RWS Diana RWS 48- Inconsistent Velocity

[NoRecoil]

like others said check the breach seal and the side lever adjustment.. also did you lube it correctly when putting in the kit.. your velocity is horrible for that gun and you definitely ruined the main spring by cutting it.. never ever cut the main spring.. if you are searching for a low power tame gun get the weaker spring 12 ft lbs I think it is..
that gun is a magnum and it takes a lot of shooting to break in but even during break in mine shot well but it was my second springer so I had already developed a steady hold..
I recently got a chronograph for checking my PCP guns and I'm doing major modifications to them.. making actual compact PCP pistol.. so I needed to compare velocity to get the regulator and hammer spring adjustment correct..I have the chronograph no more than 2 ft away from the muzzle..
you, in my opinion need to immediately get a new mainspring for the kit you got or.. reinstall the factory one.. the cut spring is trash.. unless you have experience as a spring maker and redid the cut end.. also I believe that if you shoot the cut spring in the gun very much the cut end will do internal damage to the gun..
what you have basically done now in powder guns is turned a magnum 30 caliber into a 22 rimfire..
maybe a magnum is not your style so you should have a different model that shoots the lower speeds,I don't know what your wishes are.. but the 48 definitely should be shooting 800+ fps and it's not going to be tame.. just like a 30.06 isn't a BB gun..
I hope this thread helps you..
I currently don't have a 48, wish I had never sold mine..it was 35+ years ago and well you can't get them like that anymore..
mine was a rws Diana 48.. best spring rifle I ever had.. prior one was a rws Diana 34.. the 34 is not a magnum so might suit you better.. less power and hold sensitive.. but I'd never scope a 34..or for that matter any break barrel.. breach block lockup I don't feel is good enough to keep zero on the scope because the barrel moves separately from the scope..
Mark

Hi Mark, I appreciate your input. I decided on the Vortek tune because of the plastic top hat it comes with. You can cut the spring and re-install the top hat, avoiding the reheat process of the cut end spring. Getting feedback from the forum, I think I needed to apply more lube to the piston. I still have the factory spring, so I can swap it in if this spring is too far gone lol.

 

[NoRecoil]

The breach on the 48 is very loose, the JSB is softer and the skirt is wider.

However you will lose some velocity, JSB 16’s in my full power 48 make 19.8 FTLBS every thing else is over 20.

However the 16’s are very accurate, I have shot a field target course with this setup. And no I did not win but I did better than I thought I should have.

This is great to know. You are referring to the 15.89g JSB, correct?

 

[markhooper]

Hi Mark, I appreciate your input. I decided on the Vortek tune because of the plastic top hat it comes with. You can cut the spring and re-install the top hat, avoiding the reheat process of the cut end spring. Getting feedback from the forum, I think I needed to apply more lube to the piston. I still have the factory spring, so I can swap it in if this spring is too far gone lol.

just my honest opinion you trashed your good spring with a clip.. never do that on just about anything in spite of what the know it all's say..
there's not enough money to get me to do that.. especially for the main spring on a spring gun..
I believe your problem was you wanted a tame gun but instead you bought a magnum..
if you wanted a similar gun you can get a HW with a lighter spring instead of destroying the spring by cutting it..
just my worthless 2 cents as a mechanic and machinest.. and welder
you have no idea the damage a cut off spring will do.. there's reasons why they are wound and then they are made flat on each end.. they actually rotate when compressed and released.. and now you have a point to dig itself around.. and heating it up would only make it worse because not being a steel worker you have no way to correctly temper it.
I'm sorry but I'm only telling you the facts.
Mark

 

[JamieUK]

One last thing to check....as you bought it used, has someone messed with the transfer port? It should be 4mm from factory.