construction or installation. If both of those are good then it's on the manufacturer and the innumerable variables that can lead to mis-alinement.

I agree.

I'm getting the same result using the LaRue BUIS as I am with the carry handle. At this point...I'm contacting BCM.

I shouldn't have to alter this upper on my dime to make it shoot right...i.e. change out the front sight post.

TacMedic556

04-24-12, 23:16

Is your BUIS seated into a slot in the upper?

ETA: a 100 yd zero will be low all the way out.

If the BUIS is properly seated then contact BCM.

Definately check the mounting of the Larue as stated above. If it is not properly seated into the picatinny rail slot as designed it will be off.

ucrt

04-24-12, 23:31

JohnnyNumbers

04-24-12, 23:40

.

To me, a taller FS Post isn't a solution on a fighting rifle because the post will be above the protective ears.

Just curious, are you using the large or small peep sight? I can't shoot for jack with the large peep...but it's probably my old eyes.

.

I have ruled out getting a taller site post as of now. I sent an email to BCM and should get a response here pretty soon...I hope. I'll make a determination after they respond.

I was using the small aperture.

Code7inoaktown

04-25-12, 00:59

I actually have the same problem with a 14.5 carbine-gassed upper from BCM purchased about 18 months ago. I've been too lazy to send it back in for service. I posted about it here and decided it was maybe me but enough searches indicate it happens on occasion. Here are some other posts here. I know when I talked to BCM (excellent service by the way) they said if I sent it in, they'd take a look at it. That was before Xmas and it got too busy but I'd like to know what happens when you send it back in. I had decided to just buy a Bushmaster 0.040 tall sight but may just send it back.

https://www.m4carbine.net/showthread.php?t=42485

https://www.m4carbine.net/showthread.php?t=54954

BTW, Grant sells the sight posts: http://www.gandrtactical.com/cgi-bin/commerce.cgi?preadd=action&key=TALL-FSP

Cowtown556

04-25-12, 05:46

A Matech set at 200 on a 50 yard range will bring the front post down about 3 clicks lower than the handle.

JohnnyNumbers

04-25-12, 09:19

I got an e-mail response from BCM this morning. I sent them the pictures I posted here and I will wait for their opinion before I make any further decisions.

JohnnyNumbers

04-25-12, 17:23

Chalk one up for BCM customer service!

They were very prompt and felt it needed to be returned. Shipping label was sent and the upper is on its way.

This speaks very highly of them.

deuce9166

04-25-12, 17:30

I experienced the same thing with two EAG uppers and Larue BUIS. I did not have this high of a FSP with the Troy sights.

TacMedic556

04-25-12, 18:01

I wish I could see the Larue and how it is mounted. They are easy to get mis-aligned on the rail. You really need to visualize and feel it drop into place properly.

Code7inoaktown

04-25-12, 18:21

Chalk one up for BCM customer service!

They were very prompt and felt it needed to be returned. Shipping label was sent and the upper is on its way.

This speaks very highly of them.

Yes, a lot of the "BCM is overrated dummies" don't understand how good BCM's service is. Lower chance of having problems, and if you have a problem, they fix it and fix it as soon as possible. They don't frak around and run you for weeks on end.

Let us know what the result is. I may consider sending mine in too, although I do wonder if my Troy BUIS isn't mounted incorrectly. I'll double check that.

JohnnyNumbers

04-25-12, 18:58

Let us know what the result is. I may consider sending mine in too, although I do wonder if my Troy BUIS isn't mounted incorrectly. I'll double check that.

I will most definitely update this thread when all is said and done. I'm expecting at least a couple weeks for my upper to come back. If it gets here sooner...then that's even better.

In regards to the LaRue BUIS...I now know with a degree of certainty, it wasn't the problem considering I had the same result with two different rear sights. As far as it not being mounted properly...I don't see how you could get it to clamp down if it wasn't. There is a (for lack of a better term) protrusion on the bottom of the sight that fits down in between the rail sections to keep it aligned before you can even clamp it down. I'm not debating the idea that it can improperly mounted just like i'm sure there are individuals who can push a square peg into a round hole...but rest assured, I had it properly mounted.

SW-Shooter

04-25-12, 19:03

fdxpilot

04-25-12, 22:17

Now from what I have read using M193 w/14.5" barrel and hitting about an inch high at 50 yards...should put me right on at 100yds. At least thats what I thought I read somewhere on this forum... I may be wrong.

That first group is roughly 5" high from center. :confused:.

Glad to see that BCM is making it right. As far as your understanding of zeroes, you are way off. A 100yd zero will just touch POA at 100yds. It will be low closer and further away. You should have a POI about 3/4" low at 50yds with a 100yd zero.

If you are an inch high at 50yds, you will, as you discovered, be about 5" high at 100yds.

A good source of info on various zeroes, sights, and sight posts can be found in this thread by Molon

http://m4carbine.net/showthread.php?t=65679

In fact, the first couple paragraphs address the 100yd zero, with a nice graph.

JohnnyNumbers

04-25-12, 22:24

http://www.box.net/shared/static/8xved8kfrm.jpg

According to this chart...with a 50yd zero, I should be hitting about 1.5" high at 100yds.

Maybe I had it backwards...LOL!

http://www.box.net/shared/static/c0dvpkdudy.jpg

Yeah, with a 100 yd zero...I would be around 3/4" low at 50. I'll buy that!

Thanks for the info!!

Tweak

04-26-12, 00:06

ETA: a 100 yd zero will be low all the way out.

:smile:

AKDoug

04-26-12, 00:38

There are now 4 known issues that involve BCM uppers. Now I'm not pointing the finger at that, it could be a combination of many factors but something is definitely amiss.https://www.m4carbine.net/showthread.php?t=104141
https://www.m4carbine.net/showthread.php?t=103559

So what are you pointing at? In the first link the OP has yet to confirm it's a BCM upper. The second link is a guy that can't even shoot a group yet, then some other guy jumps in for advice and he's shooting a 6920.

Beat Trash

04-26-12, 09:14

I'm glad the OP is asking for help. He didn't come out the gate bashing either LaRue or BCM. Once his testing with different sights ruled out the LaRue sight as the issue, he contacted BCM for help.

This is as it should be.

Any manufacture of any product can have something slip through. This is why it's important to test your equipment prior to usage.

To me a company's willingness to stand behind their product after the sale is almost as important as the quality of the initial product itself.

So before this becomes a BCM witch hunt, lets just see if the BCM customer service is as strong as it's known to be. I'm betting the OP's issues will get taken care of.

Doc Safari

04-26-12, 09:26

If it's a problem with BCM uppers, clearly BCM just got a bad batch of them. I'm a Bravo Company fanboy, but they probably should have caught this before assembling them. I bet they will from now on. So far everything I've purchased from them has been 100%, so I believe this will end up just being an anomaly.

polymorpheous

04-26-12, 09:28

deuce9166

04-26-12, 10:47

For me it was the LaRue BUIS. Maybe I am missing something but I just checked again and when I mount the LaRue inforont of my LMT both switched to the small app. The LaRue app. seems to sit higher.

When I have my nose to charge handle the fsp is slightly obscured by the LaRue app. I know that's not very scientific though.

djmorris

04-26-12, 15:42

There are now 4 known issues that involve BCM uppers. Now I'm not pointing the finger at that, it could be a combination of many factors but something is definitely amiss.https://www.m4carbine.net/showthread.php?t=104141
https://www.m4carbine.net/showthread.php?t=103559

What are you talking about? Four known issues? Because you found four threads with relatively insignificant problems does not mean that BCM has multiple known issues with their uppers. I would say, if anything, it's because BCM sells so many uppers now that almost anyone who is buying a quality, custom AR is buying BCM now.

I'm sure S&W never has these issues, huh? :rolleyes:

SW-Shooter

04-26-12, 16:17

What are you talking about? Four known issues? Because you found four threads with relatively insignificant problems does not mean that BCM has multiple known issues with their uppers. I would say, if anything, it's because BCM sells so many uppers now that almost anyone who is buying a quality, custom AR is buying BCM now.

I'm sure S&W never has these issues, huh? :rolleyes:

The simple fact that these issue's are concerning BCM uppers, that is why I posted the links. Several new owners of BCM uppers have posted minor/major issues about those uppers. BCM is a great company and takes great care of their customers, including me. I'm a BCM fan and enjoy their products as much as the next guy. The fact is some problems have occurred as of late, that's not a dig on BCM it's merely community notification and awareness. Every manufacturer has it's fair share of problems and BCM is not immune. But "the chart" has produced a myriad of end users that feel that unless it's a top tier manufacturer, it's crap. So let's be real, there is no immunity to manufacturer defect, chart or no chart.

What makes you think I even own a S&W ( I do not)? SW doesn't stand for Smith and Wesson, buddy.

SW-Shooter

04-26-12, 16:21

So what are you pointing at? In the first link the OP has yet to confirm it's a BCM upper. The second link is a guy that can't even shoot a group yet, then some other guy jumps in for advice and he's shooting a 6920.

Reading is fundamental Sparky. I know for a fact that these uppers are all BCM. Also, his 6920 shoots fine but when he switched the BUIS to his BCM he started having problems sighting it in. How about YOU read the posts thoroughly, and then try to make a coherent statement against the facts that I posted about.

AKDoug

04-26-12, 20:35

In your link #1 "2arbka" never mentions the make of the upper. He only mentions he bought it from Grant.

In your link #2 the OP "DeviousMind" makes no mention of owning a 6920. Then "wingspar" jumps in with his sighting problems of his 6920. It then degrades into a trigger question. Still, the upper has not been proven the issue in either case and it appears that both shooters have recognized their own shooting may very well be the cause.

Neither thread has anything to do with proven BCM upper issues. In fact you make the statement that there are four "known" problems (whatever that means) yet have no links at all that show anything at all on this sight. You have one link for TOS that obviously shows a bad upper from BCM, but there is another one linked in that thread from PSA.

This is the thread that has the guy that has both a BCM and a 6920. I know it's difficult to keep everything straight. In this thread I agree that the upper has an issue and BCM is taking care of it.

My reading comprehension is just fine..sparky. You seem to have a bone to pick with BCM.

SW-Shooter

04-26-12, 21:47

[QI'm just going to put a stop to the back and forth. Reading is Fundamental, what I posted is correct. Let's get this back on topic before we both get in trouble.

Failure2Stop

04-26-12, 22:44

This thread has jumped ship.
Nobody is in "trouble" (tremble tremble), but it's time to let BCM do what they do.
Thread is closed until further update is appropriate.

Failure2Stop

05-16-12, 17:05

Reopened at request of OP

Sent from my DROID RAZR using Tapatalk 2

JohnnyNumbers

05-16-12, 17:59

Reopened at request of OP

Sent from my DROID RAZR using Tapatalk 2

Thank you!

Ok, I wanted to add the latest update to this thread.

So I sent my upper off to BCM and as I recall, I had it back in my possession in approximately two weeks. I finally got a chance to shoot it again today...so here we are.

I have come to conclusion that I like the carry handle better than the BUIS (for now), so that is what I used when I went to the range.

First target...50 yards.

http://i53.photobucket.com/albums/g52/MH353/IMG_0382.jpg

When they sent the upper back, they had the top of FSP base lowered a few clicks below the top edge of the FSB, so IMO that's the reason behind the high shot group...plus I wasn't sure of adjustments they made, so I just fired a group and went from there.

Second target...50 yards...hitting center after making a final adjustment and finishing with what I would consider a 50 yd. zero.

http://i53.photobucket.com/albums/g52/MH353/IMG_0383.jpg

Pulled up stakes and went to the 100 yrd. range.

Now according to this chart...

http://www.box.net/shared/static/c0dvpkdudy.jpg

I should be shooting ~around~ 2" high at 100 yds. with a 50 yd. zero.

http://i53.photobucket.com/albums/g52/MH353/IMG_0385.jpg

Actually, my poor excuse of a group (I'll blame it on my eyesight trying get POA at a 2" circle at 100 yds... :D) was more like 2.75" high.

With all this being said, the main point of this thread was noticing where the FSP located AFTER getting sighted in.

Before I sent it back to BCM...
http://i53.photobucket.com/albums/g52/MH353/IMG_0372.jpg

After today...
http://i53.photobucket.com/albums/g52/MH353/IMG_0387.jpg

I think I can live with that.

Again...I want to make sure that I put it out there, that BCM was quick to acknowledge my problem and they stood behind their product and made it right for me. They are stand up guys and I look forward to doing more business with them in the future.

2arkba

05-16-12, 18:19

Doc Safari

05-17-12, 09:07

After today...
http://i53.photobucket.com/albums/g52/MH353/IMG_0387.jpg

I think I can live with that.

Mine looked like that after zeroing with one of the improved battlesight zeroes.

At this point I think you could benefit from the taller Bushmaster front sight post.

I installed one on my rifle, and now that lower flange of the front sight post does not stick up above the edge of the hole in the FSB, but is just a hair below it.

polymorpheous

05-17-12, 11:36

I never had all this trouble with my Rockmaster. :nono:

Insinuating anything by this comment?

Hehuhates

05-17-12, 11:58

Nope....... front pin still looks a lil' high though, could be the pic.

JohnnyNumbers

05-17-12, 19:52

Mine looked like that after zeroing with one of the improved battlesight zeroes.

At this point I think you could benefit from the taller Bushmaster front sight post.

I installed one on my rifle, and now that lower flange of the front sight post does not stick up above the edge of the hole in the FSB, but is just a hair below it.

I'll agree.

Right now I'm just happy to have a good zero...but later on, my OCD may have me placing an order for the BM FSP. We will see, LOL!

Shiz

05-18-12, 07:13

Johnny, do you know what they did exactly to fix it? I am curious as to a little of the repair procedure they did to remedy it.

JohnnyNumbers

05-18-12, 09:25

Johnny, do you know what they did exactly to fix it? I am curious as to a little of the repair procedure they did to remedy it.

Once I had seen through UPS tracking that the package had been received, I waited a few days and then sent an email inquiring as to whether or not they had an opportunity to look at it or not. I was told they had ... "made an adjustment"... and that the package was already on the way back to me, and a return tracking number was provided.

So to answer your question...no...I have no idea what the adjustment entailed. I was happy that they worked on it and it was already in return transit.

Shiz

05-18-12, 21:26

Curious to know what remedies would be tried like in Johnny's case. Any expert armorers out there care to chime in? How would you remedy it?

Tweak

05-19-12, 13:13

when you work in a shop you get familiar with the problems specific to that line. At Olympic if I saw damage to the face of the buffer I would check the rear of the bolt carrier in relation to the upper then the upper receiver threads. In this case I'm sure that the maker has seen it before and they could jump ahead to the solution.

If it was my shop then I'd pull a different upper from stock and ship it back ASAP then diagnose the problem upper later.

If that came over my bench I would boresight it and inspect the barrel for straightness (rare that they're bent perfectly down) then check the receiver and FSB heights against the print. I'd then change out the upper and if that didn't work then the barrel.