Radical Firearms 7.5″ 5.56 AR15 Upper First Impressions Review


That’s what I thought as soon as I fired the first 5.56 round out of a 7.5″ barreled AR15.

Ever since posting about my 6.75″ barreled .300 Blackout AR15 pistol project people have asked me about running 7.5″ barreled 5.56 uppers. For the most part, I suggested that they avoid 5.56 in barrels shorter than 10.2″ due to velocity concerns.

In short, the 5.56 round needs to have some pretty high velocities to properly expand, and typical ammunition doesn’t cut it in shorter barrels.

We talked with a few ammunition manufacturers are SHOT Show 2015 and discovered that there are a few rounds made specifically for shorter barrels. Cor-bon, Nosler, and Barnes all make ammunition that should do fine in a 7.5″ 5.56 barrel.

The She-Shepherd’s birthday was coming up, and I thought this would provide a good excuse to put a new upper on our NFA-registered AR15 lower.

As a test, I purchased the Radical Firearms Quad Rail Pistol Upper Assembly (part #RFUPPERv1.0.75) from Primary Arms. I had purchased a different one directly from Radical Firearms, but it would not have arrived in time for The She-Shepherd’s bday. The RFUPPERv1.0.75 model was $279.99 before shipping, and did not include a BCG or charging handle.



We’ve taken the upper out twice for function testing and first impressions. I want to do more testing with different types of ammunition, but here are my thoughts:

  • Shooting 5.56 out of this short of a barrel is super loud. Like really fucking loud. Way more loud than my 7.5″ barreled AK47 or my 6.75″ .300 BLK AR15 pistol. I was wearing double hearing protection and was shooting outdoors, and it was still very noticeable.
  • The muzzle blast (concussion) was also severe.
  • According to bystanders, the muzzle flash was bright and noticeable even in full sunlight. I would like to put a Simple Threaded Devices muzzle attachment on to see how it goes, but I’m not sure if we’ll be keeping these uppers.
  • We had some problems with failure to extract. I don’t think it’s the upper, but without trying different ammunition and gas block tuning I don’t want to say for sure.
  • Recoil was manageable to me, but unpleasant to two other test shooters.
  • Accuracy at 40 yards on a 12″x20″ target was extremely acceptable. Given my expected range of 150 yards or less, I am sure that the barrel used in the Radical Firearms upper is more than up to the task.
  • The short barrel handles extremely well, and an AR15 of this size is very well balanced. The She-Shepherd liked how it felt, especially compared to the 11.5″ upper normally on the SBR AR15.

Overall opinions

If you live in a state that allows suppressors, it might be worth looking into a 7.5″ for indoor use. As-is, if you don’t have a suppressor or live in a place where you can’t have them (like here), I think a 7.5″ 5.56 is way out of bounds. This is coming from a guy that has already made peace with the fact that any SBR is going to be pants-on-head crazy loud inside.

On the other hand, 5.56 is plentiful and inexpensive. .300 Blackout is still a reloader’s caliber. Yes, there are some commercially available options, but they are all expensive compared to other intermediate rifle calibers. It’s not uncommon to fire 300 – 400 rounds in a basic rifle training class. If you’re already into 5.56, trying out a 7.5″ upper is not a risky proposition.

I’m not sure what future these Radical Firearms uppers have in our home. They seem well built for the money, but I am not sure if they gain us anything over our existing 11.5″ upper or my .300 Blackout pistol. It seems like the lighter weight and better balance for The She-Shepherd is offset by the extreme sound, muzzle blast and flash.

This is not to say that a 7.5″ barreled 5.56 upper is right or wrong for you, but just may not be right for us.


About the Author:

Short Barrel Shepherd Short Barrel Shepherd is a regular guy and works to make Web sites and mobile apps easier for people to use. He spends his free time attending fight-focused firearm, knife, and combatives training, motorcycling, writing, and playing games. His daily carry is a Glock 19 pistol and an AR15 .300 Blackout pistol in a backpack.

8 Comments on "Radical Firearms 7.5″ 5.56 AR15 Upper First Impressions Review"

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  1. David says:

    Couple of comments:

    When suppressing something this short, you want to check to make sure you’re not voiding your suppressor’s warranty. Some places only go down to 10.5″.

    I also prefer 8.25″ over 7.5″. Not a ton of difference in terms of blast or dwell time, but clearing the handguard makes it easier to deal with the muzzle (for suppressing or whatever). Karri’s Guns made mine, and I’m happy with it. I use it on an NEA CCS equipped gun, and it’s HK53 short.

  2. Jim says:

    Have you considered other flash suppressors? My 7.5″ has the Noveske KX5 Flaming Pig which seems to do a good job directing the blast forward for the one time I’ve run it. I’ll be doing more outdoor testing this coming week and will try it with different types of hearing protection and report my findings.

  3. CR Williams says:

    I have a Noveske on a 7.5″ barrel and there is no flash and normal-to-AR noise levels from it. It does add overall length but the tradeoff is beneficial to me.

  4. redhawk34 says:

    I really like the 300 BLK in any barrels shorter than 11.5″. That being said, I’ll suggest the following changes to a 5.56 setup with a 7.5″ barrel for a better overall experience:

    1. Use a complete piston-driven upper with BCG as assembled from the factory. The complete Adams Arms 7.5″ uppers can be had for $500-$600 now. DI in systems shorter than 10.3″-11.5″ with their higher pressures can tend to beat up the rifle components and be finnicky depending on load, gas port size, buffer/spring combo, etc.

    2. Use a Ferfrans CRD device or similar. Everyone around you will thank you. A silencer will help as well, but SilencerCo’s Saker series is one of the few that is warrantied down to 7.5″. And it still may not be hearing safe.

    3. Use the Black Hills 50gr Barnes TSX in 5.56. According to Jeff at Black Hills, this round was developed specifically for very short 5.56 barrels and will reliably expand out past 75 yards from a 7.5″ barrel (at around a 2300 fps threshold). These are not cheap, but you can use surplus M193 as a suitable practice round.

  5. Dale says:

    I have an Adams Arms 7.5 Evo Piston Upper, and I highly recommend it.
    It’s pricey, but it’s eaten every bit of garbage I’ve fed it. I regularly run Silver Bear 75gr hollow points through it and it hasn’t missed a beat. No doubt the piston makes all of the difference. As far as a suppressor goes, I’d skip it. This thing has a concussion that is unreal. I put a Noveske Pig on it and that has done wonders. All it does is direct the blast and flame out and away, but it’s much improved. I tried a suppressor on it, dialed back the gas settings, and it’s still faaaar from hearing safe. I wouldn’t even classify it as tolerable, and that was in the outside in the open. You’d be bleeding from the ears if fired repeatedly inside with no ear pro. Even if you miss a threat, the concussion is a weapon in itself. It’s a minute of paper plate at 100 yards, which is far beyond what I’d likely be shooting this. .300blk shines in these PDWs, but getting into a whole other caliber is not something I wish to do. Especially for just one firearm.

  6. DiabloActual says:

    If your looking for a suppressor other than the Saker, which may or may not survive a mag dump, you should check out the Dead Air Sandman S. It has no minimum barrel length, user replaceable front baffle, user replaceable wear parts, and a lifetime warranty. Plus, it’s designed by Mike Pappas, who KNOWS his poop,when it comes to suppressors.

    Oh, and full MSRP for it is about $1K… Not bad

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