AR lowers affect accuracy?

[The Trinity Kid]

Good Afternoon all,

As I've said in another thread, I'm in the process of building an AR-15. My thought is to build the cheapest MK-12 imposter possible(mostly, I'd use it for coyote thumping in a place where I'd have shots out to ~300-400yards, but maybe with some 80g bullets, I might use it for deer a little closer).
Right now I've got a PSA 16' upper. 5.56, with a 1-7 twist. The barrel is stainless, and it has an A2 style fore grip, with a front sight post. Next, I'm going to get a PSA Mil-spec BCG, and a lower. Then a BSA scope, a little later.
This brings me to the point of the thread.

Does the lower affect accuracy? I'm thinking of getting a New Frontier LW-15 lower. It's cheap, and polymer, but from everything I've seen/heard about it, most people say it has a tight fit to the upper, and doesn't rattle or need spacers. But, does this lack of rattling make it more accurate, or not? Just curious.

--TK

 

[Deleted member 46119]

I used an FMK poly lower. It is a tight fit. 6mm-AR. I haven't gotten the load nailed down but not seeing problems.

My concern was heat from competition strings so I went piston and adjustable gas block.

Engineering wise, stiff solid for.

 

[ShtrRdy]

I might change Point of Impact but I don't think it would effect precision as long as it's a tight connection.

 

[rcoody]

It holds the trigger!

 

[Deleted member 46119]

It holds the trigger!

Yes it does and mine holds a Jard. Hard to tune but oh so nice once it is.

 

[Greyfox]

The effect of the fit between the lower and upper and the "rattle" could have the same effect as if your bolt action had movement in the stock. Most AR's have some degree of movement, if not when new, after repeated take downs. It's no big deal if there is a some movement since it can be easily shimmed with one of the many types of small shims, or cam pins designed to eliminate it. I'm sure 90% of AR shooters would never see the effect of the looseness typically encountered. For precision work, it becomes more critical and I would simply place a spacer under the rear contact point. With cheap plastic lowers I would be more attentive to the fit of the trigger group, safety, and other interfaces that effect function. iMO.