What sort of AR would you build on a Cav Arms polymer lower?

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MMcfpd

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I've pretty much put together the AR configurations I've wanted, well, that are reasonable. So I really didn't have another in mind when Cavalry Arms' difficulties sprang up and I've now got one of their MKII polymer lowers coming my way.

I'm open to suggestions, as I don't really know what I'm going to do with it. I already have .45 ACP ARs that work just fine the way they are, so I won't be doing another one of those. And not too long ago I built a lightweight 16" carbine.

What sort of AR would you build on the Cav Arms MKII lower?
 
An ultra-lightweight 16" carbine (or maybe even an SBR'd 10" or 14.5"). Try to get the weight as absolutely low as possible...
 
Hm. A pistol sounds good to me. Would make good use of the light weight. I'd really like to eventually get something like an 8" barreled AR pistol in 7.62x39mm. That stuff should be much more efficient than .223 out of a shorty barrel, given that Krinkovs still have 2200+ FPS on standard ammo, though I think that's the 11"-12" barreled pseudo-Krinks.
 
CMMG lightweight middie 16" - a match made in heaven.
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Now that's an interesting thought, as I don't have a middie yet. And I do happen to have an unemployed JP muzzle brake as well. Hmm...
 
I would hazard a guess that the CMMG lightweight carbin gas systems coupled with the DD Omega forearm would be as light as you could get. I'm waiting for the Omega middie to come out so I can try it on my carbines.
 
I know its personal but would the fixxed stock versus say a CTR be kind of a downer on lightweight compact rifle?

I'm thinking of building my own CMMG/Cav ultra light.
 
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I would go ultralight CAR (based upon the idea that a CAR system would be lighter than a middy, but I dunno). Flat top slickside upper, pencil barrel, carbon fiber float tube.

Mike
 
OK, this one's developing slowly, as a lightweight. As of right now I've got the Cav Arms polymer lower coming as well as a Les Baer flattop upper receiver without a forward assist.

For a barrel I'm thinking of a CMMG 14.5" pencil barrel with a perm'd muzzle device. That's an area I'm still debating. While its destiny is as a lightweight, I'm considering making the muzzle device either a Bennie Cooley brake or a Miculek brake, and I know those are both heavier than A2 birdcages or Phantoms.

The handguard and/or free float tube is another undecided quantity. Any suggestions for lightweight options there?

And finally, do any of y'all have experience with aftermarket triggers in the polymer lower? I know some setups are problematic in this application.
 
For a barrel I'm thinking of a CMMG 14.5" pencil barrel with a perm'd muzzle device.
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That's the way I'd go. I prefer the Midlength for the extra sight radius, but the CAR would work too if you are more traditional. I'm building a lightweight 14.5 midlength right now with an A2 upper and a DPMS lower (all parts I had lying around except the barrel and a bolt/carrier I have yet to buy).

Why a brake? It's only 5.56 for cripes sake. Get the Phantom. A very good flash suppressor and slightly lighter than a Vortex. You can get the 5C1 or 5C2 with the comp to kill some muzzle rise, but I doubt it matters much.

The handguard and/or free float tube is another undecided quantity. Any suggestions for lightweight options there?
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Keep the regular handguard. Don't weight it down with rails or tubes. I suppose Coronach's idea of a carbon fiber tube would be light, but really what's the gain for the added cost?

Think lightweight and handy. Keep It Simple Soldier.
 
That's the way I'd go. I prefer the Midlength for the extra sight radius, but the CAR would work too if you are more traditional.
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I wonder what the lightest non-SBR barrel configuration is. Obviously a pencil barrel, but what gas block/front sight? Assume for the sake of argument that we're talking about a front sight that sits on the gas block, not a lo-pro block and a sight bolted to a rail.

Also, how much of a weight/balance difference is there between a middy and a CAR configuration? Weight difference I would imagine is exceedingly small (probably only the weight of additional gas tube, essentially nothing). Balance is a different matter, though. It's the same weight, but moved further from the fulcrum. How much of a difference does this make?
Keep the regular handguard. Don't weight it down with rails or tubes.
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Some of the CF tubes are lighter than the handguards.

Mike

PS Note, I'm a fan of middies, and believe that the benefits far outweigh any defecit...but I'm talking about going as lightweight as possible.
 
Also, how much of a weight/balance difference is there between a middy and a CAR configuration? Weight difference I would imagine is exceedingly small (probably only the weight of additional gas tube, essentially nothing). Balance is a different matter, though. It's the same weight, but moved further from the fulcrum.
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It's going to be undetectable I'd think.

Perhaps the bigger concern is dwell time. The 16" midlength has it's gas port in the perfect spot. Far enough away from the chamber to allow chamber pressures to subside before the bolt moves and far enough from the muzzle to allow plenty of time for the gas to act against the bolt before the bullet leaves the barrel.

However, the 14.5 Midlength reduces the dwell time with its port being closer to the muzzle. The bullet leaves the barrel sooner, so the gas is acting against the bolt for a few milliseconds less time. The bandaid for this is increase gas port size. That means higher pressures in the gas tube and against the bolt.

On the other hand, the 14.5 CAR has a dwell time pretty much equivalent to the 16" midlength and 20" rifle. However the gas port is closer to the chamber. This means gas port pressures are higher AND the chamber pressures are still higher.

So I don't know which is better, but I like the longer sight radius and better looks of the Midlength. :p
 
Good food for thought here, folks. Thanks.

The muzzle brake idea was born of the fact that I've never tried one on an AR more than anything else. It doesn't seem like a great thing to do with a lightweight. That PRI tube has definitely aroused my interest. But a middy would, I guess, necessitate standard middy handguards.
 
It's going to be undetectable I'd think.
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I dunno. It's moved, what 1.5-2" further out along the barrel? And, any handguard will be that much longer, too. I agree the difference is probably small enough not to matter, I'm just curious what the actual difference in feel is between two idental set-ups, one at CAR length and one at Midlength
Perhaps the bigger concern is dwell time.
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Yeah, much larger concern...and even this one is not a huge difference for the average user.

Mike
 
I'm just curious what the actual difference in feel is between two idental set-ups, one at CAR length and one at Midlength
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Good question. I don't have two carbines setup similar enough to compare.

Keep in mind that the longer handguard might change the position of your hands also. I have long arms and feel a little crowded on a CAR. Could be all in my mind though.
 
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