Found that the action screws in my FN 300 H&H were loose after a jarring ride in a Polaris. Tightened them up snugly then found that my groups were noticably worse than before. Is there a rule of thumb for tightening, sequence of rear to front etc? May need to look at bedding at tip also, it's an ebony tip making contact with barrel, probably not very even contact. Thanks, Bob

IMO you need a pillar bedding job, by a COMPETENT workman.

The problem lies in the 'competent' part.....
Regards, Joe

Sooo. I want to do the do-it-yourself before I send it out, since it was shooting fine a few weeks ago. How about original question. Bob

By tightening the action screws you probably also inflicted more pressure on the barrel because of a tighter contact between the ebony tip and the barrel. A modest amount of fore end pressure on the barrel is used by many factory rifle makers because it is believed to dampen the barrel vibrations and therefor reduce bullet spread from shot to shot, especially with thinner sporter type barrels.
If I were you, I would untighten the tang screw until it is just snug and try again.

If it is a two screw action try tightening at 35 in./lbs. That's what is suggested in my owners manual for my winchester M70 which is similar possibly. And of course a good in./lbs. torque wrench is needed. That's with a wood stock also.

I have no science to back this statement.

I snug the rear screw, then the front screw. Then I tighten the front screw, then tighten the rear screw. My logic being that tightening the rear screw last will draw the barrel away from the barrel channel.

Like I said... no science. Just my .02.

"IMO you need a pillar bedding job, by a COMPETENT workman.

The problem lies in the 'competent' part.....
Regards, Joe"

I believe this is your answer. I'm a newbie at this, not overly experienced and try to do all I can myself. But what I've learned about Mauser's is the pillars decide. Torque numbers are probably a great thing and a pressure point may help a particular rifle, but there shouldn't be changes and that's where the pillars come in. Also, if the magazine box is touching the receiver before the pillars touch, things will never be consistent.
You can trust 99% of what those two brothers figured out in 1898.
Hope I could help.

My approach and philosophy:

The front screw does the lions share of the work, if not all of it, so I tighten that one down first and then the rear screw.

If you wanted to experiment you could try putting a shim under the front, but all that does is verify it needs bedding or pillars so might as well do that from the start IMHO.

If it was rough enough to loosen the action
screws, you had better look at the scope.
good luck1