AR 'buffer types', 'port size' and crud-in-chambers...???'s

[AJMD429]

Was gonna post this on the 300Blk forum, but sometimes answers are a big flippant there, plus. . . I forgot my password. . .

Anyhow someone on this forum will have a good answer to just about anything except "Why do leverguns suck...?"

(just kidding really, I LOVE leverguns the best...!)

So...

1. I hear about different types of AR-15 buffers (i.e. "type 'H'" and so on which I assume refer to different weights). With the 300 Blackout or even regular 223 AR's, what are the options and designations and ideas on changing buffer weight vs. spring strength and so on (i.e. when would it be better to change spring vs buffer weight). I don't even know how to tell what strength springs I have in my various AR's - I didn't know there might be differences...

2. Specifically regarding the 300 Blackout, due to problems cycling subsonic loads reliably, especially if a suppressor is NOT hooked up, I understand some barrels have larger diameter gas ports, but whereas some folks say "you don't need to worry about over-gassing a 300 Blk", others of course say not to enlarge a port no matter what, and others offer fist-thumping opinions on exactly what diameters are the ONLY proper ones for given gas-system lengths ('pistol', 'carbine', 'intermediate', and 'rifle'). Is there any definitive info on such topics out there. It seems more 'reversible' if you screw up, to use a lighter buffer or spring, but on the other hand keeping the same buffer/spring in your lower and having a 223 upper and 300 Blk upper with the right port size to swap out on that lower makes sense too. And of course if you have an adjustable gas-block then that adds another variable...

3. Shooting regular 223 ammo in a chrome-lined chamber/barrel gun with a new bull-barrel and a suppressor on, every dozen rounds or so I get such hard extraction that it practically takes a mallet to pull the charging handle back, and the problem gets worse until I clean the chamber. The brass is dirty like an under-pressure 45 Colt levergun load, but this is not low pressure/subsonic ammo - it's regular stuff. Is that common...??? I have another upper I don't like as much, as the barrel isn't as nice, but it is a 'piston' conversion vs. the gas-tube-into-bolt-carrier kind. I suppose I could try the suppressor on that, but since the crud seems to be in the chamber rather than messing up the bolt/carrier, I'm not sure if there's any point in trying that experiment.

I know these are not 'levergun' questions, but I also know we have dozens of 'AR' fans on the forum, and probably dozens of 'suppressor' fans too. Even a few who have been fiddling with the 300 Blackout, I believe...

Just thought I'd ask a bunch of questions and see what kind of advice I get (other than "WHAT KIND OF STUPID QUESTION IS THAT, AND WHY DON'T YOU TRADE THAT PLASTIC MOUSEGUN IN ON A MAN'S GUN LIKE A 45-70 OR A GARAND...???" )

(Hint - 'cuz I already have a 45-70 and a Garand. )

[MrMurphy]

Was gonna post this on the 300Blk forum, but sometimes answers are a big flippant there, plus. . . I forgot my password. . .

Anyhow someone on this forum will have a good answer to just about anything except "Why do leverguns suck...?"

(just kidding really, I LOVE leverguns the best...!)

So...

1. I hear about different types of AR-15 buffers (i.e. "type 'H'" and so on which I assume refer to different weights). With the 300 Blackout or even regular 223 AR's, what are the options and designations and ideas on changing buffer weight vs. spring strength and so on (i.e. when would it be better to change spring vs buffer weight). I don't even know how to tell what strength springs I have in my various AR's - I didn't know there might be differences...


H and H2 buffers are primarily for carbine variants. They're heavier, and with the carbine (short) gas system, keep the gun cycling when it should and not cycling too fast which can cause malfunctions from what I remember. Unless you're running something like a 12" or shorter SBR you should likely never need to go beyond a standard buffer or maybe an H buffer. Springs, there is standard rifle length and carbine (M4) length. One fits one length tube, the other fits the other is the basic breakdown. I'm not an expert or a gunsmith but i've been running the AR since the early 90s and carried them on duty and sold them through a manufacturer.

2. Specifically regarding the 300 Blackout, due to problems cycling subsonic loads reliably, especially if a suppressor is NOT hooked up, I understand some barrels have larger diameter gas ports, but whereas some folks say "you don't need to worry about over-gassing a 300 Blk", others of course say not to enlarge a port no matter what, and others offer fist-thumping opinions on exactly what diameters are the ONLY proper ones for given gas-system lengths ('pistol', 'carbine', 'intermediate', and 'rifle'). Is there any definitive info on such topics out there. It seems more 'reversible' if you screw up, to use a lighter buffer or spring, but on the other hand keeping the same buffer/spring in your lower and having a 223 upper and 300 Blk upper with the right port size to swap out on that lower makes sense too. And of course if you have an adjustable gas-block then that adds another variable...

Check out silencertalk.com Odds are, they'll know. I haven't shot a .300 BLK myself but have shot quite a few suppressed ARs.

3. Shooting regular 223 ammo in a chrome-lined chamber/barrel gun with a new bull-barrel and a suppressor on, every dozen rounds or so I get such hard extraction that it practically takes a mallet to pull the charging handle back, and the problem gets worse until I clean the chamber. The brass is dirty like an under-pressure 45 Colt levergun load, but this is not low pressure/subsonic ammo - it's regular stuff. Is that common...??? I have another upper I don't like as much, as the barrel isn't as nice, but it is a 'piston' conversion vs. the gas-tube-into-bolt-carrier kind. I suppose I could try the suppressor on that, but since the crud seems to be in the chamber rather than messing up the bolt/carrier, I'm not sure if there's any point in trying that experiment.

Make of the upper and lower, make of the bolt carrier group? Type and model of suppressor? Ammo type, weight, etc? Is the chamber .223, 5.56mm or a Wylde chamber? Any of these could affect it, without more info it's hard to say. I've shot thousands of suppressed rounds through non-piston ARs and normally the only odd thing is the extra gas blowing back through the action and leaking past the charging handle (which is why the PRI charging handle was invented)....unless the gun was truly filthy, ie shooting 500 suppressed rounds in one short session rapid fire, no real issues, even then, mostly the bolt would get sluggish on closing due to the suppressor blowing extra crud back into the action.

(Hint - 'cuz I already have a 45-70 and a Garand. )

[cas]

Were those questions?

[olyinaz]

Since most ARs have a fixed gas port, the buffer weight and spring tension can help you to tune your rifle for optimum operating. If you have "too much gas" a heavier buffer or stronger spring can help to slow down the rearward retreat of the bolt carrier so that it doesn't try to yank your cases out while the chamber pressures are still up. The heavier buffer slams home with more mass, and that's a consideration (may help, or it may exacerbate bolt carrier bounce). These items will have an effect upon cyclic rate also. Some folks like a really light mass system that runs at high speed (and can, because it's light mass) whereas some folks like to slow things down with more mass. The design of the buffer also matters (what's inside of it etc.). Some folks like hydraulic buffers that slow the rebound and spread out the bolt's recoil shock but still operate reliably, and some folks like premium springs that minimize or eliminate the "twang" sound. There are also premium springs that claim to run longer without fatigue. If box stock runs well - why mess with it? If you have issues, think about the basics above and apply your knowledge to address the issue.

The sticky extraction - it almost sounds like the loads are not developing enough chamber pressure to properly swell up the cases in the chamber and prevent back flow of gasses. Are you using light bullets for sub loads? A too-slow burning powder?

Excess gas in the action can be minimized by slowing the retreat of the bolt carrier, but you have to consider the entire cycle of function.

I don't have specifics for some of your questions - sorry.

[Hobie]

What 5.56mm/.223 Rem ammo are you using that's so dirty?

[Thunder50]

If you are getting alot of crud in the chamber, when using the suppressor, maybe you are getting more gas volume back into the action, you are getting more "crud" there and some of it is flowing in the chamber. Try a different ammo, if that doesn't help, try the gas piston upper.

I think the debate about gas port size and location is a neverending battle of one side vs. many others. I am not sure the port pressure/gas volume on the 300blk is enough to run a rifle gas port. I think people use a carbine port on rifle length tubes. I have a carbine barrel on mine with the carbine port, but it is an oversized port with an adjustable gas tube, so I can run subsonic, or open it up and run flat out. I just use a regular spring/buffer from my rifle lower. Don't know that much about springs/buffers, so can't help you there

[cas]

I have adjustable gas blocks on two of my match rifles (PRI & JP) but they're not what you want, they're "set it and forget it". You'd need something readily adjustable like the Noveske Switchblock or the one made by Paladin Machine if you're bouncing back and forth between subsonic and super sonic, suppressed and non.

Buffer weight doesn't become real relevant once you start adjusting the gas. Both rifles mentned above have lightened carriers. One is an ultra light and the buffer on that rifle is basically empty. The gas is turned down to make is function correctly though.

[Rusty]

Doc, I'm not sure this is the right video Allen has quite a few of them on "the black rifle channel" on youtube. This is his after action report on the blackout. In one of his videos he gives a very good explanation of the increased pressure you get with a suppressor.

https://www.youtube.com/watch?v=HsH_WCu ... vF8xwjsNjA

If you watch all the videos on his channel it will answer a lot of questions.

[piller]

It seems to me that dirty brass is coming from having the wrong powder in it. Try another brand if it is factory, and if it is handloaded, try a faster powder. The wrong powder was a problem in the Mattel Toy way back in the early days due to some folks in the DOD wearing their nether regions for hats and deciding to use existing stores of powder that was wrong for the application.