Pistol AR building - Page 2

peggysue · May 24, 2015, 12:54 PM

I made the black one back in 2000. It is a Bushy upper. The other colored one is HARDENED ARMS upper. Both of my 7.5" AR pistols shot flawlessly, They are very very loud and emit a flare,
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rickyrick · May 24, 2015, 01:40 PM

Looking at my 16" m4rgeys, I see that 10.5 puts it right at the cutout. Having never shot an ar pistol I pretended the carbine was a pistol. I was able to hold it in a somewhat stable position, had this been a pistol.

I'm still up in the air over a 10.5 or 7.5...

Probably going the longer first

skizzums · May 25, 2015, 12:18 AM

a pistol w/o stabilizer sits on my cheekbone. sounds painful but its not. if your stuck on .223, I would want the 10.5 for velocity.

if your going with a short .223 barrel, I would like a 1:7 to get stable with less velocity, I see a lot are 1:9 and I am not sure why

leadcounsel · May 25, 2015, 04:01 PM

Quote:

The inefficiency of the 223 is the reason for the flash and blast out of shorter barrels

Please explain this statement. A 223 has more powder than a 9x19, for instance, yet a 9x19 is effective out of a 4" barrel or even a 9" barrel such as an AR pistol.

Why would a 223, with MORE power, be less efficient? While there may be some powder waste, is surely burns at least as much powder in 9" as a 9x19 can in 4" or 9"... So why would it be inefficient?

Sharkbite · May 25, 2015, 04:41 PM

The inefficiency is based on the TYPE of powder in the rifle round. Totally different powders then used in the PISTOL round you mentioned.

Pistol powders are much faster burning then the powders found in 223 ammo. Hence the inefficiency.

tirod · June 1, 2015, 06:54 AM

5.56 ammo is traditionally loaded for 20" barrels, which are still issue. So, all the milspec ammo is configured for that much barrel dwell time to burn the powder. It's getting shortchanged out of a 14.5", which is why newer rounds were developed to improve it - but they still had to function in the 20" rifles.

It's a very tight performance envelope for the military due to conflicting uses. With .300BO, not so much. And larger bullets offer more square surface area to absorb energy, which gives them an advantage with short barrels. On the other hand, in the limited mag well length of the M16, the bullets aren't always the optimum profile for aerodynamics. And the much heavier weights aren't in a barrel long enough to get all the energy they could, compared to a 16" or 20".

They tend to have a more curved ballistic flight path, which may be moot for the short range intent. More to the point, the military limits themselves to 5.56, and has a 40+ year track record with the 10.5" barrel. If 7.5" had any value benefit being shorter, it's not factoring into military use.

The point of a gun is to shoot a projectile given the format of it's size and shape, ignoring the ballistics of the ammo is like building a car for it's show stopping looks with no regard to hp or gas mileage. Some do that - all the rest of us want more than just looks. All the gun does is launch a projectile - what the bullet does is the real job. That's why some very ugly guns have been quite successful. It's not about looks.

rickyrick · June 1, 2015, 08:23 AM

I think I'm set on 10.5 .223 for the first go at a pistol build. I have plenty of 5.56/.223 ammo, so at least I don't need to spend money there.

Will there be any buffer/spring differences than that of any other carbine length gas system?

And is it ok to have a completed upper in your possession before having a dedicated pistol lower?

rickyrick · June 21, 2015, 11:47 PM

Well, it's all finished...
Thanks for the help ...

May 24, 2015, 12:54 PM	#26
peggysue Junior member Join Date: May 20, 2014 Posts: 1,835	I made the black one back in 2000. It is a Bushy upper. The other colored one is HARDENED ARMS upper. Both of my 7.5" AR pistols shot flawlessly, They are very very loud and emit a flare, . Last edited by peggysue; May 24, 2015 at 01:00 PM.

May 24, 2015, 01:40 PM	#27
rickyrick Senior Member Join Date: March 15, 2010 Posts: 8,238	Looking at my 16" m4rgeys, I see that 10.5 puts it right at the cutout. Having never shot an ar pistol I pretended the carbine was a pistol. I was able to hold it in a somewhat stable position, had this been a pistol. I'm still up in the air over a 10.5 or 7.5... Probably going the longer first __________________ Woohoo, I’m back In Texas!!!

May 25, 2015, 12:18 AM	#28
skizzums Senior Member Join Date: July 1, 2013 Location: Douglasville, Ga Posts: 4,615	a pistol w/o stabilizer sits on my cheekbone. sounds painful but its not. if your stuck on .223, I would want the 10.5 for velocity. if your going with a short .223 barrel, I would like a 1:7 to get stable with less velocity, I see a lot are 1:9 and I am not sure why __________________ My head is bloody, but unbowed

June 1, 2015, 08:23 AM	#32
rickyrick Senior Member Join Date: March 15, 2010 Posts: 8,238	I think I'm set on 10.5 .223 for the first go at a pistol build. I have plenty of 5.56/.223 ammo, so at least I don't need to spend money there. Will there be any buffer/spring differences than that of any other carbine length gas system? And is it ok to have a completed upper in your possession before having a dedicated pistol lower? __________________ Woohoo, I’m back In Texas!!!

June 21, 2015, 11:47 PM	#33
rickyrick Senior Member Join Date: March 15, 2010 Posts: 8,238	Well, it's all finished... Thanks for the help ... __________________ Woohoo, I’m back In Texas!!!

May 25, 2015, 04:41 PM	#30
Sharkbite Senior Member Join Date: November 4, 2013 Location: Western slope of Colorado Posts: 3,679	The inefficiency is based on the TYPE of powder in the rifle round. Totally different powders then used in the PISTOL round you mentioned. Pistol powders are much faster burning then the powders found in 223 ammo. Hence the inefficiency.

June 1, 2015, 06:54 AM	#31
tirod Junior member Join Date: January 21, 2009 Posts: 1,672	5.56 ammo is traditionally loaded for 20" barrels, which are still issue. So, all the milspec ammo is configured for that much barrel dwell time to burn the powder. It's getting shortchanged out of a 14.5", which is why newer rounds were developed to improve it - but they still had to function in the 20" rifles. It's a very tight performance envelope for the military due to conflicting uses. With .300BO, not so much. And larger bullets offer more square surface area to absorb energy, which gives them an advantage with short barrels. On the other hand, in the limited mag well length of the M16, the bullets aren't always the optimum profile for aerodynamics. And the much heavier weights aren't in a barrel long enough to get all the energy they could, compared to a 16" or 20". They tend to have a more curved ballistic flight path, which may be moot for the short range intent. More to the point, the military limits themselves to 5.56, and has a 40+ year track record with the 10.5" barrel. If 7.5" had any value benefit being shorter, it's not factoring into military use. The point of a gun is to shoot a projectile given the format of it's size and shape, ignoring the ballistics of the ammo is like building a car for it's show stopping looks with no regard to hp or gas mileage. Some do that - all the rest of us want more than just looks. All the gun does is launch a projectile - what the bullet does is the real job. That's why some very ugly guns have been quite successful. It's not about looks.