7.5 inch 556 worth it?

[ARCHIVED THREAD] - 7.5 inch 556 worth it? (Page 1 of 2)

Posted: 2/17/2015 1:41:32 PM EDT

I am lookino into a new sbr upper.i currently just have a 8.5 inch 300 blk. I was wondering if a piston 7.5 inch 556 is worth the investment. I plan at some point to get a 10.5 inch that I can run my silencer on. Just right now I came across a 7.5 inch piston for $795.

Posted: 2/17/2015 2:05:20 PM EDT

[#1]

No. Especially for $795. YMMV but it I don't think that is a spectacular deal. Especially since you will still want the 10.5. LMT 10.5's can be found for around $500.

Posted: 2/17/2015 2:06:38 PM EDT

[#2]

I've been doing my homework on this subject too. Research indicates you will struggle to get the reliability we have come to expect in AR15's. Gotta go up to 10" for that. But a piston system may change that. What brand if 7.5" piston setup are you looking at?

Posted: 2/17/2015 2:26:58 PM EDT

[#3]

I discovered a new upper made by serbu called su-15. They have a special pre-order deal going on till the 20th.

Posted: 2/17/2015 2:34:24 PM EDT

[#4]

No. Not sure why you would want that short in 5.56. You would end up with unburnt powder everywhere. There is a reason most suppressors are not rated that short for 5.56.

Posted: 2/17/2015 3:01:27 PM EDT

[#5]

Since it's not your first or only upper, I'd say they're worth it for the fireball. However, DI uppers that short tend to be somewhat finicky and require tuning, including changing the buffer, spring and sometimes the gas port. I have only had one 7.5" that worked for me - an Adams Arms PDW upper that runs like a sewing machine. You're going to give up allot of velocity and enjoy some serious concussion, but I still like mine (but only with a KX5). For serious shooting, the shortest I'd go is 10.5" and even that's going to clip your velocity.

Posted: 2/17/2015 4:18:14 PM EDT

[#6]

Have a 7.5" 5.56. Running JP low-mass BCG, silent recoil spring and Syrac Ordnance adjustable Gen 2 gas block. Once you get the gas system dialed down its great. Is it a range toy? Yes. Still fun to shoot.

ETA: I guess it depends on what you use to determine "worth the investment" $800 for a 7.5" piston upper, as a range toy, to me is worth it.

Posted: 2/17/2015 5:09:36 PM EDT

[#7]

Stay 10.3" and up for 5.56.

Posted: 2/17/2015 5:37:37 PM EDT

[#8]

I love my 7.5" and shoot it often. With a kx5 it spits fire and frequently starts a conversation at the range. I would not suggest this as a first SBR for somebody but i already have a 10.5" and an 11.5" so I figured why not? It has been 100% reliable since taking out the H2 and putting in a carbine buffer.

Old pic with a PA red dot and MFT stock. Now has an Aimpoint T1 and a Magpul CTR. Fits in a backpack nicely.

Posted: 2/17/2015 8:55:57 PM EDT

[#9]

I'm also struggling with this one - 7.5" vs longer, i.e. 10.3", 10.5", or 11.5".

I paid $200 & waited 35 days to go below 16". So I want really short even if counterproductive.
I just received PSA 12" CHF upper. I'm considering cutting this down to 10.3" or 11.5".

Been doing research on Adams Arms 7.5" PDW upper, which runs about $650 at JoeBobOutfitters.
or just build a 7.5" pistol length gas system DI upper.

Posted: 2/17/2015 9:20:14 PM EDT

[#10]

I ended up with a 7.5 5.56 upper.

The only thing it's good for, is scaring people at the range(works really well with a Brakeout on the muzzle

)

I did some chrony work this weekend and I am concerned about the velocity loss out of my 10.3, I can't imagine how slow the 7.5 is.

Posted: 2/17/2015 9:33:07 PM EDT

[#11]

7.5 would be a range toy only, I would prefer to have something that could be used in other situations. I think 11.5 is the best length for an AR.

Posted: 2/17/2015 10:04:00 PM EDT

[#12]

7.5" = fun as hell to shoot!

To actually think of for serious use stick to a very well known set up with a great reputation or plan on spending the time and money to tune it for reliability. Traditional length buffer tubes, heavy buffer and a high quality upper are a good start. Unlimited options from there.

For ballistic performance use the hottest heaviest bullets you can get, that will still run reliably. Good bonded or jacketed bullets from the big makers. SD line from Hornady 75grTAP, M193, etc. Avoid light weight varmit style loads.

Although it can't compare to a rifle in performance, it still packs plenty of punch at short range. Greater velocity than most pistol rounds. It may be fun but it's no toy.

Posted: 2/17/2015 10:28:11 PM EDT

[#13]

Quote History

Quoted:
I'm also struggling with this one - 7.5" vs longer, i.e. 10.3", 10.5", or 11.5".

I paid $200 & waited 35 days to go below 16". So I want really short even if counterproductive.
I just received PSA 12" CHF upper. I'm considering cutting this down to 10.3" or 11.5".

Been doing research on Adams Arms 7.5" PDW upper, which runs about $650 at JoeBobOutfitters.
or just build a 7.5" pistol length gas system DI upper.

View Quote

Leave the 12" alone and get another one.

My PSA 12" is flat out accurate and reliable. The perfect upper IMO.

Posted: 2/18/2015 5:41:18 PM EDT

[#14]

I've done mag dumps with wolf with my 7.5" upper I built with a troy barrel. No issues. I use it mostly with my .22LR conversion.

Posted: 2/18/2015 5:59:24 PM EDT

[#15]

Quote History

Quoted:

Leave the 12" alone and get another one.

My PSA 12" is flat out accurate and reliable. The perfect upper IMO.

http://i.imgur.com/c9qDZUJ.png

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
I'm also struggling with this one - 7.5" vs longer, i.e. 10.3", 10.5", or 11.5".

I paid $200 & waited 35 days to go below 16". So I want really short even if counterproductive.
I just received PSA 12" CHF upper. I'm considering cutting this down to 10.3" or 11.5".

Been doing research on Adams Arms 7.5" PDW upper, which runs about $650 at JoeBobOutfitters.
or just build a 7.5" pistol length gas system DI upper.

Leave the 12" alone and get another one.

My PSA 12" is flat out accurate and reliable. The perfect upper IMO.

http://i.imgur.com/c9qDZUJ.png

What light mount is that?

Posted: 2/18/2015 6:02:24 PM EDT

[#16]

Mine has always run like a top.
Use the right ammo and it is just fine for defensive purposes.
A KX3/5 or linear comp will tame the blast to the shooter.

Posted: 2/18/2015 8:33:38 PM EDT

[#17]

Quote History

Quoted:

What light mount is that?

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Quote History

Quoted:

Quoted:
I'm also struggling with this one - 7.5" vs longer, i.e. 10.3", 10.5", or 11.5".

I paid $200 & waited 35 days to go below 16". So I want really short even if counterproductive.
I just received PSA 12" CHF upper. I'm considering cutting this down to 10.3" or 11.5".

Been doing research on Adams Arms 7.5" PDW upper, which runs about $650 at JoeBobOutfitters.
or just build a 7.5" pistol length gas system DI upper.

Leave the 12" alone and get another one.

My PSA 12" is flat out accurate and reliable. The perfect upper IMO.

http://i.imgur.com/c9qDZUJ.png

What light mount is that?

The IWC one for standard handguards. On my phone or I'd link it

Posted: 2/18/2015 8:45:47 PM EDT

[#18]

Quote History

Quoted:

I discovered a new upper made by serbu called su-15. They have a special pre-order deal going on till the 20th.

View Quote

The SU15 looks very promising. Not sure why Mark went with a 7.5" barrel for the introductory offer. Bad decision imo.

Posted: 2/18/2015 9:40:50 PM EDT

[#19]

I say no less than 10.5. I have a 7.5 I don't find it fun to shoot.

Posted: 2/18/2015 10:58:44 PM EDT

[#20]

Yes

100% reliable from day one. I will say it's a dirty SOB lots of unburned powder in the upper and if you shoot indoors doubling up is necessary.

Posted: 2/19/2015 12:13:39 AM EDT

[#21]

I built a cheap 7.5" out of mas defense parts. Slapped it on my SBR lower with the LWRC UCIW Ultra Compact stock kit.

So far it has run real well with m855, m193, random cheap 55gr, and handloads.

I haven't shot it on a bench for grouping, but its accurate enough to hit a 8" steel gong at 100 yards consistently.

Its a real fun plinker, and is loud as hell.

If you plan to use it for hunting or self defense, just remember with such a short barrel you will need to use bullets that will expand or fragment at much lower velocities than most 5.56 rounds.

Posted: 2/19/2015 10:18:56 AM EDT

[#22]

I personally do not run anything shorter than 10.3". To much loss in velocity, silencers arent rated for anything that short, you are barely achieving a full rotation of the bullet, it has excessive flash and concussion which sucks because you cant use a silencer on it. I cant speak for accuracy and range but i would assume it would be less than spectacular.

10.3" even when suppressed makes for a very short, light weight and easy to handle rifle, i would go for that first. Especially at the $800 price point you are looking at, you can get a Mk18 upper for that price.

Posted: 2/19/2015 10:30:12 AM EDT

[#23]

I have seen some that are reliable. I have seen some that were decently accurate. That being said, I vote no unless you want a toy or have a lot of free cash. From a ballistics standpoint they don't offer much, and if you wanted something short for home defense there are way better options that wouldn't deafen and blind you. If you just want a really short upper to play with go with a 22 conversion and go down to 4.5" with a can, or go with a 5" 9mm that could actually be a fun toy, and serve a role for home defense. YMMV

Posted: 2/19/2015 10:31:03 AM EDT

[#24]

Silencerco Saker and a few other suppressors are rated down to 7.5" on 5.56.

I'm currently waiting on the parts to show up to build a 8" 5.56 upper. If I like it I'll be getting a Saker K to put on it. I really liked the length of the 8.5" blackout I build, so I figured the 8" 5.56 would give me something similar size, but cheaper to shoot.

I ordered this ballistic Advantage barrel. Going to pair it with a 7" DD lite rail.

http://www.ar15.com/forums/t_7_25/1362721_Ballistic_Advantage_8_Barrel_5_56__Pistol___129_99.html

Posted: 2/19/2015 11:05:40 AM EDT

[#25]

8.1" fn chf barrel. Go that route. Get a kx3 or barking spider brake. I did not have to double up on hearing.

Posted: 2/19/2015 11:04:44 PM EDT

[#26]

I like my 8.1". Can makes it more than tolerable and tames the flash.

Posted: 2/20/2015 1:03:27 AM EDT

[#27]

/thread.

TDunn always waits until the last second... rolls in, posts some killer pics and it's Game Over.

Posted: 2/20/2015 5:29:19 AM EDT

[#28]

theres alot of bad out there on the 7.5, they deserve more credit than a "range toy", mine is the first one i;ve built and haven't had any problems, mine is purposed as a PDW and works great as such, i would recommend a 7.5, but i dont know about 800$ worth

" />

Posted: 2/21/2015 6:41:03 PM EDT

[#29]

Quote History

Quoted:

Leave the 12" alone and get another one.

My PSA 12" is flat out accurate and reliable. The perfect upper IMO.

http://i.imgur.com/c9qDZUJ.png

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
I'm also struggling with this one - 7.5" vs longer, i.e. 10.3", 10.5", or 11.5".

I paid $200 & waited 35 days to go below 16". So I want really short even if counterproductive.
I just received PSA 12" CHF upper. I'm considering cutting this down to 10.3" or 11.5".

Been doing research on Adams Arms 7.5" PDW upper, which runs about $650 at JoeBobOutfitters.
or just build a 7.5" pistol length gas system DI upper.

Leave the 12" alone and get another one.

My PSA 12" is flat out accurate and reliable. The perfect upper IMO.

http://i.imgur.com/c9qDZUJ.png

finslayer- that's very simular to my builds. This setup has everything one needs and nothing extra to weigh you down.
IMHO, 12-12.5" is the perfect " tastes great/less filling" barrel length for a 5.56 AR.

Posted: 2/21/2015 9:06:52 PM EDT

[#30]

I have a Ranier Arms Utra Match 7.5 barrel that I run with a Spike Tactical T-2 buffer and LMT F/A Bolt Carrier Group. Never had a problem with it, and I am using either xm193 or Speer Gold Dot 64 grain bullets. Runs awsome, light and compact

Posted: 2/22/2015 1:12:33 AM EDT

[#31]

Post out and 300m and let's see if it's effective. Quality components are essential in the short builds. I've been very pleased with this 7.5" build and would not hesitate to take and use in a bail out situation. The 75gn HP ammo on the market is showing some naughty effect, at extended ranges (if needed) on gel + clothing tests.

- SBR lower
- Mega MKM upper
- Noveske Diplomat 7.5" barrel
- PWS CQB

Posted: 2/22/2015 4:28:52 AM EDT

[#32]

Had not had a chance to shoot it but it is short and with a Carlson Comps MD it should produce a nice muzzle blast.

Posted: 2/22/2015 11:12:10 PM EDT

[#33]

I love my 7.5" upper.
Took a little tuning and a Syrac gas block but it runs flawless now.
It runs a Specwar brake and is obnoxious without the can... Its awesome.

Real loud ( When the can isn't on it ), Big fireball, Just lots o fun...

I also really like my 12" 308... Its the longest rifle I own...lol

Currently building a 5" 9mm and a 11" 5.56.

I finally have more cans than rifles so I need to even things out a bit...lol

Posted: 2/23/2015 1:54:19 PM EDT

[#34]

asdf

Posted: 2/23/2015 2:59:09 PM EDT

[#35]

No.

http://www.ballisticsbytheinch.com/223rifle.html

ETA: 7.5" ARs are kinda like desert eagles in that they seem cool and all that but once you get one and shoot it for a bit it gets old. Loud fireballs are awesome but not $795 awesome.

Posted: 2/23/2015 4:34:54 PM EDT

[#36]

Quote History

Quoted:
No.

http://www.ballisticsbytheinch.com/223rifle.html

ETA: 7.5" ARs are kinda like desert eagles in that they seem cool and all that but once you get one and shoot it for a bit it gets old. Loud fireballs are awesome but not $795 awesome.

View Quote

This exactly... you lose way too much velocity and they are not something you want to shoot all day. Sorry guys... they are range toys or designated home defense rifles (you will seriously never hear the same again tho so i honestly wouldn't recommend this). I struggle going below 11.5" in 556. If you want a really short rifle like that, go 300BLK bc it is better designed for that length.

Posted: 2/23/2015 8:31:09 PM EDT

[#37]

I have a 7.5 I got off the equipment exchange and it has been a lot of fun. I have a comp m3 on it. It's not a precision gun but can easily hit head size steal targets at a 100 yds. Real handy size to have in a truck.

Posted: 2/23/2015 10:37:18 PM EDT

[#38]

Quote History

Quoted:
I've been doing my homework on this subject too. Research indicates you will struggle to get the reliability we have come to expect in AR15's. Gotta go up to 10" for that. But a piston system may change that. What brand if 7.5" piston setup are you looking at?

View Quote

I guess someone forgot to tell my PWS MK107 not to be reliable, because it's been 100% with all kinds of ammo so far, even when I changed the buffer tube for a LWRC UC stock, And I have no problem hiting targets at 250 yards. And unless you are in the military in a war zone or a LEO , I'm sorry to tell you but your rifles are RANGE TOYS.

Posted: 2/25/2015 3:11:26 AM EDT

[#39]

I love my 7.5". It gets taken out shooting more than anything else.

Posted: 2/25/2015 6:04:43 AM EDT

[#40]

100% reliable with a adjustable gas block...

Posted: 2/26/2015 2:45:45 AM EDT

[#41]

My 7.5 upper is one of my favorite to shoot. Like has been mentioned you won't make any friends at the range but you will grin. As for defensive purposes I can't say that I'm too worried about it. With the,right ammo it still beats any handgun.

RC

Posted: 2/26/2015 12:19:10 PM EDT

[#42]

I have a 7.5 inch PDW setup - it's a lot of fun to shoot, but it's loud. If people don't notice it coming out of the case, they do when I start shooting.

With the new 5.56 TMK loads from Black hills expanding down at 1920 FPS you have an option for 50 yards on in if that makes the decision any easier. (Mk262 is just about 2050 on leaving the barrel)

Posted: 2/27/2015 6:11:53 PM EDT

[#43]

I always get a kick when people act like we are supposed to take my 7.5" with us to compete for the Gold in the Olympics' long-range rifle shooting... I don't carry one size wrench in my toolbox. I don't own just one pair of shoes. 7.5s are fine for short-range. If I wanted to shoot 300yds, I would use one of my other rifles for that...

Posted: 2/27/2015 8:46:55 PM EDT

[#44]

Quote History

Quoted:
This exactly... you lose way too much velocity and they are not something you want to shoot all day. Sorry guys... they are range toys or designated home defense rifles (you will seriously never hear the same again tho so i honestly wouldn't recommend this). I struggle going below 11.5" in 556. If you want a really short rifle like that, go 300BLK bc it is better designed for that length.

View Quote

Do you own and shoot a 7.5inch upper? Curious if your claim about not something you want to shoot all day and the noise levels are from real experience? I have one and can shoot it all day if I had the ammo to, no worse than shooting a 16inch carbine. And unless you are running a suppressor, firing an AR inside your house is going to hurt your freaking ears whether the barrel is 7.5inches or 16inches. I have a 7.5inch and with a good linear comp on it makes no more noticeable noise than my 16inch with an A2 flash hider on it either. Again, without a can, both are going to be loud as hell inside a regular room in your house.

Posted: 2/27/2015 9:14:46 PM EDT

[#45]

Quote History

Quoted:

Do you own and shoot a 7.5inch upper? Curious if your claim about not something you want to shoot all day and the noise levels are from real experience? I have one and can shoot it all day if I had the ammo to, no worse than shooting a 16inch carbine. And unless you are running a suppressor, firing an AR inside your house is going to hurt your freaking ears whether the barrel is 7.5inches or 16inches. I have a 7.5inch and with a good linear comp on it makes no more noticeable noise than my 16inch with an A2 flash hider on it either. Again, without a can, both are going to be loud as hell inside a regular room in your house.

View Quote View All Quotes

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Quote History

Quoted:

Quoted:
This exactly... you lose way too much velocity and they are not something you want to shoot all day. Sorry guys... they are range toys or designated home defense rifles (you will seriously never hear the same again tho so i honestly wouldn't recommend this). I struggle going below 11.5" in 556. If you want a really short rifle like that, go 300BLK bc it is better designed for that length.

Do you own and shoot a 7.5inch upper? Curious if your claim about not something you want to shoot all day and the noise levels are from real experience? I have one and can shoot it all day if I had the ammo to, no worse than shooting a 16inch carbine. And unless you are running a suppressor, firing an AR inside your house is going to hurt your freaking ears whether the barrel is 7.5inches or 16inches. I have a 7.5inch and with a good linear comp on it makes no more noticeable noise than my 16inch with an A2 flash hider on it either. Again, without a can, both are going to be loud as hell inside a regular room in your house.

Truth. I own many different SBRs of various sizes and full size guns. I don't find the SBRs uncomfortable. Others may find it different. Best advice is to try it for yourself.

I do like cans on all my guns when possible. With SBRs the OAL is still short.

Posted: 2/27/2015 9:39:09 PM EDT

[#46]

No problems with my 7.5" barrel runs like a top. It does have some flash but once my saker is out of jail that won't be an issue.
PS Yes I know a front sight is missing.

Posted: 2/28/2015 4:24:12 PM EDT

[#47]

Here's mine. Not my only one, but I really love it. Super fun, always an attention getter at the range. It can be harsher, huge fireball and definitely loud. But just plain fun...

Never had any issues. I use a H2 buffer and Wolff spring. It goes bang every time, cycles without issue. Have to replace the handgaurd at some point to use with my suppressor, so have not shot it suppressed yet.

If its going to be your one and only, maybe go for one of the 10"-12" options just for more all-around utility. I would not give mine up, though. Super fun!

Posted: 3/2/2015 2:08:09 AM EDT

[#48]

i keep hearing people complain about this giant fireball that the 7.5's have, and how horendus it is, and i have seen some pictures that look fairly unpleasant, i have the silencerco trifecta flash hider on mine, we went and did some night shooting and i was expecting this giant fireball, it was a little worse than my friends 16'' with a birdcage flash hider, i was shooting m193 he was shooting m855

just curious, for all the complaining i was pretty let down by my own results

Posted: 3/2/2015 2:10:30 AM EDT

[#49]

I love mine. It's got an Aero Precision 7.5" barrel and gas block and has run everything I've fed it, from M855 down to surplus steel. I have a Saker in jail right now that should tame it a bit.

Posted: 3/2/2015 3:23:54 AM EDT

[#50]

I can see the appeal of a super compact AR as fun gun. I had a 7.5" upper several years ago, but was never able to get it to run. On the other hand, when I built my 11.5" upper, it ran out of the box. Small sample size, but if you look around, you'll see my experience is common.

You will be giving up a good bit of velocity. It should still be a few hundred FPS faster than 5.7x28, but still not fast enough to fragment standard military ball.

If you want something cool to shoot and don't mind tuning a gun to be reliable, go for it. Your 8" 300blk or a 10.5"+ 5.56 will be ballistically superior.

[ARCHIVED THREAD] - 7.5 inch 556 worth it? (Page 1 of 2)

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