30-06

When we hunted the late season in Colorado we always used rifles with bullets that would not completely penetrate the elk because they would break up quickly and if they did miss and hit the ground or trees they would not go far because they would go to pieces. Shotgun slugs are notorious for staying together and bouncing around. The 30-06 or 270 win in Remington's standard ammo worked well (premium bullets will over-penetrate and end up where you do not want them . You may want to talk to the land owners and re-think this.
budsgunshop.com/catalog/product_info.php/products_id/713070456/REM+AMMO+.30-06+165GR.+PSP />budsgunshop.com/catalog/product_info.php/products_id/713070449/REM+AMMO+270+WIN.+130GR.+PSP

In general start with a fully rifled slug barrel in the shotgun of your choice. Next get a box or two of some different "Rifled Sabot Slugs" and shoot some groups with each. Narrow it down to the "Top three". Clean your gun barrel then group those three again to find what your gun likes best. Lastly, load up on the top load then go have fun and drop your Elk.

Go for a fully rifled slug barrel and sabot slugs. There are a lot of excellent choices. For a budget, i like the remington 870. If you have a high budget, I personally love the versamax, buds item 83752, with the addon rifled barrel, buds item 90835. It shoots magnum loads super soft and is very accurate with premiumslugs. (If you found this answer helpful, please mark it as the "Best Answer". Thank you.)