Well, back when I was playing around with hot stuff in my 610, I found you could increase velocity significantly with much more pressure by long-loading
the projectile beyond the 1.260 COAL restriction in a 10mm autoloader. Since these were special loads for my 610 only, I used NICKLE brass to distinguish them from the reloads (using the goldish brass) for my autos.
Long time ago a 10mm user over on THR posted several times about doing the same long-loading experimentation with his 610, and he stated that his success at developing a 100-yd "deer load" was the reason he passed on sending his wheelie to Bowen for reaming out the cylinders to 10mm mag length.
While I haven't tried reaching 10mm Mag levels, I have tried loading the 200gn XTPs out to, first, 1.325," then on up to 1.400", and increasing the powder charge slowly but steadily. IIRC, I was using AA#7. Some COALs I tried were more accurate than others, based on group sizes.
Nothing bad happened, but I eventually got tied up with something else and had to stop experiementing with finding the maximum safe load for long-loaded 10mm ammo in a 610.
Maybe someone else has attempted this long-loading alternative to having their 610's cylinders reamed?