1st Serious attempt at tuning my Disco

[Arkmaker]

This is the first string after fitting up the new to me stock and m-rod trigger frame. Accuracy is fantastic, but the goal I have in mind is for fps to be in the 800-850 range for 45 to 50 shots. Right now, this puppy is blistering them at over 950........ Starting fill pressure was a little higher than normal. I did 65 pumps from 1K and should have only done 60.  Next is to back off the PA and start the long process.
Any thoughts.

[UCChris]

Are you using/considering an SSG?

If you want to have a super flat shot string and get 90-100 shots, just cut the Disco tube down to 2" past the valve, chuck a tank block and a Ninja SHP bottle on it and you'll be cooking.

[CraigH]

Pretty much standard .177 performance.     Tuning down the PA or changing the hammer spring is a good first step.

[moorepower]

Try a smaller transfer port. Start with a 1377 and drill out if needed.

[c_m_shooter]

your going to want a smaller transfer port.  Order a couple spares for a Crosman Challenger and drill out to needed size.  Mine is at 0.080" for 12 ft lbs (8.6 gr @790fps)  I used .125" when it was at 20 ft lbs.  I didn't have good results with the free flight hammer, so I went with 2500 psi fill screw mod and a regulator.  Now the es is about 3 fps for over 50 shots.  I will do more, but I get bored counting, so as soon as I had enough to shoot a field target match without refilling I stopped.

[Dairyboy]

Try a smaller transfer port. Start with a 1377 and drill out if needed.

+1 smaller transfer port will definitely be the way to go here. Personally I think you should try to get a PN for the euro maximus transferport

[c_m_shooter]

Try a smaller transfer port. Start with a 1377 and drill out if needed.

A 1377 transfer port is .140" the same as a stock Disco.

[moorepower]

That's perplexing, because now I don't know where my smaller tp came from. I am sure your right. Lots of options given.

[CraigH]

Ditto on the 1377 TP, same as 22XX, Disco - 0.140 (nominally).    Take a look at the two Maximus EVP's that just came onto the Crosman website (Support-->Manuals).

[Arkmaker]

Ahhh!! The TP! Now how in the heck did I forget about that? I'll make a new one tomorrow and see where I am. Thank you guys. See.......sometimes it is a very good thing to ask.
 
C_M_Shooter, what kind of regulator are you using?
 
Thanks, Rich

[CraigH]

Now the es is about 3 fps for over 50 shots.

Impressive!   

Besides Rich's question on regulator brand, what regulated psi?    TKS     

[c_m_shooter]

Now the es is about 3 fps for over 50 shots.

Impressive!   

Besides Rich's question on regulator brand, what regulated psi?    TKS     

Altaros regulator, set at about 1200 psi.

[UCChris]

I have no experience with Altaros regulators, but I can vouch for Huma regs. Very easy to install, no vent hole needed. Amazing regs.

[Arkmaker]

Thanks for all the advise and help. Much appreciated! I actually had the smaller transfer port on my Disco "to do" list, but it helps if I would just read it one in a while ;-)
 
Today, I made a new TP at .08" thru. Then I made a quicky trigger guard for the m-rod trigger assembly. Came out ok, but I think I will order the Challenger one that someone suggested sometime in the future.
 
So, I had darkness closing in, but wanted to see where I was sitting with the .08 TP. I got the chrony set up and pumped up the old Disco to about 1600 psi. I was starting right at about 830 fps and after about 10 shots, I fell to about 810. I didn't record anything tonight. With a little luck, I will pump it up to around 2200 psi tomorrow and run a full string and tweak the power adjuster a little. But this is the power range I was looking for. So at least I am close now.
Rich

[Arkmaker]

2.2K start with 1.2K finish with the .080" TP and some fiddling with the PA. Started out with 20 shots (not shown) to adjust the PA and ended up with this string. Very close to where I wanted to be. Will try the Free Flight Debouncer gizmo next. But it looks like a regulator with around a 1200-1300 psi setting as suggested before will be the way I end up.