I don't think that solenoid has enough power to operate a mag valve reliably. There is a reason why many of the manufacturers use those pancake solenoids. They have a lot of power. The trade off is that they are fat.
In my research I saw this 2 of these solenoids lift the front of a 20 lb robot ~6 in
I think they have the power, I bought 3 so we'll find out
The throw of the relay isn't 6" so that can't be. It might hold that much but it won't lift it on its own.
The relays are rated based on distance from fully pulled in. At zero distance they have maximum pull. You can attach a fairly large load when they are at zero distance and it will hold. As soon as they are no longer at zero distance, the load capability drops off a lot. The farther out you go, the lower the pull force becomes. Since the starting force is always the worst one when firing a gun, you need any solenoid to be able to pull that starting force at the required distance from zero, where zero is fully actuated and pulled far enough to accomplish what you want to do with it.
Fully closed, this solenoid provides 4N of force which is 0.9lbs which corresponds to the 400g gravitation value indicated. This solenoid is the 6W version, so at 2mm out the pull force will be about 0.18lbs and at 3mm the force drops to 0.11lbs. To put it in perspective, a ULT requires almost 1lb to activate it.
It never ceases to amaze me how many experts on this kind of stuff that haunt this forum.