24" varmint extra heavy bull barrel AR-15 with C-mag -- ersatz LMG?

[Chatterbox]

Has anybody tried a build like that?

[reidnez]

It might work somewhat, but I wonder if there are metallurgical differences between a varmint heavy barrel (designed for stiffness and thus accuracy) and a machine-gun heavy barrel (designed to resist overheating.) You also have to remember that machine guns also have much beefier actions than rifles, and usually fire from an open bolt to help with the overheating issue. My guess is that if you slapped a heavy barrel and C-mag on a stock AR receiver and tried to employ it as an LMG, you would start to experience cook-offs or outright failure of the action from overheating.

As an aside, the U.S. Army tested those C-mag drums and found them to be unreliable.

[B Strong]

Has anybody tried a build like that?

I know the varmint barrel is less expensive than the true Colt LMG type upper, but there's nothing to be gained by going with the varmint type upper, and you'll pay a penalty in weight.

Better to save your pennies and get a real (not aftermarket) Colt LMG assembly.

[Chatterbox]

Given that Class III weapons permit is rather out of reach, I'm not sure if I would get much benefit from a real LMG upper...

[Q]

ersatz lmg?

Blackthorne makes a LMG replica upper. I think it is actually made by Hesse. I looked at it before and there are differences if you look closely. Good enough if you want a cheap clone but I'm not recommending them by all means.

http://akpartskits.com/cart/index.php?main_page=product_info&cPath=6_17&products_id=474&zenid=b846e8bfe3638fe77cbdd6dfe22b1878

http://akpartskits.com/cart/index.php?main_page=product_info&cPath=6_17&products_id=472&zenid=b846e8bfe3638fe77cbdd6dfe22b1878

[Chatterbox]

From people's feedback on Hesse/Blackthorn, the chances of getting a lemon seem fairly high.

[B Strong]

You're not getting a tax stamp for another type of upper either, and the LMG upper is designed from the getgo to be what you want to have.

Why spend money on a lesser assembly when you can get the real thing for not much more?

Given that Class III weapons permit is rather out of reach, I'm not sure if I would get much benefit from a real LMG upper...

[B Strong]

When you need a black coated boat anchor, get Hesse/Blackthorn.

From people's feedback on Hesse/Blackthorn, the chances of getting a lemon seem fairly high.

[Chatterbox]

You're not getting a tax stamp for another type of upper either, and the LMG upper is designed from the getgo to be what you want to have.

Why spend money on a lesser assembly when you can get the real thing for not much more?

Well, mostly because it seems the benefit of real LMG upper would be realized in a FA build. Though I agree, the price difference is not great.