Why did the military go with the 10.5 bbl over the 11.5 bbl?

[ARCHIVED THREAD] - Why did the military go with the 10.5 bbl over the 11.5 bbl?

Posted: 9/7/2010 10:06:10 AM EDT

I have always wondered why the MK18 used a 10.5 bbl and continues to use the 10.5 bbl after the "revision", when studies show that 10% increase to the 11.5 barrel will give 40% more dwell time thus making it easier on the BCG and giving it a boost to velocity.

Posted: 9/7/2010 10:07:52 AM EDT

[#1]

Quoted:

I have always wondered why the MK18 used a 10.5 bbl and continues to use the 10.5 bbl after the "revision", when studies show that 4% increase to the 11.5 barrel will give 40% more dwell time thus making it easier on the BCG and giving it a boost to velocity.

The original MK18 uppers were from cut down 14.5" M4 barrels with the accompanying M4 notch, cutting down behind the notch will yield a 10.3/10.5" barrel (I forget which).

Posted: 9/7/2010 10:09:36 AM EDT

[#2]

Because....... this one goes to 11.... point five?

Posted: 9/7/2010 10:28:53 AM EDT

[#3]

Quoted:
Because....... this one goes to 11.... point five?

I'm just wondering if there was a reason I didn't know about on why they chose 10.5 over 11.5 for there cqb role. I use 10.5 for work but wouldn't mind an extra inch if it increased reliability etc

Posted: 9/7/2010 10:30:41 AM EDT

[#4]

Quoted:

Quoted:
Because....... this one goes to 11.... point five?

I'm just wondering if there was a reason I didn't know about on why they chose 10.5 over 11.5 for there cqb role. I use 10.5 for work but wouldn't mind an extra inch if it increased reliability etc

Wouldn't we all.

Posted: 9/7/2010 10:30:47 AM EDT

[#5]

16.0 = legal
15.9 = 10 years, $250,000 fine.

Park on a Driveway, drive on a Parkway, etc.

Timeless questions for the Ages...

Posted: 9/7/2010 10:31:32 AM EDT

[#6]

Quoted:

Quoted:
Because....... this one goes to 11.... point five?

I'm just wondering if there was a reason I didn't know about on why they chose 10.5 over 11.5 for there cqb role. I use 10.5 for work but wouldn't mind an extra inch if it increased reliability etc

I think somebody here just missed a Spinal Tap joke ...

Posted: 9/7/2010 10:32:49 AM EDT

[#7]

Quoted:
16.0 = legal
15.9 = 10 years, $250,000 fine.

Park on a Driveway, drive on a Parkway, etc.

Timeless questions for the Ages...

15 will get you 20

Posted: 9/7/2010 10:36:27 AM EDT

[#8]

Of all the 10.5's I have owned, all have functioned 100%. Same with 11.5.
They know how to make an M16 run, it only requires a new buffer, gas port mod, etc
I am sure they are using 77gr bthp or some specialty round that works well with a short barrel.
M193 is going to be the same in a 11.5 or 10.5 Its under 2700 fps no matter what.

I alway though it was 10.5 becuase the gun was used exclusively from inside vehicles and on aircraft carriers.

Posted: 9/7/2010 10:44:34 AM EDT

[#9]

Quoted:

Quoted:

Because....... this one goes to 11.... point five?

I'm just wondering if there was a reason I didn't know about on why they chose 10.5 over 11.5 for there cqb role. I use 10.5 for work but wouldn't mind an extra inch if it increased reliability etc

10.3" actually, and that's the shortest you can make the barrel while retaining the bayonet lug and flash suppressor.

Posted: 9/7/2010 10:46:32 AM EDT

[#10]

Nope.

Posted: 9/7/2010 10:48:15 AM EDT

[#11]

...10.5 just looks cooler bro.

Posted: 9/7/2010 10:49:22 AM EDT

[#12]

Quoted:

Quoted:
Because....... this one goes to 11.... point five?

I'm just wondering if there was a reason I didn't know about on why they chose 10.5 over 11.5 for there cqb role. I use 10.5 for work but wouldn't mind an extra inch if it increased reliability etc

10.3" actually, and that's the shortest you can make the barrel while retaining the bayonet lug and flash suppressor.

Well, no, not really. There are other ways. Granted its custom and still in the works..

Its a 10" heavy barrel with an ARMS 41 FSB.. It is going to have a bayonet lug where the swivel should be.
The bayonet will have a full length handle and custom hilt, and will fit around a Noveske KX3.
I think the upper should be named the piggy-stick. Give me a few days and its done.

Posted: 9/7/2010 10:52:19 AM EDT

[#13]

Quoted:

Its a 10" heavy barrel with an ARMS 41 FSB.. It is going to have a bayonet lug where the swivel should be.
The bayonet will have a full length handle and custom hilt, and will fit around a Noveske KX3.

jhud I seem to recall that PK Firearms was selling a Sabre Defence upper in exactly the configuration you describe, except that it had a quad rail on it. From memory:

- Sabre Defence upper receiver
- Sabre Defence 10.5" barrel
- Noveske KX3 Flaming Pig
- Daniel Defense 7.0 Lite quad rail
- ARMS #41 folding front sight/front sight base

This was several months ago (during the post-election rush) but I think PK wanted $800 for it. You may want to ping them and see if they can build you the upper instead of going the "custom" route.

Posted: 9/7/2010 10:52:21 AM EDT

[#14]

Quoted:
Of all the 10.5's I have owned, all have functioned 100%. Same with 11.5.
They know how to make an M16 run, it only requires a new buffer, gas port mod, etc
I am sure they are using 77gr bthp or some specialty round that works well with a short barrel.
M193 is going to be the same in a 11.5 or 10.5 Its under 2700 fps no matter what.

I alway though it was 10.5 becuase the gun was used exclusively from inside vehicles and on aircraft carriers.

And ofcourse all the cool SF kids use them :)

Posted: 9/7/2010 10:52:26 AM EDT

[#15]

That's all fine and good, but in the .mil world 10.3" is the shortest barrel length they could use that allows them to retain the stock FSB and flash suppressor.

Posted: 9/7/2010 10:53:26 AM EDT

[#16]

Quoted:

Quoted:

Because....... this one goes to 11.... point five?

I'm just wondering if there was a reason I didn't know about on why they chose 10.5 over 11.5 for there cqb role. I use 10.5 for work but wouldn't mind an extra inch if it increased reliability etc

Wouldn't we all.

Nah.

Posted: 9/7/2010 10:53:54 AM EDT

[#17]

The XM177-E2 I was issued back in the 1978 was not "cut down" from a 14.5. 14.5 were not around then - so much for that theory.

Prib

Posted: 9/7/2010 10:53:56 AM EDT

[#18]

Quoted:

M193 is going to be the same in a 11.5 or 10.5 Its under 2700 fps no matter what.

M193 was over 2900 FPS in an 11.5" barrel in our tests last weekend.

http://www.ar15.com/forums/topic.html?b=3&f=118&t=509733

Posted: 9/7/2010 10:59:52 AM EDT

[#19]

Quoted:
The XM177-E2 I was issued back in the 1978 was not "cut down" from a 14.5. 14.5 were not around then - so much for that theory.

Prib

The question is on the Mk18, not the old XM177.

Posted: 9/7/2010 11:00:36 AM EDT

[#20]

Quoted:
The XM177-E2 I was issued back in the 1978 was not "cut down" from a 14.5. 14.5 were not around then - so much for that theory.

Prib

Didn't they start by cutting the 20" bbl in half, and found that 10" was not so good, then they worked their way up to 11.5 for the XM series.
But what the OP was asking about is a current model used by the Navy, I can see Crane shortening the M4 bbl for that purpose.
So, uhm, totally different theories, huh?

Posted: 9/7/2010 11:01:51 AM EDT

[#21]

What 45FMjoe said.

Go to Knob Creek or any other shoot and you'll find the 10.25 (10.3) runs better
full auto than the 11.5 does. This may have something to do with it, too.

Posted: 9/7/2010 11:06:45 AM EDT

[#22]

Quoted:

Quoted:

Its a 10" heavy barrel with an ARMS 41 FSB.. It is going to have a bayonet lug where the swivel should be.
The bayonet will have a full length handle and custom hilt, and will fit around a Noveske KX3.

jhud I seem to recall that PK Firearms was selling a Sabre Defence upper in exactly the configuration you describe, except that it had a quad rail on it. From memory:

- Sabre Defence upper receiver
- Sabre Defence 10.5" barrel
- Noveske KX3 Flaming Pig
- Daniel Defense 7.0 Lite quad rail
- ARMS #41 folding front sight/front sight base

This was several months ago (during the post-election rush) but I think PK wanted $800 for it. You may want to ping them and see if they can build you the upper instead of going the "custom" route.

Neat..
Mine will have an ARMS #50 SIR rail system.... In fact, ARMS parts are used everywhere possible.
The key point of my build is the relocated bayonet lug and custom M7 bayonet

Posted: 9/7/2010 11:07:50 AM EDT

[#23]

Quoted:
Neat..
Mine will have an ARMS #50 SIR rail system.... In fact, ARMS parts are used everywhere possible.

Why?

Posted: 9/7/2010 11:09:55 AM EDT

[#24]

Quoted:

Quoted:

M193 is going to be the same in a 11.5 or 10.5 Its under 2700 fps no matter what.

M193 was over 2900 FPS in an 11.5" barrel in our tests last weekend.

http://www.ar15.com/forums/topic.html?b=3&f=118&t=509733

Ive chrono'd IMI M193 from a bushmaster 11.5 1/7 at 2575 fps That was in the summer time and in Mississippi

2900 sounds too good to be true.

Quoted:

Quoted:
Neat..
Mine will have an ARMS #50 SIR rail system.... In fact, ARMS parts are used everywhere possible.

Why?

I am a professional.

Nah, I just like their products and the free swag has something to do with it.
The weight too.. I shoot automatic ALOT. it helps with recoil.
And heat.. The SIR system with the heatshield liner keeps it cooler than James Dean.

Posted: 9/7/2010 11:13:01 AM EDT

[#25]

Quoted:

Quoted:

M193 is going to be the same in a 11.5 or 10.5 Its under 2700 fps no matter what.

M193 was over 2900 FPS in an 11.5" barrel in our tests last weekend.

http://www.ar15.com/forums/topic.html?b=3&f=118&t=509733

Ive chrono'd IMI M193 from a bushmaster 11.5 1/7 at 2575 fps That was in the summer time and in Mississippi

2900 sounds too good to be true.

We kept running additional strings over the chronograph. We were surprised, too.

But every other load we ran gave valid information, the performance delta between the 11.5" and the 14.5" was consistent across different 5.56 loads, and the XM193 test was completely repeatable. So I just reported the results we got.

Posted: 9/7/2010 11:14:13 AM EDT

[#26]

Quoted:
What 45FMjoe said.

Go to Knob Creek or any other shoot and you'll find the 10.25 (10.3) runs better
full auto than the 11.5 does. This may have something to do with it, too.

Any reason why?

Posted: 9/7/2010 11:16:27 AM EDT

[#27]

Quoted:

Quoted:
What 45FMjoe said.

Go to Knob Creek or any other shoot and you'll find the 10.25 (10.3) runs better
full auto than the 11.5 does. This may have something to do with it, too.

Any reason why?

Less dwell time

Posted: 9/7/2010 11:20:51 AM EDT

[#28]

Quoted:
Neat..
Mine will have an ARMS #50 SIR rail system.... In fact, ARMS parts are used everywhere possible.
The key point of my build is the relocated bayonet lug and custom M7 bayonet

If you shoot a lot of full auto maybe you'd consider ditching the KX3 and substituting a suppressor-compatible flash hider/muzzle brake instead? Those 10.5" barrels are LOUD!

If you decide to go the suppressor route you might want to check out a thread in Major Malfunction's forum about erosion to blast baffles caused by short barrels. Were I to run a suppressor on a 10.5" 5.56mm barrel I'd definitely go for a suppressor-compatible muzzle brake (not flash suppressor).

Posted: 9/7/2010 11:21:55 AM EDT

[#29]

Quoted:

Quoted:
What 45FMjoe said.

Go to Knob Creek or any other shoot and you'll find the 10.25 (10.3) runs better
full auto than the 11.5 does. This may have something to do with it, too.

Any reason why?

Less dwell time

Posted: 9/7/2010 11:38:57 AM EDT

[#30]

Quoted:
16.0 = legal
15.9 = 10 years, $250,000 fine.

Park on a Driveway, drive on a Parkway, etc.

Timeless questions for the Ages...

You didn't read the OP at all did you?

Posted: 9/7/2010 11:41:29 AM EDT

[#31]

Quoted:

Quoted:
Neat..
Mine will have an ARMS #50 SIR rail system.... In fact, ARMS parts are used everywhere possible.
The key point of my build is the relocated bayonet lug and custom M7 bayonet

If you shoot a lot of full auto maybe you'd consider ditching the KX3 and substituting a suppressor-compatible flash hider/muzzle brake instead? Those 10.5" barrels are LOUD!

If you decide to go the suppressor route you might want to check out a thread in Major Malfunction's forum about erosion to blast baffles caused by short barrels. Were I to run a suppressor on a 10.5" 5.56mm barrel I'd definitely go for a suppressor-compatible muzzle brake (not flash suppressor).

I have a tac-16.. honestly it doesnt do anything for me. The length and weight is not fun. Gas in yo face, and cleaning... Not fun.

The only time I use it is at the hunting camp, if I want to show off or something.

The Kx3 vs A1 flashhider... That test I have done. I swapped from the Kx3 to an A1 tipped 10" upper. The hawt college age girls in the booth next to me pranced off holding their ears when the mag dumps started. Funny part is they had plugs in. They could handle the sound from the Kx3 but not the A1.
It is better to test everything on hot college girls....