I have been testing this round for a while, now. Which is to say, gathering data here and there from my range trips. Thus far, it has proven extremely accurate, and the terminals I have obtained from milk-jugs mirror Hornady's claims. Namely, that it penetrates like a BEAST! It actually penetrated further/better than 62gr TSX 5.56. In milk jugs, the TSX load penetrated 3 jugs, and was found in the 4th. The GMX load penetrated 3 jugs and was found in the 4th, but I think it would have exited, had a 5th jug not been behind it, as it punctured the 5th jug and caused it to leak at the impact site!

Like I said, accuracy is outstanding, and POI is very near to M193, as my photograph shows.

All testing was conducted with my 16.1" Daniel Defense .gov profile CHF barrel with a Surefire 556-212 suppressor. The accuracy testing involved a T2 Aimpoint and G33 magnifier.

I will apologize, my typical 10-shot group is not present, but a 5-shot group of this consistency leads me to think that the round is very accurate, regardless of hair-splitting over statistical analysis thereof.

The expanded slug, fired into milk-jugs from 25 yards, measures 0.501" at the widest, and 0.39" at the narrowest. The narrowest reading is as taken between two opposing petals, and is an "extreme" measurement. If the slug were placed sideways in the calipers, instead of inserting the edges of their tips into these crevices, the narrowest measure would be 0.44". The height of the expanded projectile is 0.38" across the longitudinal center-line. Average expanded diameter, using the narrowest measurement, is 0.4455". Using a more common-sense and less "technical" narrowest measure, it is 0.4705".  Considering the distance penetrated, quite frankly, this is VERY impressive!





Here is how the bullet performed at 100 yards. It penetrated, again, 3 jugs, and marked the inside of the far wall of the 4th, but did not quite cause a leak.
At the widest, it measured 0.481", and at the narrowest, 0.355", for an average of .418, or roughly, 0.0275" smaller than at 25 yards impact. It measures 0.457" in recovered length.
Also included is accuracy testing using the same rifle as above, but with a Nightforce 1-4 NXS optic in place of the T2/G33.


Multiple lot #'s over the span of 1 year have been tested, showing similar accuracy, and NO case-neck sealant, while the primers are sealed with red sealant. Hornady LE contact has repeatedly stated the case-necks are sealed. This is not been my finding.

Nice data. Thanks for your time and effort!

thanks for posting. i really want to like the GMX round and have a few boxes for a rainy day. seems like a good bullet since the pedals dont tear off like TSX. just hope factory loaded stuff in 556 TAP line stays available.

havent tried the Super-P stuff yet.

Thank you for the review.  Your data is much appreciated.

Any thoughts on the 70gr version?  I've been looking at the GMX line for some time.

^^^^
I'm curious about this as well.

It proved similarly accurate, but tumbled and shed petals and did not track straight in both pork shoulder and water jugs.

The 55gr version tracks pretty straight and did not shed petals in my testing. Here is the 70gr gmx recovered from water jugs at 25 or 50 yards, I forget which: