As many others I also had a couple of cheap plastic stocks on rifle. Until a decent replacement was made I've done a few emergency quick fixes, just to get the rifle to shoot half decent from a bipod.
First step: Bed the rifle.... quick bed job
Sand the stock rough around the recoil lug area and rear screw lug area.
wax the action and screws with good old fashioned shoe wax/polish, 2 times!
Mix metall or steel epoxy well. Not the quick setting type, better is the slow setting type. Smeer epoxy on the action lug area, rear lug area,
and on the stock recoil lug area and a little bit on the rear lug area
insert action back into stock replace trigger drop plate and tighten action screws. Remove the excess epoxy and then back off the action screws so that they are just medium tight.
Let set over night.
Remove action carefully out of stock, the epoxy will not glue very strong to the stock material so one shouldn't be so rough. Clean up action and epoxy from places where it shouldn't be. Lightly oil action.
step two: sand the stock channel until you have 2-3mm gap all round. 3mm is better than 2mm gap.
I open the channel until the rifle in stock on a bipod will not touch the stock even if some pressure is applied from the top.
If someone worries about epoxy action and stock just use a bit less, say about a teaspoon full. Better than nothing.
This will not be perfect but it will make the rifle much more reliable. One just needs to keep an eye on the action screw torque, retighten often until it stays the same. Injection moulding plastic tends to flow a bit under pressure.
The pictures are from a howa that I did during a lunch break with quick setting epoxy ( got to work very very fast) went foxing that evening.