M16 vs. M4
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Birddog1911
Member
This debate, and pretty much any AR debate, has been done ad nauseum. Not trying to be rude, but you'll find answers if you search.
Birddog1911
Member
Well, let's sum it up quickly. A 20" barrel on an M16A4 is going to give you roughly 100 FPS faster than an M4. You'll also have a longer sight radius, which tends to be more accurate. If your going to engage targets within 250 to 300 yards, a carbine will be handier and a little lighter. If you want to accurately and dependably engage targets to 600 yards, the 20" profile will be better.
Bingo. Plus the other poster who noted that the extra wear and tear of the carbine will result in less longevity.
ny32182
Member
He asked about reliability and durability, not engagement ranges guys...
The answer is basically this... they are all pretty reliable and durable, but the longer the gas system, the less stress the gas pulse puts on the internal components (BCG). This is due to the level of pressure entering the gas port and thus the BCG (the closer to the chamber, the higher the pressure) and the time it takes that pulse to make it back to expand in the inside of the carrier:
The shorter tubes will tap the gas earlier and get it back to the carrier faster, thus both running a higher pressure pulse, and starting the unlocking cycle earlier.... both of which put more stress on the BCG components.
It isn't really something to be tremendously concerned with however. The bolt, gas rings, and extractor may have a slightly longer life at the extreme end in a longer gas system rifle, but by then you would've spent so much on ammo that parts replacement costs are basically negligible by comparison.
The answer is basically this... they are all pretty reliable and durable, but the longer the gas system, the less stress the gas pulse puts on the internal components (BCG). This is due to the level of pressure entering the gas port and thus the BCG (the closer to the chamber, the higher the pressure) and the time it takes that pulse to make it back to expand in the inside of the carrier:
The shorter tubes will tap the gas earlier and get it back to the carrier faster, thus both running a higher pressure pulse, and starting the unlocking cycle earlier.... both of which put more stress on the BCG components.
It isn't really something to be tremendously concerned with however. The bolt, gas rings, and extractor may have a slightly longer life at the extreme end in a longer gas system rifle, but by then you would've spent so much on ammo that parts replacement costs are basically negligible by comparison.
DMK
Member
Good answer.
Split the difference, get the midlength.
Same barrel length as an M4, longer sight radius, softer gas pulse, the proper dwell time of the rifle length.
LRS_Ranger
Member
At the risk of rocking a few boats... look at a piston system.. I have one and it's freaking sweet..
http://www.lwrci.com/p-4-m6a2.aspx
http://www.lwrci.com/p-4-m6a2.aspx
Z-Michigan
Member
It also allows you to mount a standard bayonet properly.
As for proper dwell time, a midlength still provides a sharper, higher pressure impulse to the carrier, but it is not nearly as bad as the impulse from an M4 length. The M4 length, btw, was intended for 14.5" and shorter barrels, so using it with a 16" barrel really over-gasses the action.
Best reliability and durability is with the 20" barrel and rifle length gas.
Float Pilot
Member
When my last unit started to go over to M4s (14.5 inch barrel), somebody decided that only the top ranks ( E-7 to E-9 ) and Officers who have M4s and all the other troops would still carry their M16A2s.
The first thing I noticed is that all the pre-deployment qualification scores dropped like a rock with the folks carrying M4s. And the M4s seemed to get dirty faster.
Although they were just as reliable as the A2s when cleaned properly. (Our new FN made A2s were so tight it took 500 rounds to break them in...)
Eventually I went back to the A2. I am tall enough that I could still use it wearing my body armor, it had more velocity (chronoed 130 fps more), thus more impact force, better accuracy, better range and I was no longer pointing out my senior rank by carrying a different weapon than the troops.
About 18 months later the entire unit went over to M4s and we then spent a bunch of time and money getting batteries and repair parts for the stinking Aim Points.
The first thing I noticed is that all the pre-deployment qualification scores dropped like a rock with the folks carrying M4s. And the M4s seemed to get dirty faster.
Although they were just as reliable as the A2s when cleaned properly. (Our new FN made A2s were so tight it took 500 rounds to break them in...)
Eventually I went back to the A2. I am tall enough that I could still use it wearing my body armor, it had more velocity (chronoed 130 fps more), thus more impact force, better accuracy, better range and I was no longer pointing out my senior rank by carrying a different weapon than the troops.
About 18 months later the entire unit went over to M4s and we then spent a bunch of time and money getting batteries and repair parts for the stinking Aim Points.
Bartholomew Roberts
Member
The military has done several studies and the M16 has a slightly better rate of reliability and slightly longer service life in every one of them. It basically comes down to the M4 being harder on parts (that were designed for M16 pressures) and needing more preventive maintenance more often to run at the same rate of reliability.
more handy than a 20" rifle at 300 yards, but not at 600? How? 300 or 600, long is long, and I see no advantage a carbine would have over the 20" rifle at either range.
Now if you're talking much closer ranges and/or in certain environments, the shorter stock/barrel might be handier.
Sorry, just confused.
LRS_Ranger
Member
At the risk of rocking a few boats... look at a piston system.. I have one and it's freaking sweet..
http://www.lwrci.com/p-4-m6a2.aspx
http://www.lwrci.com/p-4-m6a2.aspx
DMK
Member
You said that already.
LRS_Ranger
Member
Stinkin' computers...
possum
Member
theoretically the 20" ar should be more reliable over a longer lenght of time. however with that said, i have over 5k through my personal 16" model ar, as well i have never had a malfunction that was caused by the gun itself in any m4 that i have been issued. (the one i currently have i had for 2.5 years and counting.) the only isues have been magazine related which was solved with using p mags!
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