New York Firearms Forum banner

1 - 10 of 10 Posts

·
Head Fapper
Joined
·
1,216 Posts
Discussion Starter #1
So the second I got home w/ my new-to-me ACR, I checked a couple mags to see how they fit. One dropped free, one didn't. This bothered me a bit, so I took all of my pre-bans that are in my cabinet out (still have to test what's in my range bag, but too lazy to go outside and get it out of the truck).

Out of the 25 magazines I tested, 18 dropped free and 7 did not.

So I got curious as to what in the hell would cause this, with thickness and weight being the key factors. Weight was all over the place on both drop free and non-drop free, so that wasn't it. I tested the thickness (vertically from the top of the magazine feed lips to the mag catch hole) of every one of them and here are my results:

Drop Free
Min - .879"
Max - .899"
Average - .889"

Non-Drop Free
Min - .892"
Max - .914"
Average - .903143"

WTF?!? The minimum of the non-drop free list is thinner than the max of the drop free list. So I re-tested to see if it was indeed "defective", Yep, still didn't drop free. As you can see, the average of the groups are indeed different (.014143").

Although my testing procedure was not laboratory-grade, it's not exactly difficult to operate a caliber, zero it, and read off of the digital display.

I also tested my two pre-ban 20rd magazines, and they were both drop free and .891" thick.

Any ideas? I wonder if it has to do with the lower receiver being polymer on the ACRs?
 

·
Registered
Joined
·
11,238 Posts
Cossey,
If you use any orlites they are all over the place.
how did "my mags" worked. I ask because I know the colts well and they work flawlessly in anything I have.
Also did you measure the magwell for uniformity. All might be is a break in period.

Do this, take out the upper, put a mag in the lower and put the mags against a light source. Then look in line
and see where the touch points are between drops vs. non-drops. See if you find a pattern where to maeasure
from. The pattern above alone looks ok to me but it is hard to say w/o close inspection.
 

·
Head Fapper
Joined
·
1,216 Posts
Discussion Starter #3
Cossey,
If you use any orlites they are all over the place.
how did "my mags" worked. I ask because I know the colts well and they work flawlessly in anything I have.
Also did you measure the magwell for uniformity. All might be is a break in period.

Do this, take out the upper, put a mag in the lower and put the mags against a light source. Then look in line
and see where the touch points are between drops vs. non-drops. See if you find a pattern where to maeasure
from. The pattern above alone looks ok to me but it is hard to say w/o close inspection.
Will definitely try your test to see how that goes shortly.

Because all of the mags are mixed together now, I am not sure how yours worked lol. I believe I put Magpul grey followers in them, and if true, they all fit fine.
 

·
Registered
Joined
·
913 Posts
sell off the ones that didn't drop free to me :) since they are defective ill buy em real cheap haha. but really if it bothers you sell em and try some different ones
 

·
Registered
Joined
·
11,238 Posts
Cossey,
If those work I am going to see If I can find another case of the colts at old army price ;-)
If so we will split evenly. do you think you need more than 50 magazines?
It would be nice to know why the others don't drop just in case.
Anyway a tight mag well to start with is not necessarily a bad thing, a loose mag well is worse.

I was hoping tifosy, evileyes and others looked at this too. I really know close to nothing about the ACR but
I can help with the mags and debugging thought process.
 

·
Registered
Joined
·
913 Posts
Cossey,
If those work I am going to see If I can find another case of the colts at old army price ;-)
If so we will split evenly. do you think you need more than 50 magazines?
It would be nice to know why the others don't drop just in case.
Anyway a tight mag well to start with is not necessarily a bad thing, a loose mag well is worse.

I was hoping tifosy, evileyes and others looked at this too. I really know close to nothing about the ACR but
I can help with the mags and debugging thought process.
colt mags? should split them 3 ways
 

·
Registered
Joined
·
2,107 Posts

·
Super Moderator
Joined
·
1,205 Posts
Measure front to back depth as well as side thickness.
 
1 - 10 of 10 Posts
Top