Round 1 of my M855A1 Magazine feed test full of unscientific info.

So round 2 is finally upon us!

Round 1 I compared multiple magazines, but today I want to compare just 2!!!

From round 1 the Army tan follower magazine with M855A1 showed less than ideal bullet presentation under the best of conditions, bullet presentation would of course be lower if the gun was running at 850RPM full auto.


So the day is here! The new Army Enhanced Performance Magazine with M855A1!

Magazine:


M855A1:


Loaded and first point of contact of the steel tip on the feed ramps of my M4A1 clone:


As you can tell the steel tip first strikes the feed ramps a significantly higher point than on the tan follower mags.

From what I can tell feed angle is on par with the Pmag M3.

Not only that, but the rounds also feed much smoother and easily from the magazine, meaning there will be less resistance on the BCG and more retained force on the chambering stroke during feeding.

Rounds are held tightly in place and I was not able to force any rounds to spit out by striking or shaking the magazine in any manner.

From my initial inspection, the magazine appears to be a overall improvement over the tan follower magazines and will remove any feed ramp wear from M855A1 feeding.

Do you or any of your friends have a hk 416 (even better a legal full auto one) that you can do a couple mag dumps through?

I've never gotten to play with an IAR, nor disassemble the 416 I got to shoot a couple mags through.

I'm now interested in the supposed stoppage inducing problems with the magazine, when used in the IAR.

Since those of us that have and use the EPM with a regular ar15 don't seem to have any issues, but of course none of us have the budget to run 10k rounds through a single mag on full auto.

Thanks for the pics.

Maybe the mods can merge all the EPM threads? At this point it's all going in circles.

Sadly I have no personal way to get a hand on a auto 416.

However I do have this.



The issue with the M27 is the forcing cone chamfer of the chamber. Notice the chamber wall damage.

Another of those H&K fixing what isn't broken, and now it doesn't work with stuff that works with every other AR type rifle out there.

Interesting, I didn't realize the M27's receiver ramps were that mild of a cut either. And I definitely see the chamber damage. No bueno

Another thing I noticed about the new EPM.

Due to the front wall being higher than on previous GI mags, it should theoretically be impossible to strike the aluminum receiver ramps.

The new front wall height completely blocks the aluminum M4 cuts and no matter what, even on a low angle feed, should push the bullet tip straight into the steel feed ramps of the barrel extension.

So the geniuses made a high cyclic rate rifle designed for full auto, that's supposed to be an upgrade, with m16 style feed ramps, and a shallow cut on the chamber?

The pic isn't the best, but I can only assume the chamfer is less, because there wouldn't be a feeding issue with a steeper cut...

Amazing.

It's significantly less than the standard chamfer of the M16/M4.

Stole this off the internet, but it shows the chamfer well.

Facepalm...

So it also uses a little plunger type thing to put extra pressure on the extractor? Was the 10 cent o ring too cost effective and easy to replace for HK?

I'm amazed they (usmc) purchased millions of the EPM without bothering to test them in the IAR first... and it's the magazines fault the gun jams. Such typical HK "you're not good enough for us"...

That isn't there to add extractor tension per say, but is there (as is the lack of a forcing cone) as part of H&K's Over The Beach (OTB) modifications. The lack of a cone aids in case head support if the weapon is fired waterlogged, and the pin prevents the extractor from blowing out (pressure taking the path of least resistance, because the extractor 'lug' really doesn't function as a bearing surface) when the bolt is fully in battery. The OTB features have been known since their inception to reduce feeding reliability some.

So you know, the Marine Corps didn't buy millions of EPM magazines. Around last October, the EPM 'suddenly' became the magazine offered through DLA with the old NSN (without warning, I might add). Suddenly, Marine Corps units were seeing these things show up, and a freeze was put in place. This is the big reason that stunted the M3 PMag approval, in addition to forward deployed Marines being issued ammunition at times from their Army counterparts. Another reason was due to the EPMs not being able to keep up with the cyclic rate of the M27 and at times the M4/M4A1, particularly when dirty. They were furthermore plagued with QC issues.

Luckily, the EPM is not long for the universe, and the Army is answering to Congress on this one. Not sure why there's so many separate threads either? Good opportunity to merge them into one.

S/F

I'm aware the NSN showed up one day, I remember seeing the civilian articles about it, then everyone got boxes of these when units ordered mags. "Millions" would be quite an exaggeration. Anyway, we bought them. They were issued to the entire unit, we had to turn in our tans (in hindsight, this is so they could give the fairly new tans we had to units closer to deployment rotation).

Is this OTB system even necessary? Since we haven't landed a massive amphibious assault since pre-m16, I guess we don't know in the real world. Still seems like hk fixing what wasn't broke and calling it an upgrade.

Of course there will be a few QC issues when you start production of a new product. I'm surprised the epm wouldn't be able to keep up with the cyclic rate.

Necessary? Probably not. But would be nice to have for sure, short of it causing other malfunctions by being there. I don't know if you've seen the really old (IMO staged in some ways) HK 416 OTB test comparison to the M4 done by HK.

Basically they dunk an M4, don't allow bbl to drain, kaboom it, then lightly dunk the HK, gets a pass. Then of course the other comparison testing they did in the video shows the HK shining like a diamond in a goats ass, and at the M4's turn they just say "couldn't continue with testing cause M4 blew itself up"

ANYWAYS before I piss myself off
Point of my post is the OTB "system" was one of HK's major selling points to this weapon system.

Turn in was guidance given because they were not authorized for use - it wasn't a LOGCOM issue at that time. They shouldn't have been redirected to outgoing units, but I can't confirm that ever occurred.

The OTB features, I'm with you on that one. I don't really think it's needed for our use, but sometimes customers ask for things like that. I see no reason to fire a completely water logged weapon one way or the other. Simply doing a brass check with the muzzle slightly up or down is pretty easy to do, or waiting a second or two muzzle down for it to drain.

I won't say feed rate is the issue, but its a symptom. Historically the US has changed one element of a weapon in question without consideration as to how it affects the system. Every modification made is applied as a band aid to another band aid. GI magazines in general are made to function optimally in guns down to 14.5" with carbine length systems, firing M855. When you start going outside those parameters, of which the spring rate wasn't ever made to handle, problems arise. The large increase of friction going around roughly the 9th-13th round in the stack, particularly when dirty, exacerbates things more. Suppress the weapon or use hotter ammo, and it just gets worse. M3s mitigate the issues relating to the 6th stage in the cycle of operations and later.

The real answer is to beat people upside the head with an angry honey badger when they change one element of a weapon and not address the other aspects and factors within it.

Not really thinking too deeply into it, I think the last true 100% constant curve magazine design was that of the Stoner 63. Someone correct me if I'm forgetting one!

S/F

If you notice in that video they compared a 10" 416 to a 14.5" M4.

10" barrels do fine in OTB tests as seen in the SCAR trials were the 14" scar required more than 3 seconds to drain to be safe.

At the same time the 10" SCAR could be fired straight out of the water.

The HK video would have been a Mk18 vs 10" 416 the results likely would have been similar.

Aren't Pmags constant curve internally?

I'm pretty sure they are, and they use the follower and feed lip design to properly align the top round when it comes out of the curve.

They are as close to it as possible in the constraints of the M16 FOW. For all intents and purposes it is, but I'm referring to a perfect model, like the Stoner 63 or AK (which has an extremely shallow magazine well). Does that make sense?

S/F

I actually believe the last rifle to have a constant curved mag was the KAC SCAR entrant.

In terms of guns that were fielded, it'll be the 63. But yes, KAC did have heavy Stoner influence.

Anyways, the answer is yes, M27s are damaged the least (to a point where it is no longer an issue) when using M3s. That's kind of a done deal.

S/F

Well, this is a cluster fuck well beyond my pay grade and education.

I'll accept this all for what it is, and continue using the EPMs I have, which will likely out last me as long as I take care of them.

I don't have a sbr/fa 416, don't plan to, and probably won't ever have the budget for m855a1 (hell, I don't even buy regular m855, I'm a m193 fan).

Maybe when I get a chance I can beat on a epm and a tan, see what it really takes to make it fail.

Why haven't we had issues with the 9-13 round area with the tans? I understand that it is an inherent design flaw using a tapered round in a straight mag, but if it was that bad, wouldn't that have been fixed in the last 50 years? Well, what, 35, 40 years for the 30rd mags?

Either muh feels are getting in the way, or in the real world the rifle and mags work just fine. Considering I've never had an issue, really, only like 3 stoppages I can ever remember,  and could see the difference in the feed lips between a good mag, it seems like the system works.

ETA: to expand on stoppages, IME, they happen randomly by some disturbance in the force, and that's it, or the mag is bad and does it every time. Again, IME, the mag being bad and the stoppage recurring is more common than the random ones. When I say just a handful of stoppages, I mean the random ones that can't be attributed to anything in particular... I've had my share of bad mags, where they'd double feed every time. I think that it is tolerance stacking and dirt, so it doesn't happen with any regularity.

How so? Is Congress going to step in and force a bit of Magpuls?

Second, and this has to do with forcing cone damage on the M27.

What specifics allows the M3 to completely remove it?

Both magazines have identical feed angle and bullet presentation, both release the round at the same time in the forward stroke, and once the rounds tip has made contact with the feed ramp it's only going one way.

Even with the M3 the bullet tip is still going to strike that forcing cone at the same angle and location as the EPM.

Can you explain this for me, maybe point out where I'm wrong in my views of the feed cycles of these two mags?

Possibly the EPM's aren't feeding fast enough on auto so they aren't being fully controlled by the feed lips during feeding.

Not saying you're wrong, as I have little evidence to the contrary, but I find that very hard believe.

These (and the tan followers) are damn smooth, take some serious effort to make jam up by canting, and the spring pressure seems equal. I only have 10rd pmags (shells, not blocked/pinned) to compare with though.

Idk, looking at the M27 chamber damage it does seem as though the end of the EPM's feed lips are losing control of where the round ends up going before the chamber ends up funneling it in (presumably on full auto) i think he could be on to something.

This is just what it looks like to me though. And the guy above that was involved in this in some way also said the problem was drastically reduced with gen M3 pmags, so that would leave one to believe its a M27/EPM/M855A1 issue instead of just a M27/M855A1 issue.

Looking at the orange/grey picture, it could actually be the flare to the front of the feed lips has the rounds going straight or outboard while the tan has them going slightly inboard.

While the epm "copies" (I don't doubt the army stole the design, at least in portion from magpul, it hasn't been proven in court yet) the angle of the pmag, does it copy the feed lip geometry? Hence if it doesn't entirely, that could be the issue. My pmags seem to constrict the rounds a bit.

Maybe tonight i can measure the distance between bullet tips in the 3 mags. I don't have much better than a fine tape measure, probably can't get an accurate reading with my small mic. Sorry no dial calipers. If any of you have a more accurate device, try it yourselves and see if we get similar measurements.

I'm thinking there may be a noticeable difference once a tape is held in front of it. Probably in the realms of 1/64", but that could be plenty enough to cause problems.