I updated the review with 20 yard accuracy tests. Once the warmer weather arrives I'll do 30 and 40 yards.
---------------------------------------------------
Crosman Optimus Review – Canadian Detuned 495 fps
Our local Canadian Tire store had the detuned .177cal Crosman Optimus on sale for a reasonable price so I picked one up to tinker with. Many years ago I had the Canadian detuned Crosman Quest that was pretty much identical to the Optimus, except for the stock contours. The Vantage model also seems to be the same rifle with a different handle. This Chinese B18/19 rifle wears many handles and name tags.
Cocking effort with the detuned Optimus is very mild and can easily be accomplished with only two fingers on the barrel. Long shooting sessions would be no problem with this mild plinkster. The rifle only weighs 7.2 pounds with the 4 power CenterPoint scope mounted.
The Optimus shoots great as a 500fps basement shooter but my preference was for a little more power to bring it up to 600-625 fps with average weight pellets. The added power will help flatten out the trajectory for 30-40 yard plinking shots.
After a complete teardown, the factory detuning method became obvious. This Optimus-500 has a non-vented 170mm piston whereas the full power version uses a shorter 150mm. The mainspring was 34 coils of light .098” wire whereas the full power version uses 36 coils of .122” wire. The shorter cocking stroke with the very mild mainspring drops velocity down to the non-PAL level. My old non-PAL Quest used an even longer non-vented piston with a thicker wire mainspring. Other versions of the non-PAL Optimus/Phantom have been reported as using a short 150mm vented piston with the thin wire spring. All versions seem to be using the 1.5” spring guide spacer.
It was interesting to notice that my detuned Optimus did not have the B19-00-4B mainspring, as indicated by Crosman for this model. My shipment of spare Crosman parts arrived with a 4B mainspring and it turned out to be 33 coils of .118” wire. There are at least 3 different springs and 3 pistons used for these rifles.
Here are a few bits of piston & spring info that I gathered from the Crosman web pages.
.177cal 495 fps Optimus >>> Piston B19-4-04-100A >>> Spring B19-00-4B 1000 fps Optimus >>> Piston B18-04-100D >>> Spring B18-00-4D
495 fps Quest >>> Piston B19-4-04-100 >>> Spring B12-1-00-4A 1000 fps Quest >>> Piston B18-04-100A >>> Spring B18-00-4D
.22cal Optimus 800 >>> Piston B18-04-100D >>> Spring B18-00-4D Quest 800 >>> Piston B18-04-100A >>> Spring B18-00-4D --- VELOCITY --- The rifle was first tested in unaltered form, out-of-the-box. All I did was clean the barrel and mount the included CP scope. A couple of dozen shots were taken to distribute the OEM lube.
JSB Exact (8.44gr) - seated pellets - 497, 500, 495, 497, 495 --- ave 497 fps
--- ACCURACY - unaltered rifle ---
--- 10 Metres – 5 shot groups --- From a rest at 10m I was averaging .40” to .45” ctc for 5 shot groups with JSB Exact 8.44gr, JSB Exact 7.33gr, RWS Hobby, and Stoeger X-Field pellets. With the mild .098” spring, the rifle seemed to like the pellets seated in the barrel so I used a Bic pen cap to push them slightly below flush.
--- 30 Yards - 5 shot groups --- JSB Exact (8.44gr) - 1.85”, 1.51”, 1.63”, 1.53” --- ave 1.63” ctc
The untuned rifle has a lot of spring twang that could be greatly reduced with a tune. A lube tune, better fitting guide and a fresh barrel crown should all help squeeze the groups down a bit. I don’t expect HW30 accuracy but a little improvement should be possible.
--- MODIFICATIONS --- I broke into the detuned .177cal Optimus to do a bit of polishing and lubrication. As mentioned above, the spring turned out to be a 34 coil with thin .098" wire. The spring guide is the same .475" diameter as used in my full power U.S. spec Optimus. The skinny spring was a sloppy fit on the guide which allowed the spring to bend into a mild s-shape. The spring maintained this double cant when removed. This sort of poor fit resulted in the typical metallic twang noise when shooting.
The piston seal and breech seal looked fine so replacements were not required. After the typical polishing and moly paste treatment, I re-assembled the Optimus with a 33 coil .118" spring and the same 170mm non-vented piston. Cocking effort was noticeably higher than with the .098" spring. The full 1.5" OEM spacer was left on the guide. After the initial dieseling routine, I shot about a dozen pellets that were quite consistent. Average velocity was now 745fps with 7.9gr Crosman HPs. Unfortunately, this was much more than my desired 600-625fps with 7.9gr pellets.
The next modification was to reduce the spring spacer length and test again. I tried 1/4" and 1/2" spacers with the same 33 coil .118" mainspring. There was no preload at all with these spacers. I ended up using just over 3/4" of spacer that left me with approximately 1/4" of preload. Perfect! I'm now getting 625fps average with 7.9gr pellets.
Trigger work was very minor. The return spring was over-bent to reduce tension, engagement surfaces polished, moly paste to all friction areas, and a longer adjustment screws was added. I adjusted the trigger engagement so it still had a little creep. The feel is much better than prior to the work.
--- ACCURACY – modified rifle ---
--- 10 metres – 5 shot groups --- H&N Sport – .21, .31, .16, .25, .32, .24, .30 ---------------- ave .26” ctc H&N Excite Hammer – .34, .33, .25, .40, .35, .30, .28 --- ave .32” ctc Crosman HP – .36, .28, .33, .38, .45, .43, .45 ------------- ave .38” ctc RWS Superdome – .31, .35, .43, .35, .27, .36, .26 ------- ave .33” ctc RWS Hobby – .36, .56, .47, .43 ------------------------------- ave .46” ctc Stoeger X-Field – .32, .36, .37 --------------------------------- ave .35” ctc RWS Diabolo Basic – groups .50” to .75” ctc JSB Exact RS 7.33gr – groups .50” to .75” ctc H&N Excite Econ – groups 0.50” to 0.75” ctc --- 20 yards – 5 shot groups ---[/b] H&N Hammers – 1.22, .83, 1.06, 1.05, .56 --------------------- ave .94” ctc JSB Exact – .74, .40, .38, .80, .84, .53, .69 --------------------- ave .73” ctc Crosman HP – .70, .76, .41, 83, .76, .57 ------------------------ ave .67” ctc RWS Superdome – .54, .71, .58, .77, .49 ------------------------ ave .62” ctc Stoeger X-Field – .60, .62, .62, .74, .67, .61, .75, .50, .50 --- ave .62” ctc H&N Sport – .63, .50, .54, .40, .39, .50, .34, .55, .48, .40 --- ave .47” ctc The Crosman HP did better than expected at 20 yards. I was careful to throw away a few fat pellets that seemed a bit difficult to start into the barrel. Now I’m curious to see how these Crosman HPs do at 30 and 40 yards.
[b]ACCURACY - after 500 pellet break-in period
--- 10 metres – 5 shot groups --- JSB Exact 8.44gr - .21, .35, .22, .36, .18, .34, .31, .34, .21, .28 --- ave .28”ctc
--- 20 yards – 5 shot groups --- H&N Sport - .63, .50, .54, .40, .50, .39, .34, .55, .48, .40 ----------- ave .47”ctc JSB Exact 8.44gr - .55, .64, .69, .35, .46, .75, .36, .45, .64, .70 --- ave .56”ctc
--- 20 yards – 5 shot groups --- H&N Sport - .67, .62, .41, .58, .56 ------------- ave .57”ctc JSB Exact 8.44gr - .57, .38, .48, .71, .58 ---- ave .54”ctc
Note: JSB Exact 8.44gr were a new lot from 2016
--- OVERALL OPINION --- The Optimus seems to be a nice rifle for the price. It’s the typical Chinese B18 with another facelift but I knew that before the purchase. We all know that the B18 gets dressed up often but maintains the basic common foundation. It shoots fine, parts are cheap, a power upgrade is easy, and the trigger is not too difficult to improve. I’m looking forward to testing accuracy at 30 and 40 yards.
|