SBR'S at long range?

[domestique]

11.5" barrel at 375 yards...... standing.


https://youtu.be/HINx3JOJ2GY


There use to be a longer video of this guy doing a walk back. I can't seem to find it right now.

[Auto-X Fil]

One major point - I don't know of any suppressor available for a barrel that short, and shooting a 7.5" barrel without a can is going to be like setting off a flash-bang in front of your face. But let's ignore that for now.

As the others have said, accuracy is a non-issue. All other factors being equal, short barrels tend to be more accurate (or at least, more forgiving of a wide range of velocities) due to being relatively stiffer. Velocity is a pretty major issue. You won't get acceptable terminal ballistics any further than you can spit with a barrel that short.

Let's assume you want to get not just a hit, but a hit with a bullet that does something other than pencil through. If you're running Mk262, which fragments down to ~2200 (on a good day), your range will be:

7.5" - 0yd
10.5" - 80
14.5" - 170
16" - 210
20" - 260

That's right - point-blank shots with a pistol-barrel AR will probably just pencil 77gr SMKs right through, even with a very hot load like Mk262. Now, I'm not going to stand at 500yd and let you stick them in me, but it's a poor defensive choice. An expanding 55-65gr bullet would have decent performance at indoor ranges, although those bullets have poor BCs compared to the Mk262's 77gr SMK, so they will die even faster at range.

In summary: If you insist on a 7.5" barrel for defensive uses - shoot 300BLK, or even a pistol caliber. 9mm or .45 would be more effective, and have less recoil and flash. And you could suppress it.

Now, let's just say you want to lob targets onto steel or paper. You just need to stay super-sonic to maintain accuracy. I like to use 1200fps as a good minimum velocity for maintaining accuracy, although SMKs do transition pretty well, so I'll round the range up. Anyway, range to ~1200fps:

7.5" - 500
10.5" - 600
14.5" - 700
16" - 750
20" - 800

Now, note that with a 10mph wind you'll be dialing 8MOA of windage and 22MOA of drop on that 7.5" barrel at 500yd. A 20" barrel will be only 5MOA wind and 9MOA drop at that range.

Put another way, shooting Mk262 from a 7.5" barrel at 500yd is like shooting a .308 Win at 1000yd. Sure, people do it, but it's pretty damn hard. You'd need to hang a 3' gong or something to hit reliably, which isn't my idea of satisfying shooting at 500, when a decent 20" gun can make headshots reliably at that range.

So, dialing it back to where windage is a more reasonable 4MOA, and drop is a manageable 8MOA, you get 300yd. The trajectory is starting to rainbow, but if you dial that 2 feet of hold-over from your 100yd zero, you can totally make hits on a 6-8" target in less-than-ideal conditions. Pay attention, because you're not exactly going to be smacking that gong with authority - 380ft-lb on a good day.

[domestique]

One major point - I don't know of any suppressor available for a barrel that short, and shooting a 7.5" barrel without a can is going to be like setting off a flash-bang in front of your face. But let's ignore that for now.

As the others have said, accuracy is a non-issue. All other factors being equal, short barrels tend to be more accurate (or at least, more forgiving of a wide range of velocities) due to being relatively stiffer. Velocity is a pretty major issue. You won't get acceptable terminal ballistics any further than you can spit with a barrel that short.

Let's assume you want to get not just a hit, but a hit with a bullet that does something other than pencil through. If you're running Mk262, which fragments down to ~2200 (on a good day), your range will be:

7.5" - 0yd
10.5" - 80
14.5" - 170
16" - 210
20" - 260

That's right - point-blank shots with a pistol-barrel AR will probably just pencil 77gr SMKs right through, even with a very hot load like Mk262. Now, I'm not going to stand at 500yd and let you stick them in me, but it's a poor defensive choice. An expanding 55-65gr bullet would have decent performance at indoor ranges, although those bullets have poor BCs compared to the Mk262's 77gr SMK, so they will die even faster at range.

In summary: If you insist on a 7.5" barrel for defensive uses - shoot 300BLK, or even a pistol caliber. 9mm or .45 would be more effective, and have less recoil and flash. And you could suppress it.

Now, let's just say you want to lob targets onto steel or paper. You just need to stay super-sonic to maintain accuracy. I like to use 1200fps as a good minimum velocity for maintaining accuracy, although SMKs do transition pretty well, so I'll round the range up. Anyway, range to ~1200fps:

7.5" - 500
10.5" - 600
14.5" - 700
16" - 750
20" - 800

Now, note that with a 10mph wind you'll be dialing 8MOA of windage and 22MOA of drop on that 7.5" barrel at 500yd. A 20" barrel will be only 5MOA wind and 9MOA drop at that range.

Put another way, shooting Mk262 from a 7.5" barrel at 500yd is like shooting a .308 Win at 1000yd. Sure, people do it, but it's pretty damn hard. You'd need to hang a 3' gong or something to hit reliably, which isn't my idea of satisfying shooting at 500, when a decent 20" gun can make headshots reliably at that range.

So, dialing it back to where windage is a more reasonable 4MOA, and drop is a manageable 8MOA, you get 300yd. The trajectory is starting to rainbow, but if you dial that 2 feet of hold-over from your 100yd zero, you can totally make hits on a 6-8" target in less-than-ideal conditions. Pay attention, because you're not exactly going to be smacking that gong with authority - 380ft-lb on a good day.

Silencerco Saker: rated to 7"





Some more reasons to avoid a 7.5" 5.56..... go 300blk for PDW size.



Attachment 35901


300BLK with the right load is effective out to 320-360 yards (9 inch barrel).... also less flash and concussion than a 8" 5.56. I personally wouldn't go less than 11.5" for a 5.56 SBR.

An example of the 70gr. TSX: 2,400 FPS out of a 8" 5.56 would yield effective expansion to 200-230 yards. A 11.5" barrel would yield 2,600 fps and reliable expansion to 300 yards...... this is even assuming you can get the 70gr. bullet moving that fast. I was optimistic in my numbers for the 5.56 load as the graphs represent the 62 gr. M855 round.

ETA:

From another thread:

-1800fps for the 70gr TSX
-1900fps for the 55,62 gr TSX
-The "non 5.56" 50gr bullet (handloading component) is also 1900fps
-The 5.56 loading by Black Hills using the 50gr Barnes has an expansion threshold of 2300fps, as it is a tougher design meant for use at close ranges against windshields, etc.
-300 BLK 110gr Blacktip has an expansion threshold of 1300fps. The blue-tip 110gr .308" dia TSX bullet has an expansion velocity of nearly 500fps higher, as it is meant for other cartridges, if you will.

Hope this helps. If anything it proves that you need to know the EXACT bullet beign discussed, and "transposing" expansion velocities doesn't work with the Barnes. It's very very VERY caliber/loading specific.

5.56 barrel lengths with 62gr. M855 "green tip"

www.sadefensejournal.com/wp/?p=1093

Attachment 35902

Attachment 35903

[C4IGrant]

As mentioned, SBR's aren't inaccurate. A good one will shoot 1" or better at 100yds (mine does). With that out of the way, what really matters is bullet selection (assuming you want to kill something). Your bonded/copper bullets are going to give you the most capability out of an SBR. From talking to the owner of Black Hills, the 62gr TSX will open up out to 200yds (from a 10.3" barrel). That is outstanding and really extends the range of SBR.

Some of the best choice for ammo are listed below:

http://www.gandrtactical.com/cgi-bin...tion&key=81265

http://www.gandrtactical.com/cgi-bin...on&key=D556N18



C4

[joshua_capitolarmory]

I've got an extremely accurate 7.5" upper. During a class, I brought a 10.5" upper and was having some issues with it. The 10.5 Barrel ended up being sent back for replacement.

I pulled out my 7.5" and was still able to do just fine due to the 10.5's issues. 200 yard shots were a piece of cake on moving targets, and brought it out to 415 yards. At 300, it's pretty easy to hit steel. Between 300-400 it dropped like a rock. I could do 415 fairly well, just with an insane hold over. Someone is going to have a real bad day if they're 400 yards away and take a 5.56 round, but they would have a bad day with 22LR. It just cripples velocity, in turn the performance of the projectile on impact.

Effective is a relative term. A deer being hit at 400+ out of a 7.5" barrel isn't really ethical in my opinion, but you could probably put it down if you were a good shot.

[K1tt3n5]

As mentioned, SBR's aren't inaccurate. A good one will shoot 1" or better at 100yds (mine does). With that out of the way, what really matters is bullet selection (assuming you want to kill something). Your bonded/copper bullets are going to give you the most capability out of an SBR. From talking to the owner of Black Hills, the 62gr TSX will open up out to 200yds (from a 10.3" barrel). That is outstanding and really extends the range of SBR.

Some of the best choice for ammo are listed below:

http://www.gandrtactical.com/cgi-bin...tion&key=81265

http://www.gandrtactical.com/cgi-bin...on&key=D556N18



C4

Thank you for this info and links. I previously assumed mk262 would be a good choice in my 10.5" sbr, boy was I wrong. Do you still recommend those two rounds for a 14.5" or 16" rifle?

[C4IGrant]

Thank you for this info and links. I previously assumed mk262 would be a good choice in my 10.5" sbr, boy was I wrong. Do you still recommend those two rounds for a 14.5" or 16" rifle?

Those two rounds are good for any length barrel. The longer the barrel, the longer the effective range. I think it is possible that you would the bullet to expand out to 500yds from a 16-18" barrel.



C4

[Watrdawg]

So where does the 50gr TSX fit into this topic?

[domestique]

So where does the 50gr TSX fit into this topic?

I already posted this info above.



Here it is again:

From another thread:

-1800fps for the 70gr TSX
-1900fps for the 55,62 gr TSX
-The "non 5.56" 50gr bullet (handloading component) is also 1900fps
-The 5.56 loading by Black Hills using the 50gr Barnes has an expansion threshold of 2300fps, as it is a tougher design meant for use at close ranges against windshields, etc.
-300 BLK 110gr Blacktip has an expansion threshold of 1300fps. The blue-tip 110gr .308" dia TSX bullet has an expansion velocity of nearly 500fps higher, as it is meant for other cartridges, if you will.

Hope this helps. If anything it proves that you need to know the EXACT bullet beign discussed, and "transposing" expansion velocities doesn't work with the Barnes. It's very very VERY caliber/loading specific.

The 50gr. Black Hills TSX (optimized) would be WORSE out of an SBR (unless you are trying to defeat auto glass) because you're losing 400 fps of distance (in regards to expansion).

Velocity of the 50gr BH. TSX.(optimized)
MV from various barrel lengths
8" = 2634 fps
10.5" = 2749 fps
14.5" = 3105 fps
20" = 3205 fps

[Watrdawg]

So basically the 50gr TSX is a relatively short distance option