I suggest you have the part installed by a competent gunsmith. If you don't know how to install it -- don't!
The new part is held in place with a stainless steel screw. Each shock ordered will come with one of each of these screws:
#6 X 5/8” Flat Head
#8 X ½” Flat Head
Note that the replacement part does not have to be bolted down like the whole force of the action will try to pull it loose. The original parts were held in place by a tiny little knob (which got brittle and fell off) – the screw is just there to keep the part from just falling out.
One difference between the two parts is the knob on the old style part was at a bit of an angle.
Close the bolt, then remove the Trigger Group. To remove it, just press the two pins out and pull it out. This will give you access to the Shock Absorber.
Remove the stock and/or pistol grip from the gun. This involves removing the big round screw from the back of the receiver. For help for some models see Stocks.
Remove what is left of the old shock,
the shock and any plastic knob sticking out the backside of the
Insert the new shock:
Decide which of the two screws you
like to use. Look and see what angle (if any) it will need to be
Next you need to use a 45°
(or a big drill bit if you must) and cut a small beveled
in the receiver hole for a flat-head screw. Be sure and cut
this at the same angle as the screw will be at. You can always
more if it doesn't fit flush -- you can't put any back:
Then use the screw to hold the shock in
Put it all back together, test it, and you're done.
Don't get too hung up on keeping the gun “stock” – the stock design doesn't work. (Anyone want the “stock” lever-style safety?) And since the receiver is the actual problem, I’d rather fix it once than modify all the different stocks I have for it. In my book, a cleanly installed replacement shock adds value to any gun.