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RomeoTango
1 October 2014, 09:25
Hey, All.

I'm putting together a 10.5 shorty build. I've read in a few places online where some people have problems with the cycling and having failures with such a short barrel and long gas system. (Carbine length) while I'm still an amateur, and relatively new to wevo, I was wondering if you guys could help me out by giving me your input on the matter.
Busy schedule at work, so I don't get to get on here as much as I'd like, but will be checking this post later.

Thanks, fellas!!

Calengor
1 October 2014, 10:19
I have a 10.5 MK18 clone. Having said that, the reason I've seen quoted most often on the intertubes is 11.5 has significantly improved reliability. See Paul from BCM's answer below:


Q: Why BCM chose the 11.5" SBR over the 10.5"

I get this question a lot. It is a good one. When we spec our program we can build anything we would like, so we sat down and looked at the pros and cons.

First Statement: I know a good 10.5" SBR can run very well. I personally own a semi MK18 type and it runs great. No problems.

A: Dwell time.
Dwell time is the time that your gas operated weapon maintains pressure to continue the cycling of the weapon. It primarily exsists from the time the bullet passes the gas port in the barrel to the time the bullet exits the muzzle. When you pull the trigger and fire the weapon the movement of the bolt carrier group unlocks the bolt, extracts, and ejects the spent casing. Then it cocks the weapon, feeds, chambers the next round, and then locks again. One of the thing that can make SBRs finicky is the dwell time (or lack of).

The 11.5" carbine is approximately 4% longer weapon than its' 10.5" counterpart, but this extra inch gives the barrel a 40% increase in length for dwell time. IMHO, this is an excellent trade off. This additional dwell time (all other things being equal) will allow the carbine to be more forgiving to different ammo types, extremes in air temperature, weak or worn extractor springs, worn extractors, buffer weights, etc.

Last Statement: For those folks who have a 10.5" that works very well, I would reply; me too. (see first statement)

If I had to "go to war" with a AR15 Carbine, I would grab the BCM 11.5".
The BCM 11.5" Runs Like a Dream.

Hope this info helps,
Paul

rob_s
1 October 2014, 10:25
If meant as a host for a full-time suppressed gun, or possibly even part-time (where the "part" is >75% suppressed) with a switchable gas I'd opt for the 10.5" barrel.

Anything else and I'd look to the 11.5-12.5" barrels for most uses.

Jerry R
1 October 2014, 10:26
RT, wish I could be more help, but the two 10.5" uppers that I have are both piston and mid-gas. Having said that, they function flawlessly. I have not had any issues with the 6.8 or 5.56 running factory and reloads in these uppers.

RomeoTango
1 October 2014, 12:03
Thanks guys!! The actual oal of this barrel I have is 11". I'll try it out and see what happens. I was thinking of putting a slr adjustable gas block on it instead of running the a2 that I have, but I just think the a2s are sexy that far out on that barrel. Lol.

Pyzik
1 October 2014, 12:32
Well, this is all crappy news for me.
I'm (sort of) in the process of a pistol build as well. HOWEVER, here in MI the pistol cannot have an OAL greater than 26" (does not include removable parts; ie. muzzle device, sig brace).

So I am stuck with either a 7" or a 10.5". And I don't want a 7".

rob_s
1 October 2014, 12:58
I wouldn't sweat it. There's a difference between what's ideal and what's functional.

toolboxluis00200
1 October 2014, 16:00
i have a 10.5 and it run awesome never had a issue

Soisauss
1 October 2014, 19:53
i have a 10.5 and it run awesome never had a issue

Except when you rapid fire......then you get fail to eject because the barrel got a tad bit warm where you can get your eggs over easy..... :P :P

GOST
1 October 2014, 20:20
Over easy is how I order them.

voodoo_man
1 October 2014, 20:35
10.5 is a weird size.

11.5 is good to go - bcm / NOVESKE

10.3 is also good to go - DDmk18

Anything shorter needs to be piston - PWS

Anything longer can be whatever since itll run fine.

Totally depends on what you need.

Kopis
2 October 2014, 07:07
Well, this is all crappy news for me.
I'm (sort of) in the process of a pistol build as well. HOWEVER, here in MI the pistol cannot have an OAL greater than 26" (does not include removable parts; ie. muzzle device, sig brace).

So I am stuck with either a 7" or a 10.5". And I don't want a 7".

Why dont you want a 7.5" ? I have one that runs flawlessly. Whatever you decide on, i do recommend the extended buffer tube with the sig brace.

http://i568.photobucket.com/albums/ss126/Papachristou/2014-08/1EAE1587-5F78-4C38-95F0-B15240FE3E13_zpsal7hzrqx.jpg (http://s568.photobucket.com/user/Papachristou/media/2014-08/1EAE1587-5F78-4C38-95F0-B15240FE3E13_zpsal7hzrqx.jpg.html)

toolboxluis00200
10 October 2014, 11:22
Except when you rapid fire......then you get fail to eject because the barrel got a tad bit warm where you can get your eggs over easy..... :P :P

I mite trow some bacon on it lol

UWone77
10 October 2014, 11:28
Why dont you want a 7.5" ? I have one that runs flawlessly. Whatever you decide on, i do recommend the extended buffer tube with the sig brace.

http://i568.photobucket.com/albums/ss126/Papachristou/2014-08/1EAE1587-5F78-4C38-95F0-B15240FE3E13_zpsal7hzrqx.jpg (http://s568.photobucket.com/user/Papachristou/media/2014-08/1EAE1587-5F78-4C38-95F0-B15240FE3E13_zpsal7hzrqx.jpg.html)

I don't do Sig Braces...

Or white dots to cover serial numbers. [:D]

toolboxluis00200
10 October 2014, 11:29
Over easy is how I order them.

don't forget the toast and butter

Nathan_Mack
14 October 2014, 10:21
Why dont you want a 7.5" ? I have one that runs flawlessly. Whatever you decide on, i do recommend the extended buffer tube with the sig brace.

http://i568.photobucket.com/albums/ss126/Papachristou/2014-08/1EAE1587-5F78-4C38-95F0-B15240FE3E13_zpsal7hzrqx.jpg (http://s568.photobucket.com/user/Papachristou/media/2014-08/1EAE1587-5F78-4C38-95F0-B15240FE3E13_zpsal7hzrqx.jpg.html)

WELL done! I have a Sig SB15 sitting around waiting for me to attach a pistol to it. SPR first.

RNMEDIC
12 November 2014, 14:06
I'm not sure why a 10.5 would be unreliable. No issues out of my 7.5".
https://farm6.staticflickr.com/5610/15433867317_cba67fcc4d_b.jpg

GunDogRandomness
27 December 2014, 19:41
Just finished my 10.5 projecthttp://tapatalk.imageshack.com/v2/14/12/27/7c94c2f3b559322494be1e24851f4cca.jpg

UWone77
30 December 2014, 05:15
Just finished my 10.5 projecthttp://tapatalk.imageshack.com/v2/14/12/27/7c94c2f3b559322494be1e24851f4cca.jpg

How is that Hexmag working for you?

GunDogRandomness
30 December 2014, 06:43
How is that Hexmag working for you?

So far so good. Haven't had them but a couple weeks. Functionality is good, durability is yet to be determined. They seem to be very well made, but so far I don't see anything that would make me replace all of my PMAGS.

DutyUse
30 December 2014, 07:21
I'm building a 10.5 w/ adj gas. Should be fine..

Just in case I'm building a 11.5 aswell lol

WHSmithIV
30 December 2014, 08:17
Well, this is all crappy news for me.
I'm (sort of) in the process of a pistol build as well. HOWEVER, here in MI the pistol cannot have an OAL greater than 26" (does not include removable parts; ie. muzzle device, sig brace).

So I am stuck with either a 7" or a 10.5". And I don't want a 7".

You could look for a 10.5" barrel with a carbine length gas port rather than a pistol length gas port or use an adjustable gas block which lets you bleed off excess gas before it heads down the gas tube.

JHoward
30 December 2014, 08:35
What about running a shorter buffer tube? Like the LWRC?

SwissyJim
30 December 2014, 10:52
Just shot my new 10" upper for the first time yesterday...ran flawless!

https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xpf1/t31.0-8/10863989_781337588603720_7332936202147420252_o.jpg
Aero 10" carbine length gas, altho holy Gas Face batman! Even with the Gas Vent forward assist, I was choking on gas. Need to tune the adj gas block, and maybe try the RTV charging handle trick? I have a dedicated BCG and handle for each upper so worth a shot I guess?

Otherwise, was happy it ran good. I'd say 10 is gtg...