AR VS. M16 BCU's in Carbines

[FortTom]

I've got 1 of the heavier M16 NiB BCU, Spikes in one rifle a 16" mid using an H buffer. The second rifle is a CORE 15 Lower with a BCM 16 in upper, and it uses a Fail Zero Nib AR 15 BCU, also using an H buffer. My third build is coming together fast. Waiting for Upper to arrive from BCM (a KMR). It too, is a 16" but will be using the heavier M16 (Rainier Arms). The reason that the one rifle has an AR (Fail Zero) BCU was that during the "Bama scare', it was all I could find, got it from Brownells, and paid a premium price for it.

The rifle with the M16 BCU feels, to me anyway, to cycle smoother than the rifle with the lighter AR BCU.

Now I'm building this 3rd rifle, also a 16in with a Rainier Arms M16 NiB bolt, and will use an H buffer, as a starting point. If this one, too, feels smoother cycling with the heavier BCU that might confirm my perception that the heavier BCU just cycles smoother in a 16" mid length barrel rifle.

I noticed on this forum, and several times on other forums, that some folks refuse to use a M16 Bolt in an AR 15 mid length rifle.

I'm curious as to why. Are there technical problems using M16 BCU's in AR's that I'm not aware of? It would seem that there is something behind this, that I'm not aware of.

Anyone with the tech expertise that can answer this, I'd appreciate your opinion. This has me curious, now, where before it never gave me a reason to be concerned.

Thanks,

FT

[Slippers]

It really comes down to the manufacturer when comparing bolt carrier weights, at least from what I've seen. I have a colt FA carrier that weighs about 1 oz less than my BCM FA carrier. I also have a Bushmaster AR15 carrier that weighs more than my Colt FA carrier. So what you can take away from this is that an FA carrier *should* weigh more than an AR15 carrier, if they're made by the same manufacturer around the same time frame. Otherwise all bets are off. :)

I found this with a 2 second google search, which further backs up my findings: https://www.ar15.com/archive/topic.html?b=3&f=118&t=347684. Most of the time it seems that the FA carrier only adds 0.2 oz to the weight, which is hardly anything, but the variance between different manufacturers is surprising, well over an ounce or two in some cases, which is like changing buffers.

Oh, and the most common reason people choose not to run an M16 carrier is that they're afraid the ATF is going to jump on them for having a component that is used for full-automatic in their rifle.

[AR-10]

On a mid-length gas system you can experience short stroking if you shoot underpowered ammo and use a heavy buffer.

This could be one of the reasons why some shooters don't want a full-auto bolt carrier, they are a little heavier than a semi-auto carrier.

I have full-auto carriers in my middies and they cycle Tula just fine with standard CAR buffers.

In both of my carbines I have H2 buffers, it seems to soften the recoil when shooting mil-surp 5.56.

Other factors to consider are the size of the gas port and the length of the barrel.

A 14.5" middy has a shorter dwell time compared to a 16".

[FortTom]

As far as the ATF, I just recently read that the addition of a M16 bolt, also sold as a M16/AR-15 BCG, a direct quote from the BATF, was the addition of an M16 bolt does not cause a weapon to become a fully automatic weapon, and therefore is not illegal. (Paraphrasing, because I can't find the document, now). I've seen people on BARF.Com sling page after page of vulgar insults arguing back and forth on this issue. The document I read was a direct quote, from BATF regulations, not something I've "heard".
Also some ambiguity here, as these bolts are sold as M16/AR-15 BCG's. No matter, what other folks do is not my concern.

I appreciate the answer. I will weigh the 2 M16 bolts, and the AR-15 bolt, and see how much weight difference there is. You're the first person that I've heard state that.
I assumed the weight of the M16 BCG would be fairly uniformly heavier, as the slot in the AR bolt is milled out approx. 1/4 inch or so.

Thanks for the info.

FT

[GOST]

I use FA BCGs cause I dream of one day owning a FA lower.

[Computalotapus]

Last build I did had a 14.5" mid barrel and we experienced short stroking with an H2 buffer. Swapped it for a standard and it has ran flawless ever since. Main ammo type used bounces between wolf brass and pmc xtac


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[FortTom]

Last build I did had a 14.5" mid barrel and we experienced short stroking with an H2 buffer. Swapped it for a standard and it has ran flawless ever since. Main ammo type used bounces between wolf brass and pmc xtac


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Comp, I've been using "H" buffers, and haven't had a problem with them,.....yet. I use them as a starting point, to see if I need to go to a standard or not. In a 16" gun, I can't see having to use an H2 buffer. So far this formula works, but then again, you never know.

Thanks,
FT