A R Rifles Gas or Piston?

[Hmac]

I'll tell you what I personally look for:

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Really nice summary.

[Tronster]

Forgot to mention chambers and twist rates:

There are .223 and 5.56 chambers in AR barrels, the main difference being the "leade" gap between the front of the chamber and where the rifling starts, slightly longer in the 5.56 chambers. The 5.56 chamber can shoot both .223 and the hotter 5.56, but it's not recommended to shoot 5.56 in a .223 chamber as it can cause pressure spikes. If you want every last bit of accuracy from .223, such as a dedicated long range varmint rifle, then use a .223 barrel. But if you want to double your ammo choices, get a 5.56 barrel and you can shoot any .223/5.56 ammo you find.

As for twist rates, older AR's used a 1 in 12 twist rate for 55 grain bullets (typical M193 milspec ammo) but had trouble stabilizing heavier bullets causing accuracy issues. Most newer AR's will now use a 1:9 or 1:7 twist and will be good for 50-70 grain bullets. The barrel chambering and twist rate will be marked on the barrel, sometimes hidden under the hand guards.

OK another tid bit; look for some M4 feed ramps. These are the two small cutouts where the tip of the bullet will ride into the chamber. An M4 feed ramp cut will have a partial cut into the receiver that matches the cutout in the barrel. google m4 feed ramp for pics.

Hope this helps.

[Snowgun]

Why full auto BCG? Many top end BCG's aren't built like that.

[Tronster]

Not saying a SA BCG doesn't work, but typically a FA BCG will also have the fully shrouded firing pin. It also adds a little weight to help slow down the bolt speed giving the cartridge more time for pressures to drop before extraction and when coming forward help aid cartridge feeding. That slower bolt speed can slightly reduce recoil and makes the top and bottom balanced inline with the recoil. Plus in applications like mine running a gas piston system the longer portion on the bottom facilitates room for raised skids to prevent carrier tilt which actually works. But this is JMHO.

[Chevydude]

Are you describing a hand build?

Not saying a SA BCG doesn't work, but typically a FA BCG will also have the fully shrouded firing pin. It also adds a little weight to help slow down the bolt speed giving the cartridge more time for pressures to drop before extraction and when coming forward help aid cartridge feeding. That slower bolt speed can slightly reduce recoil and makes the top and bottom balanced inline with the recoil. Plus in applications like mine running a gas piston system the longer portion on the bottom facilitates room for raised skids to prevent carrier tilt which actually works. But this is JMHO.

[Tronster]

No, some factory AR's use a semi auto type BCG and some (like a Huldra) use a full auto type BCG.

[Hmac]

Why full auto BCG? Many top end BCG's aren't built like that.

Can you name some of those top end BCGs that don't use FA configuration?

[t140]

Why full auto BCG? Many top end BCG's aren't built like that.

Can you name some of those top end BCGs that don't use FA configuration?

JP Enterpreises' LMOS BCG and Young Manufacturing's lightweight BCG.

Although, they're built for game guns and are not recommended for defense use.

[Hmac]

I guess I was thinking of the majority of recognized quality mfgrs. I beleive that they all use full-auto configuration bolt carriers. Not that those two aren't, but as you mentioned they tend more toward specialty guns. I am inclined to contend that a full-auto bolt carrier is pretty much a standard component of a good quality AR15 these days.

I agree that the advantages of a full-auto BCG are marginal Z(shrouded firing pin less so). More reciprocating weight...might mitigate some of the felt recoil, although that's arguable, and maybe not signficant compared to the buffer weight. OTOH, it has sort of become a de facto indicator of quality -- it's generall difficult to find a quality defensive gun that doesn't have a full-auto BCG. IOW, one could probably get away with any of the three types of bolt carriers, but what's wrong with the FA version?

I keep seeing these dialogues here. What can we get away with on our AR15s? Extruded buffer tubes? Plastic buffer tubes, for chrissake? Bolt carrier groups with less mass/material? On a hard-use defensive firearm, why would we want to head downward toward the least common denominator? Why don't we just embrace the concept that there's nothing wrong with an overbuilt rifle? Is it a cost thing? Some may be adherents to that concept but we all have our cost-benefit equations. One could argue value, but that is not my primary driving force in buying any firearm...quality is.

[Tronster]

Keep in mind that an AR can function fine without alot of these features, but when you are already dropping 700 -900 dollars on an AR, why not spend a few hundred more for upgraded parts and maybe a little tighter quality control. If its just plinking dont worry about this, but if it might be pressed into a defensive role then pony up for some improvements.

[Hmac]

Keep in mind that an AR can function fine without alot of these features, but when you are already dropping 700 -900 dollars on an AR, why not spend a few hundred more for upgraded parts and maybe a little tighter quality control. If its just plinking dont worry about this, but if it might be pressed into a defensive role then pony up for some improvements.

I agree. A consumer-grade rifle with an SA BCG and a plastic buffer tube might very well work for the majority of black rifle owners. But for $300 more you can get a rifle of higher demonstrated quality. We used to call that "penny-wise and pound-foolish", back in the old days. I don't need a $50,000 titanium AR15, but I certainly can afford better than the typical run of consumer-grade rifles on the market these days. And that's what I buy, whether I need that level of quality or not.

[Tronster]

Another saying I like is: Buy quality once, cry once. Buy cheap once, cry often.

You can however run into a diminishing rate of return. You could spend $1100 - 1400 on a nice AR from a good reputable manufacturer or spend $2500 - 3000+ on a top tier manufacturer but it won't do much more than the good AR's because the designs pretty much have the same upgraded features. You just might be spending more on some unique super engineered gas system or some fancy unobtanium materials.

If the OP is still following, ultimately each of us have to decide what price point we are comfortable with.

I know guys that bought the cheapest $650 AR they could find, they don't care about milspec this or that, and they like shooting it and that's all that matters to them.
I knew I wanted a high quality AR, but didn't want to break the bank doing it, so I spent a little more for milspec stuff and I'm comfortable with my choice.

[Snowgun]

You can however run into a diminishing rate of return. You could spend $1100 - 1400 on a nice AR from a good reputable manufacturer or spend $2500 - 3000+ on a top tier manufacturer but it won't do much more than the good AR's because the designs pretty much have the same upgraded features. You just might be spending more on some unique super engineered gas system or some fancy unobtanium materials.

THIS

Regarding the BCG, I was just curious as to why it seemed that "performance" systems tend to bifurcate in two different directions, and wanted to know the advantages of having a tank of a BCG. I can see the symmetric top and bottom, and the full shroud, but I am dubious about the weight issue, since that is something that can be dialed in with buffers and gas blocks these days.

As far as "not appropriate for self defense", I am also dubious...Unless we are talking about real military usage in bad environments, a comp gun is made to run optimally and CAN'T afford to have malfunctions. Otherwise they would be worthless for competition obviously...

[t140]

THIS

Regarding the BCG, I was just curious as to why it seemed that "performance" systems tend to bifurcate in two different directions, and wanted to know the advantages of having a tank of a BCG. I can see the symmetric top and bottom, and the full shroud, but I am dubious about the weight issue, since that is something that can be dialed in with buffers and gas blocks these days.

As far as "not appropriate for self defense", I am also dubious...Unless we are talking about real military usage in bad environments, a comp gun is made to run optimally and CAN'T afford to have malfunctions. Otherwise they would be worthless for competition obviously...

The difference is a loss of points or a loss of life. Pick whatever you want. I know what I'm going with.

[Hmac]

The significance of the point of diminishing returns will very from person to person. The returns may be diminishing but as you pay more, you still get more. The point where you decide to stop paying more is going to depend on your resources. Again, what constitutes "good enough" in a firearm choice is personal opinion. Some people have higher expectations and are willing to pay more to achieve them.