BCM 18 in. build [Archive] - M4Carbine.net Forums

diving dave

11-12-11, 11:34

Put together this "SPRish" build..quick rundown...
BCM VLTOR upper with a 18in. 1/8 twist,rifle length gas system
VLTOR VC1 flash hider
C3 defense lower
Magpul UBR and MOE grip
Larue SPR mount and a Luep. 2.5 -8 Mid-range scope, TMR reticle
Troy irons and a VLTOR/Tango down bipod
I have shot 69 grn match kings and it has shot well out to 400 yds. The only thing ,why did BCM use a 1/8 twist?Why not the 1/7?I am wanting to run some 77 grn fodder thrugh it at some point to see what it will do. Does anybody have a 1/8 barrel, how does the heavier bullets perform?Now for the gun porn..:D
http://farm7.static.flickr.com/6057/6337102019_5e5a96b20b_z.jpg

a0cake

11-12-11, 18:27

http://m4carbine.net/showthread.php?t=91538

ALCOAR

11-12-11, 18:35

Trigger?

Very nice:)

SteadyUp

11-12-11, 19:53

I have the same upper, and I can assure you that the 1/8 twist is more than adequate for the 77gr bullets. Nothing to worry about.

lethal dose

11-12-11, 23:31

righteous build. what fcg did you use?

Belmont31R

11-13-11, 11:54

I have had two uppers with 1/8 barrels and they shoot 77GR just fine.

The fun part is testing a bunch of different loads to see what shoots best, and then make sure you stock up on that load (hopefully all from the same lot).

If you haven't already keep a log book if nothing else to track rounds fired, dope, and what ammo you are shooting. Then get a free program like On Target which you can scan targets, then check to see what type of groups you got. I have a file folder system on my computer of scanned targets that way I don't have a pile of used targets sitting around. Allows quick and easy references. You can create a folder of that date, scan the images, calculate them in On Target, and even throw in a quick word document in the folder with notes and such.

DTHN2LGS

11-13-11, 14:54

My first AR15 was a DCM model with a 1:8 twist for High Power matches and I shot 80 grain Sierra Match Kings out to 600 yards with no problems.

.

diving dave

11-17-11, 11:21

Cool, thanks for the info guys..Running a standard trigger right now, but will upgrade at some point.

101ABN327

11-20-11, 08:59

Dave, Nice rig! My winter project is an 18" SPR. I ordered one go the rifle gas 18" polygon barrels from Black Hole. I've read a lot of good data on its performance. It's a 1 in 8 as well. I have a buddy in town that is a master reloader. We are going to work up the perfect load for this barrel, using a 77 gr. HPBT.

I found a couple of loads I'm going to try out on another forum in the 75 gr.

1) 75 gr. BTHP with 22.0 gr of H335
2) 75 gr BTHP with 22.3 gr of H335

I'm going to load a box of each and see how they print.

101