[Martin Kallander]

did anyone ever try making 4-5 meter long muskets and putting bayonets on them instead of pike and shot?

[Victor R.]

If they did, I'm sure they quickly abandoned the idea upon realizing that creating a gun barrel of even half that length was impractical and would be either too heavy or too weak, likely killing the person shooting it rather than being effective as a pike.

If you're making a larger/longer barrel, what you're actually producing is an artillery piece or a volley gun, and those don't need a blade on them.

A pike is a relatively simple and cost efficient thing meant to slow down formations in the era before firearms were abundant and effective, using a long length of wood and a relatively small amount of iron/steel, if any at all. They could be produced quickly and cheaply. Producing a single pike-length musket would be prohibitively expensive, time consuming, and exceedingly impractical.

[M. Nordlund]

I do not know about pike muskets, however there was a thing called "the engine of the double armed man" in England which allowed a person to attach a longbow to their pike.
Link to a blogpost about it:
https://leatherworkingreverendsmusings.wordpress.com/2012/11/23/the-double-armed-man/

[Matthew Amt]

There were a few novelty weapons such as a partizan or halberd with a wheellock built into the head, but such things were really just toys, never meant for use in combat. Like knife and fork sets with guns built into the handles.

The problem with combining a pike and a musket, even if you offset the barrel so that if fires alonside the shaft, is that aiming is going to be far worse than for a regular smoothbore. The weight of the pikeshaft will make it wobble, maybe not a big deal when jabbing the pike at a horse, but really bad for shooting. I also shudder to think at all the extra annoyance of cleaning the musket after a day's shooting! Pikes and muskets are stored and transported in different ways, as well, and combining them adds problems there.

It also means a lot of weight added to the pike, which was already heavy enough that soldiers often cut a few feet off the shaft (usually against orders!).

It ends up like being a flying submarine--great for science fiction and maybe some rich guy's toy, but completely impractical and doing neither task very well. Once bayonets were introduced, the pike's days were numbered.

Matthew

[Graham Shearlaw]

While there may of been a few novelty pike muskets, the complexities of handling a pike and of handling a fire arm safety at the same time make it near imposable to use effectively.
One point i'll bring up first is pikes are cold weapons and tend tolerate being left out in the weather over night, but the gun pike all 16 feet of it has to sleep in doors.

Even something like a built in pistol added to a pike would make the pikes usability suffer, for a start your going to want the gun part to be beyond your hands normal positions, guns didn't have great safety's and where likely to go off if dropped or bashed about.

So now we have a cut out of mid way up the pike with a wheel or flint lock in it and hole for a trigger on one side, a barrel running on the top of the other, so that is going to weaken the pike, maybe you could add a sheet metal re-enforcements there.
To aim it you now have to holding the pike at charge, rotate it so you can reach the trigger, then you can aim down the pistol barrel and fire it once before you have to fight with your heavier and weaker pike.

I said once but if the enemy pike men are kind enough to wait, the musketeers reload and the cavalry go off to have lunch, then you can hold the pike some how and reload it.

The last point is I don't think that the split role fit well into the military ideas of the time, a pike charge like the bayonets charge was meant to shock the enemy out of the position, useing speed and aggression.
If some of the men are reloading or still useing a bow then the charging unit is going to lose coherency and effect.

[Benjamin H. Abbott]

It's not exactly what you're looking for, but Xu Guangqi's ideal army in the early 17th-century included soldiers equipped with both a firearm (arquebus or musket) & a pike. I'm unsure how they used these two weapons; I assume they chose one or the other depending on the circumstances. It's possible Xu wanted them to set their pikes on the ground while shooting their pieces, as another manual from the same era describes to do with crossbow & pike. They could then drop their firearms & pick up the pikes as needed. In any case, Xu never managed to actually assemble the force he dreamed of.

Donald Lupton's 1642 text encourages getting rid of pikers & instead equipping musketeers with half-pikes.