Has anybody here used both of these bullets on a whitetail and can give me a good comparison between the two? Which one do you prefer?

The GMX is a little softer.

Either are a bit overkill for deer.

But both will work and you probably won't be able to notice a difference in them.

GMX is made from guilding metal and Barnes are pure swaged copper...How would the GMX be softer when it has roughly 5% zinc added to the copper?

Ive only used the Barnes 458SOCOM 300gr TTSX on deer. It went through the doe like butter destroying everything in its path.

I don't know how, but they are. They open up easier then the Barnes too.

I would personally save the non-lead bullets for tough animals where penetration is key or for rifles shooting above 3400fps where a regular bullet will go to pieces.

In the 452 and 458 GMX/Monoflex the hollow point is relatively large even compared to some of the tipped Barnes of a similar weight/caliber.

My best guess is they used a larger HP to help with the harder alloy. This is just speculation without having a hardness test done...obviously. The GMX/Monoflex might be a machined bullet and soft copper machines VERY poorly. Machine copper is much harder than pure but can be annealed to soften it. Hornady even claims they are tougher than pure copper.

I do know this, my buddy LOVEs the 243 80gr GMX for deer.

EDIT:
Just got off the phone with Hornady. The GMX/Monoflex is swaged. They had to buy special equipment to handle them. The tech also said they are harder than pure copper Barnes but not a whole lot.

Have used he TTSX quite a bit on deer and elk with a 30-06. Never had them go more than a few steps. No experience with the GMX.

I use Barnes everything. 100% weight retention and no lead fragments in the meat.

I don't have any experience with the Barnes since I have never found factory seconds in them, but I love the GMX for my 6mm. Since I switched to them the kids I take hunting have never lost a deer because of no blood trail or because a shot wasn't perfect. Personally, I think if you hunt with a small caliber like a 6mm, .243, or .223 then a tough non-lead bullet is a must. If you are shooting a larger caliber I think they are overkill for deer unless you are taking really long shots.

I've tried them both in the 6.8 of mine in 130 grain. It really didn't like either one of them much. Tried all kinds of loads and powders. Best group I got with either was with the GMX being right at 1.5" 5 shot group at 100 yards. I tried that load out on a hog and it did perform well. Blew through a hog at 98 yards like it wasn't even there. Judging from the exit, it opened up fully leaving around a 3 inch diameter hole on exit. Never hit an animal with the TTSX but I've never been able to get them to shoot worth a damn from either the 6.8 or my .243. I may try to get them to shoot out of my WC .223 AR since I do like to take that one on sounder hunts.