Anyone been following these polymer lowers from Tennessee Arms?

[TacticalMark]

I'd rather run a polymer lower than a cast lower. IMO MAG lowers are literally a wildcard in terms of what you get. They are cast, so there is a huge chance of getting sheer crap. Too many pics and posts around of sheared off receiver extensions, cracks, etc.

Lifetime warrenty IMO isn't worth anything if you will be replacing the damn thin every time you go to the range. As much as I wanted to like them, I just couldn't. Maybe if they weren't cast they would be worth something.

I didn't realize the consistency of their castings varied that much. I've seen the one broken receiver extension pic floating around before. I'm still a forged lower fan myself.

[daveroberts]

it is very true about the weakness of previous polymer lowers... Mostly due to bad design, instead of actually taking the material fundamentals of polymer into consideration when designing the lower receiver for the molding process they used a CAD copy of a aluminum lower. Well polymer isnt aluminum. They act different and have different characteristics.

The problems with the receiver extension area is two-fold. Polymer cannot take the point loading in the threads like an aluminum lower can. They are prone to breaking along the flat spot where the charging handle passes over the lower receiver. That is why we use a metal insert to prevent point loading and give the buffer tube threads something solid to grab a hold of. The second design weakness in previous polymer lowers was the low shelf design to allow the use of full auto equipment. Our receivers are high shelf only and the breaking along the takedown pin is no longer an issue. It has been designed as one of the toughest parts of the entire receiver.

The pivot pin area was solved by beefing up the material around the pin and extending it along the bottom area. This is a very slight change but increased the strength of the area significantly.

5584851.jpg


9245093_orig.jpg

If you were wondering about the strength of our polymer receivers.... try this with a metal one. This is a video we did on our initial run months ago. we have made incredible improvements since.

[discreet]

I didn't realize the consistency of their castings varied that much. I've seen the one broken receiver extension pic floating around before. I'm still a forged lower fan myself.

The problem with cast stuff is it is a wild card with how it turns out. Sometimes it can be perfect, sometimes it's spongy. Unfortunately there is really no way to gurantee a good cast product every time, especially with thin alloys. Best way to explain it, is porous like a sponge on the inside.

[discreet]

it is very true about the weakness of previous polymer lowers... Mostly due to bad design, instead of actually taking the material fundamentals of polymer into consideration when designing the lower receiver for the molding process they used a CAD copy of a aluminum lower. Well polymer isnt aluminum. They act different and have different characteristics.

The problems with the receiver extension area is two-fold. Polymer cannot take the point loading in the threads like an aluminum lower can. They are prone to breaking along the flat spot where the charging handle passes over the lower receiver. That is why we use a metal insert to prevent point loading and give the buffer tube threads something solid to grab a hold of. The second design weakness in previous polymer lowers was the low shelf design to allow the use of full auto equipment. Our receivers are high shelf only and the breaking along the takedown pin is no longer an issue. It has been designed as one of the toughest parts of the entire receiver.

The pivot pin area was solved by beefing up the material around the pin and extending it along the bottom area. This is a very slight change but increased the strength of the area significantly.

5584851.jpg


9245093_orig.jpg

If you were wondering about the strength of our polymer receivers.... try this with a metal one. This is a video we did on our initial run months ago. we have made incredible improvements since.

Have a few things for that strength test. Try it with the receiver cooled to -20f. Curious to see if any brittleness will occur.

I think Lav set the standard with this, but putting one of these through the same test he did in both of the DD tests would speak for themselves.

[daveroberts]

until i can do that test... here is one a customer sent me that is pretty close.

[nova3930]

I think many of us are skeptical anytime we hear claims of polymer being more rugged than metal.

In a way that's a funny thing to me. How many folks around here carry Glock and M&P pistols on a daily basis and never question the polymer construction? A darn lot. On the other hand though, the number of piss poor attempts at a polymer AR lower are well documented....

it is very true about the weakness of previous polymer lowers... Mostly due to bad design, instead of actually taking the material fundamentals of polymer into consideration when designing the lower receiver for the molding process they used a CAD copy of a aluminum lower. Well polymer isnt aluminum. They act different and have different characteristics.

I'm glad to see you guys taking the right design approach. Polymer and aluminum are different materials with different strengths and weaknesses and you can't just treat one like the other.

Have a few things for that strength test. Try it with the receiver cooled to -20f. Curious to see if any brittleness will occur.

To add to that I'd like to see a high temperature test. Will plastic deformation happen more easily and will it develop a more permanent set to it? Basically what's going to happen if this thing sits in my truck all day on a miserable August day in Alabama?

ETA

And if Dyersburg wasn't 4 freaking hours away I'd drive up and buy one just to play with for $45...

[CHIMO]

To add to that I'd like to see a high temperature test. Will plastic deformation happen more easily and will it develop a more permanent set to it? Basically what's going to happen if this thing sits in my truck all day on a miserable August day in Alabama?...

Don't see how it would be any different then a Glock sitting in your truck?

[Tarheel55]

Very interesting concept, I think it is the right approach. It is interesting to see how polymer pistols with metal reinforcement are standard but when a lower is changed many disregard it. I too am not ready to dump my forged lowers but at 45 its definitely worth a try and do some initial testing. If it holds up and saves you weight, why not.

[nova3930]

Don't see how it would be any different then a Glock sitting in your truck?

Because if it's not a glock and it's not provably made out of glock polymer, you can't reasonably infer that it will behave like a glock, it requires testing. Material selection matters after all...

[daveroberts]

actually it isnt a glock polymer... we actually developed this polymer from making the bushings from the suspension parts from Rough Country Suspension systems. So if it can handle a vehicle bouncing on top of it for thousands of miles.... well.... :-)