View Full Version : Mid-length gas system in a 10.5 in barrel, does it work?
Title says it all. Anyone has a 10.5 in SBR with a mid-length gas system, and how does it work out for you? Thanks.
MisterWilson
11-03-08, 18:59
Dude, I don't think a midlength gas system would even fit on a 10.5" barrel.
Why would you want to? What would be gained?
Dude, I don't think a midlength gas system would even fit on a 10.5" barrel.
Why would you want to? What would be gained?
"Dude", chill out. Just a question, because I'm puzzled as to why some dealers actually offer these.:rolleyes:
MisterWilson
11-03-08, 19:05
It already exists?? Who sells one?
PK Firearms has been offering these for quite some time, now, selling the Noveske custom barreled uppers.
RAM Engineer
11-03-08, 19:16
I just perused their website and didn't see anything like what you described. I can has link?:D
http://www.pkfirearms.com/store/get_items.aspx?type=0&term=131
Robb Jensen
11-03-08, 19:48
Those are still CAR length gas systems (not midlength), just with a longer rail covering them.
Yeah, I know it's the longer rail (10 in), but PK specifically states "mid length gas system". A mistake, maybe? I'll ask them later. Because a search of Noveske 10.5 in barrels only shows the carbine length gas system, no mid-length.
My guess is that someone who created the ad either did an un-educated cut and paste or didn't realize what they were posting. gotM4 has aptly pointed out that this is in fact a CAR length system with longer rails.
You can ask them all you like, but don't be surprised if the person on the other end gives you the answer you want or doesn't know the difference. Happens at gunshops across the country everyday.
I know of a guy who runs one with a can. He claims it works.
theJanitor
11-04-08, 10:22
http://noveskerifleworks.com/cgi-bin/imcart/display.cgi?item_id=b-105g-556&cat=62&page=1&search=&since=&status=
If there isn't enough distance between the gas port and the end of the barrel, all your pressure goes away before the action has had a chance to cycle. There needs to be a little time for this to happen before the bullet exits the muzzle. An inch ain't enough...
http://noveskerifleworks.com/cgi-bin/imcart/display.cgi?item_id=b-105g-556&cat=62&page=1&search=&since=&status=
That is carbine length.
The mid-length gas port would be right at the area where the threads meets the barrel. There would be no space for a gas block.
Mid-length is not the holy grail of gas systems. It is only ideal for certain barrel lengths, just like carbine and rifle gas lengths are ideal for different barrel lengths.
I think MisterWilson might be right. Working off a generally bad memory, so this is worth what you paid for it, but a carbine-length gas system's port is supposed to be at the 7.5" point on the barrel, whereas a standard rifle-length system's port is about the 13" point of the barrel. Assuming a middy splits the difference, that would put its port at 10.25", which would mean it wouldn't really fit on a 10.5" barrel (I think the FSB would stick out past the muzzle). Then again, Defensive Review (http://www.defensereview.com/modules.php?name=News&file=article&sid=360) backs up the rifle's gas port to the 12.5" mark and the Armalite's midlength port to the 9.5" mark; in this case, it would fit.
-B
Parabellum9x19mm
11-07-08, 00:38
not to hijack, because i'm not talking about gas port location at all, but defense review/david crane is not a credible source.
You are right. He made a brief appearance here once IIRC and then vanished into obscurity when people were asking pointed questions.
not to hijack, because i'm not talking about gas port location at all, but defense review/david crane is not a credible source.
Fair enough; I'm assuming he has access to all three, though, if he was able to provide measurements. Without an upper in my hands, I can't do any measuring of my own. :(
Anyone who has a middy mind confirming the distance between the chamber and gas port?
-B
Fair enough; I'm assuming he has access to all three, though, if he was able to provide measurements. Without an upper in my hands, I can't do any measuring of my own. :(
Anyone who has a middy mind confirming the distance between the chamber and gas port?
-B
Didn't use a ruler, but with my 10.5 and my 16" middy side by side, the gas port on the middy falls in the .5 to .75 piece of barrel between the end of the FSB and beginning of the threads on my 10.5".
Cool, thanks. I guess a middy system is technically possible, then.
-B
That would give you about a nano-second of gas time.
Correct. I was simply trying to confirm what MisterWilson had said. Turns out both he and I are wrong in that the middy system will fit, but I can't find a single decent reason what the point would be. You would have to fiddle with the port quite a bit to get one that works consistently with a wide range of ammo, and be mindful of the buffer. I discovered the same thing researching a 16" barrel with a rifle-length gas system, and have pretty much abandoned the idea because of that.
-B
Actually, the best solution is the good old 20 inch rifle barrel, like Mr. Stoner originally designed it. Anything shorter is a set of compromises. I saw some test data from the military that indicated that all things equal, the M16 rifle was about 30% more reliable than the M4 carbine. Lower pressure, cooler gases, more time to cycle the action, better balance with the buffer. Unfortunately rifles don't have the ergos people want. I still like them myself.
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