SBR barrel length and suppressor Dilemma, some opinions please

[Wormydog1724]

I am close to being approved for my SBR, like maybe just two more months! lol

I have built a pistol lower so I can complete my upper early, just in case the 'run on parts' gets serious as we near November.

I want to go short, and I want to go suppressed. I have a couple options I am considering. I'll list what I have and what I am considering.

Option 1.) 10.3" barrel (have), MK18 Ris II (have), AAC SDN-6 (paperwork sent this week)

Option 2.) 12.5" barrel (don't have), MK18 Ris II (have), AAC SPR/M4 (have)

I know that "ballistics" will be better with the 12.5" barrel, but like I said I want to go short. The SPR/M4 adds 4.9" to the barrel, so that would be 17.4" (12.5 + 4.9). With Option 1, I am looking at 16.4" (10.3 + 6.1). Is 1" worth it? I think the weight will be a wash, maybe the 12.5" will be heavier due the the barrel and the larger mount. I will be using a break type mount for both so baffle erosion isn't one of my concerns right now. Also, I will be using a lo-pro adjustable gas block so I think I will be able to tune it for unsuppressed, and still be OK for suppressed. I just damn sure want it to run unsuppressed because then it shouldn't have a problem with the can. If I set it up for suppressed, then I might have short strokes or something without the can and/or weak ammo.

Should I ditch the 10.3" and go 12.5" and use the can I have and sacrifice the weight and 1"?
Or stick with the 10.3", save an 1" and a couple ounces, but be loud until the SDN-6 is approved?

My initial plan was to do a MK18-ish clone but I am slowly changing things and about the only things that will be MK18 is the Ris II, KAC Micro sights, and maybe the 10.3" barrel.

Use: This will mostly be a range, cool guy, nightstand grab-n-go, truck gun. Might try to shoot a coyote here and there now that the suppressor hunting bill, Land Owners Freedom Act, has been passed and goes into effect Nov. 1st. My coyote shots are usually 50 yards and in, sometimes as far as 150 however I usually won't try anything farther than that. Also, if I decide to stick with the 10.3" I think I will eventually get a M4-2000 for it to save weight, length, and my SDN-6. I know it won't be super-quiet, probably not even hearing safe without ear-pro, its hard to make 5.56 sound 'good' with almost any can and any length of barrel. My SPR/M4 sounded 'ok' on my old 18" gun, but wasn't that great on my 16" or 14.5". I just want to take the 'bite' out of the shot so that's why I will be using a can.

What say the masses of M4C? I am not an elite tactical operator, I just like my guns to function all the time, look good, and be effective if I ever have to use it to defend myself or family. I'll have a SureFire M300a and either a Trijicon TA44SG-10 or Eotech XPS2-0 on top, the weight between the optics is a wash.

If this is completely dumb and my uses irrelevant, please let me know. Just looking for some outside perspective on the subject.

Thanks

[RyanB]

The longer barrel and shorter can is almost always the route I'd advise. Though a Mini-4 and SDN6 would have been the best combination.

[El Cid]

So long as you're using quality components I think you will be fine with either so it's mostly preference. I do prefer the 11.5" as "my" shortest as the increase in dwell time aids reliability.

Truthfully though, it doesn't matter which one you buy as it's an addictive hobby and I predict you will end up owning both at some point - especially when you consider that you can just get another SBR upper for the stamped lower.

[jonconsiglio]

I've been running a 10.5" for a couple years with many thousands of rounds and no issues. Using TSX, like the 50gr Black Hills, you can expect reliable, consistent expansion out to a little past 100 yards. That decreases dramatically when using TAP (about 40 yards with 75gr 5.56 for reliable fragmentation), FMJ (can be literally just a few yards for reliable fragmentation) or other ammunition like Mk262 (less than TAP's fragmentation).

Now, this doesn't mean it's not effective past those ranges, it's just not performing at its optimum. There have been many badguys put to the dirt at ranges far beyond the reliable frag range of 75gr TAP and Mk262. For comparison using 5.56 TAP 75gr as an example, you can expect it to reliably fragment to roughly 160 yards from a 14.5" and about 110 yards from a 12.5" compared to 45 from a 10.5". These are not exact numbers, but close. They're also not the maximum range of fragmentation, but the point where it still fragments reliably at its max.

So, for any defensive use, the 10.5" will be very effective. Especially with proper ammo. It'll also be very reliable if you go with a quality manufacturer and don't start experimenting outside the recommended buffer weights and ammunition.

Having said that, the 10.5" fills a bit more of a specialty role and will likely need parts replaced sooner than longer barrels. The 12.5" is a good general use rifle and what many consider a sweet spot for the rifle and caliber. My next will likely be an 11.5" or 12.5".

On a side note, the M4A1 CQBR and the Mk18 Block 2 use either the MaTech rear sight or the KAC standard rear sight along with the KAC standard flat dark earth front sight, not the micros. The rear doesn't matter much to me, but I prefer the standard KAC front as its protected when folded. I've broken two URX II front sights on my SR15's and the thought of the unprotected micro when folded down gives me a little less confidence than the standard front does.

[Wormydog1724]

Thanks for the replies guys.

Jon I did not know about the KAC sights on the MK18 not being micros, oh well. One less thing that isn't an exact "clone" doesn't bother me too much.

As for reliability, I have heard that being an 'issue' with some 10.5" or 10.3" barrels thats why I went ahead and got an adjustable gas block. I think that might give me enough room to play and I might be able to remedy any problems I might have.

The upper, lower, & BCG are BCM, the 10.3" barrel is a DD, gas block is the Spike's new micro adjustable. If it doesn't wanna work, I'll try something else but it seems to be well built and the adjustment is easy and solid.

Another not so desirable option would be to get an 11.5" barrel and mill the RIS II down so the SPR/M4 would fit. The 12.5" will have no problem, but to save 'that 1"' I could do that. But that just doesn't seem worth it to me. As El Cid said, I'll probably end up doing both eventually. lol

[jonconsiglio]

It's not a big deal about the sights and certainly not something that would bother me any on one of my builds, just wanted to point it out...

My LMT 10.5" has been utterly reliable when pushed hard whether suppressed or not. When I switched to the Vltor A5, it was more consistent whether suppressed or not and whether I was shooting 855 or Brown Bear, for example. The A5 really leveled that rifle out, though it was good to go from the start.

Unless you have a specific need for a 10.5", in which case you'd likely not run the suppressor, I'd go with an 11.5" or 12.5" instead. Ultimately, I'd like a 12.5" with a Surefire Micro to fill my general use role.

Munch520 has a 12.5" with a Centurion carbine cutout and that rifle handles so well, plus it's very lightweight. I really like that rifle.

[WS6]

From a 10.5" barrel using the correct ammunition you can expect near double-caliber expansion out to 200 yards. That's plenty for me.

[nimdabew]

Option 2.) 12.5" barrel (don't have), MK18 Ris II (have), AAC SPR/M4 (have)

Eotech XPS2-0 on top

I am doing this exact setup. I sourced a cheap M4A1 barrel and am having it chopped to 12.5" (I sent the rail and mount in with the barrel so it is going to have exactly 3/16" between the back of the mount and the front of the rail for the overlap of the back of the mount). I will post pics everywhere I can because finding this exact setup is hard to find for some reason in a google image search.

ETA: The length added to the host weapon is length past a standard A2 flash hider, so add another 1.3" to your length measurements.

[Ironman8]

My honest opinion, anything over ~16" (combined length -- bbl+suppressor or muzzle device) it all becomes pretty much a wash IRT compactness and manueverability in structures and especially vehicles.

Anything under 16", every inch less will help in this regard.

If you're looking at a barrel/suppressor package over 16", then manueverability becomes second to sound suppression (IMO). In this case, I think you would do better with the 12.5 bbl + SPR/M4.

If you want to go more "high speed" and optimize a "CQB" type weapon, then there are some better barrel/suppressor combinations than the two options you've listed.

[QuietShootr]

A vote for the 10.3". My LMT is my go-to gun for most use.

[BigLarge]

My honest opinion, anything over ~16" (combined length -- bbl+suppressor or muzzle device) it all becomes pretty much a wash IRT compactness and manueverability in structures and especially vehicles.

Anything under 16", every inch less will help in this regard.

If you're looking at a barrel/suppressor package over 16", then manueverability becomes second to sound suppression (IMO). In this case, I think you would do better with the 12.5 bbl + SPR/M4.

If you want to go more "high speed" and optimize a "CQB" type weapon, then there are some better barrel/suppressor combinations than the two options you've listed.

Couldnt have said it better myself. Also (im my humble opinion) the ballistics gained in a 12.5 over an 11.5 arent worth the extra inch if maneuverability is a top priority. If your case (wanting to use the SPR/M4) I can understand the argument, but I feel there are better options.