Too Short?

[Narco]

New to the forum, found out about this place from Andy @ TT.

I recently put in motion my SBR for a CQB gun, still waiting on my Form 1 (been pending 35 days now) I have a EA lower (made here locally) and a Spikes tactical 7.5" Concussion upper (configuration is still a pistol at this time).

Just curious what some think about a 7.5 for a SBR, I would like to stretch it out to 10.5 but I can drill 8" plates at 100 yds all day with it in its configuration, I just like the ability to have it accessible in my CVPI front seat and to clear doorways easy. What says the hive?

Spikes service has been nothing but exceptional, had an issue with the buffer weights and short stroking at first, Tom just sent me a new Tungsten buffer for shits and giggles, to try out.

[bigcoastie]

I think the biggest thing most people will say is to look at the velocity of a 7.5" barrel. For plinking it doesn't really matter for actual real world use 10.5" + seem to be ideal.

[rob_s]

I think the biggest thing most people will say is to look at the velocity of a 7.5" barrel. For plinking it doesn't really matter for actual real world use 10.5" + seem to be ideal.

That's my take.

.22" hole punch with the 7.5" vs. decent terminal performance out of a 10.5".

[bigcoastie]

Here's some more interesting info about barrel length and velocity as well

Using XM193

7.5" 2364 FPS ... 10.5" 2755 FPS
DIFFERENCE 391 FPS
DIFFERENCE/INCH 130 FPS PER INCH

10.5" 2755 FPS ... 14.5" 2984 FPS
DIFFERENCE 229 FPS
DIFFERENCE/INCH 57 FPS PER INCH

14.5" 2984 FPS ... 16" 3075 FPS
DIFFERENCE 91 FPS
DIFFERENCE/INCH 61 FPS

16" 3075 FPS ... 18" 3245 FPS
DIFFERENCE 170 FPS
DIFFERENCE/INCH 85 FPS

18" 3245 ... 20" 3254 FPS
DIFFERENCE 9 FPS
DIFFERENCE/INCH 4.5 FPS

[Stickman]

I wouldn't go less than 10.5" on my duty weapon, but thats just me. As a city cop, I know that just about everything I do is up close and personal, but I still get calls where I end up on perimeter duty. A long shot for me is going to be 50 yards, but I need to be able to double that to play it safe with the velocity.

I'm not sure where you patrol, or what you consider max realistic range for your district, but make sure you consider it when you figure a barrel length.

[Narco]

I wouldn't go less than 10.5" on my duty weapon, but thats just me. As a city cop, I know that just about everything I do is up close and personal, but I still get calls where I end up on perimeter duty. A long shot for me is going to be 50 yards, but I need to be able to double that to play it safe with the velocity.

I'm not sure where you patrol, or what you consider max realistic range for your district, but make sure you consider it when you figure a barrel length.

I was thinking the same, its urban/rural mixed. Most of the work takes place in urban residential high crime areas, with houses/trailers. I am loaded with TAP.. 50M zero and I have shot IPSC sized steel out to 150 with it..

I will chronograph it this weekend with TAP and XM193 and see the results. I do have a MP15T, but I am turning that into a perimeter gun. 16" with a Burris XTR 1x4 on top..

Of topic if anyone has a "Youth" Stock for a Mossberg 500 lmk.. 12" LOP or shorter would be nice..

[Stickman]

I was thinking the same, its urban/rural mixed. Most of the work takes place in urban residential high crime areas, with houses/trailers. I am loaded with TAP.. 50M zero and I have shot IPSC sized steel out to 150 with it..

I will chronograph it this weekend with TAP and XM193 and see the results. I do have a MP15T, but I am turning that into a perimeter gun. 16" with a Burris XTR 1x4 on top..

Great minds think alike, I built up a perimeter weapon a few years back. The concept of a patrol special weapon was too far outside the box, and it was denied for carry. Its a shame, because I can see a solid need for a weapon like that, especially in some of the larger schools or malls as well as on perimeters.

[rob_s]

You'll also need to take the velocities you get from your chrono testing and compare them to the fragmentation threshold for your ammo.

For the record, all of this is largely academic, but it doesn't mean it's not real.

[Narco]

FWIW.. do you think Mr. Tango/Badguy will know the difference between being shot with a 16" 11" or 7.5" At distances less than 100 yards..

I don't think any of our schools longest hallways are 100 yds. At least last time I walked one a few months back.

To me its more about control, comfortableness, and ease of movement.

So riddle me this... My barrel is a HB Chrome Lined 1:7 5.56 nato.. according to the chart above, I should be hitting 2400fps. +- a few.. Is it that big of a difference?

[rob_s]

It matters the velocity below which the projectile stops behaving as designed. All rounds for "serious use" are designed to mushroom/fragment/deform/whatever. They have to be moving at a speed above a certain velocity to do so. Below that velocity they are just going to travel straight through.

This is how barrel length --> velocity --> effective range.

[Eric]

Although ballistic gelatin is only a medium that is similar to flesh, it's one tool that gives us an idea what's going on. I would contact the manufacturer of your duty ammo to see if they have any ballistic studies they can send you. IIRC FMJ needs at least 2700 FPS to fragment. Ballistic tip and soft point rounds fragment at a lower threshold. Also, ultra short barrels are more likly to be finicky about functioning and the muzzle blast is increased.

[Stickman]

FWIW.. do you think Mr. Tango/Badguy will know the difference between being shot with a 16" 11" or 7.5" At distances less than 100 yards..

Absolutely yes. A 5.56 round that doesn't expand or fragment isn't going to reliably put someone down.

Would you carry a large .22 as a duty weapon?

Of course not, and if you are punking rounds into some POS who just shot an Officer, a homegrown terrorist who has decided to take kids in a school hostage (think Beslan), or any number of situations where putting a guy down is mandatory, you are not going to want him to slip back into an area where there are additional targets of opportunity. What we are looking for in these situations is stopping the threat ASAP, so we need reliable fragmentation from those TAP rounds.

[Narco]

Well, lets just say something is in the works, I can not reveal any details of the operation, only that I shipped my upper back to a particular builder in FL. I have a friend who does photography on an professional level, so I'll get some pics up as soon as it returns.

[Stickman]

Sounds good, I look forward to seeing your end results.

[Narco]

More can be found here Teddy Smith Photography