poly vs. steel ar build?

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SpookBoy

New member
To make a long question short, im planning my first build, m4 style, 556 cal.

They would cost about the same with either:
NFA poly complete lower for $125 & an upper at around 400( del-ton, dpms, etc)

or

A m4 kit for around $450-470 and a stripped lower for around 80-100.

Either way i figure its gonna cost me around $550 with a 1:7 twist & chrome lined barrel setup.

Is there any special tools i need for a build besides a stock wrench??
Opinions on both please and reccomendations on good parts kits, and good low priced uppers, preferably with a bcg so i dont have to shop again.
With the prices of AK's and SKS's jumping, it would cost the same for me to build an AR. Thanks.
 
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DASHZNT

Moderator
I prefer the poly hands down.. theyre lighter and perform as good if not better than steel. Youll get alot of opinions to either side. I will tell you that if youve done your research on poly, you woukld be convinced and not be asking this question. I personally have 5 of the NFA poly lowers and am very haply with them. I decided to go with the stripped ones and build them out myself but that just personal preference though.

As far as tools go, youre gonna need a good punch set. The armorers tool and moly grease and lok tite and a vise block would come in handy thats for sure... theres a couple others but my mind is having a brain fart right now.

Good Luck Buddy!

DASHZNT
 
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Fishbed77

New member
FYI - typically AR lowers are forged aluminum, not steel.

I would recommend using an aluminum lower reciever, if only for the fact that they aren't much more expensive than polymer. Maybe I would consider a polymer lower if I were building a lightweight hunting rig, but not any of the ones that use a plastic hammer/trigger. That's just silly, in my opinion.

The only specialized tool you should need is a stock wrench, though I would also highly recommend a vice block to hold the lower while hammering in pins. They can typically be found for around $15 or so online.

Other than that, you'll need a few roll pin punches. I find a c-clamp useful to slowly press in the trigger guard pin, since the trigger guard ears are about the only thing you have to worry about messing up.

As far as parts and lowers go, I typically look no further than Palmetto State Armory. Their small parts (which supposedly come from the same supplier that supplies the FN factory in Columbia SC) are nicely finished and have always worked for me, and the prices on their lower receivers are hard to beat.
 
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Palmetto-Pride

New member
I would take an aluminum lower any day over a poly while I do believe poly is okay for some things in firearms I do not believe that a AR15 lower should be made out of it.
 
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DASHZNT

Moderator
Well, all armed forces are switching over to polymer lowers. I figure if they trust their lives with them then clearly I can trust mine with them as well.
 
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kdstang

New member
I wouldn't have a problem with a polymer lower.

The only issue I can see being different from a forged lower would be the upper-lower connection strength, and might be more likely to break from a fall that puts stress on the receiver pins or buffer tube threads.

Otherwise a lower is just a parts holder.
 
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Technosavant

New member
Well, all armed forces are switching over to polymer lowers.
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No. No they are not. You are quite incorrect.

For the M16/M4 family of rifles, the military specification is still for forged aluminum lowers. If you know of any militaries using polymer lower receivers for M16/M4 family rifles, please explain who they are, preferably with evidence. As far as the US military is concerned, forged aluminum receivers are still the order of the day.

For other designs there are indeed polymer receivers. Mind you, using polymer in a design that was specifically intended to take advantage of that material's characteristics is a very different ball of wax than simple substituting an aluminum part for a polymer one. The assorted designs out there now using polymer receivers are irrelevant when we're talking AR-15s (or M16s, or M4s)... this particular type of rifle was not designed around polymer receivers. Comparing a 50 or so year old rifle design that anticipated use of forged aluminum receivers with brand new designs utilizing new materials is comparing apples and oranges.

There are a few potential problem spots with poly receivers on an AR-15... simply substituting polymer for aluminum without beefing up those areas will cause problems. There are polymer lowers that are not good quality and there are those that have a good track record (the Cavalry Arms style CAV-15 is one of these), and there are those that seem to be doing fine thus far (the New Frontier stuff). But for a polymer AR receiver to work well it will indeed require some reinforcement in a few places (specifically, around the rear takedown pin and selector switch).

IMO, if you want a poly receiver you'd better do your homework. Personally, I wouldn't get one for a rifle I might use for self defense. For a project rifle, plinker, or just a fun gun, then sure. But just make sure that whatever you get has a good reputation.
 
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DASHZNT

Moderator
Aaannnd, this is where opinion begings to step in and in the end we're right so... Im not gonna get into any argument.

Choose whatever youd like buddy, the pureists tend to like metal as stated earlier. Technology has changed alot and polymer is the wave of the future. You can choose which side youd like to go with and have fun shooting... Chao!

DASHZNT
 
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zukiphile

New member
I will tell you that if youve done your research on poly, you woukld be convinced and not be asking this question.
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Asking a question may be part of his research.

The only issue I can see being different from a forged lower would be the upper-lower connection strength, and might be more likely to break from a fall that puts stress on the receiver pins or buffer tube threads.
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That is plausible.

I read a drop test on AR back up sights this morning. The Magpul polymer sight performed better than the steel ones.

http://kitup.military.com/2012/07/back-up-iron-sight-drop-test.html

I used a New Frontier for my first build of a stripped lower. This let me leave plenty of gouging and scratches as I put roll pins in with a pair of channel locks and punched pins in with an old hammer.

It turned out well. One problem: the slot for the magazine catch was too tight with the standard magazine catch (New Frontier's is shorter)and caused binding. I broke the first rule of assembling anything and modified the more expensive part with a dremel.

Maybe I made a mistake and the NF lower will fail. Maybe polymer is better for the kind of stresses a lower ordinarily encounters (like the BUIS drop test). Either way, it isn't a lot of money.

I respect the opinion of those who have reservations about all polymer lowers, and recognise that those reservations were voiced about Glocks and aluminium lowers in the past. Time will tell, I and I seem to be one of its guinea pigs.
 
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ronl

New member
Have had no problems whatsoever with my NFA lower. As far as I'm concerned,they are good to go.
 
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scsov509

New member
I have a Plum Crazy polymer lower that we converted to full auto so we could test and see for ourselves how it would hold up under a little more rigorous use. So far we've got about 2K through it without any incidents, and most of those are mag dumps on suppressed uppers which certainly beats on the lower pretty hard. I did gut out and replace all the parts when we converted it, so I can't attest to how the polymer take down pins, fire control group, etc holds up over time. But as far as the lower itself goes, it's holding up fine and running as reliably as anything else we have. So while I prefer aluminum lowers, I don't personally have any reservations about building on polymer if you prefer that route for whatever reason. :D
 
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Fishbed77

New member
I read a drop test on AR back up sights this morning. The Magpul polymer sight performed better than the steel ones.

http://kitup.military.com/2012/07/ba...drop-test.html
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I chuckle every time I see someone post a link to this test.

Yes, drop an MBUS a few times, and it will probably be fine. The spring-loaded design allows the sights to just just "fold-in" on impact (as opposed to the "locked-open" design of the Troy sights).

However, as soon as that spring breaks (or the tiny piece of polymer holding it in place breaks), you have a useless floppy piece of plastic on top of your rifle. Search Sturmgewehr's excellent Youtube vidoes, and you will see him explain exactly what I'm talking about, and his experieces with the MBUS sights.

The Troy sights (which are mostly aluminum, not steel), on the other hand, may get knocked off their zero by a few MOA, but even after a number of hard blows, you will still have a sight suitable for emergency use.

The Diamondhead sights that failed in this test were clearly an inferior design, but the test did not make use of the newest (and supposedly more durable) version currently available at the time.
 
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bedlamite

New member
Metal god- Posting a broken Hesse/Vulcan/Blackthorne/Whatevertheycallthemselvesnow receiver is completely unrelated to this thread. They have a reputation for making garbage out of every material, and as soon as word gets out, they just change the name and keep cranking out junk.

I landed on my Cav Arms Mk2 once in '08. No damage to the gun, runs great.
 
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zukiphile

New member
fishbed77 said:
I chuckle every time I see someone post a link to this test.

Yes, drop an MBUS a few times, and it will probably be fine. The spring-loaded design allows the sights to just just "fold-in" on impact (as opposed to the "locked-open" design of the Troy sights).
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In order to fold on impact, the impact has to be in the folding direction. Neither this test nor the one conducted on Vuurwapen blog indicate that the sight folded. The damage in both tests suggests that this did not occur.

fishbed77 said:
However, as soon as that spring breaks (or the tiny piece of polymer holding it in place breaks), you have a useless floppy piece of plastic on top of your rifle.
Click to expand...

I agree that once the sight breaks, it will be useless. The point of these tests is that the sight didn't break.

I will post any failure here if the NFA I purchased breaks.
 
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Technosavant

New member
Aaannnd, this is where opinion begings to step in and in the end
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Make a claim, fail to provide support, get called on it, declare victory, and bail?

Impressive.

Polymer is indeed the wave of the future, but your statement that militaries are switching to polymer lowers is about as wrong as you can be. Sure, there's plenty of polymer receiver rifles coming out and getting adopted, but not one (to my knowledge) is just swapping an AR platform over to poly lowers. Isn't happening. But as I said, comparing the SCAR, ACR, or other new designs to the AR platform is apples to oranges. The former are designed around polymer. The latter is not.

When properly designed (and there's those doing it right), they seem to be holding up in the AR platform. When improperly designed, they don't. I wouldn't go plucking one off the shelf and expect it to hold up as well as most forged aluminum lowers. There's some that will... if the OP finds out what they are and gets one it will be a worthwhile task. Just because it's polymer doesn't mean it's better. At most it will be lighter. At worst it will fail when you need it most.

Personally, I'd have loved a Cav Arms lower for my lightweight build, but they weren't in production when I made the thing and it isn't a big enough deal for me to swap them out.
 
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