15.7 inch vs 20 inch Diemaco

They can't be sold or exported to the US.

As far as a temporary export, I just don't know. It seems that it should be OK, but I've never asked. I'll see what I can find out.
 
Jmac604 said:
"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"

Matt..thanks for the info....so barrel whip is a large factor in AR accuracy? Is it the most important factor? I was under the belief that the shorter barrels didn't suffer enough to make a difference unlike a 24" hunting barrel..
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Came across this, good info

From the moment that trigger is pressed and the firing pin strikes the primer until the bullet leaves the muzzle, a series of many vibrational impulses begin in the rifle, all of which are transmitted to the barrel in various magnitudes. These include such minor things as; the trigger sear releasing the firing pin, the firing pin moving forward, striking the primer, and the cartridge being moved forward. The powder then begins to ignite, and the bullet starts moving forward and engages the rifling. Because of the twist of the rifling, the bullet while it is being propelled forward, begins to spin imparting a small but measurable torque, but more importantly as it traverses the barrel it also sets up a circular vibrational pattern, or arc. The heat of the burning powder along with the pressure wave generated by the expanding gasses start another vibrational pattern that is induced into the barrel. All of these movements cause the barrel to stress and vibrate with a number of different harmonic patterns which if not controlled by some means cause each projectile to leave the muzzle at a slightly different point in the vibrational arc. Some people speak about the "whip" of the barrel, which would imply to some, that the barrel simply vibrates up and down like a buggy whip. Although there are some of the vibrations that are traveling in this direction, the main vibrations are circular. If this were not true, then a 3 shot group from a rifle would always be in a vertical string. This would be because, one would leave at the bottom of the "whipping action", one would leave from the center and one from the upper travel of the "whip". As we all know this seldom occurs, and if it does, it is usually caused by the barrel being under a heavy stress, such as way to much pressure exerted against it, caused by improper bedding, usually of the barrel. Most 3 shot groups you will see will be virtually triangular in shape, this is caused because as the barrel vibrates through its "circular arc" one bullet leaves the muzzle at say 12 o’clock, another at say 4 o’clock and the third at maybe 8 o’clock. The larger the arc of the barrel, the less accurate the rifle will be, and the larger the triangle. As a rule the less mass a barrel has, (the thinner) the more it is affected by the vibrations, this is the reason that a "heavy" barrel seems to shoot more consistently than a sporter barrel, and is also easier to tune. A shorter barrel of the same diameter will also have less amplitude to its arc of movement. As you tune the barrel with the Accurizer, what you are doing is changing the vibrational length of the free floated forward end of it, causing the vibrational arc, or circular vibrations of the barrel to get smaller and smaller. As the arc gets smaller the groups get tighter. Even though the bullets may still be leaving the muzzle at 12, 4, and 8 o’clock, the diameter of the arc has been lessened, so the triangle gets smaller. Until the past couple of years, when reliable barrel vibrational control devices came upon the scene, virtually the only way to control these barrel vibrations that affected the rifles’ accuracy was to custom load the ammunition until a correct combination of cases, bullets, primers, powders, seating depths and etc. could be found that would allow that particular rifle to shoot good tight consistent groups. Now however with the use of the SmartStock, it is no longer necessary for the average shooter to go to these lengths to have the accuracy previously attributed only to hand loaded ammunition. As long as you are using well made ammunition, that is consistent, whether it is factory or handloads, you can simply tune your rifles’ barrel to the ammunition of your choice.
 
Matt K said:
There is no MILSPEC mid-length system. To keep the logistics simple, there are as few parts as possible. I could get parts for my C8 at nearly any FOB or base in Afghanistan. An M4 gas tube will work just fine. The rest of the military world uses carbine length tubes, hand guards and accessories.

I have a few myself, and while they are nice, the C8's are the most reliable and accurate rifles in test after test. The improved chamber and the other changes we made have a greater effect on system reliability than anything like that. So for us, the mid-length was a solution with no real problem.

That said, if a military customer asked for it, we could do it.
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Reliability compared to what? A mid length gas system? What was it compared to? And what improvements were made to the chamber? I was aware of the barrel length and it being chf as being different but wasnt aware the chamber was different
 
The barrel "choke" is a manufacturing characteristic of the cold hammer forging process using a rotary forge. All the CHF barrels are like that, unless the manufacturer cuts the barrels. There is a paper out there on the CHF process if you google foo is strong.
 
r34skyline said:
Reliability compared to what? A mid length gas system? What was it compared to? And what improvements were made to the chamber? I was aware of the barrel length and it being chf as being different but wasnt aware the chamber was different
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Reliability compared to everything. We have participated in the toughest military trials against all other MILSPEC competitors in all the worst conditions and we win. We don't always get the contract and we can't sell to everyone.

Between Colt and Colt Canada we have fired 30 billion rounds through our weapon systems. We know what works and what doesn't. We have achieved a level of system reliability that makes the Canadian made rifles the choice for numerous SF units that could have anything they want.

The rumour that expansion and bleed off gas systems are unreliable is just that - a rumour. The Colt M4 made to the US TDP was four times more reliable than the standard required. The Colt Canada C8 made with the Canadian TDP is more expensive and produced in vastly smaller quantities and meets or exceeds a much higher standard. Every lot of rifles has ten randomly chosen by the government inspector for normal production endurance testing. Each rifle fires 6,000 rounds, half automatic and half semi. The BCG can be lightly lubricated every 2,500 rounds and no other maintenance. We see ZERO stoppages. Design testing goes much further.

The carbine chambers are improved with slightly larger dimensions and some other specifications have been upgraded. These chambers have been in service for decades and are fully certified with all NATO ammunition. The details are proprietary and patented.

There is no rifle on any battlefield that I would drop a C8 to pick up.
 
greentips said:
The barrel "choke" is a manufacturing characteristic of the cold hammer forging process using a rotary forge. All the CHF barrels are like that, unless the manufacturer cuts the barrels. There is a paper out there on the CHF process if you google foo is strong.
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You realize that a blank comes out of the GFM - the chamber is in it already - but the barrel does need to get cut and finished to length...

That area has been cut or profiled down past when the barrel is threaded.
 
KevinB said:
You realize that a blank comes out of the GFM - the chamber is in it already - but the barrel does need to get cut and finished to length...

That area has been cut or profiled down past when the barrel is threaded.
Click to expand...

The choke and barrel length is pre-determined before hammer forging begins. The only part of the muzzle and choked area that is cut is the crown.
 
Matt K said:
Reliability compared to everything. We have participated in the toughest military trials against all other MILSPEC competitors in all the worst conditions and we win. We don't always get the contract and we can't sell to everyone.

Between Colt and Colt Canada we have fired 30 billion rounds through our weapon systems. We know what works and what doesn't. We have achieved a level of system reliability that makes the Canadian made rifles the choice for numerous SF units that could have anything they want.

The rumour that expansion and bleed off gas systems are unreliable is just that - a rumour. The Colt M4 made to the US TDP was four times more reliable than the standard required. The Colt Canada C8 made with the Canadian TDP is more expensive and produced in vastly smaller quantities and meets or exceeds a much higher standard. Every lot of rifles has ten randomly chosen by the government inspector for normal production endurance testing. Each rifle fires 6,000 rounds, half automatic and half semi. The BCG can be lightly lubricated every 2,500 rounds and no other maintenance. We see ZERO stoppages. Design testing goes much further.

The carbine chambers are improved with slightly larger dimensions and some other specifications have been upgraded. These chambers have been in service for decades and are fully certified with all NATO ammunition. The details are proprietary and patented.

There is no rifle on any battlefield that I would drop a C8 to pick up.
Click to expand...


Is this an improvement from the c7 rifle chamber?

So these trials that you guys crushed was the c7 in any of them? How does the 20" compare? I am reading high praise for the c8 but nothing about the c7.
 
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