Diana Bandit Hammer Spring mod and adjustment, results!

[UlteriorModem]

I  just could not help myself. Told myself to shoot a few hundred rounds through the Bandit before I started meddling with it. But it's raining on and off and I was bored... no will power

I felt that the Bandit hammer spring was a little too much. Hard to cock, gobbled up air, more FPS that I really needed.

So I took the spring out and cut off a couple of turns. Also there was NO grease on the hammer or inside the tube, so I added some Moly Paste.

Here are the results.

(You may click the image, then once loaded click again, for a more detailed view)

Bandit String by Tom Whit, on Flickr

Above is the baseline without any mods to the spring.

Bandit spring no shim by Tom Whit, on Flickr

The above is after cutting off some coils of the hammer spring. Woops I took off too much! A tad slow for my taste. I stopped at 25 shots but the gun wasent even half empty! I stopped at 25 because I was not happy with the FPS and it was beginnig to sprinkle some rain.

Spring mod with shim by Tom Whit, on Flickr

The above: I added about a 3/8" shim, it goes up inside the hammer. I used a cut off piece of a pen barrel. I will get something more permanent soon. Thats more like it. I only shot 25 to compare to the previous string. It had a few shots left in it.

I wont address the Extreme Spread as it is not a fair test in that the baseline was 40 rounds and the strings after the mod were only 20. But I did see some improvement.

Also swapped out the stock trigger spring for one out of a Bic Lighter. It was way to light at first but was able to fix that with the trigger adjustment. It now has a definative first stage and a break of (estimated) 2 or 3 lbs.

I also considered doing the bstaely O ring mod, but the valve spring only projects out like 1/32 of an inch if that. It would be hard to find an O ring thin enough in that diamater to work.

Wish I could do further testing but it keeps raining on and off.

ps; Getting a little better at posting these graphs

[Pelletjunkie]

It’s nice to see the effects of you messing with the spring. I think there is hope but it may also involve changing the TP size and fill pressure. Will need longer string data to see what direction to go.

[Pelletjunkie]

That slow tune except with a 1/8” shim and slightly open the TP might be what I would try next. The gun is going to dictate where it wants to shoot best and you might just have to live with a velocity a little lower than what you would like. If it was regulated, different story.

[UlteriorModem]

Thanks Frank, I may try that in the near future. But I suspect the Bandit will always have a pretty good spread being un-regulated with such a small 'bottle'. But getting more shots per fill is always a good thing

I forgot to mention that when replacing the trigger spring I also polished and oiled the moving parts of the trigger, especially the lever arm (sear?) that engages the piston.

The gun is now much easier to cock and the trigger actually feels pretty good. It is a far cry from the out of the box experience! Out of the box it was stiff, crunchy, gritty, difficult to load pellets, all around 'cheap' feeling. Now it is smooth a solid latch on cocking and a nice two stage trigger.

[UlteriorModem]

Well this is interesting. It looks like I accomplished very little as far as overall performance is ccncerned. Same number of shots (40), Same spread, just lower velocity 

Bandit 03 by Tom Whit, on Flickr

[rws45user]

Do you have any photos of what you  did ? I was going to try to use this gun as a basement 10 meter  air gun . I only need  around 500 fps  with a 7.5 grain pellet . The targets I shoot at is 33 feet or 10 meters away . 500 fps seems to be what all the 2,000 dollar 10 meter guns are putting out per shot . A match is 60 shots  so I'm  wanting something what can  get around 80 shots  . Do you think its possible  to get it to shoot at 500 fps ? If you don't have any photos of what you did   will you take some  and post it  ? Thanks

[Ribbonstone]

Tom: good..logical...job.

Considering the "bandit" as a cut-down version of the SPA/Diana Stormrider......it's the same "guts" just different lengths.

It's "old school",,,,no external adjuster.  Not too hard to get just the rear end cap off,pluck out the spring, and try a different spring/shortened spring/shimmed spring.   

Just takes a bit longer,more testing....but it will not un-adust itself once you get it adjusted to where you want it.

[bplvr]

If someone can send me the OD and ID of the spring ,the wire diameter and the overall length
  I will post the number of that spring to get u started on close replacements.

[Baco]

If someone can send me the OD and ID of the spring ,the wire diameter and the overall length
  I will post the number of that spring to get u started on close replacements.

idk but the pr900 one that some ppl put on the bandit is as follows:

ID: 7,7mm
OD: 9,8mm
Length: 93,7mm
Wire: 1mm