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AR barrel lengths questions.
Posted on 2/12/25 at 3:54 pm
Posted on 2/12/25 at 3:54 pm
I’m new to this, but my opinion is that shorter AR barrel lengths are for concealability, as well as maneuverability.
1. How short is too short when considering how it will affect the 5.56?
2. How does barrel length affect suppressor?
3. How does bbl length affect bullet grain selection and twist rate?
4. Do you wish that the buffer tube was collapsible or foldable to help with concealment?
^i say that about the buffer tube, because I’ve been considering a KelTec SU16c which is a 5.56 piston drive that folds.
Seen below is a SU16 with a 16” bbl and could be concealed better if it had a 10”.
1. How short is too short when considering how it will affect the 5.56?
2. How does barrel length affect suppressor?
3. How does bbl length affect bullet grain selection and twist rate?
4. Do you wish that the buffer tube was collapsible or foldable to help with concealment?
^i say that about the buffer tube, because I’ve been considering a KelTec SU16c which is a 5.56 piston drive that folds.
Seen below is a SU16 with a 16” bbl and could be concealed better if it had a 10”.
8
Posted on 2/12/25 at 4:03 pm to dstone12
1 - open muzzle, shorter = louder. Shorter gas system, so higher operating pressures and more bolt speed . Less bullet velocity. More flash. IMO, unless you're long range hunting with it shorter=better. Its worth all the drawbacks to stay compact
2 - higher pressure at the supressor, so less noise reduction. More unburned powder, so dirtier. Most supressors are rated for a certain barrel length for a given caliber due to muzzle pressure limits
3 - not worth worrying about
4 - I never have. ARs are pretty compact as it is compared to normal long guns.
Cutting 6" off that kel tech barrel might make it unreliable, since that would put the muzzle right at the gas port. It would make a nice compact setup, but I'd greatly prefer an AR pistol to that. At least that would be designed to work at SBR lengths.
FYI (I'm sure you already know) chopping that barrel under 16" would make it a NFA firearm and require associated BS.
2 - higher pressure at the supressor, so less noise reduction. More unburned powder, so dirtier. Most supressors are rated for a certain barrel length for a given caliber due to muzzle pressure limits
3 - not worth worrying about
4 - I never have. ARs are pretty compact as it is compared to normal long guns.
Cutting 6" off that kel tech barrel might make it unreliable, since that would put the muzzle right at the gas port. It would make a nice compact setup, but I'd greatly prefer an AR pistol to that. At least that would be designed to work at SBR lengths.
FYI (I'm sure you already know) chopping that barrel under 16" would make it a NFA firearm and require associated BS.
Posted on 2/12/25 at 4:04 pm to dstone12
I have an AR in 5.56 with a 10.3" barrel. It stays in my truck (I have a garage with a door that stays closed). It's a pretty neat little weapon.
Also have a .300blk with a stamp that is 8".
They are for maneuverability and easier to put in a bag.
With the silencer though, they are almost the same length as a 16" barrel, depending on the silencer.
Barrel twist doesn't come into play on the 5.56. They should be 1:7 or 1:8.
.300blk you can get a 1:3 and they're great for subs but not as much for supers. I think mine is 1:5 or something like that.
Also have a .300blk with a stamp that is 8".
They are for maneuverability and easier to put in a bag.
With the silencer though, they are almost the same length as a 16" barrel, depending on the silencer.
Barrel twist doesn't come into play on the 5.56. They should be 1:7 or 1:8.
.300blk you can get a 1:3 and they're great for subs but not as much for supers. I think mine is 1:5 or something like that.
Posted on 2/12/25 at 4:57 pm to dstone12
quote:
1. How short is too short when considering how it will affect the 5.56?
Military has determined that anything shorter than 10.3” is useless. A 10.3” MK18 can still hit targets out to 300 meters… I think
quote:
2. How does barrel length affect suppressor?
The shorter the barrel, the less powder burn. Which in turn means less velocity. Which in turn means less distance. When there is less powder burn, it ends up in either the suppressor itself or the receivers. Which means more cleaning.
Also, the shorter the barrel, the bigger the fire ball. Which in turn means more wear in the suppressor.
quote:
3. How does bbl length affect bullet grain selection and twist rate?
I think… the heavier the bullet, the more accurate the bullet. Especially out of a 10.3” barrel. Most twist rates you find in most barrels is 1:7.
There’s a saying:
With a 20” barrel, any ammo is considered duty ammo.
quote:
4. Do you wish that the buffer tube was collapsible or foldable to help with concealment?
It’s a fad that I wish would go away.
However, PDWs could be thought of differently.
Posted on 2/12/25 at 5:17 pm to dstone12
You could run a bull pup and get a full 16.5” for shorter overall length. IWI Tavor is the most ergonomic friendly with AR users.
Posted on 2/12/25 at 5:57 pm to dstone12
1. I would stay around 11.5”+ personally, but 10.3” is very popular also. Velocity is what makes 5.56 viable and effective. Cutting barrel length directly cuts velocity. That being said, an MK18 has put a lot of bad guys in the dirt (or sand more specifically)
2. Shorter barrels also have increased noise and muzzle flash. Can lead to erosion inside of a suppressor without a blast baffle.
3. Negligible as far as I know.
4. I have a 9” 300blk piston gun with a foldable stock (brace). It’s cool but more novelty than I initially thought it would be. Maybe the foldable stock would be better suited to something shorter. Like an Sig rattler or PCC. Or if you had a certain bag kitted up that the gun needed to fit in. I would say my 9” gun is unwieldy inside a vehicle and doubly so with a suppressor on the end. I would want something like a Flux Raider and a very short 9mm can if I were looking to shoot out of a car or something like that.
2. Shorter barrels also have increased noise and muzzle flash. Can lead to erosion inside of a suppressor without a blast baffle.
3. Negligible as far as I know.
4. I have a 9” 300blk piston gun with a foldable stock (brace). It’s cool but more novelty than I initially thought it would be. Maybe the foldable stock would be better suited to something shorter. Like an Sig rattler or PCC. Or if you had a certain bag kitted up that the gun needed to fit in. I would say my 9” gun is unwieldy inside a vehicle and doubly so with a suppressor on the end. I would want something like a Flux Raider and a very short 9mm can if I were looking to shoot out of a car or something like that.
This post was edited on 2/12/25 at 5:58 pm
Posted on 2/12/25 at 6:09 pm to dstone12
I will add that if you are looking for something short and more concealable look at a PCC. I have a B&T APC9 and an H&K SP5k.
They’re spectacular for maneuverability and packability.
They’re spectacular for maneuverability and packability.
This post was edited on 2/12/25 at 8:53 pm
Posted on 2/12/25 at 6:20 pm to Whisky Dent
Only benefit of my folder is putting it in a backpack. Would be the first thing I'd sacrifice on my 8" build.
Posted on 2/12/25 at 6:27 pm to Whisky Dent
quote:
Shorter barrels also have increased noise and muzzle flash. Can lead to erosion inside of a suppressor without a blast baffle.
This.
Muzzle brakes are favored over flash hiders when suppressed on shorter barrels because the brake acts as a sacrificial blast baffle. The flash/flame will hit it first dissipating it before it hits the blast baffle of the suppressor.
Posted on 2/12/25 at 8:00 pm to bbvdd
quote:
I will add that if you are looking for something short and more conciliable look at a PCC. I have a B&T APC9 and an H&K SP5k. They’re spectacular for maneuverability and packability.
This makes me delve into a completely different subject about the 9mm being shot out of a 16” barrel.
Obviously it won’t even get close to a 5.56 out f an 8” barrel.
But the size and weight would possibly be a trade off.
Posted on 2/12/25 at 9:05 pm to dstone12
Don't go anywhere near that Keltec. Just get an 11.5" pistol and have fun. If you want to suppress, it still won't be that long.
Get a BCM or Geissele when it's on sale.
Get a BCM or Geissele when it's on sale.
Posted on 2/14/25 at 9:21 am to dstone12
There are a lot of variables that surface on this topic. Major one being caliber. A 5.56 bullet will need a longer barrel than a 6 arc or 6.5 Grendel to perform similar. A 300blk needs less barrel length than a 5.56 for pressure on the suppressor.
If you want to stick with the 5.56, there are barrel lengths to stick to, but down range performance suffers. There are guys out there that are hitting moa targets out to 800-1000 yards with the 6.5 Grendel and 6 arc on ~10-12” barrels that are reloading but those rounds are not as off-the-shelf prevalent as the 5.56. Bullet tech has come a long way but there are trade offs.
I
If you want to stick with the 5.56, there are barrel lengths to stick to, but down range performance suffers. There are guys out there that are hitting moa targets out to 800-1000 yards with the 6.5 Grendel and 6 arc on ~10-12” barrels that are reloading but those rounds are not as off-the-shelf prevalent as the 5.56. Bullet tech has come a long way but there are trade offs.
I
Posted on 2/14/25 at 10:00 am to finchmeister08
quote:
Military has determined that anything shorter than 10.3” is useless
Incorrect. Anything in .556 under 10.3" is useless. 300 BO doesn't give a shite about barrel length. 8" has the same velocity as 16" damn near.
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