Glock Magwells and Basepads: Faster Reloads Within the Rules

A magwell and a set of extended basepads are the cheapest way to take time off a reload, and they are also the parts most likely to be illegal in the division you shoot. This guide covers what each part does, which Glock generation they fit, the USPSA rules that decide whether you may bolt one on, and how far a standard magazine can be pushed inside the 141.25 mm gauge. What we hold is listed under magwells, basepads and extensions.

What a magwell actually does

A magwell is a funnel around the bottom of the grip. It gives the magazine a wider mouth to find under speed, so a reload that would have hit the frame edge and stalled instead guides itself home. The gain is largest for shooters who are still learning the reload and for stages where you are moving as you reload. It is not free: a magwell adds weight low on the gun, it can interfere with a very high grip if the flare sits too close to the hand, and on some designs it changes how the magazine drops free.

There are two families. A bolt-on external magwell clamps or screws to the outside of the frame, usually replacing the backstrap on a Gen4 or Gen5 pistol. An internal treatment opens the inside of the frame's magazine channel without adding anything outside. That distinction is not cosmetic; it decides legality.

The rules, division by division

USPSA Carry Optics allows internal magwell dimensions to be increased but prohibits aftermarket external flaring. Production carries the same restriction: no original-manufacturer or aftermarket external magwells, though internal dimensions may be opened. Limited and Open are the divisions where a bolt-on magwell belongs. IDPA and Steel Challenge write their own equipment rules, and those have changed over the years, so read the current rulebook rather than an old article. Our Carry Optics guide lists the rest of the division's limits, including the 59-ounce weight ceiling that a heavy brass magwell eats into.

If you shoot Carry Optics or Production, the practical answer is a competition backstrap or a frame that has had its internal channel opened and its edges chamfered by a gunsmith. Done well it recovers much of the benefit without the external flare.

Generation and backstrap fitment

Glock frames changed shape three times in ways that matter here. Gen 3 frames have no interchangeable backstrap, so magwells for them clamp around the grip or replace nothing at all. Gen 4 introduced the interchangeable backstrap with a locking pin, and most Gen 4 magwells replace the backstrap. Gen 5 revised the frame again, including the beavertail, so a Gen 4 magwell does not fit a Gen 5 even though the grips look similar at arm's length. Slimline pistols such as the G43X and G48 use their own parts entirely.

Check the generation printed on the part page against the pistol you own, not the model number.
Check the backstrap size if the magwell replaces one, because medium and large versions are usually separate part numbers.
Check the pin supplied with Gen 4 and Gen 5 magwells, since the longer frame pin is often included and is easy to lose.
Check drop-free operation after fitting. A magwell that pinches the magazine tube turns a fast reload into a stuck one.

Basepads, extensions and the 141.25 mm gauge

USPSA Carry Optics and Limited Optics measure the magazine, basepad included, against a gauge of 141.25 mm (5.561 inches); Limited Optics allows 171.25 mm for single-stack pistols. There is no separate round limit in those divisions, so the gauge is the limit. A factory 17-round Glock 9 mm tube with an extended aluminium or brass basepad, a competition follower and a stronger spring typically gets a shooter into the low twenties of 9 mm while still dropping into the gauge. Treat any specific number a vendor prints as a starting point and gauge the loaded magazine yourself.

Production is different. It caps you at 15 rounds loaded in any magazine after the start signal regardless of length, so a long basepad buys you nothing there except weight and a slightly easier grab off the belt.

Glock also sells factory competition magazines: the 24-round 9 mm tube listed as an option for the G34, and the 33-round tube many shooters use for practice. Those are cheaper than building a 17 up with parts, but they are longer, and a 33 will not pass a 141.25 mm gauge. Magazines are under Glock magazines.

Followers and springs

The parts inside the tube matter as much as the pad outside it. A competition follower is usually a single-piece polymer part shaped to feed reliably at higher round counts, and it is what stops the top round nosing up when the spring is compressed hard. An extra-power magazine spring keeps the stack moving when a long basepad has added two or three rounds of travel. Buy the follower, spring and basepad as a matched set from one maker where you can, because mixing a tall pad from one company with a short spring from another is the usual cause of a magazine that will not feed the last two rounds.

Fitting, and the things that go wrong

Basepad changes are simple and easy to do badly. Depress the factory retainer through the hole in the floorplate with a punch and control the spring, because the tube is under tension and the follower will travel across the room if you let it. Fit the new retainer plate that came with the pad rather than reusing the factory one. Then load the magazine to capacity, leave it loaded for a day, and confirm it still drops free from the pistol and still gauges.

Three recurring problems. A magazine that will not drop free is usually a magwell pinching the tube or a magazine catch worn round; check the magwell first. A magazine that gauges empty but not loaded is normal, because the tube bulges slightly under load, and the loaded measurement is the one that counts. And a magazine that feeds fine from the belt but not on the reload is often a basepad that has loosened; check the retention screws after every few hundred rounds.

Where this fits in a build

Reload time is one of the few places where money reliably buys a measurable result, so magwells and basepads are worth doing early if your division allows them and worth doing internally if it does not. Pair the work with a trigger you trust, which our trigger setup guide covers, and with the right starting pistol from our long-slide comparison. If you have been reading about compensators as well, the compensator and threaded barrel guide explains why they do not belong in the same build as a Carry Optics magazine gauge.

General information, not legal advice. Current as of September 2026. Laws change; check the official source before you act.