I am narrowing down rail choices and can’t seem to find much feed back on this combo. I am looking specifically for opinions on the rail used with the carbine extension.
I really wish Troy would do something like this with their extreme rail system as I’m trying to keep the FSB.
I’ve got the rifle length system on my S&W, and like it better than the Troy TRX. I haven’t found anything about the JP setup that I don’t like.
Installation is more tricky than the Troy tube, but JP’s setup is rocksolid.
I cannot speak specifically about the carbine extender on the JP handguard but I run a rifle length handguard on my 16" carbine. This is a rock solid set up. It is a little heavier than the Troy or Vtac but it feels better in the hand. Pretty much the same concept but without the front factory sight.
The JP forends are wonderful. I can’t imagine that the carbine extension wouldn’t be as well.
I installed one of these on a friend’s carbine last year. I’m not a fan of the method of attachment at the barrel nut, and for a slick-sided tube with no rails I think it’s excessively heavy. I installed exactly the setup you’re looking at. The JP design is dated, and is one of the earlier FF tube designs out there, and I think there are better options available today. However, I don’t know of any other slick-side FF tubes that offer the FSP cutout like the JP does, so if you’re set on that configuration I don’t see any other choice.
If you can make do with a little less tube, Apex Machining makes this one.
It is a great modular hand guard system. It is certainly more adaptable than any other on the market. While it is 3 or 4 onces heavier than the Apex tube, I certainly wouldn’t call it excessive. Calling it dated is overly subjective. It’s a hand guard…
Maintenance is the only other consideration for ANY carbine length rail system used in conjunction with a standard FSB. Something as simple as changing a gas tube now requires removal of the FSB. Installation can be tricky too. You will have install the FSB prior to installing the tube to verify sight alignment, remove it, install the tube and then re-install it.
Any handguard that requires thread locking an adapter onto the upper is a dated design in my opinion. Also the top rail is not in spec as I remember.
Serviceable and allows the fixed front sight and a longer handguard with a bit more weight than some newer designs.
Of course it’s subjective, it’s an opinion. 
What I did not, and do not, like about the mounting system is the use of locktite in the way that it is required in this sytem. Instructions are here.
While the weight increase is “only” whatever it is, that weight is without any rails installed at all, and climbs very quickly with the addition of rail sections. The Apex is not the only one I’m comparing it to, I only offered that as a possible partial solution with the front sight pocket.
As I said, if one wants that exact setup there really aren’t any other options, other than the FSP models from Daniel Defense, but those are full-rail options and are significantly more expensive.
M4
Omega X
Lite
The OP may also find this link helpful.
From VTAC’s website it looks like the JP VTAC w/ extension is about $265? and rail sections are extra at the following prices?
PRICE: $28.00 2" SECTION
PRICE: $28.00 2" TACTICAL RAIL
PRICE: $45.00 4" SECTION
PRICE: $70.00 CARBINE LENGTH
PRICE: $80.00 RIFLE LENGTH
PRICE: $75.00 MID LENGTH
Meaning another $70 for a top rail to go from the upper to the FSB, and then another $28 for a 2" section if you wanted to mount a light out front at 12 o’clock?
Suddenly those Daniel Defense rails don’t look so bad.
An 11.0 Troy VTAC is $175 on VTAC’s site, and I can’t help but wonder what a machinist would charge you to cut out the top section where you need it for the FSB and drill two holes (if needed) for the FSB pins in the rail.
Let me be clear, I don’t think there’s anything inherently wrong with the JP version, other than the mounting system I don’t have a lot of confidence in personally after installing one myself, but I think there are other options with better mounting systems, lighter weight, and perhaps even lower cost, currently available.
As far as cost, the JP rails can be found at a much greater discount than DD rails.
The DD rails are looking more attractive now though I really didn’t want or need all the picatinny. I noticed their 9.5 FSB rails are actually almost 10".
I’m wandering on the weight difference between a 9.5 DD FSB rail w/rail covers vs the JP rail.
I had briefly imagined modifying a Troy rail but didn’t pursue the idea. They really should make a similar rail system to the JP carbine+extension or at least a FSB cut out option like the DD.
I wonder what a machinist would charge and if it would work.
Might be better to just go with a mid 16" and 9" rail if that is enough handguard for you over modifying a handguard. The JP is fine if installed correctly but Rob_S is correct that the price goes up fast if you need a few rail sections for it.
Realistically look at how much you could sell your barrel/upper for and then buy the configuration you want vs modify you upper as well.
The rifle is a new LE6920 so I could probably get some $ for the upper but I don’t want to split up the gun. If I got a new upper it would be a mid length with a pinned LP gas block and a 11" or 13" rail. I really didn’t want to modify this rifle too much.
I very surprised that there are so few options for this application with these types of rails.
Were you the same guy that posted another thread about not wanting to make too many changes because the guys at the gunshop said you’d ruin the resale value?
In any case, you could remove the FSB, install a set-screw low-profile gas block, and dimple the underside of the barrel to accept the pins. I still prefer to pin my gas blocks, but if it’s under a rail, the barrel is dimpled, and you use Locktite or similar you should be fine.
Yes, and a bunch of people at the club (not really the M4Carbine.net types). Its not something I am really worried about but was enough to make me considered other options. Plus it would be easier and cheaper to do with no GB install and new front sight to buy.
Your suggestion is looking more and more appealing as it was my original plan (LP GB and a Troy Extreme rail). Also, the fact that you feel the dimple/set screw is an acceptable option makes me feel better about doing it…plus there doesn’t seem to be many other options.
Locktite or Rocksett?
Now I’m sure a month after I do that, Troy or DD will release a the solution I was looking for.
Along the lines of what Rob_S suggested about the low profile gas block is to just cut the front sight off. The base will be pinned and you can do it at very little cost and a little time. I run a Troy rifle length rail on my LW 16" carbine with a rifle length handguard and cut front site. Works great and is very light.
This to me is the best way, but if the OP has concerns about keeping the value, the low-profile and dimpling will preserve his factory parts to re-install later.
You can’t simply buy another FSB later on and replace the stock one. The pin holes are drilled through the FSB and barrel at the same time.
I have a franken-mutt upper with the JP carbine tube and FSP extension. Put together by Randall at ar15barrels, it’s probably my most reliable AR based on more rounds fired than I can remember.
If all you need is to mount a sling and weapon light then it should be fine. If you need to add a bunch of accessories then you’d probably be better off going with a different rail system.
FWIW, I bought a BCM middie upper with the Troy VTAC rail and ended up selling it because the tube felt too small. Just a mental thing but I always felt like I was grabbing the barrel. I like the feel of the JP tube better.
I do know of folks who’ve had problems with it but in all but one case it was due to improper installation.
A 6920 upper should be fine for almost anything you need to do- even if all you added were Magpul MOE handguards it would still be a capable platform.
that pic sure looks like their 12" handguard with a custom FSB cutout and not the carbine tube with extension…
I run a rifle length tube on a 16" upper w/ the front site cut down. As for the length it is great. I think this is one of the better systems on the market. Not as light as one would want but works well. Even though you want to keep the front site you should like the length.