Because NOBODY makes what i want. Wes at MSTN had sold several 17" guns with rifle gas....it works.
Moving along, thanks for the tip to nordic, i hadn't looked at them yet.
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A guy on TOS cut a rifle barrel flush with the FSB to get rid of damage done to the bore and the rifle operates fine, even when shot hard. Dwell time* has nothing to do with how the rifle runs or BCG speed. It's "blow down" time, how long the pressure stays up in the rifle after the bullet uncorks the muzzle, that's important. I would agree that a 17" barrel with a rifle length gas system would be less forgiving, but with a competition rifle, shooters usually tune the rifle/ammo combination for best performance and stay with the same ammo
*Dwell Time as defined on this website, the time it takes the bullet to travel from the gas port to the muzzle. The difference in time between is measured in less than one millionth of a second and as the bullet has cleared the muzzle before the gases pressurize the BCG, the time the bullet spends in the bore between port & muzzle has no affect on rifle function
I've discovered that if no one makes what you want.... There is USUALLY a reason for that. You just don't know it or don't want to believe it.
I don't think Noveske ships any 18" with rifle length anymore just intermediate length similar to KAC... So if 18" has issues for those two companies why would you think 17" is a good idea?
You don't seem to actually have a real understanding of ports and dwell and what makes an AR work from a manufacturing perspective, and in this thread people are telling you there are better more reliable and less complex solutions. I bet I know how this will end.
I bet you don't know what you don't know. It's ironic that you mention Noveske, since he is the one making Wes's 17" rifle gas system barrels. ;) check Wes's face book page.
Nobody made a 14.5" middy gas popular until BCM brought it out of the shadows. Even then, they said it was going to be too finicky. See my other thread that thoroughly disproves THAT notion. Again, please don't post here if you can't be productive and provide useful info.
I bet that you DON'T HAVE TO SPEND A DIME on my little project....so what you say has no bearing on it's success or failure right now.
If I do succeed and the upper is reliable even with .223 ammo, then what will you say?
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I'm interested in how this will turn out; nothing wrong with trying something new. My tinkering side lives vicariously through projects like this :D. If it trumps your 14.5" middy-A5H3-enhanced carrier-Sprinco green setup for smoothness while running 100% when dirty and weak ammo, that will be something.
I agree that with the Syrac, you might as well start with a larger gas port than you think you'll need. If the barrel is going to Adco, have them pin the gas block (superior to clamp/set screw) while they're at it. And though I'm a big fan of FN CHF barrels, I advise against cutting one down because FN uses a tapered mandrel to improve accuracy. I'm partial to Rainier Evo handguards, though if you prefer Troy most regard the Alpha as an improvement on the TRX.
Yea, your probably on to something! You should check out that thread about the 16" rifle length DPMS.
I don't doubt it will work with a large enough gas port. Just like every of combo you could dream up. But alike the 14.5" do you want something that requires dicking with just to not be on the ragged edge of working?
Personally, I don't have the time to really test things like that under different ammo and temperatures. But please have at it! Mess around with springs and carriers, gas ports and buffers - all to get 1"-2" off your OAL. Sure seems like a great idea, and yea, you're probably inventing the next 14.5" Middy.
Please post results!
That is exactly the kind of info I'm looking for. Thank you!
Okay, so FNH is out. I am a fan of theirs also, but not for this application anymore.
I was unaware that ADCO could pin a set screw gas block. I guess they simply pilot hole the GB and barrel. I wonder if they have an extra taper pin laying around. ;)
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I certainly will. I already have a perfectly reliable upper for my patrol carbine....so this could be an abject failure and I'm still okay. If it works it could be considered a hybrid setup. Like a 3-gun upper for hard use.
That's a long way off. I'll update along the way. I'm leaning strong toward the BCM 20" at this point.
Does anybody know if ADCO chamfers gas ports as well?
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I believe they do. Check out their shop services section on their website. I know they used to offer a service of gas lort relocation which involved welding up existing port and drilling a new one, and I'm assuming included everything needed to do this properly (chamfering, etc.). You'll just have to check with them if they still provide the drilling service and if they have a recommended gas port size for a non-std barrel length for a gas port that would remain at the rifle-length location.
Since you're using an adjustable gas port as well, that ultimately will constrain how much gas enters the DI system, but discussion up to now seems to be centered on delivering enough gas to the adj gas block which will be barrel gas port diameter sensitive. From reading this thread, and given the shorter dwell, I suspected that the port would have to be enlarged a tad if starting with a 20" barrel.