I shoot 46.5g of C2 with a 168. So, 51 is not that unrealistic(135g bullet), but chambers and bore dia vary, so work up to those compressed loads. Long drop tubes made from Arrow shafts work well, start off with one 12" long. Just go to a Shop that tunes bows, they also make arrows. Show them your powder funnel dia, they can mix and match shaft dia that they have on hand. Then using some type of epoxy, glue the shaft into the bottom of your powder funnel, and using a simple flaring tool, flare the end that goes over the case mouth...plumbers tool. Hornady makes a powder funnel with different ends for different calibers. You can epoxy one of those ends on the end of the arrow shaft.
I have shot a lot of compressed loads. Caution must be exercised as small ball powder can work it's way back through the flash hole, then you compress it, the compression can force the anvil in the primer into the priming compound. I have read of this, but I have never experienced it.
I had one 308 douglas 10T barrel that just loved 52.0g of Win 748 with a 135g Sierra single- shot pistol bullet, and I killed a bunch of large bucks with that bullet and load. Every one of those powder charges are VERY compressed. Bullets have been known to "walk out" of cases that are heavily compressed.
Win 748 with a cci 200 or Federal 210 are extremely accurate with the 125-135g bullet weights, never seen one that was not! Hold the forearm down on the rifle rest when you are shooting off the bench for some bug hole groups.
When ever I am shooting a mono bullet, I want all the velocity I can get to get them to open up at ranges past 300 yards.