FSP vs. Rail mount front sight?

[RWK]

Ok, I'm tracking with you now. I'm used to the reference FSB (front sight base) for what you're referring to as the FSP.

Were I to purchase a new upper, I'd opt for a BCM 16" lightweight mid-length and attach a DD Lite 12 rail. I'd mount a DD rail-mounted, fixed front sight, leaving enough room to mount a light at 12:00, in front of the front sight.

[ra2bach]

Ok, I'm tracking with you now. I'm used to the reference FSB (front sight base) for what you're referring to as the FSP.

Were I to purchase a new upper, I'd opt for a BCM 16" lightweight mid-length and attach a DD Lite 12 rail. I'd mount a DD rail-mounted, fixed front sight, leaving enough room to mount a light at 12:00, in front of the front sight.

ah, gotcha... I've always heard of the FSP as the Front Sight Post. anyway...

I do track your choice of uppers, though, as I've been swaying a little to that music myself...

[rob_s]

Just as a little clarification, "FSP" usually means the little "post" at the top that screws up and down to adjust for elevation while "FSB" usually means the large, cast, "A-frame" assembly. FWIW

ra2bach you've pretty much hit on exactly the issue. Depending on hardware chosen you can get a longer handguard, with rails to mount accessories to, and a clamp-on front BUIS over a low-profile gas block well within the same weight for a standard FSB and either plastic handguards or rail behind it. What it essentially comes down to is that in most cases 2" of rail weighs about the same as the weight savings of FSB vs. BUIS/gas-block. To try to illustrate...

FSB: 4.5 oz - GB: 1.4 - BUIS: 1.5 = 1.6 oz saved
TRX 11.0: 9.93 oz - TRX 9.0: 8.46 oz = 1.47 oz gained

Net difference is less than 0.20 oz. It should be noted that more weight can be saved by chopping, shaving, and halving the stock FSB to be held on with only one pin, and that some FSBs may weigh even more than the 4.5 oz quoted, so these are rough numbers and there may be some deviation in different applications.

Personally, if I had decided to go with a rail system anyway, and the TRX Extreme in particular, I see no reason to go with the 9.0 behind an FSB and would instead opt for the 11.0 over the chopped FSB.

[bkb0000]

FSBs are forged, by the way..

[JimT]

^^^^^

Good FSBs are forged. I had a DPMS upper in my youth that had a cast unit.

[ra2bach]

ah, now I see. sorry for the confusion guys... nomenclature is not my strong suit and I was taking FSP from the DD literature for a rail that allowed the FSB to protrude through the top of the rail.

at any rate, I think I see my direction now. I still have a preference for pinned FSB's but I do understand the attraction/benefits of a gasblock/longer rail/ rail mount sight, especially on a carbine length gas system where the FSB is exactly where I want to put my hand.

I'm even seeing the benefit on a longer gas system like a midlength where the FSB pushes the weight further toward the muzzle. a 16" govt. profile middie with FSB and 9" rail is no lightweight. I've been using Emod stocks to balance the forward weight bias but I'd like to bring the whole thing back down in weight. at the end of a long training day I feel like the guy at the bottom of the ladder who has been loading bales of roofing shingles on the elevator...

and this is what prompted my question - I'm thinking I'm going to chop one of my middies to 14.5, shave the FSB, and go with a longer rail. now the big question - TRX or VTAC Extreme???

[bkb0000]

^^^^^

Good FSBs are forged. I had a DPMS upper in my youth that had a cast unit.

i haven't seen a cast FSB in many o' long year... DPMS would be the one to hold on to that failed endeavor the longest, though. colt stopped casting 'em in the 60s, as i recall.