Be safe - don't shoot any factory ammo - cast your own bullets. Buy Veral Smith's book "jacketed Performance with Cast Bullets and revel in how 'nice' you're being to your double rifle.
Yes - properly hardened lead bullets can give exactly "FMJ" or "Stiff Softpoint" or "Lion Loads". It's easy and simple with a very short learning curve.

It is so cheap to shoot, anyone can actually afford to practise!!!!!!!!!!!!!!!!!!!!! Something few DR shooters do much of, I'll wager - expecially at over $5.00 per shot (some many times over).