XVR issues with hardcast bullets?

I caved and bought an 8-3/8" .460 and fitted it with a Romeo1 on a Weigand mini-rail.
Looks nice and is easy to shoot. I managed a 50-yard 1.5" group with handloaded 250grn XTP over 26grn of H110 but cannot group with hardcast. 255grn Doubletap come in around 5-6".
Is this common with XVR's or is a trip to a gunsmith warranted?
Should have mentioned, I want to avoid handloading because I load enough in other calibers already. Looking to find factory hunting loads in 45Colt +P or Casull.

IMHO, YOU BOUGHT THE WRONG GUN FOR SHOOTING SHORTER ROUNDS. I HAVE NEVER SHOT 45 COLT NOR 454 OUT OF MY 460 SO THE FOREGOING IS JUST MY OPINION. IF YOU ARE GOING TO BUY FACTORY AMMO ANYWAY, JUST BUY SOME 460 FACTORY AMMO.

shot 454 casull out of mine with great success. 45 colt not so much. 460 worked the best. hornady and handloads worked best for me.

btw- one poorly grouping cast load doesn't mean a trip to the gunsmith. I would try a different load or two_ mine shot 335gr hard cast great

That`s a long jump for a bullet from a 45 Colt shell to the forcing cone in an XVR but as Dave said "one inaccurate load does not mean a trip to the gun smith"....

The problem with using the shorter rounds is the immense (relatively speaking) distance the bullets have to travel unsupported from the case mouth to the chamber's throat. Unlike the 357/38 and the 44 Magnum/Special, which have only .1" of jump, the 460/45 has about .5" to travel unsupported. That's not to say they'll never shoot accurately.

Someday, when I have enough free time again, I'm going to test how much the difference in length affects accuracy.

I have a 5 inch muzzle-brake equipped 460V X-frame revolver. I have accurate loads for 45 Colt use and 454 Casull use. The 460 is also tailored to specific accurate loads. The chamber lead is not any issue in mine.

Thank you all for the input. I'll check out a few more, longer loads.

All the above is good advice. If really want good cast loads then reloading and casting your own is usually necessary or some custom bought loads. Cast bullet needs to fit well to your gun and need gas check and proper hardness, maybe find reduced 460 or 454 load to mimic 45+p without jump. If compensated the xvr is pretty manageable with 460 loads. You are gonna love it!