Well not sure what a sledge is (use a sledge hammer?  I just used a regular punch and regular hammer)  but the pin holes were fine.  I test fit the pins through the holes before attempting install.  They were tight but they would still fit.  The issue was the over sized pins trying to go through the pin hole in the actual hammer and trigger.  Those were very tight.  This caused binding inside the trigger and hammer which then eventually sent the hammer and trigger through the polymer pin holes.  Originally I got the hammer in place ok.  But then on the trigger install that breakage happened.  Then when New Frontier told me to strip it and send it back the huge part of the hammer pin broke off trying to get the hammer pin out.  The pin had binded in there so tightly that the polymer pin hole came apart before the pin would move from the hammer.  Anyways the entire point of the story is - make sure your pins are sized to .154 and not anything bigger (like .156)

Also new pictures added to original post of the completed gun.

i never said i use a sledge on my parts...someone said you could have done the same thing with an aluminum lower and i simply said i doubt you would unless your using a sledge hammer.

Ah, my mistake.  Yes I agree, I really doubt that you could punch holes in an aluminum lower like that without using a lot more force then I was using.  I would imagine that the pins would bend out of shape before the aluminum lower would.  I really couldn't imagine an aluminum lower having this sort of issue.

I've put 500 rounds through my NFA with no issues.
I like it enough that I got 2 others for a pistol build and 300 blackout build.

I still want to see a 2k after report with this lower...I suppose after 2k rounds and nothing is broken yet might be an ok lower

If you take a 1/4" drill bit through the Pivot and rear takedown pin holes and a 3/8" bit through the safety selector holes the pins will function normally tight but not too tight that you need a tool to push out pins. The safety selector hole allows the selector to "click" when going into safe and fire. Another issue with using real LPK's in the polymer lowers.

Also if you take a little material off the mag catch side the catch will work smoothly as well as taking a small amount around the edgeds of the mag button side to allow the button to move inside the lower a little further.

I have been able to get the mag catch threads just as far into the button as on a forged lower with no problems.

I have smithed a couple of these NFA lowers with no problems. Now whether I want to put a hefty upper on them is another question.

I would leave these lowers to a more expensive, better setup dedicated .22lr build to use regular AR .22lr mags and just get a dedicated upper with the option of being able to run .223/5.56 as a back up.

I would not trust this as my primary weapon. I will keep my spikes / seekins lowers for that responsibility.

1 out of two aint bad right?

I own two NFA complete poly lowers.  One of them I use on my 3-gun rifle and have shot over 1k rounds through it and not an issue.  People will give you a hard time since its poly.  Would I rather have an aluminum lower? YES but for a $100 for a complete lower why the hell not.  Plus the lifetime warranty comes in handy.  I also own a aluminum lower which I use for 3 gun.  No complaints on my end.

Has anybody ever had to try and get warranty on a reputable forged lower?  I don't think this is ever an issue.

I don't have a dog in this hunt; all of my lowers are forged, and I cannot speak to the quality of the poly lowers.

I just keep seeing posts talking about the fact that if they break, they can just get another.  I would never want there to be a possibility of this happening, especially at the worst possible time.  Lowers and LPKs are beginning to come back down in price and availability is increasing.

I am only trying to understand what has been posted.  There should be no reason to worry about warranty, nor should one have to modify something to accept parts that should fit.  When people ask me about poly lowers, what should I really be telling them?  "If it breaks don't worry?"  "If you have an exacto knife, you can fit the parts..." ?

Building an AR is pricey, and there are some ways to save money, but I am not sure if $30-$90 saved on a lower purchase, and risk these situations is worth that savings.

I have had friends, family, and co-workers ask about them.

To me the word warranty means "we expect it to fail so we will replace it free of charge"

I have around 1500 through my carbon 15 and it's been really solid so far!..  we'll see in another 1500

I want one. Thank you OP.

This is not a 3D printed Lower. It is also not a run of the mill ABS injected plastic. It's all about tensile strength and I think these lowers will meet the requirements. All the real force should be going straight back into the buffer tube. I seem to remember when Stoner was ridiculed for using Aircraft grade Aluminum in a automatic rifle. Or laughing at the idea of a "plastic" Glock in military service.

It's simple evolution and it will only get better.

All the force goes to the buffet but what breaks is that small part or plastic by the rear take down pin which gets a lot of force...that's where they all break

In the video on the NFA site one guy holds the barrel while another guy holds the buffer tube and they use the rifle as a step to get into a truck I am sure that put a considerable amount of force on the rear takedown pin in that area.This is after they shoot the rifle on full auto and play a game of hot potato with it.....................But yeah its complete junk!

I've got about 4k through my NFA.  A mix of 2/3 22 and the rest 5.45 with a S&W 5.45 upper and no problems other than the pistol grip screw working loose sometimes. I overtorqued it on reassembly once and stripped the plastic threads.

You must buy a lot of infomercial stuff...

Regardless of what I think or other  people think were going to have differences...if the OP wants polymer that's his choice...I do admire that he took the time to write his review and respect his opinion on it...do I think their good? Maybe on a .22 but that's my opinion.

I'll stick to aluminum and the OP can stick to polymer.  I do wish the best for him and hope that it last and serves his needs.

Still i want to hear a range report from the OP after a few thousands rounds

Good luck stay safe and happy shooting friend.

I’ve got a PSA aluminum and a NFA polymer. I like them both. Wouldn't bash either.  

With regard to the NFA brand polymer lower specifically. The number of independent YouTube videos are far more telling, I think, than suspicious pictures of broken brand-x units floating around the internet or the not so flattering statements from some opinionated individuals in a forum.

NFA LW-15 lower with:

7.62x39 - link

300 Blackout - link

Teardown after 1,700 rounds of rapid fire - link

350rds of .223 - link

.450 bushmaster - link

Sure, the last video, not independent, but whatever, take it for what its worth.

I really don't think it's fair to compare a glock to an AR poly lower.

The glock was designed from the start with the use of poly in mind. There are no significant forces at play on
the polymer frame.

The poly AR lowers are a poly version of a component that was designed to be made from aluminum, and it's
a simple materials property fact, that unless the polymer being used meets or exceeds all properties of the
aluminum component its replacing, that it's going to be weaker, and fail sooner.

As another poster commented, without a redesign, or a polymer chemistry that exceeds the properties of
machined aluminum, it's not going to be as durable.

As for whether or not most AR15 users aren't going to war with their poly lowers, well, I would phrase it more
like, "most AR15 lowers aren't going to war, but if they do, the polys wont last long under stress as a replacement
for parts designed to be made from aluminum," unless you happen to think that duct tape is a viable replacement
for welding.

It's one thing to panic buy a plastic lower, and accept it for what it is. It's another thing to panic buy a plastic lower
and then delude yourself and others into thinking it's just as good as one made from aluminum. It's not.

I should add, if you do build an AR from a poly lower, and you do understand its not as durable, and you treat it with
kid gloves the entire time you own it, because you know its not as durable, and you never accidentally tweak it the
wrong way while cleaning it, and you etc etc etc ... it might last awhile.

As for it being warranted, my time is worth more than the cost of the part. I personally am willing to pay more for
a part or item that will function flawlessly, as opposed to, saving a few pennies on a product that I continually have
problems with and have to constantly spend time messing with fixing it.

Videos of NFA firing a poly rifle ... useless propaganda. I'd be much more impressed with 3rd party audited material
property specifications. The video is a marketing tool. Material properties are engineering data.

Did i buy it to replace an aluminum lower? No, i have one its great. It was on the shelf, good price, looks decent, little rough around the edges. Polymer insides? meh, ill shoot the bazongas out of it and if it breaks then at least ill know for myself. Will i use my 'Kid gloves with it", nope.  Im not saying its better, and im not saying its not as good.  Im on the don't knock it till you try it wagon. So IF it breaks then ill either send it back for a new one or hang it up on the wall so i can show all my buddies how rugged i was, you know, Breaking my lower in all :)

Side note, i quick read through the posts, has anyone ever SEEN one break of have ACTUAL photos of one broken?
And to the guy who said he "had to laugh when he read the posts and looked at join dates" well I'm sorry that you think because i joined this website a month ago means i know nothing about an AR platform. Poly lower is a fairly "new" concept, I've never used it so why not try something new? i'd rather have rifles with completely different components than a bunch of ARs sitting in the closed with all the same lowers and parts on them.

Don't you know, the only people who know anything about a rifle that's been around for this long are the people with 1000+ posts on an Internet forum. Get with the program and ditch your rifle(s) until you've spent more time on the Internet

WOW. it really bothers me to hear people on this forum rate another person from their number of posts.  i have been reading this forum for over 2 years, never joined because i did not even have a rifle.

i just read this post because i too found a lower and it happened to be a new frontier.  i have wanted an ar15 forever, and after the libs started all the crap my boss(wife) said i could get one built.

crazy when i am feeding 5 people!!!

i could not even find a lower 2 months ago, but found an nfa complete with the lpk, even though most of the expersts here say it is junk.

99$ plus 20 ffl fee is cheap i will say, but all i read and and heard from some of my ar buds is the lower means nothing in the end...its all upper and barrel.  while i am a newbie to this site, i have read every review and OTHER SITES for information on building your own rifle.

so forgive me to all the high post count people, and remember you were too once a newbie

I guess the crush test were the aluminum lower broke and the poly bounced back just wasn't good enough!

Duh...it bent lol