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PostPosted: Sun Mar 22, 2015 11:59 am 
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Joined: Sat Mar 21, 2015 2:11 pm
Posts: 9
Re: Crosman Optimus

http://www.canadiantire.ca/en/pdp/crosm ... Q6ucfzF8TI

I need instructions on how to remove spring from compression tube assembly.


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PostPosted: Sun Mar 22, 2015 12:45 pm 
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Hi Gander, welcome to the forum.

Have you taken any other springers apart, or is this the first time? From the link, I'm guessing you have the non-pal 495 fps version?

The issue with springers is releasing the tension on the main spring safely. For full power guns you need a spring compressor to hold the gun while you take out the drift pin. For some low power guns there's so little pre-load that you can do it by hand (I've done my ruger airhawk this way). I don't know what the optimus is like, so unless someone else chimes in, safest bet is to use a compressor. They can be made fairly easily, or you can use pipe clamps or a similar thing that fits on 2x4:

http://www.canadiantire.ca/en/pdp/stanl ... Q7_Xc1GjUY

You need to stabilise the compression tube against the pipe/2x4 so that it doesn't all go flying as you back out the spring.

Jim


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PostPosted: Sun Mar 22, 2015 2:03 pm 
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Thanks for the reply, Jim.

This is my first springer disassembly attempt. I've taken this (new) gun apart 2-3 times, but stopped at the point where I may/may not need a compressor. And yes, this is a 495fps jobbie. I don't think there's much tension going on, although I haven't fashioned a compressor yet. And I'm not sure what should be removed next... the stock link bolt, the fixed pin, or the trigger assembly.
And given my lack of experience, my only aids are the parts diagram & some rye whisky, the latter likely less of an aid & more of an impediment. :)


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PostPosted: Sun Mar 22, 2015 3:08 pm 
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Location: Alberta Canada
Words of wisdom.....If in doubt, compressor it out... :mrgreen:
There is suficient preload upon the spring that if not careful it could become an issue if your not ready for it. JMO

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May the cry of the pack be with you upon your hunt

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PostPosted: Sun Mar 22, 2015 3:11 pm 
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Location: United States
First you need to remove the square headed bolt that holds the trigger down. Then you should be able to remove the plastic cap at the end. It may come right out, it may be a fight, it may not come out at all. If it does come out then you can see inside where you need to apply pressure to counter the spring so you can get the pin out. If you cannot remove the plastic cap then you have to push on the cap itself.
If the cap is out then you can see the guts are a bit recessed in the tube so you'll need a way to apply pressure in there. I use a chunk or rubber ~20mm round x 10mm thick (but you can use a couple washers, coins, wood etc), which I set on the floor and put the end of the tube over it. With the tube vertical I push down on it to compress the spring. I usually have the barrel off, but if you keep the barrel on the remove the cocking linkage from the tube then bend the barrel to horizontal or let it go all the way down. I push straight down with one hand, while the other uses a dowel or whatever to push the pin out. Once the pin is pushed out you simply let up on it and the parts will come out a bit until tension is gone, maybe 20-70mm depending on the spring used. Once that tension is off you can remove the trigger and or spring. Your 500fps model should be easier to compress the spring, but it depends on which spring it's using. A full power spring can have 50+lbs preload when new, so expect maybe 20-30 but up to 50lbs downward force needed. You can use a thick leather glove or towel over the end of the gun, place your hand on there, then your chest on your hand to apply body weight to it. I do that with nitro spring guns which have over 150lbs preload, but coil guns can often be compressed with a thumb.
So are you going to tune the gun??


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PostPosted: Sun Mar 22, 2015 4:00 pm 
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Jeez, thanks for your detailed input, Chevota!

When you say "plastic cap", do you mean the "tube cover"? ... mine appears to be knurled metal... not sure how it's removed.

P.S. I'm having trouble attaching parts diagrams...


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PostPosted: Sun Mar 22, 2015 4:05 pm 
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Here's a link to the parts diagrams & labelling.

http://www.crosman.com/optimus-with-scope-177-105461


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PostPosted: Sun Mar 22, 2015 4:22 pm 
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My mistake, Chevota! You are correct... it's plastic. I removed the square-head bolt... could not remove the cap, but pushed the pin out... hardly any pressure on it. Currently assessing what I have done! :)
Many thanks... I'll post again shortly...


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PostPosted: Sun Mar 22, 2015 4:43 pm 
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OK, things are moving right along. :)
I removed the spring, but I have to remove the trigger assembly to get the piston out. I don't know how to do that.
Obviously, I have no future in gunsmithing. :)


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PostPosted: Sun Mar 22, 2015 5:37 pm 
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Posts: 1271
Location: United States
The trigger just slides back ~5mm and comes right out. Getting it back in you have to be sure to hold up the sear while sliding back in. Once the trigger is out you can tap the gun against wood or carpet to get the piston to slide down, or stick a screwdriver in there and slide it.
The plastic cap no doubt has holes where the pin and maybe the bolt pass thru? Other models have slots so the cap can slide in and out, so if you want, and it will make reassembly easier, just cut the plastic so it can do that. It won't show one in the parts diagrams but I can take a pix if you like.
So are you tuning it and/or replacing the main seal? The slots in the receiver tube all have sharp edges which likely tore up the seal, so imo the seal needs to be repaired or replaced,and the edges need to be removed or it'll do the same putting it back in.


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PostPosted: Sun Mar 22, 2015 6:12 pm 
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I don't know what a "sear" is... but I hope to. :)

Excellent idea re the plastic cap!

I'm just trying to squeeze a few more fps out of it. It seems pretty weak to me... don't think it's even at 495. So, if I can get it up to that, great. And if I go over (highly unlikely), I don't mind getting a PAL.

You've been very helpful so far, my friend.


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PostPosted: Sun Mar 22, 2015 6:14 pm 
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http://en.wikipedia.org/wiki/Sear_%28firearm%29

So much to learn... :)


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PostPosted: Sun Mar 22, 2015 6:18 pm 
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Location: Ontario,Canada
You've been very helpful so far, my friend.


Yeah...Chevota is the best! He will go out of his way to give you a good detailed description of what he is trying to tell/show you. He has helped me a lot! Huck

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PostPosted: Sun Mar 22, 2015 7:07 pm 
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I've reached a point in the disassembly where I've determined that only a heavier spring will give me more power. I'm guessing I'd need a PAL to obtain that legally. Don't know if I want to pursue that. Hmmm.

Now if only I knew how to put all these parts back together! :) I'd say that trigger assembly is gonna be a bitch... especially since I couldn't identify a "sear" if I was struck in the head with one.

Learned a few things, though. Thanks again for the assistance, Chevota... you're a good man... couldn't have done it without ya!


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PostPosted: Sun Mar 22, 2015 7:22 pm 
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Joined: Sat Jan 25, 2014 9:16 pm
Posts: 1271
Location: United States
I assume yours is a 177? If your piston has a hole in the end, center of the seal, then it's not only dropping your power but increasing stress on the scope and half your cocking effort is being wasted. Other things they do to reduce power is shorten the piston stroke by making the piston longer (a normal piston is ~150mm),and using a weaker spring. So it's basically a 1000fps+ gun that's been cut at the knees, but if you want to exceed 500 it's there for the taking.
I'm in the US so I've never seen a 500fps gun, only pix from people here. Imo I think if you need power cut back from the full power model you should only reduce spring strength, so I would use the full power piston with a reduced spring to get what. Doing it that way the cocking effort would be incredibly light, less recoil, less noise, and your scope will no doubt last for life. If I had to guess I'd say cocking effort for a 177 @ 500 would be ~7lbs, which is no doubt much less than what you have now. I have one gun I dropped spring pressure on which dropped cocking effort to 12lbs and it shoots 177 >700 to over 800fps depending on the pellet weight. Or you could plug or reduce the size of that hole to bump power, which would leave cocking effort the same but power would go up and scope problems go down.
You should email me at chevota at hotmail and I'll send you a tuning guide for the gun which should help you a lot. Way too much to post. Lots about improving the gun and trigger. It'll also show that sear dealie which is different than in a firearm, and how to get it back in easily. Stuff on the scope, barrel etc for more accuracy, smoother cocking, quieter etc. How to mod the main seal for better performance, transfer port etc. So let me know if you have the hole in the piston, how long your piston is, and if possible the spring size, which would be OD, wire dia, and # of coils. Then I can better tell you what options you have.
Huck is doing similar with a 22 version I believe, and if you do stay at 500fps I think a 22 would be worth having, double the power and all that, depending on your needs of course.


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