Disclaimer: I'm not a lawyer, I'm not your lawyer, this isn't legal advice. All opinions on the law presented in this post and in this thread are layperson opinions, not professional legal guidance. For all you know, one of the posters below bet me that I could get you thrown in jail. I'm not saying he did, but I'm not saying he didn't, but I will say he's a bit mean spirited at times and I could use a little extra cash. Do your own due-diligence. Disclaimer: I'm not a Glock Armorer, I'm not your Glock Armorer, this isn't armorer advice. All opinions on the modification presented in this post are layperson opinions, not professional Glock guidance. For all you know, that mean-spirited jackass offered me twice as much to see if I could get you to blow your own hand off, and maybe that money is worth more to me than your hand. Do your own due-diligence. Ohio has an unusual law that doesn't technically restrict magazine capacity, but does reclassify your 9mm Glock into an "automatic weapon" if you "modify" it to be capable of firing more than 31 rounds between mag changes. Which is a bit silly, but leaves us with a little wiggle room. To the best of my knowledge, the magazines themselves aren't directly prohibited. You can buy them from a gun shop. You can own them. You can load them. You can juggle them. You can stick one up your nose for all I care; it's your magazine. To the best of my knowledge, (that means if I'm on your jury, when you're tried for doing it, I'll vote in your favor, regardless of what those other 11 folks think) it's legal to modify a 33-round magazines to hold a maximum of 30 rounds, and use these converted magazines in your semi-automatic firearm. I haven't yet acquired a 33-round magazine, but I do have an old 17-round magazine to play with. I haven't seen anything to suggest that the 33-round magazines are so different that this won't work. The height of the spacer might need to be adjusted a bit; YMMV. Above, we have the magazine insert from the magazine, and a spacer cut from 1/8" Kydex. This spacer is cut such that it sits flush on the insert like this: Here are another 5, 1/8" Kydex spacers, cut to fit fairly snugly inside the magazine tube. I used aviation snips to cut the Kydex, and used the insert as my basic pattern. I needed 6 spacers total - 3/4" - to reduce the capacity of this particular magazine by 3 rounds. The 33-round magazines may have different tolerances; YMMV. I have not yet tested gluing these spacers together. If you decide to do it, you can't just stack them up straight, you have to offset them a bit so that they fit in the slide. I've exaggerated the offset of the stack a bit, and placed it next to the magazine to show you what I mean: Assemble as usual, but with the spacers between the spring and the insert. Check that it's limited to what the state wants, crank the dial up to a legal 91% and rock out with your Glock out. Then go home and write to your state representatives; order them to repeal the silly little rule that made you think this mod was a good idea. Then check to make sure that your mags still only hold 30 rounds, that you can't force in that 31st round once everything settled into place. And watch out for that havasu fellow... I'm not saying he wants you to be behind bars with a bloody stump. I wouldn't say that.