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PostPosted: Mon Feb 13, 2017 1:22 am 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
The part # for the full power spring is # B18-00-4D, regardless of 177 or 22. They may had diff #s in the past or maybe just on certain 177 guns? Hard to know what goes on at Crosman or the China factory than makes them for Crosman.
The 22 and 177 guns make different levels of power so a 177 gun needs more detuning. At least two diff low power pistons, several diff low springs and a hole are all ways to drop power, so guns may have one or two things. Like maybe a weak spring and a hole, a weak spring and long piston, or regular spring and extra long piston. The springs could be thinner wire, shorter oal, wound tighter or any combo of those, hard to say. until you open 'er up.
The power of an unmodified full power 177 can be all over the place, but once tuned it can easily break 1000 with a std 7.9 pellet. But as TC mentioned it's adjustable. I prefer to use heavier pellets than drop power, but all that matters is what you want from it, and if you need help we can assist.


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PostPosted: Mon Feb 13, 2017 11:22 am 
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Joined: Tue Aug 30, 2016 3:24 pm
Posts: 106
Location: Sidney Bc, Canada
Well, after all your advice I ended up ordering the stock .22 optimus spring from the gravel agency website. It's currently out of stock and could take 2-8 weeks (think it's about 4-5 weeks ago) before it's back in stock. After I get the spring I will pull it apart and see if has the longer piston or the shorter piston and then I will make my plan from there. I bought this more as a project gun, but now I'm debating if I made a good choice as far as platforms go.. I'm still trying to find a .22 barrel assembly that will bolt on to the pre-existing mechanism. I was told any of the b19 barrel assemblies from crosman in the 5.5mm will work, but I haven't actually had enough time to go through the Exploded Parts Diagrams and find the relevant barrel number. Darnn life getting in the way of my air gunning! Oh well, what can you do.. I still get to go out and shoot the others. As of late, my crosman tr77 seems to be spanking it. Shooting 1nch spinning targets at 40yards consistently with the stock Centre point 3x9x40 scope that came on it. I have had 0 problems with that rifle so far, except for the some what squishy trigger, which just took a while to figure out where in the pull it makes it's final snap. Any ways. Thanks as always for the information :P

Ps. Chevota - I e-mailed you in regards to grabbing that .pdf file off you, you did reply and send it but I had some sort of error while attempting to open it (I'm not quite sure why as .rar is easily accessible with Linux machines) If you could resend it to me I'd be very grateful


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PostPosted: Mon Feb 13, 2017 12:14 pm 
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Joined: Tue Nov 01, 2016 5:59 pm
Posts: 88
Location: Dryden,Ontario
I had problems opening his file too the first time.I used a free 7 zip download and had to download a free office program that would read it.The one already on my computer would not"open office" is what worked for me.Tons of info in that guide.I learned more in that guide than I thought I ever needed to know.Hope this helps.Good luck with your project.


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PostPosted: Mon Feb 13, 2017 5:04 pm 
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Joined: Thu Mar 24, 2016 7:33 pm
Posts: 240
Location: Yukon
TCooper wrote:
Hi tango... Read through the postings about my detuned .177cal Optimus. It's basically the same rifle as the Quest. Mine has the 170mm piston with no vent hole. It started with a very light .098" 34 coil spring that shot right at 500fps with 7.9gr pellets. I installed a .118" 33 coil spring last night and velocity bumped up to 745fps. I'm looking for 600-625fps so I plan to reduce the guide spacer from 1.5" down to 1/4" or 1/2".

I also have a full power U.S. spec Optimus (150mm piston). It has the .122" 36 coil spring. As a new rifle, it was shooting the 7.9gr at 960fps. I removed the 1.5" spacer and installed a 3/8" and velocity dropped to a sweet 800fps (almost no preload). A lighter wire spring would be needed to go lower.

A 150mm piston, with plugged vent hole, should do over 900fps with a fresh .122" 36 coil spring (.177cal).



My stock non PAL Optimus has the 33 coil sping and short piston, now plugged. but no chrony. i will try some before and after penetration comparisons but by your numbers I should get slightly more than your long piston version. (745) Im not looking for a full power just an improvement on non Pal numbers which are not chosen for optimizing my shooting.


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