Canadian Airgun Forum

I just finished tuning a new .177cal Crosman Optimus that wears a Phantom stock (long story). I got this detuned "Canadian Tire" rifle in unfired condition and I disassembled without shooting the weak OEM mainspring. The piston was unscratched with no bluing wear and the sear engagement was still fresh with bluing. The barrel was gunked with shipping preservative.

I shot a few dozen pellets after tuning and the rifle has quickly settled down so I cleaned the barrel, mounted a 4X Leapers AO scope and shot a few groups at 10 metres. It’s a good shooter and might even get better after a couple thousand shots (barrel conditioning). My supply of the Finale Match pellets is low so I only shot a couple of groups with them. I haven't tried other pellets yet so these might not even be the best choices.

Accuracy @10m
H&N FTT -------------- .18". .27", .23"
H&N Finale Match – .23", .22"

Velocity
FTT (8.64gr) – 688, 687, 686, 691, 688 fps
CPHP (7.9gr) – 708, 705, 707, 708, 702 fps

This rifle seems to shoot with about the same accuracy as my full-power .177cal Optimus rifle from the USA. The bore is good with no tight spots noticed. I used the Cdn 170mm piston rather than chopping to 150mm. More power is possible but I'm more interested in a comfortable plinker. Here is what I did on the rifle.

new crown
bevelled pellet leade
extreme barrel cleaning (WD40 soak, bore solvent, JB Paste)
new metal hinge pivot washers sized for thickness
transfer port work to remove crater inside compression chamber
mild compression chamber polish
bevel sharp edges on slots and smooth slot surfaces
piston liner
new 4D spring (.122" wire/36 coils)
shorter spring spacer
longer trigger adjustment screw
burnished moly into chamber
moly paste application where needed

Yup, I've had my FAC/PAL for over 40 years.

Phantimus ...lol good one...These "lower end " guns are so much fun to improve and turn into a nice shooter...very satisfying for sure ..good job

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Have you ever tried a maccari square wire spring in one of these? I tried one once, it seemed smooth and gave medium power. At the time I wasn't paying attention to it because I was just after maximum power.

Currently I have a phantom 500, wearing a nitro venom .177 barrel, a medium spring (? Haven't measured it), and a delrin guide and spacer. Turns out it shoots smooth enough. Good candidate for an accuracy test.

Some fine shooting by the way.

I haven't tried a Maccari or Vortek spring. I have a few Crosman B18 rifles and all have the cheap Crosman springs ($12-$14). One Optimus has a 170mm piston, short spacer and the 4B spring (34 coils, .118") that gives 600fps with 7.9 grain. My newest B18 example (above) has the 170mm piston, short spacer and 4D spring (36 coils, .122") that gives 700fps. My full power Optimus has the 150mm piston, short spacer and 4D spring that gives 750fps. I also have a B18 nitro piston that spits 7.9gr at around 920fps.

I use the OEM spring guide and I sleeve the piston with .027" of #5 recycle plastic to eliminate the twang. I have a few spring spacers that Rick made up so I shorten to 3/4" or less. With the wire springs I can push the spring flush with one finger while I slip the crosspin into position. Getting 900fps is always an option but firing behaviour gets harsh and I don't need all the power for 60 yards and under.

The B18 rifles can often be tuned to shoot quite well. They don't have choked barrels so typically they are pellet picky. Sometimes you get one with a barrel constriction at the front of the breech block but careful sanding can remove most of the problem. Thanks to previous member Chevota for that great tip. When the rifles are all tuned up I have had them shooting 1 1/4" to 1 3/8" at 50 yards on a calm day. Not bad for the price.

The crowns on the Crosman B18 rifles often need work. Sometimes you can see the roughness or burrs using a loupe. Other times you can feel the snag at the muzzle when pulling a patch through.

My compliments TCooper, that sounds like a really nice shooter. I think a very accurate, and very comfortable, cycling rifle like that makes a "keeper" sometimes as compared to a obnoxious maximum power effort that's harder to control.

I recently tuned a Cdn Tire CS5M77 manufactured 920 and it was originally quite underpowered compared to advertised speed and my expectations. I have had several Phantoms and the older ones "just worked", for anybody, and without mods etc, at least as far as power and comfort, and the twang was minimal in my experience. This one has the 170mm piston and weak spring, and a bleed hole in the piston head, typically shot an unacceptable 360-380fps. After small changes, deburring, sanding off the oem 'fringe' from the piston seal, some moly lube, and a few dimes in front of the top hat, heat shrink on the guide, it's now typically 465-480fps, quiet/twangless, comfortable and accurate. With my old eyes and open sights it's easy to get .250-.375 c-c at 30ft from standing position. I re-used everything it came with and am happy. These are a a great basis for tuning and I like what you did with yours, especially the 4X Leapers AO scope. Congrats, looks nice!

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