Forgive me if this is long, really looking for advise of more experienced gun tinkerers than I.
Ok so I finally bit on a Backup 45, a gun that has long fascinated me. I found one that appears unfired / as new and then found a shop that still had new magazines on the shelf and got 5 for 8 bucks a pop.
This is the pre firing pin safety model, prior to various takeover / buyout and so forth. Actually a pretty low serial number so my thought is hopefully better quality control than what AMT is know for. Thus far it's accurate, and I like the size etc.
So far the only issue with the gun is feeding. What it appears to me is happening is that the AMT magazine follower design is frankly flawed in that it has almost no support or stability at the front end of the magazine therefore with a mag loaded with 5 or even 4 rounds it tends to tilt down allowing just enough of a change in the nose angle of the round that it nose plows into the feed ramp rather than feeding. This seems worst with the top 2 rounds in the mag and some mags basically would not easily chamber a round from a full mag and would not feed reliably from a 5 +1 configuration sometimes having issues with round 4 as well. This seemed to be all of the feeding problems with this gun.
The stock AMT follower is of the simple USGI flat steel design with a bent leg that rides in the back of the mag column and a small step for the slide stop that stabilizes it at the front of the mag. Yes I have tired new mag springs despite seemingly "new mags. Even cut down 1911 springs for more "power" to no good effect.
Sitting around at my bench I started looking at an Ed Brown 7 round mag, this is one of the metal form ones he sells, not the newer 8 round mag with a removable base. This mag has a follower that is 2 pieces with significant front support for the follower riding in the mag tube and a fixed / slanted base for the rounds to ride on. So I put this in one of the AMT mags and other than requiring the removal of a few coils of the mag spring it seemed to work in that it keeps the rounds from nose diving and the top rounds now feed with absolute reliability.
This has however come at the expense of 2 other issues --- even with coils removed this follower makes the mag darn tight to seat in the gun when the mag is loaded to 5 rounds. In addition the last round has low spring strength pushing it up so occasionally the last round mis-feeds.
I know that many have discussed the feed lips on the AMT mags, I have examined the lips on all of my magazines and the lips all appear identical and within spec for a 1911 mag which it is based on as I have plenty to compare to. I
So my question is where to go from here. Overall I feel like I am making progress in I have identified some issues and fixed them and the issues that are there are happening less frequently than when I started. Options I am considering are:
1. Add a few coils to the mag spring with the new follower and simply call it a 4 round mag and be happy, a 5 shot 45 acp of this size is still a good carry gun to me and flatter than a J frame which appeals to me. Looking at that mag size it strikes me that 5 might be… well over-optimistic.
2. Go on a spring buying spree and see if I can find one that can be cut to a size that will work in the configuration with what I believe is the better follower…. Maybe try power mag 10 round springs or sig P245 mag springs… basically I need something that has a very high spring rate so I can have relatively few coils under the follower and still have ample power for the last round.
Any other thoughts from anyone would be much appreciated, I will work on posting pictures to better illustrate the progress of this gun project.
Ok so I finally bit on a Backup 45, a gun that has long fascinated me. I found one that appears unfired / as new and then found a shop that still had new magazines on the shelf and got 5 for 8 bucks a pop.
This is the pre firing pin safety model, prior to various takeover / buyout and so forth. Actually a pretty low serial number so my thought is hopefully better quality control than what AMT is know for. Thus far it's accurate, and I like the size etc.
So far the only issue with the gun is feeding. What it appears to me is happening is that the AMT magazine follower design is frankly flawed in that it has almost no support or stability at the front end of the magazine therefore with a mag loaded with 5 or even 4 rounds it tends to tilt down allowing just enough of a change in the nose angle of the round that it nose plows into the feed ramp rather than feeding. This seems worst with the top 2 rounds in the mag and some mags basically would not easily chamber a round from a full mag and would not feed reliably from a 5 +1 configuration sometimes having issues with round 4 as well. This seemed to be all of the feeding problems with this gun.
The stock AMT follower is of the simple USGI flat steel design with a bent leg that rides in the back of the mag column and a small step for the slide stop that stabilizes it at the front of the mag. Yes I have tired new mag springs despite seemingly "new mags. Even cut down 1911 springs for more "power" to no good effect.
Sitting around at my bench I started looking at an Ed Brown 7 round mag, this is one of the metal form ones he sells, not the newer 8 round mag with a removable base. This mag has a follower that is 2 pieces with significant front support for the follower riding in the mag tube and a fixed / slanted base for the rounds to ride on. So I put this in one of the AMT mags and other than requiring the removal of a few coils of the mag spring it seemed to work in that it keeps the rounds from nose diving and the top rounds now feed with absolute reliability.
This has however come at the expense of 2 other issues --- even with coils removed this follower makes the mag darn tight to seat in the gun when the mag is loaded to 5 rounds. In addition the last round has low spring strength pushing it up so occasionally the last round mis-feeds.
I know that many have discussed the feed lips on the AMT mags, I have examined the lips on all of my magazines and the lips all appear identical and within spec for a 1911 mag which it is based on as I have plenty to compare to. I
So my question is where to go from here. Overall I feel like I am making progress in I have identified some issues and fixed them and the issues that are there are happening less frequently than when I started. Options I am considering are:
1. Add a few coils to the mag spring with the new follower and simply call it a 4 round mag and be happy, a 5 shot 45 acp of this size is still a good carry gun to me and flatter than a J frame which appeals to me. Looking at that mag size it strikes me that 5 might be… well over-optimistic.
2. Go on a spring buying spree and see if I can find one that can be cut to a size that will work in the configuration with what I believe is the better follower…. Maybe try power mag 10 round springs or sig P245 mag springs… basically I need something that has a very high spring rate so I can have relatively few coils under the follower and still have ample power for the last round.
Any other thoughts from anyone would be much appreciated, I will work on posting pictures to better illustrate the progress of this gun project.
