There are several things that make me raise an eyebrow at this test.
What state were the standard M4A1 rifles/uppers in? Were they brand new production, or were they just used guns taken off the rack? Previous military tests have been notorious for using clapped out old M4s (ie, the sand tests in 2007)
They were using M855A1, an insanely high pressure round. Compared to reliability figures done by the Army in 2009 showing the M4A1 having 3600 Mean Rounds Between Stoppages in a baseline reliability test, even the midlength in this test did rather poorly. Many government weapons contracts require at least 2000 MRBS. How would this test have gone if they were using a round that the weapons were actually designed for that isn’t damn near proof pressures, rather than one that isn’t compatible with any of our NATO allies’ rifles and even many of our own (M27 IAR)?
Non-military are not using M855A1. I suspect that in certain conditions with certain ammo (.223 pressure), the 14.5" Mid could possibly be undergassed under certain circumstances. Granted, that’s just speculation on my part.
They should’ve tested the CHF barrel variable and midlength gas system variable separately. Was the longer barrel life due to the gas system length or the CHF barrel? Or some combination? If so, to what degree each? Testing them separately could’ve told us that.
Personally I have experienced some midlengths being a little more picky on ammunition, with a 14.5" Midlength BCM not being able to reliably run quality brass case .223 (PMC Bronze that runs just fine in my carbine gas and rifle gas guns). And although it’s slightly longer than Midlength, a friend’s KAC also would not run .223 with acceptable reliability. BCM’s statement that their 14.5" Midlengths are meant to be used with full power 5.56 NATO ammo seems to support this.
14.5" and 16" Carbine gas guns with proper gas ports (ie, a Colt LE6920 with a .0629" gas port) have proven to be extremely reliable. Considering many manufacturers hog out their midlength gas ports anyway, I’d take a properly gassed carbine length system like a Colt or LMT over most Midlengths, or a 20" Rifle Gas.
choose what you want. the middy will be a better shooting experience felt (depending on gas port size and other factors). the carbine will typically be more reliable as it is under a longer dwell time to pressurize the system. the M4’s in the military have been fine as a carbine gas system. That is not to say the middies will not be reliable, we know for a fact they are reliable just stating what could be argued.
There is zero evidence a 16 inch midlength is less reliable than a 16" carbine. It is not “what could be argued” it is not true.
A quality 16" carbine is absolutely no more reliable than a quality 16" midlength. There is no advantage to buying a carbine gas 16" gun over a midlength.
I may be wrong in my thinking, but I buy 16” barrels with mid length gas set ups.
Carbine gas was developed by Colt for the 14.5” barreled M4 and the port pressures are higher than necessary for a 16” civilian barrel.
Either will work, obviously, or you would hear all sorts of issues with LE6920’s with carbine gas systems and you don’t.
I assume the lower pressure and hence lower bolt velocity of a 16” mid length setup is easier on the moving parts. The gas is also cooler at that length which may also decrease the stresses on the components.
I usually try to match the gas system to the barrel length.
I do agree that the mid length is a better mousetrap on a 16” barrel, but done right, a carbine is pretty dang good. I’ve ran a bunch of 16” Colts over the years, the last two to well over 15K rounds with no parts breakages or malfunctions attributable to the gun.
No, I get that. I’m just wondering how you arrived at half-price. I’m local to PSA, and their rifles are about $150 less than a feature-equivalent Colt. Also, that recall didn’t affect every Colt rifle, much like not all PSAs should be recalled.
The recall was on a small number of subcontracted hammers, iirc. Out of all the Colts we’ve had on the shelf during that time, only one had the hammer in question. I don’t consider that to be very major.
Compared with all the QC issues I personally see with PSAs, yeah, I’ll go Colt every time. I’m glad ARMED CITIZEN’s PSA and Taurus work for him, but I don’t cheap out on things that I might depend my life on. A Colt OEM 2 is less than $750 online, I don’t care about a $150 difference between it and a PSA. Colt isn’t the end all be all either, it’s the minimum of quality in a self defense carbine.
I’ve sold countless Taurus G3s, and Tauruses are probably one of the main pistols customers bring back with RMAs to send back to Taurus. For me, a pistol is not trusted unless it can go 1k consecutive rounds without a stoppage, and 2k rounds proves long term reliability. Same with a rifle.
Has anyone had any issues with midlengths of any barrel length running lower pressure .223 like PMC Bronze? I experienced it with both a DD 16" and BCM 14.5". A friend of mine also had this issue with a KAC 14.5" in cold weather. My Colts with carbine gas systems will run anything I feed it, same with my 20" rifle gas guns.
I can confirm what Clint’s saying. I specifically asked him to test that barrel/ammo combo when I was building my upper. I don’t run PMC Bronze unless I have to, but I like that it works with it.
After reading the last couple of pages in this thread, I’m feeling like Rip van Winkle- except I’ve woken up 20 years in the past. I thought we’d put all this ignorance behind us.