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View Full Version : Sight-in problems -- WTF !


Force
08-29-09, 21:10
Went to the range today to sight in my M4 16 " carbine after putting magpul mbus sites on.
At 25 yards I was shooting about 18-20 inches high !
I adjusted the front sight post damn near all the way up and was still about 4-5 inches high at 25 yards.
Rear Mbus is mounted on a DPMS flatop, as far to the rear as i can get it.(about where carry handle sight sits)
Front Mbus is at the very end of a Larue 11" FF handguard (larue gas block).

So, What am i doing wrong?
I am about out of threads on the Front sight post.
Do the Mbus sit that much lower than a factory front sight?
87GN
08-29-09, 21:15
Huh...sometimes, if the LT rail's "keeper" screws are tightened too much during installation, the front of the rail can shift upwards...but that would not cause this problem...
johnnywitt
08-29-09, 22:39
Do the Mbus sit that much lower than a factory front sight?[/QUOTE]

Looks like you need a taller front sight post.
Is your rear a dual "flip" aperture rear? If it is, are you using the larger aperture.
technique
08-30-09, 01:09
Well....Can I ask where you acquired your sights? Or can we see a pic?

I ask because a buddy of mine wanted MBUS so bad he couldn't wait for them to be released. He purchased the airsoft version (they were out long before the real deal).

He had the very same issue you are having. Rear was fine but the front, even twisted all the way up......was still way off.
Dave L.
08-30-09, 05:33
Ok, more info on your weapon is needed. I highly doubt it's an "M4" as you stated.
Be specific, for example (Bushmaster carbine w/16" barrel and a BrandX Rail System".

My guess is that your rail system is not properly aligned. I had this happen to me. I didn't own a rail alignment tool and didn't want to gamble on buying one, so I just mailed the gun to Grant at G&R Tactical and he properly aligned it.
perna
08-30-09, 06:48
Rear Mbus is mounted on a DPMS flatop, as far to the rear as i can get it.(about where carry handle sight sits)
Front Mbus is at the very end of a Larue 11" FF handguard (larue gas block).


He did.
mark5pt56
08-30-09, 07:08
I would take a pic and post it showing the upper receiver and rail, side view with a straight edge. There has to be some alignment issues to be that far off.
CarlosDJackal
08-30-09, 09:29
...Front Mbus is at the very end of a Larue 11" FF handguard (larue gas block)...

Do you think that installing a plastic front sight onto a gas block is a smart idea? If it is a true gas block, it may be slightly lower than a handguard which might explain your problem.

FWIW, I had the same issue way back when I installed a 4-rail gas block onto my older carbine. I had to buy a tall front sight for it to work. ood luck!!
sdcromer
08-30-09, 10:44
Isn't the Front Mbus designed to be mounted to a handguard rail and not the gas block? Maybe I am reading the original post wrong. Is the Mbus on the free float handguard rail?

Gas blocks are lower and get very hot.
Dozer
08-30-09, 10:49
Unless things have changed, Larue doesn't make railed gas blocks so it means his sight is mounted on the end on the rail on the same plane. Post some pics so we can see what is going on. Also, try contacting Magpul directly.

S/F
Dozer
RAM Engineer
08-30-09, 11:17
Reason #58 why all front sights should be mounted to the barrel.
SHIVAN
08-30-09, 11:36
We've got no idea if this is a rail, sight or user issue. Until we can say for certain what it is, I have edited the title of this thread. There is no reason to lay blame on Magpul this early in the game.

Thanks.
bkb0000
08-30-09, 11:39
Reason #58 why all front sights should be mounted to the barrel.

my index shows we're at more like reason #5658...
Force
08-30-09, 12:39
Unless things have changed, Larue doesn't make railed gas blocks so it means his sight is mounted on the end on the rail on the same plane. Post some pics so we can see what is going on. Also, try contacting Magpul directly.

S/F
Dozer


Exactly right!

I stated in an earlier post that my setup had a Larue 11" FF handguard, with a Larue gas block. The Larue handguard slides over the Gas block. The front sight IS NOT mounted to a GB with a pic rail on top of it

The Mbus front sight is mounted in slot 35 on the HANDGUARD.
The Mbus rear sight is mounted in slot 3 on the UPPER RECIEVER.

I just checked square on the flat top reciever to the handguard.
It is perfect. I removed the handguard, and remounted it. Still square.
I ran my straight edge down the side of the upper rail, and the handguard, perfectly aligned.

I removed the flash hider , slid the stock front sight back on, up to the handguard.I leveled across both sight tips.
The mbus sight tip appears to be very close to where my original sight tip is.
The front sight tip on the mbus is barely protruding above the sight ears when i straight edge across.

I am not in anyway blaming Magpul for any of the Issues I am having. They make kickass gear, and it's all top quality.

The Mbus set was from a reputable dealer on E-bay. They are new, genuine Magpul, complete in the boxes w/ instructions. Not airsoft junk

I simply wanted to know if anyone else had a problem where they had to raise the front sight tip that much,to where it is unprotected by the sight ears or if it is normal.
I was only able to get one picture. The others didn't turn out do to the fact my daughter seems to have ruined my good digital camera. So, I was stuck trying to use, what I am sure is, the 1st digital camera ever made.

Thanks for the help.

http://i88.photobucket.com/albums/k184/Deblo/DpmsLarue.jpg
kmrtnsn
08-30-09, 14:48
I'd like to see a good down angle shot from the rear of each sight, a shot of where the LaRue meets the upper and a head on shot down the barrel showing the space between the barrel and the LaRue.
RAM Engineer
08-30-09, 18:47
my index shows we're at more like reason #5658...

I think your count is probably closer than mine. I believe it was a board SME who said something like "Are you trying to aim the barrel or the rail?"