My Solution to the FNP 45 Magazine Issue

Discuss the FN Handgun lineup; the High Power, FNP, and FNX line.
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My Solution to the FNP 45 Magazine Issue

Post by Vafrum » 29 Sep 2011, 13:29

It is well documented that the FNP 45 magazines have produced a few feed related issues.

1. Winchester White Box C.O.A.L causing a jam within the magazine.

2. Various HP rounds failing to chamber.

This post IS NOT discussing the Winchester White Box issue.

I first discovered issues with a few HP rounds failing to chamber with my own hand loaded ammo and them methodically started to find the point of failure. My findings were settled with the C.O.A.L being potentially out of spec. They were slightly under sized in comparison to successfully feeding rounds such as Hornady TAP. My mistake, I loaded them. Problem corrected.

The second issue was discovered with Remington HP in about one in forty-five rounds. Initially it seemed to be the same problem by the manner in which the rounds had lodged themselves just outside the chamber in the feed ramp or the top side portion of the early chamber.

I spent hours loading magazines and cycling the weapon and documenting where the failures occurred. I separated the rounds that failed from the ones that were successfully
feeding. I then tested those rounds in each magazine and chambered them in a variety of ways.

1. Slide locked then slide released.

2. Chambering by racking the slide and releasing to allow the full force of the spring.

3. Slowly chambering by grasping the front serrations and following through the slide function effectively buffeting the slides momentum.

This narrowed my findings down a bit. I noticed that the case mouth on the very last round was catching the leading edge of the magazine just enough to disrupt the smooth transfer of the cartridge. It appeared that the leading edge of the magazines were a millimeter or two too high. Causing the squared edge of the magazine to meet the squared edge of the case mouth and prohibit smooth transfer.

So I decided to take a very fine grit sandpaper and smooth out the magazines leading edge. Possibly only a millimeter or even half of a millimeter in change. Feeding now greatly improved. All but for one magazine. I made comparisons to the magazines and found the follow over to be recessed just slightly. So I disassembled them and assembled with two variations. The spring was turned in 180 degree and the opposite 180 degree in another magazine. (They only fit in two ways, and I'm not talking about flipping them bottom to top. I refer to them front to back.)

What I found is that the spring is more effective in only one of those two ways. The highest portion of the spring must be to the front end of the follow over. This allows the round to be pushed up in just enough of an angle to feed properly. If the spring is not placed in this manner, the round when coupled with the case mouth collision issue will jam on the feed ramp. So it's my humble opinion that the issue is not attributed to any single point of failure but a combination and easily solved.

I hope this helps.

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