Want more rail-estate

[Jeffy]

I have a 14.5" LMT upper and I've been thinking about putting a longer rail on it for a while. It has a FSB so something like a Daniel Defense Lite 12 FSP or RIS II M4A1 FSP, maybe. Here's the the problem, it has a pinned flash hider. I can think of several ways I could get around this problem but I don't want to screw it up in the process. The first and probably the proper way would be drilling out the pin, then getting a new FH and setting it. I don't quite like the FH on there (YHM 5C1) but it came on the upper. Might be a bit of challenge to line the new FH up with the drill mark in the barrel. I would assume that I'd need to set the drill press up then back it off enough to fit the FH on then drill slowly so the bit doesn't walk off.

Another option might be to grind down the FSB and then just go with an RIS II and get a flip-up front sight. Looks like the RIS is wide enough to leave the bayonet lug and swivel tabs intact so all I'd need to do is cut off the top?

A third option would be to get an Omega 12 then mill out the inside to accept a FSB, essentially turning it into a FSP. The problem I see with this is that it might lose some strength from the cutting and not being hard anodized in those area. I noticed DD gets around the strength issue by leaving the holes in the rail uncut around the FSB.

The last option would probably be the easiest, sell the upper and buy a DD Omega X FSP upper but then it's 16 and not 14.5...

Thanks for the help.

[spamsammich]

If you have access to a mill or something, try hitting the weld with an endmill to give you a flat surface to start drilling on. Make sure you use a short drill bit to start out. Oh yeah, use something like a #31 drill bit, most people use 1/8" pins and I find that going just a little under size gets just enough material out of there to be able to re-use the hole if I want.

A RIS II would necessitate removing the pinned FH and you might as well go with one that doesn't require shaving like the M4A FSP.

IMO, your best bet is to go with removing the pinned FH and slapping on whatever system you want, if you're really married to the 14.5" barrel. I chose to go with Lite rails on my 14.5" pinned LMT because I can change rail lengths pretty easily if I choose and I can even throw an Omega X on if I wanted to (supposedly) if I just cut the lockup ring off.



I'd probably just buy the DDM4 upper.

[MIKE G]

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[spamsammich]

The answer to that is "hell no".

[MIKE G]

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[spamsammich]

yeah, I don't even mess with barrel extensions and I'm an incurable tinkerer. That stuff takes talent and tooling that I don't possess.

[Belmont31R]

The easiest thing to do is to just cut the FH off. Yeah you ruin the thing but its impeding you getting the configuration you want.

[Jeffy]

I dont know the answer to this as I dont mess with building uppers, I have them built for me.

Can you take the Barrel extension off more easily than the FH and would that allow you to put the barrel nut on for the rail?

DOC

From my understanding that's not possible since the pin goes through the extension and locks it to the barrel. Then there's the problem of having to index everything back up so the headspace as well as the gas port are back to what they were before.

The easiest thing to do is to just cut the FH off. Yeah you ruin the thing but its impeding you getting the configuration you want.

I'm not too worried about the YHM FH as it wasn't my first choice. I'm not sure how it was pinned though. I'm hoping the weld is only on the upper portion so I can drill out the hole then unscrew it and not have to futz around splitting the FH. The aligning part is what seems a bit harder since I can't just drill the FH and barrel together. The FH hole has to match the barrel.

If I went with the M4A1 RIS II (non FSP), how much of the FSB would have to be removed? I know the top has to come off but what about the bottom?