There are some that work well for freeshafting, and other brands that won’t. You can tell by looking at the way the spear is held close to the barrel at the front. If it’s held down by the line, it’s not an ideal setup for freeshafting. Riffe guns, for example have a loop of line.
Most freeshaft guns have an enclosed muzzle. Ocean Rhino,AB Biller, and several others have an enclosed muzzle, and are often used for Freeshafting. If you look at the muzzle of an Ocean Rhino and compare it to the AB Biller, you’ll see that the shaft hole is larger. This allows for back loading. Instead of backing the shaft all the way through the muzzle to the mechanism, you can poke the shaft through the back of the muzzle.
Koahs are another brand that is often used, but instead of a muzzle, they have an enclosed track. The track pretty much surrounds the spear. You must muzzle load this type, and use special shark fin shafts. But, the enclosed track guns are incredibly accurate.
Another thing you’ll find is that wood guns are best for freeshafting. Most freeshafters take along a spare shaft or two mounted to the side of the gun. Most freeshaft guns also have a butt after the handle. That makes it easier to load the bands.
Another thing to look at is the line. There will be times when freeshafters may need to lineshaft to get a fish up in the water column, or deep under a ledge. Ocean Rhinos come with a speed load line kit. This makes it easier to wrap the line on the release. It works well, but there are some drawbacks, as there is no way to attach a line to a standard freeshaft. So, if you need to lineshaft, you need to unload the freeshaft first, then hook up the lineshaft. Koah Battleaxe uses a ring that you can slide over the tip of the spear, and it will catch on the shark fin on the shaft. Speargods also makes what they call the Evolution ring and Evolution shafts for AB Biller, Ocean Rhino, Sea Hornet guns. It’s a pretty slick adaptation. The Evolution shafts have a milled section by the flopper to allow the ring to pass over the flopper, and there is a crimped section at the bottom of the shaft to catch the ring.