I spent the afternoon building a hammer to put what I learned from Lloyd's spreadsheet into practice.... I needed a hammer that would fit into a Disco tube, but had no "waist" as I will be using an MRod trigger group.... I also wanted a bit more weight, so a straight cylindrical shape met all those criteria.... The length and diameter are the same as a 22XX / Disco hammer.... and since I was using a 22XX Crosman steel breech (with the forward breech screw location) I didn't need to relieve the top front portion of the hammer.... I wanted to be able to use the hammer spring from a QB 7X, which is 3/8" longer and slightly bigger in diameter than a Disco spring.... so I made the travel adjuster from a piece of 3/8"-24 NF bolt and threaded the drilled and tapped the inside of the hammer appropriately.... A spring guide was threaded into the travel adjuster, and moves with it.... The hammer spring sits against the back of the adjuster, so the preload doesn't change when you turn it.... What happens is that the front of the adjuster rests against the end of the valve stem, and the hammer moves back and forth over it as you change the adjustment setting.... Since the sear is in a fixed position, the further forward the front of the hammer the further it has to be pulled back to cock the gun.... You therefore have adjustable travel but constant spring preload.... Here are the parts, and the assembled hammer, which weighs 70 gr. including the guide, about 10 gr. heavier than a 22XX hammer....



In the photo of the assembly, the travel adjuster is protruding beyond flush about 0.1".... It can move back inside the hammer about 0.2" which increases the travel over stock.... Eventually the face of the hammer will hit the back of the valve, and that will be the effective limit of the available travel.... I shortened the threaded adjuster so that the hole in the hammer is deeper to accomodate the extra length of the QB spring without having to make a very long RVA....



The extended spring guide runs in a hole in the RVA screw.... It will be cut to length so that it protrudes through the screw only when the gun is cocked, acting as a cocking indicator.... The threaded hole in the top front of the hammer is for an 8-32 setscrew pressing on a small piece od Delrin which will act like a brake to hold the travel adjuster from moving.... There will be a screwdriver slot in the end of the guide to adjust the travel.... A standard Crosman cocking pin sits in the back hole on top of the hammer, but it is moved back 1/16" from the stock location so that it won't hit anything at the forward end of it's stroke....

I made a couple of other small mods while I was at it.... I lengthened the front of the cocking slot in the tube about 1/8" so that it is slightly further ahead than the front of the cocking slot in the Crosman steel breech.... I also shortened the back of the bolt 0.110" for the same reason.... The hammer face will now hit the back of the valve before the pin hits anything, and in fact I may turn off a small amount from the back of the valve to get the maximum possible travel possible.... Unless I lengthen the cocking slot in the breech, it (and the back of the valve) becomes the limiting factor on hammer travel....

I will likely just use the adjustment to find the maximum possible hammer travel where the hammer hits the back of the valve, and then set it so that it doesn't quite hit.... That will allow me to get the highest possible hammer Energy and Momentum with the least preload on the spring, and therefore the easiest cocking.... Once that setting is determined I will back off the RVA until I reach the final tune desired.... At least that is how I think the adjustments will be made.... At least now, increasing the hammer travel will have an instant, and definite, affect on the velocity....

Bob