So you have a good stock of ammunition and magazines for your Glock series handgun and are looking for a pistol caliber carbine that uses the same of both. Well you are in luck as there are several on the market. These magazines are inexpensive, functional, durable, and, in the case of 9mm, offered in 33-round extended versions. Let us look at some of the more popular carbines that take these mags.
The Thureon Defense Carbine
Thureon produces a blowback designed pistol caliber carbine with an Integral Picatinny rail sight mount and M4-style stock. Using an upper and lower receiver milled from aluminum bar stock they chamber them in 9mm NATO, .40 S&W, .45ACP, 10mm, and .357Sig to accept standard Glock mags. The base price for their Glock compatible carbines is $689.99. Adding a M4 telescoping buttstock will add $15. Weight for this Glock/AR hybrid comes in right at 6.2-pounds.
The ATI Just Right
New York based ATI produces the Just Right series of pistol caliber carbines offered in chamberings of 9x19mm, 40 S&W, and 45 ACP. Their offerings bring many nice features to the table such as an ambidextrous bolt handle and ejection port that can be switched either left or right. It uses the familiar M4-style collapsing buttstock on a 16.25-inch barrel made by Mossberg for the company. Unlike some companies that use a lot of polymer, the receiver is aluminum and a lot of the functionality mimics the AR15/M16 platforms, which is useful for those use to that operation. Overall length of these carbines is just over 30-inches with the stock collapsed and weight is a respectable 6.25-pounds. Best yet, they use Glock standard magazines for all three chamberings. They run about $625 if you search around.
Lone Wolf Lowers
Lone Wolf R&D of Oldtown Idaho offer a complete AR-Glock lower receiver including mil-spec trigger parts and an M4-style buttstock. Their receiver is CNC machined from Mil-spec 7075 aluminum forging and is Type 3 hard coat anodized. They offer it in capabilities to accept 9/40/357/45 GAP caliber Glock magazines. The only bad part is that you have to BYO upper receiver and fit it, which is well within the capabilities of the average AR guy. The price is appealing at just $350 (plus upper).
The Kel-Tec SUB2000
Kel-Tec, known for a wide array of pistols, shotguns, and rifles, has long produced their excellent SUB2000 series of pistol caliber carbines. http://www.keltecweapons.com/our-guns/rifles/sub-2000/ The SUB uses a lot of polymer and looks more like a laser blaster than the other carbines. However, it folds nearly in half and makes one of the best backpack and trunk guns ever made. It's the smallest of the offerings at 29.5-inches open (16-inches folded) and right at 4-pounds. KelTec offers them in both 9mm and .40S&W chamberings that take Glock mags. Is also rather inexpensive at an MSRP of $409.
So bottom line, if you have a bunch of mags and ammo for your G-series pistol, and want a companion carbine, the choice is literally, yours.