The new Chip McCormick Railed Power Mag is an excellent design, addressing several key issues which have plagued greater-than-seven-round 1911 magazines since they were first tried.
Among the most significant changes, the feed lips are folded. McCormick chooses to call these "rails". Whatever the name, they provide unparalleled toughness and the ability to slam the full magazine home on an open slide without the fear of spreading the feed lips.
This allows the other two other innovations, those being the full-power mag spring and full-length follower leg.
As you may know, most extended magazines do not use full-power springs as found in standard seven-round magazines. McCormick does on the RPM magazines. When eight-round magazines were introduced, they were generally seven-round mag tubes modified with a Devel follower and smaller diameter (weaker) magazine spring. These were compromises which allowed an eighth round to be squeezed in. These magazines still did not seat well on a closed slide, at least in my experience, due to that eighth round allowing absolutely no more room.
I found out about the full-length follower when I was troubleshooting (more on that later). Though a modified Devel design, a standard GI dimpled follower fit and functioned fine in the 10-round magazine I tested:
The length of the RPM tube allowed a full compliment of 10 rounds even with the dimpled follower. The only caveat was that, like the old seven-round magazines with increased capacity to eight rounds, it was difficult to seat on a closed slide.
It's interesting in that the modified Devel follower that is the RPM seems to exist only to provide easy seating of a full mag on a closed slide.
Shooting with this magazine was interesting. I started off with 11 230grn Hornady +P XTP defensive loads. These ran fine.
I moved on to a couple-few mags full of 230grn handloads. These were comprised of Lee Truncated Cone 0.452" traditional lube boolits over 4.5 grains of 700x. Again, these ran fine.
Then I grabbed a box of these:
There were over 200, 200grn Xtreme Plated SWC handloads in that box. The first few mags ran fine, and then I began experiencing malfunctions, two per magazine, at predictable points. The malfunctions were partial feeds. A firm slap on the magazine (first part of the tap-rack-assess-bang drill) allowed the slide to return to battery under spring power.
I could have crimped those handloads a bit more. However, since they're plated and not jacketed, I like to just kiss the bell off the case mouth and nothing more. I'm sure gunk in the chamber contributed to the stoppages, but it wasn't completely at fault.
Both gun and magazine were filthy when I was done:
I took the opportunity to detail strip my 1911, and then moved on to the magazine:
I noticed uneven contact of the follower with the mag tube:
Upon cleaning, the issue became obvious:
The follower was bent!
I tested the tube with a known-good GI follower, pictured above. It ran just fine.
Among the most significant changes, the feed lips are folded. McCormick chooses to call these "rails". Whatever the name, they provide unparalleled toughness and the ability to slam the full magazine home on an open slide without the fear of spreading the feed lips.
This allows the other two other innovations, those being the full-power mag spring and full-length follower leg.
As you may know, most extended magazines do not use full-power springs as found in standard seven-round magazines. McCormick does on the RPM magazines. When eight-round magazines were introduced, they were generally seven-round mag tubes modified with a Devel follower and smaller diameter (weaker) magazine spring. These were compromises which allowed an eighth round to be squeezed in. These magazines still did not seat well on a closed slide, at least in my experience, due to that eighth round allowing absolutely no more room.
I found out about the full-length follower when I was troubleshooting (more on that later). Though a modified Devel design, a standard GI dimpled follower fit and functioned fine in the 10-round magazine I tested:
The length of the RPM tube allowed a full compliment of 10 rounds even with the dimpled follower. The only caveat was that, like the old seven-round magazines with increased capacity to eight rounds, it was difficult to seat on a closed slide.
It's interesting in that the modified Devel follower that is the RPM seems to exist only to provide easy seating of a full mag on a closed slide.
Shooting with this magazine was interesting. I started off with 11 230grn Hornady +P XTP defensive loads. These ran fine.
I moved on to a couple-few mags full of 230grn handloads. These were comprised of Lee Truncated Cone 0.452" traditional lube boolits over 4.5 grains of 700x. Again, these ran fine.
Then I grabbed a box of these:
There were over 200, 200grn Xtreme Plated SWC handloads in that box. The first few mags ran fine, and then I began experiencing malfunctions, two per magazine, at predictable points. The malfunctions were partial feeds. A firm slap on the magazine (first part of the tap-rack-assess-bang drill) allowed the slide to return to battery under spring power.
I could have crimped those handloads a bit more. However, since they're plated and not jacketed, I like to just kiss the bell off the case mouth and nothing more. I'm sure gunk in the chamber contributed to the stoppages, but it wasn't completely at fault.
Both gun and magazine were filthy when I was done:
I took the opportunity to detail strip my 1911, and then moved on to the magazine:
I noticed uneven contact of the follower with the mag tube:
Upon cleaning, the issue became obvious:
The follower was bent!
I tested the tube with a known-good GI follower, pictured above. It ran just fine.
