Picked up a half dozen CheckMate 9mm Match magazines for the STI Spartan V 9mm...
SKU: CM9MM-9-S
Finish: Stainless Steel
Rd Capacity: 9rd
Floor Plate: Welded Base
Follower: CMI Patented
Feed Lips: Wadcutter
Spring: 9mm 9rd Spring
9mm 1911 mags are unique in comparison to most other 1911 caliber mags in that they are made from modified .38 super mag tubes. Because .38 super rounds are longer, manufacturers have come up with various means to shorten the inside of the mag tubes to ensure proper bullet seating and reliable feeding of the shorted 9mm rounds. CheckMate welds a spacer bracket into the rear surface of the mag tube that keeps the 9mm rounds seated to the front of the magazine...
The Spartan came with a 9 round stainless Metalform mag. Where CheckMate uses a spacer in the rear of the mag tube to push the rounds forward, Metalform creases the front surface of the mag tube inward to seat the 9mm rounds against the back wall of the magazine. The photo below shows the creased front surface in the Metalform mag compared to the rounded surface of the CheckMate...
Top: CheckMate / Bottom: Metalform
You can clearly see the difference in seating of the first round. In the CheckMate mags the rounds sit further forward and higher up, more level with the feed ramp and chamber. There is less distance to travel for the round to close into battery. Here's a couple more photos illustrating the difference in seating...
Left: CheckMate / Right: Metalform
Left: CheckMate / Right: Metalform
Overall, the CheckMate mags keep the rounds seated more firmly in place. Because of the gap at the front of the mag tube, the Metalform followers allow a bit of downward tilt in the nose of the top round. The upside is that I had zero feed issues from the Metalform mag through the 250 rounds I put through the Spartan last week, but the inconsistency in seating could potentially end up creating feed issues, especially once the mag springs have been loosened up a bit from use...