Backing out primers are a typical sign of the handload being too weak. There should be no resistance when chambering and ejecting decent ammo such as Privi - are you sure the bolthead on your rifle is fully screwed into the bolt body?

You probably just need to shoot a few more groups, in order to deduce a pattern between the ammo types you are using.

Some No1s are highly sensitive to variations in ammunition and bullet shape, and/or the bedding system (the interaction of front trigger guard screw, inner band, front spring stud and nosecap). An average No1 group should be roughly circular in shape, bigger or smaller depending upon the accuracy of the rifle/ammo combination. Some of your groups display vertical stringing and/or split groups. This would indicate to me that the bedding needs to be checked - that the screws are firm, and that nothing is missing from inside the forend, and that the forend is a good fit.

I'd personally use one batch of decent ammo - probably the Privi - and then work through this sequence:

1. check that the forend is undamaged, particularly in the recoil faces. Repair if necessary.

2. Make sure that the inner band spring is present, and also the front spring and stud;

3. assemble the rifle, ensuring the front trigger guard screw if firm. Tighten the inner band screw, then slacken it off so that the spring is just under compression - about 1 turn;

4. fire a sequence of five-shot groups, tightening the inner band screw by about 1/8 turn - observe to see if the rifle reacts significantly (I've seen some rifles show a 3-4 moa group difference on just a fraction of a turn of the inner band screw);

5. if (4) does not produce an effect, try fitting a different nosecap.

6. If you can find any, try a few test groups with surplus cordite ammo - this will provide a benchmark for the rifle.