Home Forums Hunting & Shooting AR and Tactical Rifles Light weight bcg

I went down this road several years ago with a 3.9oz aluminum carrier, empty buffers, and adjustable gas. What I found was that the juice just wasn't worth the squeeze. Yes, there is a difference in sight movement when you go really far down this rabbit hole. Compared to an off the shelf, overgassed, carbine length AR the difference is tremendous. Compared to a properly built and gassed gun, not so much. There's still a difference for sure. The question I finally had to answer is whether I was able to exploit the difference. And for me, the answer was no. Sight movement between shots, comparing something like my 13.7 and that aluminum carrier build, was definitely not what was holding me back in a match.

And that little bit of advantage does come at a cost. Once you start fiddling and straying that far from the standard your window of "this works" becomes increasingly narrow. You'll have to pay attention to everything and keep an eye on ammo, weather, cleanliness, and lubrication more than ever before. All of that is a hassle and distraction that I wasn't willing to deal with.

As far as what parts you need to get, it depends on what your goal is.

If you want to minimize sight movement in recoil get a reduced power buffer spring, a carbine buffer, and adjustable gas block. Try it with the carbine buffer. If you want to go lighter I'd recommend replacing the buffer weights with appropriately sized wooden dowels, one at a time, and test it as you go. IME having the dowels in the buffer helped in reliability. Somebody told me it has to do with the way the weight reciprocates in the buffer vs having an empty buffer. I don't know, but it seemed to help. Remember that it's a system. You can't just remove all the weight without consideration to the gas. And removing too much weight reduces forward momentum of the carrier, decreasing reliability when you're feeding ammo from the magazine.

If you just want to build these guns and use the RTB carriers because that's all you could find... Get an adjustable gas block. Don't be lazy, dimple the danged barrel and install it correctly. Then I'd start with a carbine or maybe Springco white-hot spring and an H buffer. If I had one handy I'd try an H2 buffer as well but it's probably not necessary. Since the carrier is so light you'd want to go heavier to compensate for the missing mass. Then turn down your gas until your ejection is at 3 o'clock and your bolt locks back on an empty magazine every time.

You're getting advice to go both ways, and they're both right, depending on what you're wanting to accomplish.

After I made this post earlier this morning I got curious as to how much difference there really was between a lightweight BCG and a standard BCG so I took apart 2 of my rifles, one just a run of the mill AR and the other with the JP LMOS. I didn't have anything to accurately measure the weight of each so I went to the post office (luckily no one was there at 6;00am). The standard BCG weighed 11.50 oz and the JP light weight weighed 8.50 oz exactly a 3 oz difference.
The standard buffer weighed 3.11 oz and the JP weighed 2.91 oz , a difference of only .2 oz but the JP is shaped differently. it is longer than a normal buffer and is turned so that it engages the buffer spring 1" farther up from a standard buffer giving the spring an additional 1" of preload

Completely agree, that's why I only have one rifle with it

Thank you gentlemen , now the information even i can understand is coming in!
Its going to be a while, the charges from righttobear for the carriers just posted this am. I ordered them wed. Oh well . Its snowing like a big dog so i either plow snow or go write my great american novel😐

I agree with all that you've said & concluded from your trials, & that's exactly what my advice if he really wants to use those carriers............& he did say that he has (Seekins) AGB's already.

As far as light carriers, there's those that have the weight reduced by a couple of oz, then there are Ti & Al carriers that another 3-4 oz lighter.

The ones are are only a couple of oz lighter are easy to run, but as the weight goes down further, a lot more dicking around, different buffers/springs & AGB's need to be tuned to get them optimized.

MM

That can work, and I’ve done it that way myself, but it WILL result in carrier bounce which I’ve verified by slow motion video. I now prefer to stick with a standard carbine buffer for most lightweight carrier applications. Going the other way to a heavy buffer as some people recommend doesn’t make sense of course.

To the original question- yes you can make a 6-8 oz carrier run just fine and there is some benefit. You’ll just need to restrict the gas a little more than you would with a standard carrier. The gas block adjustment process is the same as normal.

Still waiting on the bcg's. Took a standard ole psa bcg out of my 1 6" 7 .62x39 rifle that runs like a rolex.
3 oz buffer and gas wide open the carrier will catch on the last round but not the bolt. Single shot.
Took one segment out of buffer. Same same at 2.63 oz. Took 2 coils foo spring .same same.

Wondering if i should take out more. Don' t like that idea but i do want the sucker to run
. Like a dope i didnt check the size of the gas port. And one set screw the wrench rolled in so now its drill time.
Shoulda slept in.

The 223 wilde rocks! Thats the good news.
30 round dump . brass 4 feet away at 4 oclock. Laying atop each other.
Standard bcg and buffer. May just leave it and dump the lite weight bcgs if they ever come.
One itch scratched.

Got the two projects done.
Light weight bolt carriers changed nothing as far as i can detect.
762x39 wouldn't run with anything ,light weight or standard , even with the agb cranked wide open. Tried everything from empty buffer to cutting 6 coils off a spring.

Finally mic' ed the gas port. One full half port forward on the barrel. Made a spacer for the gb setting it forward. Runs like a rolex.
I am a happy dog.
Next project? Maybe another long barreled 224 valk.?? Yotes have been yapping.

So the gas port on the barrel didn't line up with the gas port on the block?

Yea, that will cause problems.

As I've previously mentioned, I have the $50.00 Teslong borescope. It's great for checking gas port alignment. It's part of my trouble shooting regiment now.

Glad you figured it out.

Me too! I get the stink eye when i buy gun parts and then cuss because something wont work😬

Gas blocks should normally be about.030-.035" off the shoulder of the barrel.

In most cases, if both the barrel & the GB are done right, it you push the GB up tight against the barrel shoulder, you will not have optimum alignment,

But the GB port is a fair amount bigger than the barrel gas port to allow for some amount of misalignment...............like with many things, it a question of how much.

I always measure the center of the barrel port distance from the shoulder & the GB port center distance from the rear edge of the GB. Never don't work....................measure twice, cut once.

MM

I built a 243 LBC 22' barreled rifle for deer hunting. I used RTB's lightweight carrier with a standard rifle spring and buffer.

With an adjustable gas block the rifle runs smooth as silk.


Dan








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The problem with most light weight bcg's from this thread is that some company will sell you one and you have to figure it out for your self how to make it function properly, I bought mine from JP and they did the research and development so all I did was plug and play and it has worked flawlessly for years !!!

Maybe I've been lucky but it hasn't been a big deal at all to get mine running.

An understanding of the physics of the system & a little common sense goes a long way......................just sayin.

MM

Truer words never spoken, no matter what endeavour .

Sounds like you got'er dialed in; if it function at that temp, it will be fine in warmer weather too.

MM

I am hoping, for warmer weather mostly getting tired of freezing my bullets off trying to put in a day shooting😤