Here is a demonstration of exactly what we are talking about on this thread.
A while ago I acquired a 30-06 with a FN Supreme action, with Sako trigger, made into a rifle by Marlin about 1952, who put a 22 inch micro groove barrel on it. I guess they allotted a batch for Eaton's to sell, because this one is marked into the barrel, "EATONS OF CANADA TRUELINE MODEL 100."
I took a very well known load for a 30-06, 57 grains of 4350 behind a good, standard hunting bullet of 180 grains.
As soon as I got on the paper I fired five shots, one after the other, so the barrel will heat up. That group is shown in the first picture. I was sure the rifle was capable of better than that, so took it home and went to work on it.
I tweaked up the seating of the recoil lug, with a hardening glue, sanded a bit in the barrel chamber and tried again. Picture 2, not good enough.
Pressure under the barrel, Still not good.
So I sanded out the barrel channel and my pressure point, making sure it free floated.
Got the five shot group that probably my built in wobbles moved one less than have a hole out of MOA. picture 3.
I then changed powder to 60 grains of Norma MRP and made MOA, but only fired four shots. I feel the rifle will now shoot any descent ammunition just fine.
By the way, the rifle barrel is thin at the muzzle, but has quite a taper to it, so that would indicate free floating would work fine.
