[HiBC]

Your 798 is a commercial 98 Mauser.A lot of really fine rifles have been made on Mauser actions.That is not your problem.

First impression on your pictures of the stock:
That gob of epoxy was done wrong.

That little ,irregular pad under the barrel shank helps nothing.I prefer to not have the barrel shank touch anything,I like the barrel fully free floated.

What you want to achieve ,in the long run,is having your receiver supported.Now,Glass bedding will conform to the steel OK,but there is one more important point.The reveiver must be relaxed...not under strain.From what I see,that gob of epoxy is about as useful as a pebble in your shoe.Its a shim,a high spot.

When you tighten the guard screws,you are distorting the action.

The web of wood behind the recoil lug looks unusually thin.Ordinarily ,a glass bed job would reinforce the wood behind the recoil lug and give 100 % bearing under the receiver ring,behind the recoil lug,and under the flat floor of the receiver.I also prefer a glass pad under the tang at the rear guard screw.You want clearance behind the rear tang.That wood is unsupported,and will not take recoil.

One more thing I learned from an old Gun Digest article on stocks for heavy recoil rifles: the front face of the mag box should support the wood behind the recoil lug.From there,the recoil should be transmitted to the wood behind the lower tang..I'm afraid you are well set up to split the web of wood behind your recoil lug.

I understand a DYI spirit and a desire to gain experience.Getting it right must be based upon a thourough understanding of what you are trying to achieve.

Even then,learning about all the things that can go wrong with your first glass job as the resin is kicking over and beginning to gel can be a disaster.

It may be best to let your gunsmith do a good glass job on a relatively virgin rifle rather than making a mess for him to clean up .

Unless something else were wrong,like a bad barrel,I have a pretty high level of confidence your rifle,properly glass bedded and free floated,with good ammo,will do 6 inches at 300 yards or better.Thats not too wild of a claim.

4 inches at 300 yds would not surprise me.I think that may be the zone of reasonable expectation.It may do better,sometimes you get lucky.

Square the receiver face,a premium barrel,tune the ammo some,and you might get 2 in to 3 in at 300 yds.Maybe better,but not much better.

Wild speculation,I know,but probably not too far wrong.