Congrats on the chrono- I'm thinking you will come to find it's a VERY useful tool!
The 499 funnel appears to be fully tightened onto the barrel tube. There's no lock nut or set screw that helps retain it, it's just tightened down until the threads bottom. or so it would seem.
For shooting over the chrono, I set the muzzle about even w/the front of the chrono, and a couple inches above. Unlike powder or CO2 guns, there's no plume coming out of the barrel to cause issues w/errors or faulty readings from being too close. If you heavily oiled the barrel, piston or chamber at assembly (which really isn't necessary with synthetic seals in my experience), shoot it several times to rid the system of excess oil before using the chrono. You don't want oil settling on the sensor covers. And FWIW, an over-oiled barrel just
slays accuracy until it shoots out or a patch or three is run through it to get rid of the excess oil!
Some oil is okay- desirable, even- but don't overdo it.
On the old Daisy, don't get carried away w/cleaning it. If you sand the finish or somesuch, the collector value dies. A collector would rather have a gun w/honest, original patina than something spit shined. If you plan on keeping it, do whatever you think is right.
It's possible for there to be rust inside the gun? Yes. Most times, the front half where the shot tube resides will have rust if the previous owner used the "put a wad of BBs in your mouth, then blow them into the loading port" method of loading the gun- this was an
uber popular thing among my crew when we were kids. And w/o knowing how the gun was maintained and stored, rust could be inside the compression chamber as well. All that said, it wouldn't hurt to start the process of soaking the seals before disassembling the gun. Heck, you might find it shoots fine! A lot depends on how it was cared for. Disassembly for inspection and maintenance wouldn't be a bad idea, IMHO. But I'd probable oil it real good and give it a try before going into it further.
What you may also find is a spring that has distorted badly (example below). I have several vintage plunger assemblies that I bought in search of the 'holy grail' heavy duty plunger tube, and one of them even has the old style rigid air tube and leather seal. On
all of them, the springs are distorted to some degree. And a couple of them are so bad that I have no doubt the deformation would have caused the gun to shoot very poorly. The springs can most likely be replaced w/a new production Red Ryder-type spring but a few of the old guns had springs w/considerably more spring rate than the RR spring, so performance might be subpar- but the gun would at least be useable. These guns are notorious for breaking off their air tubes. That was one of the reasons for the switch to pinned on air tubes and synthetic plunger heads (US Pat No 2,758,586 w/publication date of Aug. 14, 1956 (filed Aug. 18 1953) is for buna seals and pinned air tube.
Spring from a Model 95
I've never made seals but there's info online. I believe JG Airguns sells leather seals and there are other vendors that I don't recall the names of.
Looking forward to seeing what you have!
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