Recently, I was at a major gun manufacturers facility to work on a project. During that time, they showed me a test they had run on their guns utilizing different types of ammo. All of the rounds fired were via semi-auto at a fast pace. The ammo used was 55gr M193, soft point/hollow point 62gr and 75gr Blackhills MK’s. The magazines that were used were new NHMTG mil-spec thirty rounders.
They fired THOUSANDS of rounds and captured every time there was a malfunction. What they found is that the M913 ammo (55gr) had very few malfunctions, but the 62 and 75gr ammo had a lot more. As we talked about their findings, we began to examine what is actually going on as the bullets comes up to the feed lips.
As rounds enter the top of the mag, they cavitate (bounce around forward and back). This creates less than ideal feed angles for them. Because of this issue, rounds do not always impact in the correct spots (creating malfunctions).
The reason that the 55gr ammo had little to no issues with feeding is because of their length. They TEND to make direct contact with the barrel extensions and not below it. The 62gr and 75gr ammo tended to impact BELOW the barrel extension and drive the round up into the receiver (causing a malfunction). The reason for this is because of their length and the fact that they are hollow points. I believe that the HP is the main issue for the malfunctions as the tip of the bullet is wider and allowed it to impact just below the barrel extension.
The question is now, what are some ways to improve the reliability? The first thing you can do is use anti-tilt followers in your magazines. These help with the alignment of the rounds greatly. The second thing to do is buy an AR with M4 feedramps as this will help guide rounds that are coming out of the magazine at a bad angle.
The reason for this post was to help educate folks on why you want M4 feed ramps and what they do. You could make the argument that if you use mags with anti-tilt followers, shoot 55gr ammo (non hollow point) via slow fire, that you do not need M4 cuts in your receiver. I would say that you are probably correct. The problem is that you are betting that you will never have to fire your AR aggressively, will ALWAYS have mags with anti-tilt followers and will only shoot 55gr ammo. That is “perfect world” thinking and just does not fly in the real world.
Always better to have something and not need it, then to need it and not have it.
Thanks for the info. I watched an old AR15 Armorer’s video, and the guy suggested the same thing since some of the bullets would tend to ‘feed low’ as you stated. If M4 feedramps didn’t come with a gun, he suggested modifying the lips of the magazine (this was before anti-tilt followers and polymer magazines came out) to where the bullets would tilt slightly upwards. I’m not so sure if this latter idea was a good idea or not.
What about all those years before the M4 feed ramps?
The AR-15/M-16 gained a worldwide reputation for reliability
with ordinary ramps? They didn’t seem to be needed back
then.
Are the M4 ramps there primarily because of bullet weights
higher than 55gr?
I’ve fired thousands of rounds of different types ammo and of
the extremely small amount of malfunctions, 99% can be traced
to the Ammo or Magazines. Usually magazines are the culprit.
Maybe the M4 feed ramps are just another solution looking
for a problem? Most of today’s “enlightened improvements”
to the AR-15 are just that.
We’re dangerously close to over-engineering the AR-15/M-16
system. All this technical nit-picking is just noise.
The reason that the 55gr ammo had little to no issues with feeding is because of their length. They TEND to make direct contact with the barrel extensions and not below it. The 62gr and 75gr ammo tended to impact BELOW the barrel extension and drive the round up into the receiver (causing a malfunction). The reason for this is because of their length and the fact that they are hollow points. I believe that the HP is the main issue for the malfunctions as the tip of the bullet is wider and allowed it to impact just below the barrel extension.
If the primary rounds used by the military are the M-193
and the M-855, and the regular feed ramps support them
just fine, why do we need M-4 ramps for heavier bullets?
Wouldn’t you want the heavier bullet in a longer barrel
for maximum accuracy? It seems the M4 feed ramps
should be on the rifle not the carbine.
Is there a known functioning problem with bullets heavier
than 62grs?
I’ve fired lots of Black Hills 77gr match hollow points in regular
feed ramps without problem.
I didn’t even know there was a difference until I read it here.
Huh. Okay, folks familiar with the M16’s, which to my knowledge don’t have M4 feed ramps, how do they fare running M855 through them? Generally better or worse than M193? I’m wondering if any Marines have found the same thing you have, Grant.
Any idea how far down the face of the receiver the rounds contacted? I’m curious, because as we know, there are ramps, and then, there are R-A-M-P-S. Is there a standard regarding how deep the ramps need to extend to catch any nose-down rounds?
Does “captured” mean they were somehow video taping the events? In slow motion perhaps??
I would like to see some video of tests like this. Would be interesting. Thanks for posting Grant…
I first read about them on another gun forum about six/eight months ago.
(When I said here, I meant the internet)
I looked into one of my 6920s and there they were.
Until then I never knew there was a difference.
And I’ve never been able to tell any difference in firing between the two.
So now I’ve been honest. bkb0000, where did you first hear of them?
I don’t appreciate being called un-informed just because I question the
need for something.
I think some people forget that the Military did a ton of research into this and realized that the M4 feed ramps just make the weapon more reliable (which is really the most important thing).
Very good question, but it has already been answered. 55gr ammo is really the reason why.
The AR mag IS the weak link in the system. By giving the ammo a longer “runway” to feed into the chamber, we are compensating for the mags in abilities.
As mags improve, there maybe less need to M4 cuts. We shall have to see, but as right now, they are needed.
A lot of information was left out of this study. Was a gun with M4 ramps also used as a control to see how the 62+ grain HP/SP stuff cycled with the ramps. I don’t think you need any tests to figure out that ball ammo will run, however slightly, better than HP/SP in any given gun. The question is how much of an advantage will the M4 ramps give you over the regular ramps with the offending ammo.
Remember that I did NOT say the test was PERFECT for the 55gr ammo. Also remember that this test was done on SA. By going FA, you are increasing the cavitation.
Wouldn’t you want the heavier bullet in a longer barrel
for maximum accuracy? It seems the M4 feed ramps
should be on the rifle not the carbine.
You need longer bullets in shorter weapons WAY more than you need them in longer guns. Why you ask? Because the longer barrels allow the bullet to get up to higher speeds at greater distances. SBR’s (like the MK18 do not have that capability).
Is there a known functioning problem with bullets heavier
than 62grs?
Depends on if the weapon has M4 cuts in it and if you are using a mag with an anti-tilt follower. I typically shoot 75gr Tap ammo in my AR’s. I have no issues.
I’ve fired lots of Black Hills 77gr match hollow points in regular
feed ramps without problem.
I didn’t even know there was a difference until I read it here.
What is the definition of “lots?” Remember that you are NOT going to get a malfunction ever time (even if you are using a standard GI mag).
Also remember that this test was done on SA. By going FA, you are increasing the cavitation.