I am wondering if functioning issues will substantially increase with a 7.5" AR15. In the past I heard rumors of anything under 10" being a real hassle, but without substantiation.
It’s been beat to death. In my opinion, it’s harder to find the right combination of buffer, spring and gas port to make them run, but after you’ve found it you should be good to go. Inspection of parts for wear should be escalated for a micro AR, but I would not call them finicky. Mine has eaten everything 50 gr to 62 gr I have fed it, but I do not feed it really low pressure stuff like wolf. American Eagle, Prvi, Black Hills, WWB all work fine for me. Accuracy with irons will be less due to the shorter sight plane, but me and my eotech can stay on a torso at 100 yards easily.
So far, mine function reliably all the time. not even a single malfunction was experienced since it was built. estimated round count is around 2k. I even ran it suppressed.
i would do extensive reliability testing before putting one in a duty/defense roll, and i would only trust one built by a known-righteous company like NRW. or myself… but only because i’ve got the time and money to fiddle with it if it doesn’t run on the first/second/third/fourth/etc tries.
thats a pretty sweet lookin little blaster…
I wouldn’t touch anything under 10.3’'.
Reliability, ballistics, parts, etc.
I don’t like the micro AR platform.
I have a Noveske 7.5" Diplomat (as in your pic) but in 6.8. I’ve only fired 40 rounds (6.8’s about $1.00 a round), but it worked flawlessly with a spike ST2 buffer.
From what I’ve read, don’t go under 10" in 5.56 for SD use (that’s why I went 6.8 for my 7.5" but I also have a Noveske 10.5" in 5.56).
For a fun gun, do anything you want.
I’m also a big believer in quality. Noveske makes quality kit and stands behind there product. You’ll pay more, but you know you have something that works.
If your LEO, they’ll also give you a 10% discount.
I have a 7.5" Noveske Diplomat chambered in 6.8 SPC as well. I am running a heavy ass 7 oz. Spikes ST-SST (they no longer make them) solid stainless buffer. I have about 4,500 rounds through mine with ZERO malfs. No FTE’s or FTF’s or stove pipes, or ride overs, etc. The 90gr TNT BTHP rounds that I am using clock at an average of 2,600 fps. more than enough (reliable fragmentation) to get the job done.
I trust mine,
MadDog 
I built my 7.5" from scratch and its true, its a pain to get it working properly. A lot of Fail-to-Feeds, some Fail-to-Fire’s and the bolt wasn’t held back after the last round. My remedy was a new gas key & H2 buffer.
As of now, it works like a champ! No problems at all.
If you buy directly from Noveske, you shouldn’t have any problems 
I had a 7.5" for a short time, ran it hard, wanted it to choke, and couldn’t get it to.
Evidently the real short AR Gods smiled at me.
I’ve been running a 7.5 AR for 4+ years. My rifle has seen well over 30K rounds and runs flawless with everything I have tossed at it with the exception of wolf. I have also been known to run it suppressed but the barrel is pretty shot out now so I keep the can off of it.
My secret, it is a model 1 7.5" upper. Yea they get the worst reviews but my research at the time showed people had 100% reliability with their 7.5" setup.
I had a DPMS KittyKat upper. I had to open the gas port. After that, it ran great.
I used an M16 B/C, BCM extractor up grade and a 9mm buffer.
I’m building another using a Rainier Ultra Match 7.5". Can’t wait to get it together.
I also run a Levang comp.
Man, I wasn’t going to tell that part of it… Mine was a 7.5 inch M1S upper, too…
Model 1 has a history of making very reliable uppers. FDLE had 10.5 uppers by some big name and they switched to M1 because of reliability. Hell it took me forever to get my LMT 10.5" upper to run right and LMT was useless for support.
i’m afraid this is entirely incorrect… there is no manufacturer that i know of that has as firmly established record on this board for reliable un-reliability as M1S.
not even vulcan has made as many appearances on this board.
https://www.m4carbine.net/showthread.php?p=576825
https://www.m4carbine.net/showthread.php?t=31567
http://m4carbine.net/showthread.php?...ht=model+sales
https://www.m4carbine.net/showthread.php?t=25122
https://www.m4carbine.net/showthread.php?t=16978
https://www.m4carbine.net/showthread.php?t=25649
https://www.m4carbine.net/showthread.php?p=440128
https://www.m4carbine.net/showthread.php?t=4664
If I had time, I would look for posts trashing LMT and Colt. When it came to 7.5" uppers, they had the best reports and mine, as well as others on this post, have proven to be reliable.
You should read these posts, for every second hand negative report about M1S there is a first hand positive report.
Why are we turning this into a M1S bash fest??? The OP wanted to know about the reliability of 7.5" AR’s. I had a M1S upper that I used extensively for about 6 years. It ran 100% from day one with so many rounds it was time to change out the barrel. That included 1,000’s of Wolf rounds. I finally replaced it with a 6.8 SPC Noveske Diplomat upper. I venture to say you hear about problems with any platform but when they run well most people don’t bother to post about how great it is.
MadDog :rolleyes:
one post isn’t a “bash fest.” we don’t let incorrect information go unchallenged on this board- since its a very well established fact that M1S guns are prone to QC issues, a statement to the contrary to this fact must be refuted. otherwise, this board ceases to be a place of reliable information.
i will have nothing further to say about M1S in this thread- if you want to debate me, PM me or start a new thread.
I prefer to use a piston operating system on anything 10.5" or shorter. I’ve had excellent reliability with the LWRCi 8" guns. My 6.8mm PSD has been through several carbine courses and has a total of about 3500 rounds on it without issue. I recently bought one of the 5.56mm PSDs, but it only has a couple hundred rounds on it.
Stephen
To me this is the one place a piston system excels.
Chris