Here are some more data points for anyone that is interested regarding the:
-Model 95 and
-Model 499b
unless otherwise noted, all data is using Walmart Daisy Precision Max BBs, the cheap ones.
-Model 95:
I have what I think is a late 1960's early 1970's Model 95. My results from modifications to the Model 95:
It was shooting ~240 fps with the original spring and replaced seals.
Added the 7/64" air tube replaced made no difference in the fps.
Added Cobalt's high performance spring and the fps went up to 314 to 322 fps, but the overall noise and jarring of the character did not work for me shooting in the backyard with the family in a residential area. This is not a complaint about Cobalt's spring, I think it is a great product and I am very happy he brought it to market, it just did not work for me for my specific use. I am positive I would have been thrilled to have had this high powered model to walk around the fields with instead of my anemic version.
I went back to the original ~50 year old spring but installed a new Model 25 shot tube and got a nice velocity bump to ~255 fps.
Looking for a bit more power, I installed a new production Red Ryder spring with a 1/2" spacer to preload the spring, leaving the 7/64" air tube installed.I also applied a coating of ARH brand Heavy Tar to the spring guide rod/plunger rod. That did a great job killing the "twang" sound of the spring that I really hate hearing. That got me to 300-315 fps without an offensive level noise with the family sitting around in the backyard. The accuracy is also excellent.
I used some of the fancy Avanti match BBs and that pushed the velocity up to ~325-330 fps.
-Model 499b:
Factory velocity was a consistent 238 fps.
I installed a new production Red Ryder spring with a single washer at the rear to assist with an easier installation. I also applied a coating of ARH brand Heavy Tar to the spring guide rod/plunger rod to kill the spring noise. That brought the velocity up to the high speed of 450 fps and no spring twang.
However, the muzzle report was noticeable, so loud that the family found it annoying for me to be shooting it with them in the backyard. It was on the same noise level as one of my high powered springers, like a TX200.
For me the goal of these bb guns was to let people enjoy target shooting in the backyard without annoying others who were not shooting and the Model 499b in that configuration was not acceptable.
Instead I went back to the original 499b spring and preloaded it 1/2". Once again a coating of Heavy Tar was applied to kill the spring noise. With that configuration I was getting the same incredibly consistent velocity of 299 fps with WM bulk Daisy Precision Max BBs.
Oddly the muzzle report from the 499b is noticeably louder compared to my Model 25, which has more velocity and a stronger spring.
All of the above velocity numbers are for guns that have less than 100 shots through them in their current configuration. I expect they will speed up some more as things work in with more shots.
Thanks again everyone for all of the info that let me get to this point very quickly and benefit from your experiments.