It's all a question of local laws. Our 25pdrs can fire blanks only. The Canadian government I suppose, likes it that way. We could fire a live round, of course, but only once.
When firing blanks, there is practically no recoil. I say practically none, because any time you set off a half pound charge of black powder in a barrel it generates some rearwards pressure, but you won't see it on the 25pdr which brakes and base plate to keep the gun from budging under a blank charge. I've noticed from the videos I've shot however that the 12pdrs, which have no brakes and are fired with the barrels more or less parallel to the ground do move slightly when fired, even when chocks are put behind the wheels. If you've ever seen the John Ford directed film "The Horse Soldiers" with John Wayne and William Holden, there is a scene where Wayne's encamped cavalry brigade comes under fire from a hidden Confederate battery of two guns. The guns look to me like they were the old 1842 guns, not Napoleons and are fired using linstocks rather the more historically correct friction primers...but the thing that grabbed me about the scene is that they are bucking backwards...really jumping when being fired, which means they had something up the muzzle when fired. John Ford was just too fine a director I think to accept anything less than something that was visually perfect.
Recoil systems are quite easy to disable. However I suppose that even if some of the parts were welded so that they could not move, it would still not be impossible to replace the entire recoil system with a new one. The thing is that 25pdr recoil systems are kind of rare these days, as are any parts for these guns.
In the US, the laws are different and guns of up to a certain caliber can be fully functional as long as the only ammo used is non-exploding. There further more I believe, something called a "destructive device permit" you can obtain from ATF for the bigger stuff. It's all kind of silly really because it's pretty much impossible for a civilian to obtain exploding ammo for just about any kind of artillery piece, and in any case, 25pdr ammo is only made in Pakistan, and even the shell casings are very hard to come by.