I have played around with stuff like this extensively over the years. Like others, I am not sure I tried the exact combination that you refer to, but, I have tried something similar.
I am just repeating what has already been posted, but, if this is a Russian rifle, slug the bore. I have slugged a couple 91/30 barrels and they are all over the place. And I am not talking about a couple thousandths. The way I slugged my bores was what I read somewhere on the internet. I used a lead fishing sinker that had a hole through the center of it (where the fishing line threads through it). The idea is that you get some springback when the lead sinker is driven through the bore so the hole through the center gives the lead somewhere to compress to and give you a better measurement. I drove the sinker through the bore with a dowel rod and then carefully measured it with a micrometer. This is one guy's method as an example (not exactly the same thing I did, but close enough):
I did this mainly using a couple Finn M-39s which had much better quality control in the manufacture of the barrels. I have also shot cast bullets with pistol powders in all kinds of other rifles in other calibers. I am by no means an expert and I never got into it enough to try a lot of the "tricks" used by much more serious cast bullet shooters. I never really spent enough time with it to try to achieve really great accuracy. I did get decent accuracy and what I ended up with was adequate for what I was doing with it. But as mentioned, there are guys that are really into cast bullet shooting who know way more about achieving great results rather than just decent results.
Don't forget that if you are loading cast bullets, you need to flare the mouth of the case so the bullet enters the case without shaving lead from the bullet. I am sure you know that flaring the case mouth is part of pistol loading but is not normally done in rifle loading. So, you need to buy another die to do it, with rifles because rifle die sets don't come with a case expanding die. I used a Lyman die for this, called an "M" die
https://www.lymanproducts.com/brand...fle-die-sets/rifle-neck-expanding-m-dies.html . Lee also makes a universal case mouth expanding die that is very nice because it is not caliber specific. The Lee die is quite inexpensive and is something handy to have on your reloading bench:
https://leeprecision.com/universal-case-expanding-die.html
