SPR / CQB one or two builds?

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05-07-2008, 11:58
Cameron

AS

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05-07-2008, 13:25
Atrain

Very nice!
05-08-2008, 18:05
John Moses Browning

Wow, some great looking firearms you have there, that certainly took some money to complete.

Just one question, why didn't you go for the standard length barrel for your long-range version?
05-08-2008, 20:23
DocMedic

Quote:

Originally Posted by Cameron

You mean a 18" or 20" barrel?

They extra length doesn't provide an advantage for accuracy and the velocity loss isn't really important either.

Cameron

I disagree... M4 at 300 meters drops 4inches more then a M16. Though I like your build.
05-08-2008, 20:36
Sucka

Very nice rifles.

The line on your BUIS; so that you tighten it to the same spot each time, or monitor if it has loosened itself? Never noticed that, just curious.
05-08-2008, 22:00
sniper7

very sweet
05-08-2008, 23:57
John Moses Browning

Quote:

Originally Posted by Cameron

You mean a 18" or 20" barrel?

They extra length doesn't provide an advantage for accuracy and the velocity loss isn't really important either.

Cameron

The longer the barrel, the more accurate, the longer the range, and subsequently more lethality.

.223/5.56 is completely velocity dependent, without it, it doesn't fragment and consequently loses it's effectiveness. If I recall correctly, 5.56 has to be moving at about 2900-3000fps in order to fragment. Most carbine length barrels produce that 2900-3000fps at the muzzle, while a standard 20'' barrel does about 3100-3200.

All that extra longer range performance is worth it to me personally, even at the consequence of adding four inches to the barrel.

But to each his own, they're still nice guns either way you cut it.
05-09-2008, 14:21
Ah Pook

Nice!

All I can say is where's the light on the Colt CQB? :D
05-09-2008, 16:54
John Moses Browning

Quote:

Originally Posted by foxtrot

2700 fps is about the threshold for fragmentation, but it is wholly dependant on the round. Not all 193's or SS109's fragment at all. Bullets without a cannulure probably have a very reduced chance of breaking up.

SS-109's *do* fragment like the M-193's in spite of having the penitrator.

In terms of ballistics, a M4 shooting 193's will drop below the 2700fps line before 200 yards, and a M4 shooting ss109's will drop below the 2700 fps line before 100 yards (usually about 40 yards if I remember).

*but* the chance of you having to pick off a person at 500 yards with your 16" AR is less than the chance of you winning powerball, so I'd start buying tickets. [Beer]

There is still supersonic shock even if they aren't fragmenting anyway, and for better performance you can use a vmax for all sorts of game to greatly improve the "squishy" effect. Military can't use rounds like the V-MAX so thats why fragmentation is more of an issue.

I was close, only 200fps off. [Coffee]

You are right though, 5.56 is a short range round by all means. Sure you can hit something at 500 yards with one, but it's effective range envelope is probably about 200-250 yards if you want to stop a man.

Either way, there's no denying a longer barrel means improved long range performance, more accuracy, etc.
05-09-2008, 22:08
John Moses Browning

Quote:

Originally Posted by Cameron

I would have to disagree with the accuracy part. Accuracy is NOT improved by simply lengthening the barrel, in fact a short(er) barrel is relatively stiff(er) than a long(er) one, and is therefore inherently more accurate. Seems counter-intuitive doesn't it? Consider that the above Lothar Walther 16" barrel is capable of sub 0.5MOA groups and we can see that accuracy isn't diminished by a 16" barrel.

In regard to velocity the trade off is of much less consequence when you are using the heavier rounds available outside of 55gr and 62gr mil loads. 69-77gr loads are less dependent on velocity for fragmentation due to thinner jackets and greater mass, than the M193 and M855, they also retain more energy at longer ranges and are also less effected by wind.

Ask yourself why they (military Marksmanship Units) would use an 18" barrel on the Mk12 SPR rather than a 20" or a 22"??

Who are we kidding with fragmentation thresholds though, it is not likely that you will be shooting anyone, let alone someone at 200+ yards!

If I personally want to reach out any further I would use my .308... Oh God it only has a 20" bbl [Help]

Regards,
Cameron

Like I said before, to each his own. There's no convincing me a shorter barreled 5.56 is better than a longer barreled one, and vice versa for you my friend.

Concerning the MK12 SPR, from what I've just researched about it, the military was trying to make a compromise between maneuverability and weight, with accuracy and distance. So what better than an in-the-middle-of-the-road approach landing at 18''? Two more than a 16'', two less than a 20''.

Just remember, we're all on the same side here, there's no need to patronize me. .
05-10-2008, 00:38
DocMedic

Ok, you guys have way to much free time to look this stuff up. So let me dumb it down for ya

Pull trigger
Gun go Boom
Bullet miss target
Aim Gun higher
Pull trigger
05-10-2008, 05:47
Hoser

Quote:

Originally Posted by Cameron

makes you wonder how they really came up with the length at all...

They took a look at competitive shooters equipment and a lot of guys in the SPR program were/are 3-gun shooters. The AMU had a lot of input.

18-20 inch barrels are the norm when targets are past hallway distance.