Diana 48 and Vortek full power spring kit............

[1BadDart]

When the stem came out of my 48 piston a couple weeks ago I ordered a full power Vortek spring kit and a new (warrantied) piston. Initially Umarex sent me a TO5 piston instead of a TO6, I didn't figure it out until the gun was back together and wouldn't shoot, so I had to order another on Monday. The piston arrived today so I changed out the pistons and put the new spring in.
The first thing I noticed is it's harder to cock, it's also louder and has more recoil, there is a more pronounced thwack when it goes off. I only ran 25-30 shots through it so hopefully it'll settle down. I didn't get a chance to chrono it with the factory spring but will after the Vortek spring as 1000-1500 pellets on it.

 

[Wadcutter]

Glad you got it sorted.
I have a D48 in .177 with Vortek parts. Produces 970fps/17.6 fpe with JSB exact 8.44gr.
One day i was plinking with my FWB300S then switched over to the D48. The difference in cocking force is a real eye opener.

 

[1BadDart]

With the factory spring this rifle was easy to cock, the shot cycle was smooth and there was very little recoil, I didn't realize how smooth it was until I bought a RWS 34. However after installing a Vortek kit the 34 is a completely different rifle, it's much more enjoyable to shoot. I'll shoot the 48 for a while with the kit and see what it does. If I still don't like it the factory spring will go back in. 

 

[Butch]

Did you use the vortek seal? I put the factory blue seal back in mine and the shot cycle became much smoother. Before I changed my seal back to factory I run about half a tin of pellets through it (250) and the cycle was still very harsh, so back in the blue seal went and all was good. Plus if you got a little to happy with the lube it could be dieseling. 

 

[1BadDart]

I used the blue seal that came on the piston, if it's dieseled I couldn't smell it, no smoke either. For the first month when this rifle was new it smoked like a semi from the 70's. lol

 

[Butch]

Mine too when it was new. Lol. Don’t know what cal you have but mine being a .22 shoots the smoothest with heavy pellets (18-22grain). The gun still lets you know it is a magnum. But it is fun to shoot and accurate. 

 

[cosmic]

This is a suggestion and many might frown on it.. Cock the gun and leave it cocked for a few days to set the spring.. Might have to be done a few times.. It will help.. Maccari put his springs in a compressor to set the spring if you pay for it to ease the breaking in ...