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Posted: 10/24/2013 6:50:11 AM EDT
| Asked in the BIY section, but figure I'll get more traction in here. I'm working on my first pistol right now and still on the ord process. I got my lower built up and just ordered a VLTOR MUR 1 without FA last night so now its on to my barrel, and this is where the question comes in. I am stuck between either 7.5 and 10.5 and just cannot make up my mind. What is the sweet spot for AR pistols, or is it completely up to the individual in that regards? After I get the barrel I'll finally be able to get my rail picked out and complete the remaining pieces needed. |
| Really comes down to what you want out of your pistol. I have built both a 10.5" and a 7.5". If your looking for a fun close range AR that makes a lot of noise and looks nice and short, go with 7". If you actually want some accuracy out of it down range, go with a 10". In my opinion, the 10" balances much better and doesn't look a whole lot longer. (Still keeps a nice short profile) |
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Quoted:
Really comes down to what you want out of your pistol. I have built both a 10.5" and a 7.5". If your looking for a fun close range AR that makes a lot of noise and looks nice and short, go with 7". If you actually want some accuracy out of it down range, go with a 10". In my opinion, the 10" balances much better and doesn't look a whole lot longer. (Still keeps a nice short profile) This is relevant to my interests too. Up to what range would you say the 7.5 inch is reasonably accurate to? |
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Never tested my 7.5" past 75 yards, but ive heard they do fine out to 100-150. Don't forget, length isn't the only factors in a accurate barrel. The barrel is no place to pinch pennies on a AR build.
You do lose a lot of velocity when you go to 7.5" however. (If that concerns you) |
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Quoted:
Never tested my 7.5" past 75 yards, but ive heard they do fine out to 100-150. Don't forget, length isn't the only factors in a accurate barrel. The barrel is no place to pinch pennies on a AR build. You do lose a lot of velocity when you go to 7.5" however. (If that concerns you) It's really not as much velocity or kinetic energy as you would think...somewhere around 300/400 fps with federal greentip. As for accuracy, it has already been debunked that a shorter barrel is less accurate. Case in point I can hit a one foot by one foot steel plate out at 300 yards every time with my POF and a 7.25 inch barrel and an ACOG 4x32. |
| Thanks for the replies, all. I can definitely live with 100-150 yards, and if I can stretch it even farther then so much the better. I ultimately am thinking I would like the most compact build I can put together while keeping it functional in all the ways that one would obviously want an AR to be. |
Thanks for the replies. I'm leaning towards 7.5, I have a 16" and a 20" so I figure the 7.5" will be like the bastard love child of them both  . Last build I had a complete upper, but I'm testing my luck with a stripped upper this go round. Now to find a barrel.
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As stated above the accuracy of the shorter barrels will be very close to that of longer (16"-20"). The big difference is going to be the velocity lost on the shorter barrels. This is important because the general "wounding" mechanism with the .223/.556 is bullet tumbling and/or fragmentation with most fmj rounds. The tumbling/fragmentation is very dependent of velocity which is being lost like virginities at the prom. If you want something to make holes in paper, and not much more, it is no big deal. If you are looking for something for house or truck use, it will still work, you need to select ammo that meets the task, as well as the engagement distances. I have a 7.5" that has been flawless and for social purposes I use the Black Hills 50 GR TSX. Below is a quote of mine from another thread that is a little more specific. Good luck.
"Contrary to what I've been told my whole life, size does matter, especially with the AR platform. The .223/5.56 in military applications does its damage by tumbling (yawing) and fragmentation once it hits its intended target. The fragmentation is very dependent on the bullet velocity. For 55 grain XM-193 the critical velocity is 2700 feet per second. Reliable fragmentation will not always occur at speeds slower than that. Barrel length has a direct correlation on velocity. With a 16" barrel, 55 grain bullet will have a muzzle velocity of about 3100 fps, but that same bullet from an 11.5" barrel has a muzzle velocity of around 2850. Drop an inch off and now a muzzle velocity of about 2725 fps from a 10.5 barrel. Remember the 2700 fps for reliable fragmentation? You are almost at that threshold at the muzzle. In the event you don't get any fragmentation you will basically have a through and through .22 injury. With a 7.5" barrel you will need an expanding design round, preferably a bonded HP, but not necessarily a varmint round because they don't penetrate deep enough. A very recommended round for the 7.5" is the Black HIlls TSX 50 gr. It can be expected to expand reliably to about 25 yards from your barrel." |
| Thanks X, If nothing else this will be nothing more than a fun paper puncher with the added benefit of a more close range setting IF needed. I keep a 10mm by the bed for those instances in home and on my carry, but having something like an ar for different close quarter type stuff would be the main reason for the pistol build. Not talking about 200+ yds even except paper. Thanks for all the replies. |
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Quoted:
As stated above the accuracy of the shorter barrels will be very close to that of longer (16"-20"). The big difference is going to be the velocity lost on the shorter barrels. This is important because the general "wounding" mechanism with the .223/.556 is bullet tumbling and/or fragmentation with most fmj rounds. The tumbling/fragmentation is very dependent of velocity which is being lost like virginities at the prom. If you want something to make holes in paper, and not much more, it is no big deal. If you are looking for something for house or truck use, it will still work, you need to select ammo that meets the task, as well as the engagement distances. I have a 7.5" that has been flawless and for social purposes I use the Black Hills 50 GR TSX. Below is a quote of mine from another thread that is a little more specific. Good luck. "Contrary to what I've been told my whole life, size does matter, especially with the AR platform. The .223/5.56 in military applications does its damage by tumbling (yawing) and fragmentation once it hits its intended target. The fragmentation is very dependent on the bullet velocity. For 55 grain XM-193 the critical velocity is 2700 feet per second. Reliable fragmentation will not always occur at speeds slower than that. Barrel length has a direct correlation on velocity. With a 16" barrel, 55 grain bullet will have a muzzle velocity of about 3100 fps, but that same bullet from an 11.5" barrel has a muzzle velocity of around 2850. Drop an inch off and now a muzzle velocity of about 2725 fps from a 10.5 barrel. Remember the 2700 fps for reliable fragmentation? You are almost at that threshold at the muzzle. In the event you don't get any fragmentation you will basically have a through and through .22 injury. With a 7.5" barrel you will need an expanding design round, preferably a bonded HP, but not necessarily a varmint round because they don't penetrate deep enough. A very recommended round for the 7.5" is the Black HIlls TSX 50 gr. It can be expected to expand reliably to about 25 yards from your barrel." Just to expand...I use the Black Hills TSX 50 on feral hogs at ranges between 25 and 80 yards with a 7.5 inch setup and it's one hec of a wopper. |
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