Mannlincher shoenauer 1950 problems

[JOSE LUIS LEON]

I have a mannlicher schoenauer 1950 model, does not group bullets of 100 gr, some knows that twist have

 

[RT2506]

I am pretty sure it has a 7 1/2". I have some 6.5x55 Swede military rifles and they have 7 1/2" twist and they will not shoot the 100 gr Sierra HPs I tried. Jump up to 120s through 160s and they drive tacks. You can measure it yourself. Use a tight fitting patch and a cleaning rod. Push patchless cleaning rod through the muzzle end and when it comes out the action end place the patch on the jag. Pull the rod pulling the patch until it goes into the bore a couple inches. With a Sharpie pen make a dot or mark on the cleaning rod right where the muzzle is. Now pull the cleaning rod out until that dot or mark rotates back to the same orientation it was when you marked it. Now measure from the muzzle out to your mark. What ever the measurement is your twist because it made one revolution in that distance.