I think it’s time to build a Kenosha upper

[Trigger Time]

Nothing wrong with 10.5 or 11.5" 5.56 DI, AR15's.
Here are my recommendations based on real world use. Real world means more than at a shooting range.
- use the heavy grain ammo. 77gr is best
- use a 1/7 twist barrel
- use a H1 minimum, but better, H2 buffer.
Never use crap parts to build a firearm. Why would you? Why?
Save money on food, not guns.

 

[Tyler-The-Piker]

My 10.5" 1:7 twist barrel does just fine with M193, really likes M855 though, but absolutely shines with 75 and 77gr!

 

[Trigger Time]

My 10.5" 1:7 twist barrel does just fine with M193, really likes M855 though, but absolutely shines with 75 and 77gr!

Yep good thing about them, it will shoot anything. But for max felons, use 77gr

 

[Hohn]

Hey brother here to help. I spent the afternoon fitting this 10.5" up. Not done by any measure and waiting on the 1911 grip adaptor and grip panels.
And yeah my bench is a mess.
Here to help...

10.5 with a brake. OUCH OUCH OUCH.

 

[Hohn]

This is what I put together for short range social work should I ever find myself in that situation. Its a DD 10.5 upper with an older Eotech. It rings steel well at 200 yards, so I have no doubt that it will work for situations under 10 yards.

Sent from my SM-G986U using Tapatalk

Make that 11.5 and replace the guards with the Magpul or BCM units and it's pretty much what I had in mind. Especially if it can be done in a pencil barrel.

 

[Hohn]

Looping back on "straight buffer tube" using the sling for outward tension. BTDT years ago. First pistol build in the days long before braces, LMT 10.5". My first two pistol lowers still have the receiver end plates with left side hole extending for an HK hook single point sling, which is still useful to quickly ID them. After shooting the twin to my upper (ordered at the same time) on an LE friend's SBR lower with a proper stock I went ahead and did a Form 1; the cost and the trouble were worth closing the speed and accuracy gap. The no-stock sling approach is better than throwing rocks, but very much not better than the alternatives, and there are more options today. Just my experience and conclusion, but as always encourage first hand experiment. Pretty inexpensive (other than the ammo these days) to pull the stock or brace off and just run the receiver extension alone. Might be a little more work to install a sling mounting point. I'd probably use one of the end plates with a QD socket if I was to do it again today.

Also repeating the advantages of 11.5" over 10.5" all else equal. It brings everything back away from the edge of not quite working with extraction.

Agreed on all points, and since I have spare lowers sitting around doing nothing else, I can see this upper landing on an registered lower sooner rather than later.

 

[churchmouse]

10.5 with a brake. OUCH OUCH OUCH.

All my AR's are equipped like this. And yes these are serious loud makers.

 

[MCgrease08]

Make that 11.5 and replace the guards with the Magpul or BCM units and it's pretty much what I had in mind. Especially if it can be done in a pencil barrel.

My 11.5" BCM fluted enhanced lightweight upper.

 

[Hohn]

10" barrels are so long ..... suitable for a .308, however !

In 5.56, drop down to an 8" barrel, and you'll only lose another 235 fps.
Graph courtesy of Ballistics by the Inch.

.223 Rifle Results in fps

Click here for a Muzzle Energy graph for the tests in this caliber.

barrel length	Remington UMC 45 gr. JHP	Remington UMC 50 gr. JHP	Remington UMC 55 gr. MC
18"	3354	3179	2983
16"	3257	3076	2943
14"	3099	2901	2878
12"	2943	2964	2724
10"	2776	2682	2616
8"	2536	2478	2380
6"	2189	2153	2041
5"	1939	1921	1861
4"	1709	1674	1564
3"	1277	1276	1147

I don't care about FPS in the abstract, it's just a number. But it's undeniable that small caliber 5.56 was developed to use the fragmentation wounding mechanism and are remarkably effective with cheap 55 fmj. And that requires some minimum MV to work.

Going shorter and slower doesn't that you can't find an effective load. It just means that instead of EVERY load being effective, now you have to ensure you've loaded up some 75 Gold Dots or 77 SMKs or 75 Hornady TAP or a handful of other loads. The system is pickier in delivering terminal capability.

It's also pickier in mechanical function once you get down towards 10.5/10.3. Might need to fiddle with buffers or an AGB or such to make it run at bet-your-life reliability. Yes, the 10.x is proven many times. But lots of times tradition gets things repeated more than merit.

11.5 feels like a better sweet spot and it's only got a little to do with MV as a number.


Even though a Grendel is categorically superior in shorter barrels, with every Grendel load being devastating at short range (even Wolf steel case--it's like mega 7n6) I think I'll stay with 5.56 for now. There are enough loads that work well enough in the short guns that it's not a question of "best" terminals-- it's a question of "good enough" and absolutely there are short barrel loads that are more than good enough. They are devastating in their own right (hello new Gold Dots).

Given the stated purpose of such on upper, I think one could argue that a basic plastic hand guard job with FSB and irons is more than enough. 11.5 carbine. Add the rear sight of choice (DD for me).

That said, I'm not above an AGB and aluminum guard from Centurion or such.

Will likely go with Dead Air flash suppressor.

 

[indysims]

This is similar to my plan for a utility 14.5" upper that can host my Dead Air can. 14.5" BA Hanson, Forward Control Design A2 Birdcage with Dead Air Keymo compatibility. 12" or 13" handguns.

 

[two70]

I don't care about FPS in the abstract, it's just a number. But it's undeniable that small caliber 5.56 was developed to use the fragmentation wounding mechanism and are remarkably effective with cheap 55 fmj. And that requires some minimum MV to work.

Going shorter and slower doesn't that you can't find an effective load. It just means that instead of EVERY load being effective, now you have to ensure you've loaded up some 75 Gold Dots or 77 SMKs or 75 Hornady TAP or a handful of other loads. The system is pickier in delivering terminal capability.
.

Since this carbine is intended for relatively short range one could simply forget the silly(for this purpose) heavy bullets and use quality normal weight bullets which would give one plenty of options to choose from.

 

[DadSmith]

Since this carbine is intended for relatively short range one could simply forget the silly(for this purpose) heavy bullets and use quality normal weight bullets which would give one plenty of options to choose from.

Oh goody 40gr Vmax all the way.

 

[Hohn]

Since this carbine is intended for relatively short range one could simply forget the silly(for this purpose) heavy bullets and use quality normal weight bullets which would give one plenty of options to choose from.

Bullets like that generally won’t penetrate 12”+ at short barrel speeds. It’s not that light bullets don’t work, it’s that the seem to suffer more from short barrels than heavier bullets when you test them in gel and such.

I’d rather have even an “inferior “ varmint load though over any 9mm or 45, so it’s a relativel scale for sure.

 

[two70]

Oh goody 40gr Vmax all the way.

Do you really think 40 gr. is a normal bullet weight for .223/5.56 or that Vmax are quality bullets? Or do you just assume that there is nothing between the two extremes?

Bullets like that generally won’t penetrate 12”+ at short barrel speeds. It’s not that light bullets don’t work, it’s that the seem to suffer more from short barrels than heavier bullets when you test them in gel and such.

I’d rather have even an “inferior “ varmint load though over any 9mm or 45, so it’s a relativel scale for sure.

I said "quality" normal weight bullets, meaning controlled expansion bullets that are designed to expand and penetrate. Failure to penetrate is often more of a bullet construction problem than a bullet weight problem. Though in many situations over penetration would be far more of a problem than under penetration.

 

[Hohn]

Well, a bump for this thread since I have finalized (mostly) my BOM for this upper. Recall that I'm building off a basic forged Aero upper. (I have a VLTOR MUR I'm keeping for a future build where it's extra strength is more valuable).

As a concession to availability and the ATF's bracing reinvention of rules, I'm going 16" on the barrel. It is what was used in Kenosha, so yes a Kenosha upper can be 16". But I think shorter would be better. HOWEVER. Because of the barrel profile in question (criterion core) and a slightly rearward weight bias of the rifle relative to other 16", it should handle and move like a LW 14.5 or a gov't profile of something shorter. If my estimates of MOI are correct, it will feel and handle like something lighter than the 1.7# barrel weight suggests. Criterion will ship it with a matched BCM bolt. The barrel will have a Wylde chamber and 8tw so it can handle anything up to single fed 80gr loads without issue and should run heavy OTM like a champ.

Since reliability is paramount, we're going with good stuff where it's critical. Geissele REBC is probably the best bolt carrier on market today from a material quality and tolerance holding perspective. It's pricey, but it's what we're doing. Yes, it's unobtainable right now, but I believe it's worth waiting for. A toolcraft or BCM will work in the short term and then assume backup duty to the REBCG. I'm sure even a cheap Aero nitrided works fine, but I feel strongly the that BCG (especially bolt and cam pin) are the places to spend every penny you can as they are the core of AR reliability.

Gas block will be a VLTOR 17-4 non-adjustable. If the clamp on-fits, it will be chosen over the set screw version. I've seen test data that VLTOR's clamp on is stronger in torque capacity than the barrel extension locating pin. I have no concern for its robustness relative to a pinned FSB. Plus, a LPGB underneath the protection of a handguard is less prone to getting whacked in any way than a FSB which gives more leverage to knock the block out of alignment. Adjustable gas blocks are cool for dialing in a sporty upper. But this is not that kind of upper. This is a carry-all-day-in-a-war-zone-if-you-must kind of upper. AGBs need not apply. Nobody has time to fiddle or deal with carbon locking or function issues because it was narrowly tuned for a sporty load.

I'm not blindly brand loyal, but I've come to trust VLTOR and Geissele a great deal, so they will get first look for most parts.

Handguards have not been finalized yet, but the #1 contender is a Centurion CMR 15". It has better availability than the Geissele Mk4 which was also a top contender, and is a bit lighter while still having similar features like anti-rotation/positive location features and a heavy duty barrel nut. And since Monty is a Hoosier and located here, I will support a fellow Hoosier whenever I can. And while I don't know him, several acquaintances of mine speak highly of him.

The muzzle device will be a Dead Air Flash hider that supports KEYMO. Gotta plan for the future, and KEYMO is emerging as an industry standard with many others making KEYMO compatible muzzle accessories and cans.

Fixed iron sights will be used up front with a folding rear. Scalarworks gets the nod here. Not cheap. But again, this is a "one upper for the rest of my life to save my life" kind of build.

Irons will be the primary sights until an optic can be added. Micro t2 is the easy (but expensive) choice, but I think the MRO is where I will end up. This is not final because I'm keeping my options open for the time being. Newer sights are constantly coming out, and if the Sigs prove to be as rugged as the Aimpoints, I might consider Sig. It will ride a QD mount whatever it is because I will assume it will fail at some point and I'll be using irons for primary anyway.

Thats it. I'll sort out the weapon light situation later, but I think between the Nitecore P30 I already have and some of the better Cloud/Surefire/etc options, this is a problem that is easily (but not cheaply) solved.

 

[Hohn]

Orders placed for toolcraft BCG, Centurion CMR 15”, criterion core 16”.
Finished upper will come in right at 3# slick, 3.5 with irons and red dot.

 

[BR8818]

Sounds like a solid build. Don't know your preferred optic height, but if you like a higher optic I'd recommend the Unity fast mount. The unity has built in irons, but a short sight radius. Though you can remove the front sight post and then your optic mount will be your rear iron sight and run a scalarworks front. It would save a little weight, money, and give you room to run a magnifier if you ever desired.

 

[Hohn]

Almost done:

https://imgur.com/gallery/8vRQ2cE

 

[Hohn]

So we’re done, as of months ago. Centurion Mlok over a pinned lpgb DD LW 16” . Splurged on Scalarworks irons and a dead air Keymo hider. Runs perfectly with both carbine H1 lower and A5h2 lower.