Suggestions

[irocracer89]

I used a YHM Specter Length Diamond Forearm on my MP15, and used alignment tool from Brownells. Also purchased a Troy M4 folding front sight, to match on already on the back. FSB when deployed is off with the back, it,s not spot on. Is YHM forearms good any problems, and would YHM forearm tool be better.

[SpankMonkey]

There can be several problems depending on what you use the rifle for. First, that yhm rail has no way to stay locked in that position and will come loose with time. It's not a matter if it will come loose, it's just a matter of when.

That will then move your front sight out of position. Is sounds like your rail is already giving you problems. I would look into other designs.

If the gun is just a range toy you need to line the two top rails. This can be done by using a detachable carry handle to span across both rails. Take your time and line the rails up before tightening the barrel nut/rail nut.

Good luck.

[irocracer89]

Thanks, The YHM forearm I have does have the anti-rotation screws. After this tool, also placed levels on the rail and receiver both sections where level.. Use it for home defense, and range gun, with a Eotech sight...

[SpankMonkey]

Thanks, The YHM forearm I have does have the anti-rotation screws. After this tool, also placed levels on the rail and receiver both sections where level.. Use it for home defense, and range gun, with a Eotech sight...

Did you check to see if the rail is square? It may be warped.

[irocracer89]

Thanks, No I did not consider that.. Guess you could use a framing square, it's the only one I have..

[Sanpete]

First, that yhm rail has no way to stay locked in that position and will come loose with time. It's not a matter if it will come loose, it's just a matter of when.

Nonsense.
It does not differ from 99% of the other free float handguards out there, in that they rely on proper torque and installation. The rail has 2 anti-rotation set screws and a jam nut that locks it in place. The gas tube travels through the barrel nut. The barrel nut needs to be torqued into position, just like a GI nut. If you install it right, that handguard isn't going to budge.

I don't care for those rail systems for a number of reasons, but they're not sloppy and falling off of guns.

[irocracer89]

Come on people.... I merely asked if the YHM forearm alignment tool would work better, than the one from Brownells. Basically because it is longer, and use more of the rail to align it..

[SpankMonkey]

Op if you can, take a square and hold it to each side of the rail. Look to see if there are any gaps between the front and rear of the rail. Your problem sounds like one of the sides may be out of spec. Normally if one side is out of spec, the other is also out of spec. This can put your front sight way off.

Take a look and let us know. It's not often I have seen this but it has happened. Even with high dolor rails.

ETA: I forgot to ask, are you able to get on paper with the current set up? have you been to the range yet or does it just look like its out of spec?

[irocracer89]

Thanks SpankMonkey, It was hitting the paper on a standard M16 zero target, at 25y. The FSB is not off by that much, you have to jack with your head positing. Look through the back aperture the FSB appears off to left. Planning on using the Troy units as BUIS only, Eotech as primary. So this may not make a big hill of beans, I prefer them to be right on..

[SpankMonkey]

Well since your on paper your really done. The only real way to get a perfect line up, so the front site is centered would be to tweak the rail. It will take some time to get it just right but it can be done.

[irocracer89]

Thanks, I may still order the one from YHM sometime in the future. And see what happens..