Hey Randall! I didn't know you still posted here! I had you reprofile feed ramps on a Brownells 20" A1 barrel for me to M4 profile at the very start of the year and I wanted to say you did an excellent job! Probably the nicest and smoothest looking set of feed ramps on any of the ARs I have.
I just put that barrel and upper together within this last week and sighted in the iron sights on it a couple of days ago. Just need to get the ACOG for it now.
Last edited by 556Cliff; 05-22-24 at 17:51.
Double post.
Last edited by 556Cliff; 05-22-24 at 17:46.
Not that small an influence.
The gas port is essentially a small pipe with a diameter of the port, and a length equal to the wall thickness.
Flow through a pipe is highly dependent on the length of the pipe. The fluid constricts as it enters the pipe, reducing the maximum possible mass flow and and as it expands back up the pressure drops. The longer the pipe, both more the mass flow and the pressure drop. In an AR, the thicker the barrel wall, the lower the pressure in the gas tube, and the lower the mass flow. The speed is little effected, but the lower pressure and mass flow mean it takes longer for the carrier cavity to pressurize, and reduces the carrier's acceleration. This means unlocking will take longer.
indeed, as a plumber and electrician i get the fluid dynamics of pipe size and length. ty for the illustrations. All my barrels are .75 diameter, so I think the wall thickness is not an issue. I do have a .625 on the shelf to build yet. thanks for the notable consideration.
I like how the buffer and spring thread got hijacked by the gas port..LOL
Last edited by zeus100; 05-24-24 at 16:18.
"We must all hang together, or, most assuredly, we shall all hang separately."
Any idea what the approximate amount of force the buffer strikes the end of the buffer tube is?
You won't outvote the corruption.
Sic Semper Tyrannis
I have been wondering the same. Does this infer that the design of mil spec carbine set ups is intended to fully compress the spring? my rubber end of the buffer protrudes about 3mm past the fully compressed spring, so is buffer on buffer tube impact intended and ok?
In pursuit of a lower than normal mass recoil set up, I consider this would likely increase speed and transfer of energy at the end of the tube
The answer to the amount of force is “it depends”. Mainly on mass of the buffer, bolt carrier velocity, and spring rate. In a competition setup where avoiding sight movement during recoil is a top priority, light buffers are used, and the gas is turned down in combination with that, to minimize the impact in the bottom of the receiver extension, and at the end of the forward stroke returning to battery. This works well in a competition setting, where a gun may get shot a shitpile and get quite dirty, but won’t ingest sand or mud, and the ammo and gun can be tailored for each other. The competition gun is also unlikely to get limpwristed. The “tactical” gun needs to work under broader circumstances, and it is not necessary for you to be able to double-click the mouse with only one sight picture at 50 yards. Thus a buffer with more weight and more gas to drive it.
No, the spring is not meant to be “fully compressed” (solid height) in normal operation.
Yes, the bumper of the buffer should strike the bottom of the receiver extension, and it should not be made of rubber. A constant recoil system could exist, but would require a longer system, otherwise the gas key is likely to strike the bridge. The difference between “doesn’t lock back” and “strikes bottom of receiver extension” is what, like a quarter inch?
RLTW
“What’s New” button, but without GD: https://www.m4carbine.net/search.php...new&exclude=60 , courtesy of ST911.
Disclosure: I am affiliated PRN with a tactical training center, but I speak only for myself. I have no idea what we sell, other than CLP and training. I receive no income from sale of hard goods.
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