BCG weight and dependability

[King Chicken]

I have a strike industries jcomp on my 16" middy 5.56. It's cheap and awesome. It does a great job with reducing recoil, but directs gas far enough away from you that you don't really get blasted in the face like you do with a miculek type brake. It also does reasonably well at flash reduction for what it is.

5.56 Muzzle Brake / Comp / Flash Hider Shootout!

Testing 35 muzzle devices for the AR-15. A recoil-measuring test rig was created, and a recoil reduction winner has been declared! TTAG muzzle brake comparo

www.thetruthaboutguns.com

Annnd here's me with it in 3gun...

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Nice depth and amount of info. I went through comps, brakes, etc not too long ago. I decided against aggressive brakes for range etiquette and room clearing capabilities. I think I will go w the AFAB in the end. The flash size is also something that guy goes through very well.

 

[Magnumite]

Smokey, thank you for that info. And you sent some lead down range...nice shooting.

 

[omegared24]

I've been running a Tubb spring, an H buffer and a standard, quality phosphate BCG with zero issues. That's for both carbine and mid.

I run cheap Tula and Wolf 99% of the time.

 

[King Chicken]

In short, I would go with a 16" barrel with mid length gas, standard full mass BCG. H1 buffer with a "Whitehot" Springco buffer spring.

If you don't intend on shooting suppressed, there is little need for adjustable gas as long as you go with a middie barrel. It will be a softer shooting gun with great reliability.

Thanks for your advice. Need all i can

Questions: Couldn't i go with a 14", add 2.25" comp, weld smallest portion possible? I see people say that welding means you get so much hassle from weld but a small weld and reweld doesnt seem too bad?

I could not find "whitehot" springco buffer spring, i did find hot white? what makes this spring different?

lastly, and thank you for your time, i've read many places that most ar15's are way overgassed and could use a little adjusting down?
obviously i would never want to decrease dependability of stripping rounds off mags but would that decrease recoil a tad?

Thank you!

 

[dannyp]

You have to understand the balance of things, and the tradeoffs with gas and mass tuning. As soon as the bullet passes the port in the barrel, gas feeds into the system, it stops soon after the bullet exits the muzzle. During that time(aka dwell) a certain volume of gas at a certain pressure is fed into the carrier through the key, it forces the bolt forward, the carrier is pushed back, this unlocks the bolt from the extension for a tiny distance of powered movement, gas then is exhausted from the side of the BCG out the ejection port. Inertia alone keeps moving the carrier and buffer rearward against the recoil spring until it ejects and reached the rear of the buffer tube. The spring alone then forces the BCG and buffer forward, stripping a round from the mag, feeding it into the chamber, latching the bolt to the extension, and engaging the extractor over the case rim.

Dwell or how long the gas is available is fixed by the distance between the port and muzzle. Pressure is regulated by the gas port size, the location(shorter gas systems have higher pressure available), and potentially by a restriction in an adjustable gas block. The volume of gas is a function of pressure and dwell, aka how long gas is fed, and at what pressure. This is gas tuning, you need enough gas to cycle, but too much can push the carrier too hard, can increase recoil, reduce reliability or increase noise and gas blowing in your face. The adjustment of this at any point, either by restricting or leaking gas contributes to the "gas tuning". Leak too much gas, and a rifle won't function, too large a gas port, and it can be overgassed etc.

Mass tuning is simpler, the more mass aka bolt and buffer weight that resists the gas force, the more consistent it's speed, and the more gas that can be fed without adverse overgassing. There is fixed weight, aka the BCG and buffer body, and floating weight, the weights inside the buffer. All of the mass resists the rearward movement, and helps increase momentum to plow through a dry or dirty action, but floating weight smooths recoil and resists bolt bounce.

Some things happen as you change gas pressure and fixed/floating weight. The heavier the weight, especially floating weight, the more consistent BCG speed is over a wider range of conditions, the more gas you can run, and the more reliable a rifle will be when dirty. This is why for a rifle that will be used defensively, or even a range rifle, you want a M16 profile carrier and heavy buffer. Often times with a 16" with mid-length gas you can run an H-H2(3.8-4.6oz) and have an ideal setup that will be reliable without an adjustable gas block. Some shorter builds can benefit from an H3(5.4oz) buffer, and may even run well with the added pressure/dwell from a suppressor, although that is where the ability to reduce pressure with an adjustable gas block can be useful. Recoil can be soft and mild as the bolt is moving at a comfortable speed, but the sheer mass can move sights around on target a little more.

Reducing mass requires less gas as it takes less force to push the lighter carrier/buffer back. While a standard M16 BCG weighs about 11.6oz, and usually runs with a 4.6oz H2 buffer, some BCGs can weight 8oz or less, and using just a buffer body with aluminum weights at 1.5oz can reduce the force of the carrier moving around SUBSTANTIALLY. add on an effective muzzle brake, reduce gas just enough to power it, and the sight moves very little when fired, and there is practically no recoil. This is ideal for competition, but the gas must be tuned just right as any small changes, even in weather or temp can push that BCG too fast, or too slow and jam. As greater mass makes the BCG more consistent over a range of conditions, lighter mass makes it less consistent and tuning it frequently becomes critical to be reliable. It's a different purpose, different strategy, and does have some benefits and drawbacks.

that's a really great explanation , thank you !

 

[outrider58]

Thanks for your advice. Need all i can

Questions: Couldn't i go with a 14", add 2.25" comp, weld smallest portion possible? I see people say that welding means you get so much hassle from weld but a small weld and reweld doesnt seem too bad?

I could not find "whitehot" springco buffer spring, i did find hot white? what makes this spring different?

lastly, and thank you for your time, i've read many places that most ar15's are way overgassed and could use a little adjusting down?
obviously i would never want to decrease dependability of stripping rounds off mags but would that decrease recoil a tad?

Thank you!

Sorry Chicken 1, I 'misspoke'. That's right, Hot White was the correct answer. It will help soften the impulse a bit while still maintaining reliability.

The 14.5" middie will be okay as long as you stay with standard ammo. I've read about people having problems with that setup when they tried to develop a light rifle shooting 'lite' ammo. While I'm sure that can be overcome, you would really be narrowing your choice in ammo and the build could become too much of a ballasting act. Something I, myself, would want to avoid if I was setting out to build an all-around AR.

As for adjustable gas, meh. Most people use them for shooting suppressed and or sub-sonics. You're really tuning to avoid beating up the gun more than beating up your body. In most cases(and all my AR have adjustable gas) the user finds that sweet spot where the gun runs reliably in both suppressed and un-suppressed without any further adjusting.