View Full Version : Lessening a BCG's weight
caelumatra
06-19-11, 12:29
Does anyone have any experience with turning down a carrier to lessen its weight?
In particular I'm asking about the Armalite Ar-10 BCG. Yes of course it is a 308 BCG so its larger and heavier but there is something different about the ar10 bcg as opposed to all other 308 bcgs.
Somehow I don't have any pictures of my own armalite 308 BCG, so DSG's will have to do.
http://i1238.photobucket.com/albums/ff489/caelumatra/ARM10501001.jpg
It's solid on top. There is no gap on the carrier like a standard ar15 carrier. However the JP low mass BCG has the gap (as well as lots of other metal cut out)
http://www.brownells.com/.aspx/pid=42981/Product/_308_AR_LOW_MASS_BOLT_CARRIER_GROUP
What I'm wondering is what harm will it bring to have the carrier turned down to be lighter and have that hole cut into it
Something like this
http://i1238.photobucket.com/albums/ff489/caelumatra/IPSCBCG2.jpg
I know thats an ar15 BCG, but the idea is the same.
I also wonder why the hole isn't there to begin with. And why is only the Armalite carrier that is like that? Even the dpms carrier has the hole.
From a materials standpoint the machining shouldn't create any issues if done correctly. From what I can see you would loose your forward assist capability. A lighter carrier would also have an affect on your buffer spring rate, buffer weight and potentially increase your cycle rate. All of that can be tuned with component matching I would think. Any reason you don't just change the carrier out to one that has the features you want? Machining and replacement part costs might be a factor.
caelumatra
06-19-11, 22:08
Well, I am going to contact some machine shops in the area and get some quotes on the work. I just wanted to know if it would somehow mess the BCG up or effect the way the gun functioned. I suspected I would need to do something about the buffer or spring if I had this done.
It seems JP rifles only offer the 308 complete BCG for $430, so... that route is out if they don't sell it separate.
And this will be going in a ma ten, so, no forward assist. And from what I understand, ar308's don't really need a forward assist...but I may if I lower the mass so much :lol:
But regardless, the ma ten doesn't have one anyway, so no loss :)
If you know of any other carrier mfg's I'm interested :)
Its going to be paired with a noveske barrel, so if anyone with an N6 wants to chime in here and say what their BCG is like, I'd appreciate it :)
Well, I am going to contact some machine shops in the area and get some quotes on the work. I just wanted to know if it would somehow mess the bolt up or effect the way the gun functioned. I suspected I would need to do something about the buffer or spring if I had this done.
It seems JP rifles only offer the 308 complete BCG for $430, so... that route is out if they don't sell it separate.
And this will be going in a ma ten, so, no forward assist. And from what I understand, ar308's don't really need a forward assist...but I may if I lower the mass so much :lol:
But regardless, the ma ten doesn't have one anyway, so no loss :)
If you know of any other carrier mfg's I'm interested :)
Its going to be paired with a noveske barrel, so if anyone with an N6 wants to chime in here and say what their bolt is like, I'd appreciate it :)
The N6 BCG is a standard Armalite unit. Are you really just looking to lower the weight? There is a lot of meat that can come off there.
caelumatra
06-20-11, 08:26
Yeah. The weight reduction is my 100% desire. I'm not looking to lessen or worsen recoil, slow or speed the action. Its just the weight.
The ar10 carrier is silly how meaty it is, as you said. Having no experience with any other ar308 BCG my question stemmed from a mechanical stand point. Was there any reason that thing is so beefy?
If not, the thing's going in for some surgery
You mean bolt carrier.
Sorry it was bugging me.
caelumatra
06-20-11, 08:37
lol yeah. In my previous posts I corrected my own typing just out of habit saying bolt meaning the whole bcg. But yeah
Any time you change the reciprocating mass you are changing the cyclic rate. You may need to reduce the gas to compensate, now with less mass and less gas the rifle will not be able to overcome dirt/carbon/lack of lube as well.
I think the low mass operating system is a neat way to reduce recoil in a game gun but don't like it for a duty gun.
caelumatra
06-21-11, 07:52
Thanks Todd. That's something I hadn't really considered.
Here I was thinking if it were lighter it would be able to over come those things you mentioned if the spring were the same. But then I thought about a ping pong ball in a pinball machine. The spring would be the same but the ball wouldn't have the right weight to move through the machine properly.
This gun won't be going to war but I hope to take it to some of the land nav shooting courses/competitions and dirt may well be an issue there.
Don't do it! You'll run into the same problem I'm having by using the Armalite AR-10 carbine receiver extension, buffer and buffer spring, with a DPMS BCG. The DPMS BC is too light for the buffer and spring, thus the action cycles too quickly for proper extraction. The fired casing gets caught by the forward motion of the BCG and is trapped between it and the port. Since you have an AR-10, maybe you could weigh the BCG and give me the number. I asked in a separate post, but nobody has responded.
caelumatra
06-21-11, 12:50
I would weigh it but my complete upper is at Marvin Pitts getting the barrel dimpled.
But what you're saying would make sense as well. Its too light and not dwelling in the receiver extension.
What receiver extension are you using? I have an Vltor 5 pos Ar10 RE with the ar10 spring and h3 buffer as well.
What receiver extension are you using? I have an Vltor 5 pos Ar10 RE with the ar10 spring and h3 buffer as well.
I'm using the Armalite AR-10 carbine receiver extension. It should be dimensionally the same as your Vltor part, or close enough.
caelumatra
06-21-11, 22:23
Well, your probs and Todds comments about dirt are leading me away from this.
I'll email Marvin and see if he'll throw the BCG on the postal scale for me
You are probably better off just going with a lighter rail like the TRX to drop some weight.
M90A1, I think you have something else going on. The spring is different but the H3 buffer is heavier than the DPMS carbine. What barrel is it and did it function before you changed the buffer tube or did you build it that way?
M90A1, I think you have something else going on. The spring is different but the H3 buffer is heavier than the DPMS carbine. What barrel is it and did it function before you changed the buffer tube or did you build it that way?
It functioned perfectly with the original DPMS A2 receiver extension, DPMS .308 rifle buffer and DPMS .308 rifle buffer spring. What makes me think it has something to do with the Armalite spring, buffer, receiver extension setup is the fact that Armalite uses the heavier BC with the exact same receiver extension, spring and buffer. Removing some of the recoiling mass by using a lighter BCG should, in theory, make that entire mass move more quickly, thus my reasoning. I'm going to re-install the original DPMS rifle setup that came on the gun for my next range session, and see what happens. If it still doesn't operate correctly, I have a different problem, as you suggest.
BTW, you guys supposedly use the Armalite BCG in your .308 rifles. Any way you could weigh one of them for me?
I don't think there is more than an ounce difference between them from what I remember looking at them side by side.
I'll see if I can dig out a DPMS to weigh them both.
19.4 oz for the AR-10 BCG.
18.8 oz for the LR-308 BCG.
Thank you, Todd. You're right, that's not much difference. I'll report back after I try the original DPMS parts again.
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