How fast IS a speeding bullet?

[Anduril]

About a month ago I put 3 rounds of factory (smokeless) 45/70’s through a friends Marlin 1895 and it almost brought tears to my eyes it thumped so bad.  Today, I just got back from a short range session with a new to me 9 or 10 pound Rolling Block shooting 65 grains of Goex FF behind a 440 gr cast bullet.  I was ready for another beating, but the thing is a pussycat for recoil.  Anybody got a guess as to the velocity I might be getting out of this 28” barrel?
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[filmokentucky]

For a guess, somewhere between 1150 and 1200 f.p.s. But that is just a guess--it could easily be a tad slower. You don't state what the smokeless load was-generally they come in 405 gr. and 300gr. varieties-
but in a light weight Marlin recoil from either will be noticeable. BP loads always seem mellower to me, but it has been quite a while since I fired a smokeless load so I don't have anything but memory as a comparison.