Spring binding

[leftcoast1]

I have a custom rear guide top hat and JM spring for my Sierra Pro. Got her all lubed up put together but it's not right. I cock the gun then on the upstroke I can feel the cocking foot riding over the spring. I take the gun out of the stock while it's cocked and you can see the spring coils are touching and it's humped up right at the end of the stroke. Any ideas in a fix for this.

[Gene_SC]

If this is a used spring then you are experienceing sping cant. Does the gun cock and seer engage??

[leftcoast1]

The spring is new. The gun cocks fine the sear engages and holds and the gun fires normally.

[Gene_SC]

Jason, did you true up the ends of your main spring? Did you debur the end coil properly? What model springer is it. Which spring are you using? Did you make sure the spring guide wasl snug in the spring?  All very important.

Gene

[leftcoast1]

Not sure how to true the spring ends so no on that one. The spring is a E3650 and the guide is fitted to the spring. I debured the spring ends. The gun is a Crosman SierraPro in .177. Thanks

[Gene_SC]

What spring guide are you using Jason?

[leftcoast1]

PM sent

[tjk]

Try flipping the spring. By that I mean remove the spring and try the rear guide on the other end of it. You may also try turning the spring 180 degrees, re- assemble the rifle back together and see if that solves you spring rub problem. tjk

[speedturtle]

IMO your E3650 replacement spring is a bit longer than the stock spring. When fully compressed the E3650 spring has no space left for the spring to relax a bit causing it to bulge during the final cocking stage. Since it has a longer length it will definitely bulge and the cocking link foot can scratch the outer surface of the spring coils. You might also have an issue with your front and rear spring guides. Do a measurement comparison on the spring and the guides assuming the spring is fully cocked and compare this "compressed" spring distance to the piston unit sear engagement distance. It should have at least 1/8 of an inch gap to safely lock the piston unit to the sear. A good way to know the fully compressed spring height would be to multiply the spring coil thickness with the total number of coils of the spring.

[kiwi]

Hi ...As a compression spring is compressed it trys to unwined
and in doing so it exspands in dia... So if there is not enough clearance
between the piston ID and the outer Dia of the spring when in the
uncompressed state..As it compresses it will increass in Dia and
bined on anything that has a smaller ID than the springs compressed OD...

In your case the cocking shoe....

Pete