15.7 inch vs 20 inch Diemaco

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ricohman

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I am going to buy one of these with the green furniture. Having never shot one I can't decide what length to order. My boy is an active CF member and he is buying the 20 as that is what he was issued and trained with.
But for my use I just don't know. To me, the 20 almost seems like a carbine size to begin with. I like the looks of the 15.7 and I'm aware of the reduced muzzle velocity and sight picture.
But which would be better in hand? I'd probably buy an optical sight with either.
 
TDC said:
Short barrels are lighter, stiffer and obviously shorter making them easier to swing.

Tdc
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That would be the case with any carbine ...except the C8A3. It is ridiculously heavy. OP, If you're set on a Colt Canada, I'd get the 20". With a collapsed stock, it's as short as the carbine with the stock extended.
 
Depends what you will be using it for.

I got the 15.7 because I don't plan to go pass 200 Yards, And It looks better IMHO...

By the way, Just looked at my Visa bill and Korth only charged 5% tax... WoOt WoOT
 
The 20 makes 3100 fps or 946 m/s with 62 gr. The 15.7 makes 2900 or 890 with the same ammo.

The 20 has a "government profile" light under the hand guards barrel.

The 15.7 has a heavy sleeved barrel, about the same size as the M4 SOCOM barrel.

They both weigh close to 3kg. (20 - 3.31 kg and 15.7 - 2.97 kg)

The carbine is typically more accurate than the rifle because of the heavy barrel out to about 300 m. Beyond that the rifle's velocity has an advantage with wind and stability.

The carbine will also make better hot groups because of the extra thermal mass and the more rigid barrel.
 
I am with Matt except if you want to shoot in the US. I had ATRS make me this custom with a S/S 16.5 match barrel.
ATRS.jpg

Henry
 
TDC said:
The loss in velocity from a 20" to a 16" is less than 4%. Short barrels are lighter, stiffer and obviously shorter making them easier to swing.

Tdc
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I'm familiar with the merits of short barrels; I just don't get the appeal. I would take a rifle over a carbine any day of the week. The US shoots thing is also another good reason to go for 20".
 
That extra 4" of barrel gives a bit velocity to make the 5.56mm FMJ fragment reliably upon impact at 150m. For combat purpose, I would choose nothing less than 14.5" or velocity at muzzle no less than 2850 fps. The rifle/carbine must capable to maintain 2700+ fps at 50m at least. For range toy I don't mind any barrel length, I love em all.
 
Matt K said:
The 20 makes 3100 fps or 946 m/s with 62 gr. The 15.7 makes 2900 or 890 with the same ammo.

The 20 has a "government profile" light under the hand guards barrel.

The 15.7 has a heavy sleeved barrel, about the same size as the M4 SOCOM barrel.

They both weigh close to 3kg. (20 - 3.31 kg and 15.7 - 2.97 kg)

The carbine is typically more accurate than the rifle because of the heavy barrel out to about 300 m. Beyond that the rifle's velocity has an advantage with wind and stability.

The carbine will also make better hot groups because of the extra thermal mass and the more rigid barrel.
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That's great info Matt, thank you for that.

I think what everyone also wants to know is what the deal is with the sudden price drop from your distributor, what they will do for those who paid full price Vs those who bought one today.

I plan on asking the same question in person at SecureTech in November, so if you don't/can't share the info today, hopefully you'll be able too in a couple of months.

Thanks
 
BenL said:
That's great info Matt, thank you for that.

I think what everyone also wants to know is what the deal is with the sudden price drop from your distributor, what they will do for those who paid full price Vs those who bought one today.

I plan on asking the same question in person at SecureTech in November, so if you don't/can't share the info today, hopefully you'll be able too in a couple of months.

Thanks
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Good question

I have yet to hear back from Korth or CC. Its clear these were priced wrong at start

Interesting comment on barrel thermal mass and rigidness etc

In the end I guess its all about how fast you pull the trigger

Shooting is a subject with many variables indeed
 
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Matt K said:
The 20 makes 3100 fps or 946 m/s with 62 gr. The 15.7 makes 2900 or 890 with the same ammo.

The 20 has a "government profile" light under the hand guards barrel.

The 15.7 has a heavy sleeved barrel, about the same size as the M4 SOCOM barrel.

They both weigh close to 3kg. (20 - 3.31 kg and 15.7 - 2.97 kg)

The carbine is typically more accurate than the rifle because of the heavy barrel out to about 300 m. Beyond that the rifle's velocity has an advantage with wind and stability.

The carbine will also make better hot groups because of the extra thermal mass and the more rigid barrel.
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Thanks for this info.
I think the 15.7 in green will be my choice. This way we can have one of each in the house.
 
That's great info Matt, thank you for that.

I think what everyone also wants to know is what the deal is with the sudden price drop from your distributor, what they will do for those who paid full price Vs those who bought one today.

I plan on asking the same question in person at SecureTech in November, so if you don't/can't share the info today, hopefully you'll be able too in a couple of months.

Thanks
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Yes please. An answer either way would be appreciated (I also haven't heard anything back from Colt Canada or Korth since e-mailing them early last week). Thank you in advance.
 
Can anyone answer what is the difference between a 15.7" and a 16" barrel?. I realize the size difference but is there a practical / tactical / accuracy difference?
 
Jmac604 said:
Can anyone answer what is the difference between a 15.7" and a 16" barrel?. I realize the size difference but is there a practical / tactical / accuracy difference?
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The 16" barrel is US legal. Otherwise there is no measurable difference in performance between the two.

EDIT: PLEASE DISREGARD. GOT SCHOOLED BY MATT K.
 
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Blastattack said:
The 16" barrel is US legal. Otherwise there is no measurable difference in performance between the two.
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This is also just not true, there are very definitive and measurable results between the two. Nor is it that true that we don't know how to measure barrels.

Small arms barrels have a number of different nodes of vibration. These vibrations cause the muzzle to move. If you shorten a barrel 1 mm at a time and graph the accuracy, results vary in a pattern of larger and smaller groups. The smaller group sizes along that graph are the accuracy nodes.

When you combine the accuracy nodes, with customer requirements, functional requirements such as dwell time and terminal requirements such as stability and velocity, you get what we found to be the ideal carbine length - 15.7 inches.

This is not an inexpensive test to conduct, as you might imagine. This required firing thousands of rounds in a number of samples to be statistically relevant. Further, the C8 has a choke hammer forged into it to improve accuracy and barrel wear. That means this was not a hack saw test, but that each set of test barrels needed to be hammer forged specifically for a pre-determined length.

15.7 inches (as measured from the breech face to the muzzle) is one of the accuracy nodes. 16" is not an accuracy node (though it may be for some steel and some profile), it is an arbitrary legal requirement in the US just as the Canadian 18" length restriction has nothing to do with accuracy or function. With the flash hider, the barrel is just slightly over 17". I suspect the M203A1 sleeve also enhances accuracy just as barrel tuning weights have an effect on group size.

These rifles are not permitted to be sold to the US, nor is it legal to export them because of US export and import laws and our licence agreement with the US state depts. The lengths have nothing to do with US laws. The barrel length was determined exclusively based on performance for a military customer requirement.

Cheers,

Matt
 
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