POF picture review.

AR/M4 AR General Discussion
1

Gents, I got my first POF upper in late April or early May of last year. Today my second POF upper was brought by the Big Brown Truck of Happiness. Comparing the two proved interesting.

The two uppers in question:

They both are built on POF 416 lowers with CMT LPKs.

This was interesting. The new upper has some new tricks, like the three pieces of rail mounted on the M4 handguards and the new snag-free sight. I like the pieces of rail, saved me the trouble of adding a piece for the flashlight. However, I’m not a fan of the sight for most uses. I liked the old sight which looked like the top of a normal AR-15 sight tower sitting on a rail. The problem with a fully hooded set up is the tendency for shooters to instinctively align a circle within a circle (the principle H&K uses on their sights). This may cause misses if the front sight isn’t centered.

I use H&K style rear sights, and I like this set up better than the 1/2 circle front sight that came with the sights I bought. I’ll probably get another to retrofit to the older upper.


The first thing I noticed when I lifted the new upper is how light it was. The older upper is a 13.6" with Krink and it is heavier than the 16" upper with the A2 flash hider. As you can see the barrels are slightly different. It appears that the newer barrel is slimmer in profile than the older barrel.

The piston systems have some knocks on them. One, they’re heavier than DI. Two, the piston mass creates a more pronounced recoil (something I noticed on the H&K 416, but I didn’t feel it to that degree on the POF). Three, the reciprocating mass creates a situation where accuracy is diminished. This is speculated to be the reason why POF uses heavier barrels; in order to alleviate this phenomenon. Four, the size of the piston doesn’t allow the use of standard FF rails.

I don’t have a use for #4. And since the barrel appears to be slimmer in profile how do they get around #3? And how to reduce the felt effect of #2?

It looks like this may be the answer. As you can see the piston system on the bottom is quite a bit smaller than the older version on top. Now, I don’t know if this has anything to do with barrel length, but I don’t think so. The system on top is what I remember seeing on their website.


This is a shot showing the difference between the new “no lube” uppers and the old uppers. I subscribe to the philosophy of oil is cheaper than metal, so I will run it lubed. I don’t run the older upper, nor will I run the new upper, “wet” like I would a DI gun.


Here’s a comparison of the new one piece BCG and the older two piece BCG and the “no lube” charging handle.

So that’s nice, but how does it shoot? I’ll find out tomorrow.

2

Nice carbines!

I am a little confused on the sights, do they work like HK sights?

3

The specific sets I use are H&K copies.

Normal AR sights are not supposed to work that way.

As for range testing, it’s going to have to wait. Even the best laid plans hit snags.:mad:

4

Thanks for the great photos and comparisons. I’m looking at either a POF or Bushmaster gas piston upper myself. I’m leaning toward the POF because of the lubeless system. I’ll be interested in reading your range reports.

5

Wait, the front one is a POF? Or are you using the HK clone front too?

6

I had heard once the Bushy was the POF. Is that true at all?

7

On the older gun is an H&K clone front sight. On the newer gun is the POF front sight.

Between the two, I believe I prefer the POF front. I like the full circle with H&K style sights.

I hope that clears it up.

8

I can see now!

Thanks.

Wanna sell an HK front? Do they work with AR rears? I’d actually prefer an LMT rear and like the looks of the HK fronts. I’ve got a KAC rear but I don’t much care for flipups.

9

I’d rather not. I’ve been known to be fickle. :smiley:

10

word is that bushmaster is under license from pof for the pof piston .

11

Do you think?

:smiley:

Your new POF looks great.

I cannot wait to put some round through it.

12

Back from the range.

I fired 280 rounds, WWB and Remington green box (RGB), in just over an hour. Boy did that thing get HOT.:eek: I even got the burn mark to prove it.

Anyway, 280 rounds expended, shooting at a steady pace with the only real breaks to reload magazines. No failures to fire. No failures to extract. No failures to feed.

The only problem I have had is the bolt won’t lock back on the last round with some of my mags (H&K mags to be specific). I have 20 round USGI mags and other H&K mags that work fine. Just four H&K mags that won’t lock the bolt back.

Since it works with the USGI mags and about half of the H&K mags I took with me, I don’t think this is a gun problem. My other POF “build” does not do this.

So I looked at the buffers and springs on the two guns. The newer “build” has an H marked buffer and a spring that is 1/2" longer. I can only theorize that the combination of mags, buffer set up, and the weaker “budget” ammo is causing this anomaly.

13

I’ve had and seen some ARs not lock back on HK mags. Sometimes this is do to a out-of-spec bolt catch and sometimes it’s a weak mag spring. Because of the longer body on the HK mags I find them to be weaker than USGI mags.

With USGI mags get weak you can add a Magpul follower and a Wolff XP, ISMI or SAW red mag spring for better use. As far as I know HK doesn’t sale mag springs.

I now only my 7 HK mags for competition since I never run the rifle dry anyway and the HK mags will seat with 30 rounds in them.

14

My bolt catch is CMT. Have you seen any problems with those?

I’m really tempted to sell the HK’s and buy PMAGs, but I don’t know whether or not to trust them either.:confused:

15

Not CMT but I’ve replaced a DPMS and a Colt bolt catch because of HK mag failing to lock back. Neither rifle failed to lock back on non-HK mags. It’s more of a HK spring problem than bolt catch, if the catch is just a little short or you have a new spring in it a weak HK mag will fail to lock the bolt back.

I haven’t tried the P-mags either but I want to get some to try out. I wonder if Wolff or ISMI would make stronger HK mags springs if I send them one of my tired HK mags?

16

Makes sense. The build is rather new. I think I installed the LPK into the lower in December, and it’s been sitting there waiting for the upper until last Thursday.

17

I thought the reason everyone buys HK mags was because they were supposed to be more reliable.

Maybe it’s just because they’re cooler. :eek:

18

Another 232 rounds expended today. So the total is up to 512 rounds, Winchester 223, a couple of UMC 223s and Fiocchi .223. Not exactly burning through ammo, but grad school has kept me busy. The issue with the HK magazines is gone. I’m told POF complete guns come with a carbine buffer, not an H buffer. I replaced the H buffer with a carbine weight buffer and it worked fine.

I did not have any issues with the mags or the gun. I did have a shooter issue. (Well, I’m 99% sure it was a shooter issue, unless someone else has an alternate theory).I didn’t know you could limp wrist a rifle, but I found a way to do it. Managed to do it with the POF and a Colt.:eek: I got tired and I got sloppy. The result was a misfeed each time.

19

I can somewhat de-bunk #4.
Even though you don’t have a use for rails, other people do…
A Troy can be made to fit with some careful machining inside to clear the piston housing.

20

I posted that long before I knew you provided that service.:wink:

ETA: Well maybe not a long time, but more than two months. https://www.m4carbine.net/showthread.php?t=5521