Rail-mounted flip up front sights on a mid-length rifle

AR/M4 AR Technical Discussion
1

I’m looking to buy a parts kit to go with my Spikes stripped lower that I bought 3 years ago and let it sit on the shelf. I want to go with a mid-length system since I hear they’re better than M4geries.

However, I want a flip up front sight as well. Assuming I have a low-profile gas block, will I need to run rifle-length free-float rails or will mid-length rails work?

Second question. Are free-float rails overrated? I want a 2-piece rail system for easier installation but none of them seem to be free-floating.

2

Longer rails = longer sight radius. If you have a gas block with a rail, your options are limited to mounting the sight on the gas block. If you are getting a low profile gas block that will fit under a rail, you can get the front sight further forward which is a good thing. Go with a rifle length 12"-13" rail system.

3

So I take it longer sight radius is a good thing then. Cool. I do want a low-profile gas block that will fit under the rail.

Second question. Are free-float rails overrated? I want a 2-piece rail system for easier installation but none of them seem to be free-floating.

4

Daniel Defense Omegas are free floating and are two piece. They may be out of your budget though ($300+).

FF is nice, but I don’t think you’ll see the benefit of one as much on a 16in barreled gun. Maybe for precision guns, but not so much for carbines.

5

longer sight radius gives you finer adjustments per click when you zero. You have a greater capability of accuracy too. Think subcompact pistol vs full size, full size is much easier to shoot more accurately because of the longer slide aka sight radius. Also longer rails mean you can reach more on the weapon. If you want an easy install go with the Daniel Defense Omega rails, you can install them without gunsmith skill.

you have to get free float rails if you want to cover a low pro gas block.

middy with low pro gas block and 12" free float rail:


6

My carbine had a 7 inch free loat rail when I got it. I wanted a longer handguard because I prefer a support hand grip further out than the carbine length hand guard allowed. I modified my existing gas block so that the new MidWest SS-12 would fit over it and I really like the set up.
I’d never given much thought to the extra sighting radius, but I seem to pick up the front sight when shooting with irons much quicker. The front sight seems to be sharper too. I’m 48 and my eyes ain’t what they used to be. BTW, I’m using folding front sights because we’re required to have iron sights on our rifles (department policy for personal rifles).

7

Are free-float handguards overrated? I don’t think they’re overrated. I also don’t think they are absolutely necessary for every application, including my own use. But I do believe a free-floated handguard can contribute to a rifle’s accuracy.

For what it’s worth - and it probably isn’t worth much, becuase I don’t shoot a ton, and therefore I suck - I have two nearly identical mid-gas carbines with the same brand, same heavy profile, and same twist rate chrome-lined barrels. One has a free float handguard, the other has standard handguards. I had an opportunity to spend an afternoon at the range with just the two carbines; shooting the same distances, with the same ammo, and in the same conditions. I have found that I can get the free float handguard carbine to group a little tighter than the standard handguard carbine using iron sights, at 100 yards, and off a sand bag rest.

The difference wasn’t night and day, but it was apparent. I think my better groups with the FF handguard had around 4" spread, where the standard handguard gun grouped between 5"-6". I shot slow ( a few seconds between shots) 10-shot groups, and alternated carbines after each group. For the last couple groups with the standard handguard gun, I did try varying where I rested the handguard on the sand bag, but I was not able to determine where the sweet spot was. And if it makes a difference, the standard-type handguards were Cav Arms C6 ‘M4’ fat handguards with a Midwest Industries #03 rail mounted on the lower handguard half (no accessories were attached to the rail at the time of the comparison). The standard handguards are OD green, too. I went with OD green instead of black because I read that colored handguards (FDE, OD, etc) will give you an extra 0.5 MOA of accuracy at 100 yards. Yes, I am kidding about that.

The carbine with the standard handguards is still very capable of shooting ‘minute of man’ at 100 yards, so I the difference in accuracy, be it actual or just perceived by me, makes little difference to me at this juncture. But if I had to grab one gun before running out the door, I’d grab the one with the free-floated hand guard - because the lower receiver is painted tan, and painted receivers are good for at least an extra 1.0 MOA of accuracy at 100 yards. Yes, i’m kidding about that, too.

As with everything, your mileage may vary.

8

If you have a torque wrench in either 3/8" or 1/2" drive, get this barrel nut wrench from Brownells:

http://www.brownells.com/.aspx/pid=27412/Product/AR_15_M16_AR_10_reg__BARREL_NUT_WRENCH

I’d also recommend the YHM LW Specter length rails. I have one just purchased and it was $122.xx shipped with 4 OD green rail ladders and 2 black rail ladders from here:

http://www.jsesurplus.com/specterlength4railfloatlw.aspx

http://www.jsesurplus.com/lowprofileladderrailcover-black-1.aspx
These are $3 ea…

You can make your own low-profile gas block by dremeling the FSB off and cutting the sling swivel and bayo-lug off as well. A little paint is all that is required to make it look better and provide some protection against the elements. Good luck on your build. Sounds very nice.

9

I would go one piece if your going FF. why not just take the extra time to install it or have it installed? its well worth it. Larue, DD, KAC, Troy, VTAC and PRI are all great options. I run a Larue 11.0 on my middy w/ shaved down A2 FSB. The 11.0 rail comes just past the gas block. Get a 12in or longer if you want it a little farther inside the rail.

I’m not a fan of YHM rails on serious rifles. Theyre cheap for a reason.

As for BUIS… Id go with TROY or KAC for flip ups. If the gun is for adverse social purposes, I wouldn’t go with the MBUS. Thats preference, though, others might feel differently. I personally am not really a fan of plastic sights.