Detuning Norica/TF89/Beeman?

[Artie]

I went through a beautiful nos Beeman GS1000 I came across. Debur, polish, new seals etc and the gun is a fine shooter, about the purtiest breaker I own. Problem is too much bump in the thump as expected for these guns.
The tophat is a hammer of a steel lug and the spring is longish, 44-45 coils, fairly small, Gamo like diameter.  I figure if I decrease tophat weight that in tandem I should swap in a lesser spring to prevent the piston slam that probably will result.
So GTA tuners, I'm seeking suggestions on tophat/spring combinations specifically for the frequently cloned Norica air rifle. Any personal experiences or advise is welcome..
Artie

[Roadworthy]

Go one change at a time.  Lightening the moving mass (the lighter tophat) will tend to reduce the power a bit and hence the piston slam.  Of course cutting coils and going with thinner spring wire will help, too.  Any weight removed from the piston will also lower the gun's power.  A correctly sized piston seal may increase your speed a bit but will also make more consistent shot placement. You're balancing a lot of different factors as you strive for your idea of perfection.

[OleTomCat]

You can make a new top hat out of delrin or other tough plastic make it fit the spring and piston tight, put a hardener washer between the spring and delrin...

Go to Air Rifle Headquarters, he may have a light weight drop-in kit or find a spring that is close to yours but shorter or softer. 

When I detune a Gamo I usually use an ARH Merlin spring...

Good luck and feel free to contact me if you have any questions...

[Artie]

Thanks Thomas and Al for the input. I've got delrin ready to turn, it's the spring choice that's holding me up. I don't want to chop the OEM spring until I've had a shot at a tried and trued, soft tuned alternative. 
I'm familiar with the Merlin XL spring, having dropped two of them in Gamo's but I will need to measure the oem set length first. Normally I record all specs when going thru a gun but I guess not this time? CRS... I reckon cause if I did it would be in the danged data book I put somewhere where I wouldn't forget.
I know the Merlin coil count is several less than the Norica oem so I suspect with a Merlin dropped in I would be spacing in addition. The Gamo's with 1/2-5/8" spacing were dialing in around 12 fpe +/-  (gun dependent). If I remember correctly with the Gamo's, only so much spacing increased power before returns diminished and coil bind resulted.
Thanks for suggesting the spring Al, easy enough to yank one from a Quest and give it a shot.

[d-cuttler]

I recently purchased a reduced power spring from ARH for my Diana 52, and was so pleased I decided to do the same for my Norica Black Eagle. I contacted Norica directly and they gave me a spring part number for rifles that produce about 12 foot pounds of energy.

They do not sell directly, but I found a dealer in Portugal who is going to order it for me and ship it to me in California. The company is Mundilar Airguns.

I found both Norica and Mundilar Airguns to be great responders. I hope this helps.

David

[Artie]

Thanks David, exactly what I was was looking for. Would you mind forwarding me the contact information and cost estimate. I would certainly appreciate it.

[d-cuttler]

Contact gorka@norica.es and give him your air rifle model, and ask for a reduced power spring part number.

Then contact loja@mundilar.net and request that he order the spring for you.

I have no idea what the price will be, but it cannot be much. Whatever it is I am buying it.

MUNDILAR is planning to order the spring with one if their stocking orders soon, so it may tak a month or two before I have the spring, but I am in no hurry.

[Artie]

Thanks. Interestingly enough, I posed a question to the forum a while back regarding Norica trigger pedigree and it was Gorka who responded. He is a Norica rep and apparently also a forum member.
The air rifle, though manufactured in Spain (Norica) is Beeman branded so I'll have to ask about that..

[d-cuttler]

Thanks David, exactly what I was was looking for. Would you mind forwarding me the contact information and cost estimate. I would certainly appreciate it.

I just paid for the mainspring, which including shipping came to a little over $24.00, and I already have a tracking number

The spring appears to include a seal, which is something I will be happy to have.

[lefteyeshot]

I wonder what would happen if you just removed the top hat or replaced it with a washer?

A few years ago I bought a TF89 at a pawn shop. Kicked so hard it would rattle your teeth so I did the poor man's de-tune . I cocked it, put it in the back of a closet and forgot about it. Four or five month later I remembered it was in there, got it out, shot it across the chrony. It didn't loose one FPS and still kicked like a mule and still does. My Norica Black Eagle and Massimo seem just right.

[Artie]

Removing, replacing or modifying the tophat would be fairly easy and step one most logically. The head of the tophat is @ 1/2" so it could easily be reduced 3/8" to lessen preload. I could reduce the existing top hat or by producing another. That would be a comparative reduction of 1- 1 1/2 active coils I'm guessing..
I'll likely make a fresh one from delrin with a 1/8" head and go from there, anticipating some spring coil reduction ultimately.