Did you even read the OP?
The guy wants to use existing cases with different bullets so you made a post about destroying the cases to salvage the bullets? READING AND COMPREHENSION!
It's like watching the news on TV; more of a "This answer was inspired by your question." rather than being a direct answer to a question or a retelling of actual events.
But, to stay very directly on-topic, I will mention:
Keep in mind that lead-core SP bullets will have a higher average density than the steel-cored ones you are replacing. Since the area is unchanged, that means the length of the bullet will have to change to keep the mass the same. I you replace a 147gr steel core bullet with an equivalent weight lead-core one it will necessarily be shorter.
You may find that you have to move the bullet further back into the casing (reduce overall length) to still have a secure neck interface (I did when I tried it). That can change case volume, which affects pressures. It can also complicate feeding depending on what you are firing this in (although my SVT actually prefers to feed the shorter overall length).
The original 147gr lead core bullets (from way back) for this form factor had a cone shaped indentation in the back (like a Minnie ball), so that you could still get an acceptable neck interface in a geometry originally designed to take a much heavier (220gr or so, I think) round nose bullet. The ones you are using likely won't have such an indent (at least, I couldn't find any) meaning their bearing surface will be shorter.
Usually this would be followed by a statement saying "Read and follow your reloading manual", but you can't, because you don't know the powder (well, you do if you still have the spam can, but the info won't help you much). You're likely going to end up with a shorter-than-published OAL and an unknown powder. Fun!
Are you loading for a Mosin, an SVT, or something more exotic?