Firearms Talk banner

1 - 20 of 21 Posts

·
Registered
Joined
·
317 Posts
Discussion Starter #1
I have noticesd myself giving the SBR a little more attention than usual . I'm really liking the look of the rifle. I have a 11 1/2 in on my DPMS with a 5 1/2 FS . Would you cut and rethread the barrel or just get new barrell .Are mist SBR flat top At15? And of course get your tax stamp before any of the above happend.
 

·
Supporting Member
Joined
·
11,986 Posts
I would just get a new barrel. I am sure that you are aware that once it becomes a registered SBR it is always an SBR!

03
 

·
Premium Member
Joined
·
20,098 Posts
Yes but is that Bad thing ?do you think it's devaluing the gun?
its not a bad thing in and of itself but it does revalue the lower receiver to 0$. there is no resale value of a sbr lower. its engraved(federal requirment) with your information. it cannot be resold.

even if you could no one is going to pay 200$ (nfa transfer tax) + the cost for a used lower. they are just going to register their own new one.

going shorter than 14.5 on a 556/223 rapidly drops that cartridge somewhere around 22magnum levels. if your going to go shorter than 14.5 i would go 9mm 40sw or 45acp
 

·
Registered
Joined
·
3,494 Posts
Or 6.8 spc or 300 aac blackout.
 

·
Registered
Joined
·
77 Posts
JonM said:
its not a bad thing in and of itself but it does revalue the lower receiver to 0$. there is no resale value of a sbr lower. its engraved(federal requirment) with your information. it cannot be resold.

even if you could no one is going to pay 200$ (nfa transfer tax) + the cost for a used lower. they are just going to register their own new one.

going shorter than 14.5 on a 556/223 rapidly drops that cartridge somewhere around 22magnum levels. if your going to go shorter than 14.5 i would go 9mm 40sw or 45acp
I guess I'm not understanding what you mean by it "rapidly drops the cartridge somewhere around 22magnum levels", please explain.
 

·
Registered
Joined
·
2,520 Posts
xRacerX75x said:
I guess I'm not understanding what you mean by it "rapidly drops the cartridge somewhere around 22magnum levels", please explain.
Because of the short length of the barrel the powder doesn't burn completely reducing pressure and therefore velocity. It may look cool but it's ineffective past 100 yards or so.
 

·
Registered
Joined
·
77 Posts
pagj17 said:
Because of the short length of the barrel the powder doesn't burn completely reducing pressure and therefore velocity. It may look cool but it's ineffective past 100 yards or so.
Ok makes sense but for a patrol rifle application? Clearing houses and buildings which create distances from point blank to maybe 10 or 15 yards(in a small warehouse) a 5.56 SBR would fill the roll well right?
 

·
Premium Member
Joined
·
20,098 Posts
Ok makes sense but for a patrol rifle application? Clearing houses and buildings which create distances from point blank to maybe 10 or 15 yards(in a small warehouse) a 5.56 SBR would fill the roll well right?
Your better off with a 12ga shotgun and a sidearm. But yeah it would work ok at that range
 

·
Banned
Joined
·
258 Posts
Yes thats what he is saying. Basically, any powder that burns after the bullit leaves the barrel is wasted. The shorter the barrel the less time for the powder to burn. Conversly, any barrel lenth added past the point of powder expansion, slows the bullit down. So the trick to maximising bullit energy is to have the bullit exit the barrel at the instant before, max pressure.

You can clock your round, using diferent barrel lenths and as you shorten a barrel, velocity will drop off, conversly as you lenthen a barrel to far velocity will drop off.
 

·
Registered
Joined
·
3,494 Posts
I think a 12 in barrel will be adequately long enough to keep velocities above the optimum fragmentation speed for 5.56 at cqb distances. If you are going to rebarrel, look into .300 blackout.
 

·
Banned
Joined
·
1,427 Posts
I need to get the BLK out again. Ammo is down to $10.99 a box which is good for what it is.
 

·
Registered
Joined
·
3,494 Posts

·
Registered
Joined
·
4,795 Posts
going shorter than 14.5 on a 556/223 rapidly drops that cartridge somewhere around 22magnum levels. if your going to go shorter than 14.5 i would go 9mm 40sw or 45acp
I wouldnt say its at .22 mag levels the difference between a 7.5" barrel and a 20", both .223 is roughly 430 fps at the barrel and roughly 600 fps at 80 M, sighted in at 50 yards still hits 10" steel plates at 100 yards . Now further than that its lost a ton of velocity and falls off pretty quick . I need to run it thru my chrono with some 5.56 and see how much difference there is between it and the standard .223 FMJ ammo on the velocity. Shortys have their special place of use and most cant justify the need or the want to spend the $200 for the stamp when they can get basically the same thing in a pistol with out jumping through the hooplah and the wait
 

·
Banned
Joined
·
1,427 Posts
The .300 BLK guys posted some 125gr for $10.50 on FaceBook a couple days ago as well. I thought it was from CTD but can't find it now. I'll check FB.
 

·
Registered
Joined
·
3,494 Posts
I wouldnt say its at .22 mag levels the difference between a 7.5" barrel and a 20", both .223 is roughly 430 fps at the barrel and roughly 600 fps at 80 M, sighted in at 50 yards still hits 10" steel plates at 100 yards . Now further than that its lost a ton of velocity and falls off pretty quick . I need to run it thru my chrono with some 5.56 and see how much difference there is between it and the standard .223 FMJ ammo on the velocity. Shortys have their special place of use and most cant justify the need or the want to spend the $200 for the stamp when they can get basically the same thing in a pistol with out jumping through the hooplah and the wait
I'm not really agreeing with the numbers you are posting here.
Optimally fragmentation occurs at velocities above 2700 fps.
Muzzle velocity for M193 55 gr fmj is in the 3200 fps range with a full length barrel.

430 fps is a really fast paintball.
250-1000+ for pellet guns.
230 gr fmj .45 acp shoots in about the 900 to 1000 fps depending on barrel length.

Um here you go....
http://www.ar15.com/content/page.html?id=213

Once you go under 2700fps, fragmentation gets really spotty so for the most part you are just punching holes. But much deeper holes than a .22 magnum. :rolleyes:
 

·
Banned
Joined
·
1,427 Posts
They have developed 300 BLK that is designed to work at subsonic levels.
 
1 - 20 of 21 Posts
Top