AR-15 BS Thread

primary arms

 

Good point, I've still got a flash hider and a trigger group from when I upgraded my current AR

 

I'm building an AR this summer but still on the fence with what I want. Can't make up my mind between mid-length and rifle length. I suppose that's far from the worst dilema one could face

 

build a pistol while the ATF is still ok with the sigtac brace!

 

I actually started looking into that a bit after you built yours and I'm finding that the BATF isn't my issue with building an AR pistol in MA. I have a lot more hoops to jump through at the state level. While it's not impossible, it would take doing a lot more research on my end and being extremely meticulous with parts selection. It's not impossible, the state has just made it extremely difficult and I'd rather not risk it until I know exactly what I'm getting into. Plus the lower I bought wasn't built as a pistol lower. Right now, I have the upper sitting and waiting, and a stripped lower and Timney trigger bought and on their way.

 

Was at FrontSight last weekend and this happened to someone's polymer lower. Roughly 300rd thru it when it decided to stop working.

 

what brand poly lower is that?

 

Vortex makes a sweet scope

I've actually got to handle an AR with the vortex on it, didn't get to shoot it, but it was really nice

 

FMK is the company.

 

was the guy injured?

 

Nope, pulled trigger and it fired, second pull it didn't do anything. He lowered the rifle and noticed the stock just fell off.

 

This is my surprised face.

Polymer lowers are a bad idea for that exact reason

 

I have a couple poly lowers that I've put a couple thousand rounds through that have held up fine. They are drop in the dirt rifles too that I take out to the desert for a weekend of wheeling.

 

This poly lower failed where it gets the most beating. With only ~300rd thru it, I wonder if it had defects already in that general area. I've heard of people having zero issues with their poly lowers like yourself. S

 

yup, every picture of poly lowers I see that have failed have been in that exact area where the rear take-down pin is, and it usually happens early in the life of the part. Carrier tilt may play a roll in it too, perhaps the user likes to manually cycle the action, which I heard causes more carrier tilt and stress on the buffer assembly than the action self-cycling when fired.

 

Buddy of mine, RIP my friend, used to pull his AK trigger as fast as he could to see how fast he could dump a magazine. He did this for years and soon enough he had actually "wallered" out the trigger pin hole in the "metal" receiver. Trigger assy. got so loose it would not reset anymore. I can imagine a Polymer lower doing that in short order just to name one reason I don't care for them. That picture above just chiseled it into stone.

 

The fact that any polymer receivers are failing AT ALL, is enough for me to not get one or mill a JMT polymer 80%. Not all of them can handle the higher pressures of 5.56/300BLK. I won't do a polymer build unless it's a dedicated .22

 

This dude has a cool story about his poly lower: http://www.perfectunion.com/vb/ar-15-talk/91141-damage-testing-polymer-lower-ar.html

 

x2. Haven't seen any benefits to them so far when the price of those. I looked into them for a budget build but found I could get a traditional quality lower for about $25 more and threw the idea out.

 

I picked up a complete New Frontier poly lower recently and I'm fairly impressed with it, especially for $120.00 shipped. A lot of the problems with poly lowers came with the earlier generation parts and I don't start my day at the range by jumping on my rifles or anything like that. I was an armorer in the army, I've carried M4s/M16s through some pretty harsh conditions, and I have zero concerns about poly lowers for non-military / non-LEO use. Hell, my poly framed carry pistol has held up fine after many years of use. That said, my tricked out AR will likely be built on a billet lower.