They are designed to disintegrate on the slightest impact. Having experienced personally bullet disintegration on the skin (failing to penetrate into the chest cavity and vitals), in my opinion it’s unethical to use them on deer (or large vermin) and conscientious stalkers won’t. Barnes make very good hunting bullets X, TSX, TTSX, etc. but Varmint grenades do not fall in that category.
Varmint grenade construction (to prevent penetration) is a copper jacket and a compressed copper-tin powdered metal instead of a solid core.
From the responses so far it’s clear everyone would not agree but below is a demonstration from Barnes on a single grape.
. I’ve used them for long range squirrels and crows. They’re fine for squirrels. Could not find any load data for Vhit so I used the data from Barnes and had to buy Hodgon for that reason. It was a long time ago so not sure if the powders is still available in the UK. Got good accuracy from them all the way from MIN to MAX. Found it a bit pointless however and like to stick to a single load now suitable for everything. 
