Mag Capacity - Kahr vs Kimber

[Rustynuts]

Took my Kahr MK40 and my Kimber UC 45 to the range and I noticed the Kahr's +1 mag (6 rds of 40) is almost exactly as tall as my Kimber's normal mag (7 rds of 45)! Both are single stack.

How is this possible? I would think I'd get at least 1 more 40 round than a 45! The Kimber does have a steel follower vs the Kahr's plastic one. Do they really take up that much space? Or just poor design/springs on Kahr's part?

[DefensiveCarry.com]

[Redneck Repairs]

Do they really take up that much space? Or just poor design/springs on Kahr's part?

Yes .... ermm and NO LOL . Part of it is the follower design/material Kahr uses , part of it is that the .40 is not and will not be a 9mm in any mag ( a 13 round 9mm becomes a 10 round .40 typicaly ). and finaly part of it is the angle the round must be presented at to reliably feed . In all honesty you get .45 capacity when you bump up to .40 that 1mm makes that much difference when it comes to feed and function . On the bright side you can get .40 in a 9mm form factor which " nearly " equals the .45 " for what that is worth . I like the .45 , and i like the 9mm . I dont care for the .40 but its just my personal opinion since i have never had a .40 grab me and shoot as well as many 9 or .45s .

[ks_shooter]

Single stack capacity is fairly easy. A .45 case is 0.476" in diameter. A .40 case is .424" in diameter. That is a difference of 0.052". For the extra width to equal the diameter of one .40 case would take about 8 rounds of .45.

8 rounds of .45 are 3.808" and 9 rounds of .40 are 3.816", which is just 0.008" longer. 7 rounds of .45 are 3.332", but 8 rounds of .40 are 3.392", which is .060" longer. Depending on how close the magazine spring is to its stacked dead length, that could be too much difference for the spring to accommodate.

[Rustynuts]

8 rounds of .45 are 3.808" and 9 rounds of .40 are 3.816", which is just 0.008" longer. 7 rounds of .45 are 3.332", but 8 rounds of .40 are 3.392", which is .060" longer. Depending on how close the magazine spring is to its stacked dead length, that could be too much difference for the spring to accommodate.

Yes, but remember the 40 Kahr mag IS ONE LESS (7 vs 6)! Why can't Kahr at least get 7 rds of 40 in the same space as 7 rds of 45!

[Redneck Repairs]

KS honestly that is oversimplistic . it in no way takes into account the feed angles necessarily for each round ect . Different diamiter and leingth rounds take different presentation angles even on the same ramp angle . then you combine the floating chamber of a 1911 and the fixed offset ramp of a kahr and you get into real math ( to the level that for me its bend a bit on a mag lip and try it if a mag wont feed ) . I am sure that some where there is a formula to form a mag for a feedramp with variables to plug in , I am just as sure that designs are not done by formula lol .

Edited to add: Rusty part of it is Kahr chose to go with a plastic follower , which will take more space than a steel one , but is plug and play on assembly . One of the first aftermarket .45 extra conversion mag kits was shooting star , it used a clever spring steel follower to help make up for variances in the mag bodys it could go into . With a bit of " tweaking " the design of the " ledge " that supported the round would feed in dammed near anything .

[ks_shooter]

Yes, but remember the 40 Kahr mag IS ONE LESS (7 vs 6)! Why can't Kahr at least get 7 rds of 40 in the same space as 7 rds of 45!

Sorry, mis-read that. I agree that for magazines of essentially the same length, there is no good reason that the same number of rounds of .40 couldn't be made to fit in the space as the same number of rounds of .45.

7 rounds of .40 would be nearly 3/8" shorter than 7 rounds of .45. 6 rounds of .40 would be over 3/4" shorter. That's seems like a lot of wasted space.