Increasing USP capacity

L

leadcounsel

Moderator
I've got an HK USP .40 full size. The magazine holds 13, which is adequate. I'd love to plus it up 1 or more rounds. This may be simply academic but would be great if it works. Someone must have tried this.

Comparing it to a Glock 23 magazine, the body is larger but the capacity is the same. I wonder if a replacement spring of some sort, HK or other brand, would fit and work to increase the capacity. I have to wonder what would prevent stuffing 15 in this magazine body...

Anyone look into this or try it?

I know there are "jet funnel" and larger capacity mags holding 16... but I'm not keen on spending $70!!!! for a magazine if a $10 spring will punch up the capacity.
 
You are right to describe your question to be "academic" in nature and my thinking is that adding a round or two to the magazine capacity is probably not worth the trouble and, worse, might negatively affect the reliability of the pistol. I have owned a USP 40 for many years and have always considered the thirteen round capacity to be more than "adequate"; actually, plenty more than will ever likely to be needed. But it's an interesting question.
 
Just swallowed hard and bought the Jet Funnel kit and 4 mags. Buy once cry once. Works good and lasts a long time.

Then I had to buy a Hornady Lock-N-Load AP to feed it....

Best of luck,

Wes
 
I only put 12 rounds in mine, if I cant hit what I want with 12 a few more probably wouldn't make a difference.
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This comment adds nothing to the question and is the same logic the antis use to limit our magazine capacities to 10 and even 7 rounds.


Just swallowed hard and bought the Jet Funnel kit and 4 mags. Buy once cry once. Works good and lasts a long time.
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This would cost what, $200 - $300?! And the other problem I have with the Jet Funnel is that it makes the factory mags obsolete because they are no longer long enough to fit in the weapon. So, I'd be losing the 5 mags I have worth $250 (I could sell them and recoup most of that).

Anyway, all that is not worth the effort. While I do want every advantage possible, I'm not going to recreate the wheel just to plus up my capacity marginally. I was hoping I might just spend maybe $50 on 5 new springs that would easily increase capacity. It would take 10 minutes to swap out 5 springs.
 
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So, I'd be losing the 5 mags I have worth $250
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:confused: Standard USP 40 mags are about $25-27 brand new.... (CDNN, Grab A Gun, Bud's, Cheaper Than Dirt)

You can pull apart the mags and see if you can trip some off of the follower or spring base. In the USP 45 you can do that to make it a 13rd magazine.... i've done it with success but it does create that annoying bullet rattle when the magazine is seated into the gun. Don't get that with my 12 rounders. Reliability has been 100% though.

To directly answer your question, there's no common knowledge 'hack' to increase the magazine capacity. Length is not the only thing to take into account. Width is also a factor. The internal dimensions of magazine body is going to be different. But if you pull the mag apart and take a look, you might figure something out. I have like 8 mags for my USP 9. Perhaps I'll pull one apart tonight and take a look.

I am also not a fan of the mag well kit. The metal base plate on those mags and steel mag well add a TON of weight to the gun besides the weight of a few extra rounds. HK has never really pushed for maximum capacity like Glock has. For example the P30/VP9 mags are only 15rds where they could have made minor tweaks to increase that.... Reliability is of paramount importance and overcompressing the spring will make it wear out faster. To wit, I've had to replace magazine springs in Glock mags, especially in 40s&w.... I have not had to replace any HK magzine springs.
 
I'm not sure how you expected this to work. The only option would be to reduce the volume the spring or follower occupy to fit more rounds. I'm not aware of other followers and if you cut down the spring you run the risk of it not having the strength to feed the last rounds which defeats your goal.
 
Just got home and pulled a 9mm mag apart. Looks basically the same as the 45. If you shave down the long tongue on the back of the follower you can probably fit another round or two. You may also shave down the protrusion on the base plate where the spring seats, and similarly, the protrusion into the spring on the follower.

It may affect reliability... but it's probably possible. I'm not doing it to mine.. because I don't have a problem with 15rds... but let us know how it works for you.
 
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