Vulcan Hammer spring adjustment for 34gr JSB

I tried to turn up my Vulcan genIV. It didn't have enuff hammer to keep the 880 of where the 25.4 were at. They shoot fine with a lower POI. The cool thing about the Vulcan's, the magazine is deep enuff for the MKI 34.9gr. Giving you the ability to try both MKI and MKII. I finely settled in with the 25.4 gr at 880FPS. The gun shoot's so dang good with the 25.4. I wonder why do I think of trying any thing else. Mont

I think it could be done with some modifications. The firing-valve would need porting and transfer ports opened and radiused toward down stream side. Apparently a Cricket power plenum can me modified slightly to fit the Vulcan air tube. 

On the down-side, with the Gen 4 smallish air tube (260cc), your shot count will be cut into getting the 33.95s up to 875 fps or more. 

to achieve those speeds with 34gr pellet, yo may need to increase also the regulator pressure.... factory settings are only for the 25.4gr

I'm inclined to agree with Mrshosted and zx10wall. The velocity in my Vulcan2 Tactic was a little on the slow side shooting the 34 grainers, but it shot the 25.4 gr pellets so darn well (like a laser as some like to say, but still an accurate assessment) that I decided not to touch it. If I want to blast away with a 34 grainer I simply use my Cricket which has a power tune by Charlie at Georgia Airguns. His power tune will throw the 34 grainers in excess of 940fps, but I get my best accuracy at 915 to 920 with stunning results … less than a half inch at 60 yards. I say stunning because of the POS scope I have mounted on it which I plan to change soon. 

Shalom

John