Diana To tune or just respring?

[Chocula]

I have a Diana 48 .177 which I purchased used around 1990. Though I have not shot it much the past few decades, I ran it across the chronograph last night with some 30+ year old Crossman premier 7.4gn wadcutters, and some H&N Barracuda Hunter Extreme 9.52gn pellets that I was able to acquire locally. A tissue over the breach does not move when fired, so I suspect my underwhelming energy at just under 12 ft-lbs is likely just a tired old spring. This is a US market gun, so I would not think it to have been a restricted version. What might I expect out of a tuning kit vs just a new spring? I would like a bit more power for small game hunting, maybe somewhere closer to 18 ft-lbs would be nice. The gun seems smooth enough, but I don't really have anything to compare it to. I was looking at the Air Riffle Headquarters VRT kit or GRT spring, either of which seem to be drop in compatible to an untuned Diana 48. I don't understand what the VRT or GRT mean. There also seem to be several different piston seals available, I am not sure what the differences between them are. Thanks in advance for any guidance or options.

VRT Kit - RWS-Diana 48-52-54-56, Chinese Sidelevers-B21,22,30, SM1000
or the
NEW-GRT RWS 31,34,36,38,40,45,46, 48,54,300 Spring

10 shots with the Crossman 7.4gn @ 21 feet from the muzzle
Avg 824.45
StdDev 6.04
Min 817
Max 833
Spread 16

11 shots with the H&N 9.52gn @ 21 feet from the muzzle
Avg 709.91
StdDev 3.6
Min 705
Max 715
Spread 10

 

[bdzjlz]

Personally, I would use a Vortek PG-4 Steel HO kit and a matching Vortek piston and breach seals. Relube sparingly with Air Venturi’s Tune-in-tube and the rifle will shoot super smooth and better than new.

 

[tnt68]

I would not do anything before the accuracy will be lost. The power you have now with the H&N is just a bit less tha 16Joule/12ft/lbs(15.9/11.7) wich is an optimal potential.The stddev you have is very good and in when the spread on target will increase then you may have from a simple "refresh" with std parts to whatever tuning you prefer. In my experience in servicing and mild tuning 977/77, my one and several other, from 7.5Joule/5.5ft/lbs to 19Joule/14ft/lbs I've discovered that increasing the power to the limit is not the best solution to obtain better results.

 

[Shuggoth]

I installed a ARH vrt kit in a B30 (Diana 48/52 clone) and it had it shooting at almost 19ftlb, they are a good tune kit.

 

[EMrider]

Any ‘kit’ will come with a fitted spring guide and top hat. The Vortek ‘kits’ also come with a piston seal, whereas the ARH kits don’t and you need to add a piston seal to your order. A spring is just that alone. FWIW, if you buy a spring from ARH, you need to have it set, otherwise it will be too long to fit. It is a PITA to set a spring yourself (as I once found out) and well worth the $2 extra cost.

Vortek kits come with a small tub of lube (plenty for a single gun) and you can buy a small container or moly lube from ARH. With lubes, less is best and using too much will just make a mess and cause the gun to diesel when firing.

A regular tune kit from either Vortek or ARH should have your 48 shooting in the 14-17fpe range, which is plenty for small game hunting. Personally, I would not go above 17fpe for a .177 gun.

Good luck and let us know how things turn out

R