In an Appleseed shoot, the only time I can see use for these larger mags is when the shooter is standing. However, in a plinking or non-prone shooting environment, are these mags any good? Do they require time to be broken in?
If you are using an extended mag I would go for the 25. They cost the same OT less than the 15. I have a couple of the 25s but use the 10 round mags almost exclusively.
Open up your mag well so they drop freely. The clear ones seem to be a little bigger and tend to need some work not to stick.
I have a couple BX 25 mags somewhere, but I quit using them years ago because they didn't feed reliably. It may have been the ammo, but the 10 round rotary mags work so well that I haven't felt like messing with the 25s again.
Many people have experienced reliability issues with the Ruger BX15 and BX25 magazines. The most common malfunctions are failures to feed, but there have also been failures to eject (stovepipes). There seems to be two issues with these magazines.
First, the front to back dimension of the portion of the magazine that inserts in the mag well is shorter than that of the BX10 magazines. This allows considerable wobble both front to back, and some side to side, that allows the magazine to rock in the mag well. The weight of the banana-shaped magazine tends to make it droop backwards which misaligns the top round with the barrel causing the failures to feed. Since the primary ejector on the Ruger 10/22 is actually a lip on the top of the magazine, misalignment can also cause ejection issues.
A second issue is wobble within the follower mechanism of the magazine itself which can cause the follower to bind within the magazine body.
Take a look at youtube and search for "Ruger BX25 magazine fix". You will find a bunch of videos. The fixes tend to fall into two categories.
The first type of fix involves some attempt to tighten the fit of the magazine body in the mag well to reduce play. Suggestions include applying tape, or an epoxy such as JB Weld to the rear of the magazine body to keep the magazine from drooping rearward. Other suggestions include replacing the magazine latch plunger spring with a stronger spring, or modifying the magazine latch plunger so it sticks further forward. The idea being that increased pressure of the magazine latch plunger against the magazine will prevent the magazine droop.
The second type of fix involves using a spent 22lr case to manufacture a simple brass bushing to be used within the magazine follower mechanism itself to reduce play in the follower.
I have heard some say they have had BX25 magazines that have proved reliable for years, so the problem, while frequently reported, does not seem to be universal.
I only have one BX 25 mag but it has worked 100% of the time for me with no failures or issues of any kind. I haven't used it in a long time because I can go through ammo plenty fast with the 10 round mags. It's short enough I can easily get into prone position.