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What weight buffer would you use in a 5.56 SBR? I have a friend in another state who is building one as his first AR. (Still doing the paperwork). Having read up on short barreled (10.5") military M4's, I noticed they used a very heavy buffer. Would something along the lines of 4.4 ounces be enough??? If not, I have a hydraulic carbine buffer I can send him.....
 

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I started out with an H2 buffer in my carbine. I haven't put enough rounds through it yet to see if I'm going to need an H3 or not.

The 10.5" initially gave a lot of trouble, from what I understand. Thanks to aftermarket parts (heavy buffers, springs, extra length gas tubes, ect), a lot of them have been fixed though.

I think he'll have to put it together, and play with it until it runs right though. Everybody's combination of parts and ammo causes each carbine to run differently.
 
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Thanks!!! I told him I had a few extra parts on hand I would give him if he needed them, so I was just trying to figure out what would work in advance.... Someday, I am going to build an AR pistol, so some of this information will come in handy for me as well.....
 

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OP,
I have an older mil-spec Colt 10.0" M4 LWT upper, current Colt 10.3" RO923CQB monolithic upper, and a commercial Noveske 10.5" SS 1x7 upper. All (3) of these barrels have proven reliable firing suppressed/unsuppressed on semi/auto firing .223 pressure/full 5.56MM NATO pressure 77gr. SMK OTM ammunition with any buffer from a standard carbine buffer to a steel SMG buffer/H3 buffer to a standard rifle buffer in a rifle length lower. Why these short barrels are reliable over this wide range is simple. The manufacturers did the R&D necessary to find the optimum gas port size for each of their barrel lengths. Different weight buffers are used to fine tune the speed of the recoil system on semi/ROF on auto. If you want a 10.0"/10.3"/10.5" 5.56MM weapon that is reliable, choosing the barrel wisely is paramount. I am no expert but do have experience with the AR15/M16/M4 platform going back to the '60s. HTH
 
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OP,
I have an older mil-spec Colt 10.0" M4 LWT upper, current Colt 10.3" RO923CQB monolithic upper, and a commercial Noveske 10.5" SS 1x7 upper. All (3) of these barrels have proven reliable firing suppressed/unsuppressed on semi/auto firing .223 pressure/full 5.56MM NATO pressure 77gr. SMK OTM ammunition with any buffer from a standard carbine buffer to a steel SMG buffer/H3 buffer to a standard rifle buffer in a rifle length lower. Why these short barrels are reliable over this wide range is simple. The manufacturers did the R&D necessary to find the optimum gas port size for each of their barrel lengths. Different weight buffers are used to fine tune the speed of the recoil system on semi/ROF on auto. If you want a 10.0"/10.3"/10.5" 5.56MM weapon that is reliable, choosing the barrel wisely is paramount. I am no expert but do have experience with the AR15/M16/M4 platform going back to the '60s. HTH
Thanks for the input!!!! Do you happen to know the gas port size on your barrels? I don't think his barrel is going to be one of those big name, high class barrels. While he got a chrome lined chamber/barrel, he bought the complete upper from Model 1. Don't think they use the absolute best in parts, but I could be wrong as I don't have any experience with them... He did install a DD BCG and a PRI gasbuster charging handle.....
 

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Please forgive my ignorance - I've never quite understood the attraction of SBR/Pistol ARs. This seems to be a group I can ask. Perhaps one of you who has some experience with the short barreled ARs can help me understand the "why" of the ultra short barrel. What, besides vehicle access, does a 10.5" barrel offer to justify the inconvenience, tax stamp, fingerprints, background check, etc?

A recent article I read shows the 10.5" barrels as just reaching a little over 2550fps at the muzzle - the bottom threshold for fragmentation. Ballistically, this greatly reduces the rounds lethality beyond conversational distance. The article below mentions extra noise and blast as a real problem.

http://sadefensejournal.com/wp/?p=1093

I understand it better when the military or police AR becomes essentially a full auto submachine gun for 50 yard and under work. Lots of hits make up for poor ballistics, just like it does with a 9MM subgun. But the loss in ballistic performance, (5.56MM below 2550fps is only a hole punch, losing it's fragmentation effect) is great enough that, in a semi auto only SBR, I cannot see the usefulness, unless just the "tacticool/CDI" factor is the goal.

I am not trying to be flip. We live in America, and I am absolutely good with anyone having anything they can afford and just want to own. I am trying to understand the reasoning for accepting the lesser performance, and registering a weapon with the ATF, fees, fingerprinting, etc, just to have a shorter barrel on my semi-auto AR. If they would throw in the full auto option, that might be worth it. But on a semi? Someone enlighten me. CC
 

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I'm with you on that! 16" is the shortest barrel I have, and the shortest I want. I think some people want one for the so called "Cool" factor. I keep thinking about building an AR pistol, but again, what would you use it for that a regular pistol wouldn't work better for. Now if you could legally own a full auto, maybe it would be a good "bugout vehicle" weapon, at least until you get to where you're going, then you'll be wishing you had a full size upper.....

As far as the Navy using them on ships, it is much easier to manuver a short barrel weapon on board a ship that a full size M-16 or especially the M-14's we had on our ship back in the day. Personally, I liked using a shotgun, but these days soft body armor defeats buckshot with ease where the SBR would take care of that, especially at the ranges you would be firing on most ships....
 

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my shorty is a .300 blackout soooo. whole different deal.


as far as a reason , compact is king. seperate the uppers and it fits in a briefcase. fully loaded and ready to finction it fits in a tennis bag.

they also make a great backup to a dmr style full size cartridge rifle.

they are also a lot of fun to shoot.
 

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Please forgive my ignorance - I've never quite understood the attraction of SBR/Pistol ARs. This seems to be a group I can ask. Perhaps one of you who has some experience with the short barreled ARs can help me understand the "why" of the ultra short barrel. What, besides vehicle access, does a 10.5" barrel offer to justify the inconvenience, tax stamp, fingerprints, background check, etc?



A recent article I read shows the 10.5" barrels as just reaching a little over 2550fps at the muzzle - the bottom threshold for fragmentation. Ballistically, this greatly reduces the rounds lethality beyond conversational distance. The article below mentions extra noise and blast as a real problem.



http://sadefensejournal.com/wp/?p=1093



I understand it better when the military or police AR becomes essentially a full auto submachine gun for 50 yard and under work. Lots of hits make up for poor ballistics, just like it does with a 9MM subgun. But the loss in ballistic performance, (5.56MM below 2550fps is only a hole punch, losing it's fragmentation effect) is great enough that, in a semi auto only SBR, I cannot see the usefulness, unless just the "tacticool/CDI" factor is the goal.



I am not trying to be flip. We live in America, and I am absolutely good with anyone having anything they can afford and just want to own. I am trying to understand the reasoning for accepting the lesser performance, and registering a weapon with the ATF, fees, fingerprinting, etc, just to have a shorter barrel on my semi-auto AR. If they would throw in the full auto option, that might be worth it. But on a semi? Someone enlighten me. CC

The reason why I went with SBR's if you have a 16" barrel and have a can on it that's 22" barrel now, if you have a 10" barrel with a can on its 16" that's way I went with 10"barrel for a sbr.As far on the range 100-250 yards shoots great, never had a jam and as far as a buffer I use the H3 in mine works great.
 

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Thanks for the input!!!! Do you happen to know the gas port size on your barrels? I don't think his barrel is going to be one of those big name, high class barrels. While he got a chrome lined chamber/barrel, he bought the complete upper from Model 1. Don't think they use the absolute best in parts, but I could be wrong as I don't have any experience with them... He did install a DD BCG and a PRI gasbuster charging handle.....
Never measured the gas port size but you may be able to find it on the net. The 10.0" Colt makes a measured 2575 FPS MV with a 5.56MM 70gr. TSX load which will expand out to 300yds.
 

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You just need to try different weights. I have a DD upper that only works with a carbine buffer and a BCM that will loves an H2. It's a way to tune a gun, not a set standard.
 
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