Practical AR SBR

General Firearms NFA
1

I always thought the Mp5 would be a great HD weapon, but the price always out of my reach. Found a little info about how the experts are switching to the mk12 config. I am more of an Ak-74 fan than an AR enthusiast as far as going to the range. My S&W M&P15 AR usually sits in the safe, love the ergonomics, lightweight, but with its 1:9 barrel its fair at everything while good at nothing and I can’t help but think what a fantastic package it would be if the barrel were shorter. To me a 16" ar is one that should be loaded down with a heavy optic, a free floated rail and shoot 70+g ammo for long distance target shooting or serve “recce” duty should the world end:rolleyes: My S&W could never serve that purpose with its stupid barrel.

I don’t own any SBR’s but the cleo here said he signs. Being a collector more than anything I want one, but I like my purchases to have potential practical purpose.

I guess I am looking for direction for an SBR AR. I handled a BCM 14.5 LW middy with an H2 buffer, brake and the 3 oz red dot. Really liked it, it was very fast in both movement and quick follow up due to the low recoil/muzzel rise. Seems they quit making this, but it would be easy enough to build a similar upper with a 14.5 dd pencil barrel.
But is a $200 stamp really worth -1.5"? I am not into pinning brakes on barrels.

I have never handled anything shorter than 14.5+brake. Is there a big advatage with CQ defense with an 11.5" barrel? Or do the improved ballistics of a 12.5" make the sweet spot?

I am not looking to suppress, for me if a SBR AR inside as HD has such a percussion that a supressor is required then I would stick with my 9mm.

I guess what I am getting at is why the move from the Mp5 to the mk12? And for HD and CQC (which I hope I will never see) what is a good practical barrel length, or are these un-suppressed more of a novelty rather than a practical tool ?

Also studying the ballistics of the SBR AR’s one can’t help but consider the 6.8SPC, however reliability is huge importance for me, I know very little about these. To be honest most of the AR ammo I would by would be the surplus, I could afford a few mags of BH 50g 5.56.

Last I may just stick to what I know and grap a draco or AMD-65, I know the 7.62x39 has good ballistics out of the shorter barrels. But I just think a proper lightweight built AR SBR would be handier, more ergonomic, easier to control, probably more practical?

2

I run a 10.5 (Suppressed) SBR for HD. It is a very good choice (maybe the best choice). With that said, getting one for HD and not wanting to put a suppressor on it is a bad idea IMHO. They are VERY loud and inside of a room would be off the chart in regards to pressure on your ear drums.

With the more modern defensive loads (SPEER 24448, Barnes TSX, etc), the length of the barrel is no longer important. So I would stick with something between 12.5-10.5.

C4

My HD gun.

3

I wanted to go as short as possible on my SBRs (no suppression) without sacrificing reliability. According to Paul at BCM, the break-point on the barrel-length vs dwell-time curve is at 11.5 inches – there is a 40% increase in dwell time going from 10.5 to 11.5. I don’t know what the barrel-length vs muzzle velocity curve looks like, but I was less concerned about muzzle velocity since they’re going to be 50-yards-or-less rifles. If you’re more concerned about bullet performance, you might want to investigate the muzzle velocity issue on various barrel lengths. For my expectations, I considered 11.5 inches to be the sweet spot. Suppression would change that whole equation, I suppose. Suppressors aren’t legal in this state, so for me that whole question is moot. Noise in the house in a home defense situation? IMHO, the low round count in such a situation as well as auditory exclusion makes me think that’s less of an issue and I probably wouldn’t be inclined to think a suppressor is that big a deal on a HD weapon. In my inexperienced opinion. Again, I can’t have a suppressor anyway, and I would consider using a rifle for home defense in my situation to be extraordinarily unlikely. My home defense plans have little or nothing to do with any of my rifles. For me. In my situation. YMMV.

I built both of my SBRs with BCM 11.5 inch barrels. Both use BCM BCGs and H2 buffers and reliability even with PMC Bronze ammo has been perfect.

4

That is a dead sexy weapon. Have you been able to test the db level produced in a room/closed range for it in suppressed vs unsuppressed? I’d be interested to know what kind of sound level it produces in a HD setting.

5

I prefer my 10.5" MK18 upper but before I deployed I built a 12.5" Noveske barreled upper that I was playing with. They both handle well and do everything I need them to do close in.

Is the $200 tax worth 3-5.5"? That is completely up to you. Personally, the only black rifles that I have now that are 16 or longer are for hunting at longer ranges. My hog gun is a 9" 7.62x39 or a 11" 6.8 SPC.

I wouldn’t want to shoot my MK18 inside without ear pro. I was speaking with some door kickers that I support out here about shooting inside and they love running the MK18 without suppressors, they said it was like a small flash bang going off every time they pulled the trigger inside (they wear ear pro) buildings. They said that the effect on the bad guys was noticable.

As was already stated, for HD ranges (unless you live on a large ranch type area) you will get all the performance you need out of a 10.5" barrel with quality ammo.

I did just buy one of those Draco mini pistols that I plan to SBR, it will be my first AK. I can’t wait to get home and try it out.

6

No, but I do shoot it a lot in BlackWater’s shoot houses and even with the can on it, the thumping is pretty good (always wear hearing protection).

C4

7

I was in the back of a vehicle once when someone let out a burst with a shorty AK. To say that my teeth rattled was an understatement. I couldn’t imagine doing it indoors.

8

I asked a SWAT guy/Sheriff’s Office Instructor about this because he ran a 10.3 M16 when he was on the TOU. He said it was only really a problem in the older parts of town where the homes had plaster walls and stuff.

I run my 11.5 for HD with no can… based on Grossman’s assertions in ON COMBAT.

9

Now HMAC’s set ups above would likely kill you indoors. Battlecomp and PWS are loud even on 14.5-16" barrels. I get a headache just looking a that PWS on his SBR.

10

Yeh, I just switched the PWS to a BattleComp 1.0. I always recommend that the guys I shoot with wear ear protection.

11

Are you talking about auditory exclusion?

12

11.5’’ IMHO is the sweet spot.

Suppressed.

BTW: Mk. 12 is a SPR, and Mk. 18 is the CQBR.

13

I’ll play since I haven’t been able to find the specifics he’s looking for, either, and have the same question. What about subjectively? Would you say it’s like a 12 ga.? 30-cal?

I’m filling out paperwork for a build like HMAC’s MOE carbine (with something else on the muzzle). I’m saving my duckets for a suppressor, but I’m curious in the meantime.

Thanks!

Edited to add:
After doing a little research at: http://www.silencerresearch.com/Reviews/aac_m41000_vs_yhm_stainless_phantom.htm (registration required), the unsuppressed dB on the 14.5 upper ran around 165. The 10.5 upper ran around 166. This was with M193. Guy seems to be independent and legit. The methodology I’ve read so far doesn’t seem to explain where the meter is located, but to me, it doesn’t matter as long as it’s consistent. In other words, I know how loud an M4 is. I was just curious about the magnitude of the difference.

I am not going to pretend to understand decibels, but I do know the difference between 165 and 166 isn’t that great.

So what’s up with that? I usually read here and elsewhere is “Dood, shooting the SBR unsuppressed will make yr fillings shoot out of yr face!” Is it a function of the muzzle being so much closer to the shooter’s ears?

FWIW, I shot next to a fat kid at the indoor range once who was shooting a Rem 700 in .308, scoped, at 25 yards. Once I doubled up with plugs and muffs, the sound wasn’t as bad as the shock wave that would wash over me ever time he fired. He was next to the wall, so I figured if he could handle it, so could I :wink:

14

If one was looking at a Noveske Mk.18 with DD rail, is there a suppressor that would interface with the rail?

Sorry for the hijack…

15

how about the noveske kx3 on a 11.5 or something for indoor use? obviously not the smallest or lightest muzzle attachment… but would still be a pretty compact setup overall. It’s essentially a tiny suppressor right?
have these fallen out of favor?

16

The KX3 doesn’t really suppress but it does a decent job of directing the blast away from the shooter and those around him.

As for the DD rail on a MK18 length upper, you can use a quality peel washer or a machined fixed spacer to give you the 1/4-3/8" offset from the shoulder for the QD attachment to screw onto. I have my M42K mounted on my DD MK18.

17

Not to get too far off topic, but you mentioned wanting an MP5 except for the expense…There are options available that bring a quality SBR’d MP5 type into the 15-1600 range.

The MKE imports are drying up, but they can still be had for 1300ish dollars. Buy your stamp, add stock, 922r parts, and its still relatively affordable, and not much different in price than some of the short barreled AR setups.

The SBR outclasses the MP5 subguns in a lot of ways, but the other side has its advantages too.

18

Yea I saw those MKE imports, I don’t know how do you make a 5 figure gun for $1500 without sacrificing reliability?

I think I am leaning toward a 5.56 14.5" AR Pencil Middy, to me it is worth the $200 stamp vs pinned muzzel attachment. Maybe a 12.5" but then for HD it might be so loud as to send one in a state of shock.

I’ve shot a 16"AK-74 with the full comblock brake indoors (20x15" room drywall) and it really wasn’t shocking loud, wouldn’t want to do that on a regular basis of course but for HD the percussion wouldn’t disorient you, but the thing is too long and heavy to be a primary HD choice.

19

I’ve been wondering this myself? MarkM says he runs a 11.5 unsuppressed for HD, but I wonder how loud the 12.5 would be compared to a 10.5/14.5/16??

20

The MP5 isn’t a five-figure gun. The prices have skyrocketed due to the 1986 FOPA legislation that closed the registry for machine guns, meaning no normal civilian can buy a new one. Constricted supply and high demand equals very high prices.

Imagine if nobody was making HDTVs anymore. The price of a $499 Walmart special would skyrocket to thousands. The same principle is in effect for machine guns, but it’s the law that’s doing it.