which upper 7.5" or a 10.5" ??? - Page 1

[ARCHIVED THREAD] - which upper 7.5" or a 10.5" ???

Posted: 4/20/2014 9:05:33 PM EDT

I am having trouble trying to decide which upper I want to build for my SBR. I like the small compact size of a 7.5" but think the extra length in the 10.5 might be better? What are some of your guys experience with these uppers. Most of my shooting would be 0 out to an occasional 300 yards if that matters. Also what flash hider do you use to tame the flash

of a 7.5" upper? thanks for any help in advance, hopefully some of your responses can get me off the fence. I know some would say get both but under a budget right now.

Would a 1/7 twist barrel be better or a 1/9. I would be shooting 55gr most of the time except maybe a few 62gr every now and then. thanks again guys

Posted: 4/21/2014 6:36:04 AM EDT

[#1]

Go with 10.5. With a 5.56 less than 10", the bullets don't stabilize well (very bad news with a suppressor, high chance for a baffle strike, and also bad for accuracy) and you lose quite a bit of velocity (5.56 is such a light bullet, even at the heavier grains, that you lose a lot of stopping power). Also, it's like a flashbang going off in front of your face every time you shoot because you have a ton of gas coming out of the barrel right in front of you and all the powder isn't burned yet.
1:7 will be better to stabilize the bullet with a short barrel and handle heavier grain bullets (but will be fine for 55 gr as well).
Hope that helps.

Posted: 4/21/2014 6:49:37 AM EDT

[#2]

10.5" (or 10.3") and longer for 5.56 (with carbine length gas).

For 10" and shorter, go for 300 Blackout (with pistol length gas).

Posted: 4/21/2014 7:05:01 AM EDT

[#3]

Another vote for the 10.5

With the 7" and the 1:7 twist, you're only going to get on full turn of the bullet in the barrel. Couple that with the lower velocity and you've got projectile stability issues. If you're wanting to "occasionally" shoot out to 300m... I don't think you'll get that with a 7".

Also, if you ever want to get a suppressor, most of the suppressor manufacturers I'm familiar with won't warranty cans mounted on barrels less than 10"-10.5".

Posted: 4/21/2014 10:59:40 AM EDT

[#4]

10.x" is my vote as well. Having an ultra compact PDW is kind of cool but I think you'll get more use out of a little more length. Longer is less persnickety is my understanding to get running well.

And not all cans as someone mentioned are warrantied for super short systems in 556 and they wear out of faster is my understanding even if they are.

Again as someone said, if you really want a short system then consider 300BO, the cartridge is designed for short barrels, the 5.56 isn't. I'm in the process of building a 10.5" right now actually in BO.

Not that you can't get a 7.5" in 5.56 to run obviously, lots of people have done it and if you really want the shorty then go for it. There are just some advantages to a few more inches for me personally.

Posted: 4/21/2014 6:21:29 PM EDT

[#5]

saker 556 can is warrantied with 7in barrel full auto.

I have an 11.5 inch and a diablo piston upper (7.75in).

I like them both. I have yet to get approval for my saker, so I only shoot the 11.5in suppressed as of now.

I do like the diablo upper. I think it will probably be my primary SBR once i suppress it. It is a blast to shoot (pun intended)

Posted: 4/22/2014 5:11:06 AM EDT

[#6]

I’ve done 1.25”, 5 shot groups @ 100 yards on three separate occasions with 7.25” POF so I wouldn’t say it’s bad for accuracy.
That was with 1:8 twist and Hordany TAP 55g ammo.
A noveske pig works great for throwing the blast down range. Sometimes I take it off when I shoot indoors to work on my suntan.
You do lose power with such a short barrel but my redfield battezone has gradations that work perfectly at 200 and 300 yards. At 300 yards I use the 5th tick mark so it’s kind of a lob to get them in.
It may not have enough kick to kill a man at 300 but that’s not why I shoot. I mostly shoot at 25 yards but once I shot some groups at 100 I bought the redfield to see what I could do at 200 and 300.
I did have a round strike the end cap of my AAC Ranger2 once but that was because it loosened up on me. AAC fixed it for a nominal fee.

Posted: 4/22/2014 7:33:21 AM EDT

[#7]

http://sadefensejournal.com/wp/?p=1093

Furthermore, a 7.5" barrel will never be above the fragmentation velocity (~2600 fps) for a normal 55 gr 5.56 round. So instead of the round tumbling causing cavitation, it will simply put a .223" hole in the target. Still not pleasant to be hit with for sure, but not near as deadly as a faster shooting 16 or 20 inch barrel with much higher velocity.
I believe a 10.5" barrel will keep that 2600 fps for something like 50 yards or so.

Posted: 4/22/2014 6:49:37 PM EDT

[#8]

10.5" just for the extra velocity.

Posted: 4/23/2014 2:27:29 PM EDT

[#9]

10.5 +

Posted: 4/23/2014 6:26:09 PM EDT

[#10]

Go with the 10.5 (or 10.3) if you want a serious gun any less is just a range toy.

Posted: 4/23/2014 10:25:59 PM EDT

[#11]

get the 10.5.

Posted: 4/23/2014 11:16:41 PM EDT

[#12]

Quote History

Quoted:
10.5 +

View Quote

Posted: 4/24/2014 12:39:24 AM EDT

[#13]

10.5" - I built a 7.5" and had nothing but problems out of it. Replaced with a 10.5" and now it runs like a top. I also more managable, not as loud, and more accurate.

Posted: 4/24/2014 2:26:23 AM EDT

[#14]

This is relevant to my interests

Posted: 4/24/2014 3:30:29 AM EDT

[#15]

sounds like everybody is sold on a 10.5 inch upper. what kind of flash hider do you guys recommend, cause its going to be awhile before I get a 223 can to hang on the end. thanks for all the input fellows. I will be ordering all the parts for my next build here shortly.

Posted: 4/24/2014 3:41:39 AM EDT

[#16]

Quote History

Quoted:

sounds like everybody is sold on a 10.5 inch upper. what kind of flash hider do you guys recommend, cause its going to be awhile before I get a 223 can to hang on the end. thanks for all the input fellows. I will be ordering all the parts for my next build here shortly.

View Quote

Blackout and trifecta work well. If you are planning on getting a can I would look at a brake mount. If you will just be using the SBR stick the hider since the brake will be very loud.

Posted: 4/24/2014 3:48:20 AM EDT

[#17]

Having played with several SBR lengths, I too settled on a 10.5"...cans are the best, but while you are saving/waiting for one, I would suggest either the Noveske KX3 or the Ballistic Advantage Kuuma. I also like Smith Enterprises vortex, but the first two will do more to manage the flash than the third.

Lots of options here though. I think the Kuuma is the best value. There are 4 variants, depending on if you want a big fat one or a smaller skinny one, or somewhere in-between. I've had good luck with them. I'm sure lots of folks here have other options to share.

Posted: 4/25/2014 4:46:50 AM EDT

[#18]

Get BOTH! Yeah, I know you said you were on a budget, so the question is which to get FIRST!

I would (and did) get the 11.5" first. I then got a 6" Olympic Arms and regretted it. It shot well... sometimes, but was too much of a toy. I ended up selling the 6" upper and getting a 7.5" that is still built as a pistol waiting on a form 1. Still have the 11.5" upper built as a pistol as well.

Posted: 4/25/2014 7:52:24 PM EDT

[#19]

Meh, I want my 10.5 SBR to look like a plain jane AR, so I'm using a standard A2 birdcage

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[ARCHIVED THREAD] - which upper 7.5" or a 10.5" ???

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