Canadian Airgun Forum

I have three Crosman B18 variant rifles but one has always been outstanding. The other two had the mild bore constrictions in front of the breech blocks (had to be sanded out). The outstanding rifle is an Optimus springer model in .177 calibre that I bought from the USA. I did the standard tune with polishing, moly paste, piston seal change, hinge tightening, trigger work, loctite stock screws, etc. With the favoured pellets this rifle will bench group just under 1/4" at 10m and just over 3/4" at 30 yards. I have had days where it will average 2.25" at 75 yards (from bench).

The rifle is still using the same Crosman spring that it came with 3 1/2 years ago. It's detuned to 750fps with 8.64 gr H&N FTT (Daystate Kaiser) and seems to be staying there even after years of shooting during the summers. The rifle wears a 3-9x32AO UTG scope.

Today I did all my shooting offhand. The session started at 30 yards with a hanging spoon as a target. Once I figured out the holdover as one mildot, the spoon was an easy task. At 40 yards my shooting buddy had a small metal swinging rimfire target that was also an easy hit. After a while we put a small bean can on a rock at a measured 74 yards. It took me a few shots to find the holdover but with a 4 mildot holdover I smacked it on the first attempt. The can was set up again and I knocked if over after 2 more shots. We then moved the can a bit further out to around 90-100 yards. It took about 10 shots to find the holdover and 5 mildots seemed to work fine. I probably hit the can 6 times and was averaging about 1 hit every 5 shots. I didn't think the rifle was accurate enough for that distance but it seemed to be doing okay on the calm day. My offhand shooting was Zen Zone today with very little wobble. It definitely wasn't typical but made for a great shooting session. This rifle is now dubbed the Optimus Prime.

Does anyone here still shoot an Optimus or other B18 variant? I know forum member ricksplace has a .177cal Fury springer that is even more accurate than my Optimus Prime.

I will be shooting mine tomorrow at HAHA in my first ever FT event and the first time in decades that I have shot outdoors.

I just got my (used) chronograph a few days ago and discovered that with an upgraded spring and reduced preload, I am getting 695 fps with 7.4gr Crosman pointed pellets.

I worked on the trigger and am fairly happy with it.

Very much looking forward to it.

What is on the muzzle in your picture?
Mine has a front sight that I would like to remove but don't want to add more length to an already large gun.



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I wish we had FT events around here. I would try with the above Optimus.

I removed the sights on the Optimus and installed a cheapo Crosman plastic muzzle brake/device. It slips on but only adds a little bit of length. The actual barrel crown is not far below the end of the brake. I prefer grabbing onto the brake rather than the skinny barrel. Stock number CD1K77NP-01-1

https://store.gravelagency.com/en/cd1k7 ... e-177.html

The front sights are a tight fit. You can usually remove them with an open end wrench. Find a size that is a close fit to the barrel and line it with a couple of layers of electrical tape so it doesn't scratch. Put the wrench on the barrel and gently tap with a hammer. Some people will use a bit of heat on the sight but be careful not to melt it.

Hi Todd.
I can't remember (nothing new for me there...) what combination of spring/preload you used to achieve that velocity. Was it a 12 fpe spring with a reduced preload or a full power spring with minimal preload? Weren't you messing around with different piston lengths too?
I detuned my Ruger Blackhawk Elite to 750 fps too, but I used a Vortek "docile" spring to detune it.
My Fury springer (phantom without sights) you mentioned uses a full power spring with a 50% reduction in preload spacer length for around 13fpe. When detuned with reduced preload the spring seems to last forever. My .22 Phantom is detuned in the same manner. It shoots around 13fpe too.
Rick

_________________
Theory is when you know how something works, but it doesn't.
Practice is when something works, but you don't know why.
In my shop, Theory and Practice are combined!
Nothing works and I don't know why.

Two lathes and too many projects

Hi Rick... The Optimus Prime still has the original full power spring installed (36 coils of .122" wire, 150mm piston). I removed the OEM guide and used a short 3/8" section that you made. Velocity has been about the same for over 3 years now. I'm getting 750fps with 8.64gr for 10.8 FPE.

I also have a Canadian detuned Optimus with the longer 170mm piston. This one uses your short 3/4" spacer and the 12 FPE spring (33 coils of .118" wire) to give low 600s for velocity. Preload is about 1/4" of push to get the end cap installed. It feels like almost no pressure and I push the plug in with my thumb. The Optimus Prime also takes only thumb pressure to install the end cap.

Cheers ... Todd

I had the .22 Phantom for years, mostly in storage. I could hit targets, that was it. I was sort of starting from scratch when I picked it up again in January. Started taking it apart, etc. I bought the .177 Optimus, used, in April. It wouldn’t shoot. It was a small world of trouble to find out that the spring was tired and could not push the piston. All was fine after that. In an accidental experiment, in June, I suddenly started to learn how to hold the rifles, it started with the other two. I found a way to hold the Optimus, especially. I still struggle with the Phantom but after countless piston swaps, chrony sessions and spring changes, I can get right back to bulls with the Optimus. So yeah, I’m digging the whole Optimus Phantom fun thing.

And I had members here helping me along the way. I read plenty of your posts too, TCooper, learned what I could. I liked reading about the long distance shooting, like in this post. Almost all my shooting has been indoors, at 17m. I saw your cool new target box with spinner. It’s great to see this Optimism. Ha.

Do I still shoot one? Oh yeah. Ok, the photos.

Photo one. Some things had converged. I was using the stock power plant from the Phantom. I had found a pellet, the heavy RWS MK. A very stable combo, I only needed 5 shots in the session. A nice low Standard Deviation of 2, at a cozy 620 fps. I had a benchmark. I was testing some freshly-machined spacers, just arrived in the mail from ricksplace. The 2nd session had reduced preload, you can see the change in the numbers. Still shot well tho.

Photo two. Like that.

Photo three. Different power plant, less preload reduction. Spread numbers creeping up again. Still shot well tho.

Yep, Optimus. Still shootin’. Thanks TCooper

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Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

This one is mine. The first air rifle I bought in Canada 7 years ago...
The only major modification I did to it was recrowning the barrel. It does improve its consistency by a lot!

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Hey oldspringer. It sounds like you have a cool Optimus there. I’ve seen crowning mentioned but don’t really know about it. Is it just removing some material from around the bore? Does it require special tooling?

Also, thanks so much for those kind words 3 months ago. I only half believed you at the time but you were absolutely correct. Compared to before, it has become a laser, more or less.

Cheers,

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Stephen
low- / mid-level springers

.177 Cometa Fusion, Vantage 3-9x40
.177 Cometa Fenix LT, Endurance 4-16x50
.22 Cometa Fenix, Airmax 3-9x40

I use a brass screw in a drill with some valve lapping compound. Works great.

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I have some airguns.

It's easy for a handy man to work it out in home, no hurt to give it a try. However result depends... I didn't re crown all my rifles but just 3 barrels (so far). One 2240 long barrel really impressed me but the other 2 barrels for my PP700 carbine didn't make big changes...

I used the below stuffs to complete the job...

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~Plinkers~
FX-M3-22 Compact#PP700-Carbine#Diana48-177#XS28M-25@26fpe#HW45 Beast#AW-Custom Z-Killer DE
~Competitors~
FWB300SU#Tau-7#IZH-46M#FWB-65#CP88-C
~Target~
HW 30s/35e/97k/40+Extender/P3+Scope/70#CZ200s Laminated@10fpe#AA ProSport-177@12fpe

For crowning a barrel you can use a reloading case chamfer tool. It's just a tapered reamer. I have had good results. I find it cuts clean and doesn't leave any burrs.

I use the brass screw and electric drill trick for crowning. The first step is with valve grinding compound. Then I use a blend of jeweler's rouge and JB Bore Paste to get a nice polish. Use a high power magnifying glass (loop) to inspect the crown for burrs and a crisp transition to the rifling.

I hope Crosman continues selling with the Optimus rifle as it is. I noticed on their American web site that most of their break-barrel rifles now have a long plastic barrel sleeve. I'm guessing they went the Gamo route and use a soda straw barrel inside the bulky plastic.

The Optimus/Fury/Phantom is a nice design and can stay great if Crosman puts some pressure on the Chinese manufacturer to put more effort into getting consistent bores. Sometimes you get a nice bore that drives tacks and other times it has tight and loose spots throughout the length. The common tight spot in front of the breech block can kill good accuracy. I would rather see them epoxy the barrel in the block than drive it in tight so it constricts the bore. I have an one excellent Optimus barrel that can nail small cans at 75 yards. I didn't have to do anything to it. I have two others that needed lots of work because of constrictions. They shoot fine now but not quite as well as the good barrel.

I like the Optimus because it can be made to shoot well, parts are cheap, the trigger can easily be made very acceptable, and the rifle price is reasonable. The sights suck but a scope fixes that.

I have seen two different approaches online.

One uses a round headed brass bolt as pictured above where the shaft and threads of the bolt are gripped in the chuck of the drill and the round head of the bolt (plus the grinding compound) is what grinds the crown.

The second approach uses a flat top bolt (think of the shape of a head that would fit into a countersink) where the shaft of the bolt is wrapped in tape (to protect the rifling) then inserted into the bore and the angled bottom edge of the bolt head (plus grinding compound) is what grinds the crown as it is driven by a drill with a screwdriver bit.

The thing that appealed to me with the second approach is that the shaft inserted in the bore will keep the bolt centered while the first requires me to keep the drill centered to avoid carving an oval.

I have also seen several online suggestions that start with some type of grinding or reaming with a different tool and the brass bolt used for final polish. Does the bolt cut well enough to use as the first and only step?

Thoughts from experienced folks?
Thanks,
Rob

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It's the compound that does the cutting but yes. I only use one brass screw to complete one crown. There is a bit of self centering going on as the thicker edge will wear slower but I would periodically check. The screw itself wears away too so it's done after the one job.

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I have some airguns.

I use 2 or 3 roundhead bolt sizes when doing a crown. When shopping for brass dome headed bolts I carefully select the best examples that have the threaded shaft centered. Lots of them can be off-centered and won't work for your needs.

A terrible looking crown might need a bit of careful filing or if you are cutting off a bad piece of barrel then filing is needed. I had one that bad. I removed 5/16" of gouged barrel and then filed and crowned. To get a straight cut I first drilled a hole in a piece of hardwood using a drill-press. The hole was a very snug fit on the end of the barrel and I used it as a cutting guide for the hacksaw and then a filing guide to keep things square. I filed and polished until very smooth. Only the jeweler's rouge and JB paste mixture was needed to get a good crown. The barrel now shoots ragged hole groups at 10m. I wouldn't try this on a firearm for 200 yard shooting but for a cheap airgun it's fine. I have a friend with a lathe so a back-up plan was ready if I messed up.

Here is the old posting on my slightly uptuned Canadian Optimus. I sanded the constricted barrel and recrowned the muzzle. It now shoots close to 1 1/4" at 50 yards.
topic77370.html?hilit=crown