180 gr XTP
Here is a not so "apples to apples" comment on the .44/180 XtP slug.
I experimented with this slug from a Ruger .44 carbine (tube feed) while searching for a load that would give better accuracy than the traditional 240 grs were producing. The 1-38" twist of the old carbines seemed to indicate a lighter slug, and I gave the XTP's a try, and they did shoot considerably better. My load was 23.5 grs of H2400, which was safe in my carbine and I believe I reduced the charge based on those from the Sierra manual as a guide line, as Sierra made a .44/180 as well.
However, at carbine velocities, (1985 fps, 18.5" barrel) the slugs were entirely to explosive for whitetails, and would fragment badly. Although I never lost a deer shot with that combo (5?), I never had a slug exit either, nor did I have one that maintained integrity and did not slip its jacket. I eventually learned that the Hornady people have published a table that show the .44/180 XTP as essentially intended for velocities up to 1400 fps. Driving those slugs nearly 500 fps faster from the carbine, I was way over their intended range. I switched to 200 gr XTP's, and now recover the slugs intact and impressively mushroomed. I finally had one (200 grs) exit this year on a 138 lb meat buck.
I did indeed see your post that your rig would be for varmints and target, and I mention the above only to encourage you to limit that slug to that purpose , as I do not see it as an adequate a deer/hog slug when pushed hard.
As an aside, I ran some factory Rem 180 jacketed soft points from the carbine and they clocked an amazing 2160 fps!!!!!!!