Welcome! Please take a minute to introduce yourself.

Noob from New England

More
11 years 5 months ago #23775 by Lizardette
Replied by Lizardette on topic Noob from New England
Occasional headless squirrel... :rotfl:

I know what you mean though.

Honestly I was thinking things like opossum, raccoon, skunk, etc.

Back on topic:

Those are some good arguments for a short barrel. Dammit. Now you've got me curious. I need a 600 yard range and someone with a 16" barreled .308 to compete with.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #23777 by OleCowboy
Replied by OleCowboy on topic Noob from New England

Siscowet wrote: A couple of thoughts: One, when it is used repeatedly, a longer barrel of the same diameter will more likely to suffer from oscillation due to heating, which can affect accuracy as much as the 100 fps loss. The velocity loss would most affect bullets after they went subsonic, when yawing would more likely to occur. So you are talking out at the longer ranges. You could argue that a shorter, high mass bull barrel might be just as effective all around. More heat sink mass, and less overall barrel length to oscillate as it warms up. Raley, Colt, BMS, and 11-B, what do you guys think? Also, unless using iron sights, you don't need the extra barrel length to give you a longer, hence more accurate, sighting plane.

Interesting in that you bring this up and I just read this am:

TECHNICAL NOTE 48: THE EFFECTS OF BARREL DESIGN AND
HEAT ON RELIABILITY
BACKGROUND:
The M4 Carbine has developed a reputation for poor reliability. The excessive
malfunction rate of the M4 Carbine is due to physical imbalances in the mechanism itself,
exacerbated by heat. Analysis of the problem requires a good understanding of the carrier
group and barrel of the rifle, and the functions of the cartridge case.
FACTS:
Relation of carrier group design, barrel length, gas port location, and propellant gas
pressure. The distance from the chamber to the gas port, the length of barrel beyond the
port, and the pressure of the propellant gasses determine the amount of energy provided
to the action of the M-16 series rifle.
The heart of the M-16 operating system, the carrier group, was designed to function well
with the original 20 inch long barrel of that rifle. The carrier group and the location of
the gas port were carefully balanced to provide outstanding reliability with the
ammunition that was designed for the M16.
A change in the cartridge (bullet weight or powder), the length of the barrel, or the
location of the gas port along the barrel can substantially change the pulse of gas that
enters the carrier group and drives the rifle action. Short versions of the M16 (including
the M4) suffer from relocation of the gas port and changes in barrel length

www.armalite.com/images/Tech%20Notes/Tec...ility,%20030824….pdf

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #23779 by 13fcolt
Replied by 13fcolt on topic Noob from New England
Shorter barrels tend to have better harmonics, being stiffer than longer barrels of the same profile. Although it's the exception and not the rule, 1000yds has been reached with a 16" barrel, and I'm sure handloads tailored for the task. There are a few videos on youtube, I'll see if I can find them again.

Barrel length effects velocity simple enough, but the way velocity effects accuracy is a bit more involved. The drop through transonic flight causes the bullets to become unstable. Berger has developed a bullet with a redesigned tail that supposedly copes with this. Special projectiles aside, the sweet spot between a long bullet with a high BC that is light enough for high velocity, and still loadable to magazine length poses a certain challenge for us AR shooters. The simplest work around is just have more barrel, if you can live with the downsides. All other things being equal, I would expect a measurable accuracy benefit to having a shorter barrel up to the point that velocity comes into play.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #23788 by Siscowet
Replied by Siscowet on topic Noob from New England

OleCowboy wrote:

Siscowet wrote: A couple of thoughts: One, when it is used repeatedly, a longer barrel of the same diameter will more likely to suffer from oscillation due to heating, which can affect accuracy as much as the 100 fps loss. The velocity loss would most affect bullets after they went subsonic, when yawing would more likely to occur. So you are talking out at the longer ranges. You could argue that a shorter, high mass bull barrel might be just as effective all around. More heat sink mass, and less overall barrel length to oscillate as it warms up. Raley, Colt, BMS, and 11-B, what do you guys think? Also, unless using iron sights, you don't need the extra barrel length to give you a longer, hence more accurate, sighting plane.

Interesting in that you bring this up and I just read this am:

TECHNICAL NOTE 48: THE EFFECTS OF BARREL DESIGN AND
HEAT ON RELIABILITY
BACKGROUND:
The M4 Carbine has developed a reputation for poor reliability. The excessive
malfunction rate of the M4 Carbine is due to physical imbalances in the mechanism itself,
exacerbated by heat. Analysis of the problem requires a good understanding of the carrier
group and barrel of the rifle, and the functions of the cartridge case.
FACTS:
Relation of carrier group design, barrel length, gas port location, and propellant gas
pressure. The distance from the chamber to the gas port, the length of barrel beyond the
port, and the pressure of the propellant gasses determine the amount of energy provided
to the action of the M-16 series rifle.
The heart of the M-16 operating system, the carrier group, was designed to function well
with the original 20 inch long barrel of that rifle. The carrier group and the location of
the gas port were carefully balanced to provide outstanding reliability with the
ammunition that was designed for the M16.
A change in the cartridge (bullet weight or powder), the length of the barrel, or the
location of the gas port along the barrel can substantially change the pulse of gas that
enters the carrier group and drives the rifle action. Short versions of the M16 (including
the M4) suffer from relocation of the gas port and changes in barrel length

www.armalite.com/images/Tech%20Notes/Tec...ility,%20030824….pdf

With the M4 you have a firearm, that in my opinion, should never have been brought out. A 5.56 cartridge with a 14.5 inch barrel does not add up to the man stopping ability needed. Especially when combined with a cartridge(XM855) designed to give greater distance in standard M16A2 20 inch barrels, but not initially designed for use in a weapon with much less barrel. Maybe you vets out there will correct me, but it just doesn't make sense. Reliability aside, it is smaller and lighter, but you pay the price in vastly reduced performance. With the 7.62x51 you have a heck of a lot more wiggle room in terms of energy. A 16 inch barrel still gives you pretty decent performance, and an 18 even more so. Just need to follow MrRaleys advice about having Armalite properly resizing the gas port in the barrel if you go that route.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #23821 by Lizardette
Replied by Lizardette on topic Noob from New England
"Special projectiles aside, the sweet spot between a long bullet with a high BC that is light enough for high velocity, and still loadable to magazine length poses a certain challenge for us AR shooters."

Believe it or not, I actually have an idea regarding this. I love the .308 Winchester cartridge. I do. I think usability of longer VLD type bullets could be improved measurably by going to a slightly shorter case. No need to design a new cartridge. Just chamber a barrel for .300 Savage and throat it appropriately for the longer bullets. Loaded to an equal pressure level, the velocity shouldn't be greatly decreased, even while loading to magazine length. I'm not sure where this idea is going to take me, but I plan on trying it.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #23822 by Siscowet
Replied by Siscowet on topic Noob from New England

Lizardette wrote: "Special projectiles aside, the sweet spot between a long bullet with a high BC that is light enough for high velocity, and still loadable to magazine length poses a certain challenge for us AR shooters."

Believe it or not, I actually have an idea regarding this. I love the .308 Winchester cartridge. I do. I think usability of longer VLD type bullets could be improved measurably by going to a slightly shorter case. No need to design a new cartridge. Just chamber a barrel for .300 Savage and throat it appropriately for the longer bullets. Loaded to an equal pressure level, the velocity shouldn't be greatly decreased, even while loading to magazine length. I'm not sure where this idea is going to take me, but I plan on trying it.

Interesting concept. The .308/7.62x51 was originally made be adapting the 300 Savage case. It was made possible by powder and bullet improvements in the late 40's and early 50's that allowed near 30-06 performance in a shorter case. Now we have had another 50 years of tech improvements, it might be possible to put that performance into something not much bigger than a 7.62x39. The only bugaboo might be chamber pressure. The same amount of energy in a smaller space. Been a lot of efforts in that direction from different angles. The .30 SOCOM, the 6.8mm the 7.62x39 itself, why not try a shortcase .308? It would be an interesting experiment if nothing else.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #23824 by Lizardette
Replied by Lizardette on topic Noob from New England
The 6.5 Creedmoor was what made me think of it. It's essentially and shortened and improved .260 Remington, designed to feed through a magazine even with longer/heavier match bullets.

As far as powders go, Hornady's Superformance powder is a pretty exciting concept. It's supposed to give higher velocities without increased chamber pressures by virtue of an extended period of peak pressure. The company says that it's safe to use in a AR style weapon if (and it's an important "if") it has a rifle length gas system.

Please Log in or Create an account to join the conversation.

More
11 years 5 months ago #23826 by OleCowboy
Replied by OleCowboy on topic Noob from New England

Lizardette wrote: "Special projectiles aside, the sweet spot between a long bullet with a high BC that is light enough for high velocity, and still loadable to magazine length poses a certain challenge for us AR shooters."

Believe it or not, I actually have an idea regarding this. I love the .308 Winchester cartridge. I do. I think usability of longer VLD type bullets could be improved measurably by going to a slightly shorter case. No need to design a new cartridge. Just chamber a barrel for .300 Savage and throat it appropriately for the longer bullets. Loaded to an equal pressure level, the velocity shouldn't be greatly decreased, even while loading to magazine length. I'm not sure where this idea is going to take me, but I plan on trying it.

My fav rd is and has always been the .270 Win. IMO is one of the best overall cartridge when you view it from a lot of viewpoints. I would give great marks for a NATO rd. That said in the same thinking I see the 6.8 as the most overhyped and disappointing rds maybe in my lifetime... But then the purpose of the rd was to make a hand full of folks very rich, nothing else. And on that it failed.

That said I call the .270 the 'just right' cartridge, neither too cold nor too hot, just right. It will do almost anything asked of it in N America and do it quite well. I see the 5.56 as 'adequate' in the M 16 config. But introduce it into the 14.5" form factor and its weaknesses are really magnified. This may beg the question...how long a bbl on a combat weapon. I can tell you for a fact the M 16 and its 20" is too long in all but big spacing of trees in all but areas like deep S Texas, Arizona desert etc. I think from my military Infantry viewpoint that 16" meets most of the combat soldiers requirements...

Please Log in or Create an account to join the conversation.