5.56 Water Expansion Testing; 55/70gr GMX, 62gr TBBC, 55/64/75gr GDSP
Did some water jug testing today. Please do your own research about this as it is NOT a tissue simulant. However, it is good for comparative purposes. All shots delivered from my 16" BRT Optimum 1:8 5R duty rig except for the last shot, 6) Speer 55gr GDSP, which was from my buddy's 16" middy 1:7 BCM CL'd upper. All shots were fired from approximately 15 yards, without a chrono, at 80 degree F ambient temperature. Rounds were tested today in this order:
1) Hornady 55gr Superformance GMX 5.56 NATO pressure
2) Hornady 70gr GMX TAP (only made in 5.56 NATO pressure)
3) Federal XM556FBIT3 62gr TBBC (5.56 pressure FBI Load)
4) Speer 64gr GDSP (.223 pressure)
5) Speer 75gr GDSP (.223 pressure)
6) Speer 55gr GDSP (.223 pressure)
A half pallet was used. 5 1-gallon water jugs were used for each shot. Penetration and effects description:
1) 55gr GMX NATO Superformance. fully split the first two jugs; just literally ripped them completely in half. Heavily damaged the 3rd jug. Punctured and was captured in the 4th jug.
2) 70gr GMX TAP. fully split the first two jugs. Same as 1). Partially split the third jug (heavily damaged; more so than 1 or 3). Bulged and partially seam-split the 4th jug. Penetrated 4th AND 5th jugs and was captured in the 5th. 5th jug was flipped over onto its back.
3) 62gr XM556FBIT3. fully split the first two jugs; just literally ripped them completely in half. Heavily damaged the 3rd jug. Punctured and was captured in the 4th jug.
4) 64gr GDSP. fully split the first jug with a connecting piece of plastic on the bottom. Partially split the second jug. Captured in the third with little to no damage.
5) 75gr GDSP. fully split the first jug with a connecting piece of plastic on the bottom. Marginally more damage to the second jug than the 64gr above. Captured in the third jug with same amount of damage as above.
6) 55gr GDSP. Fully split the first jug with a connecting piece of plastic at the bottom. Bulged the second jug and dented the back wall, but was captured in the second jug.
General observations:
The effects from the 70gr TAP GMX were notably better than either the 55gr GMX or the vaunted 62gr TBBC. Another shot was taken with a 165gr Remington Hog Hammer TSX from a 16" Faxon barrel in an AR10 I built for my buddy. Not super dissimilar performance from the 70gr TSX for the first 3 jugs. However, no slug was recovered.
Both the 62gr XM556FBIT3 TBBC and the 55gr GMX NATO Superformance performed identically. Which is to say that they were both very impressive. They were head and shoulders above the GDSP rounds in terms of their effects on the first three jugs; both penetrated into the 4th jug (both of them knocked the fourth jug over onto its back side). It was even clear to my terminal ballistics neophyte buddies that the first three rounds were clearly in another league compared to the Gold Dots... and that their increased price did indeed net observably superior performance in both penetration depth and terminal effects on the first three jugs.
The over-expansion of the lighter 64 & 55gr GDSP bullets was easy to see, with this acutely affecting the 55gr. Though, this may make them particularly well suited to SBR use.
The 75gr GDSP had solid performance and was clearly the strongest recoiling .223 pressure round tested. Again, without a chrono reading I cannot comment intelligently on the actual velocity. But it felt strong.
Pictures of expanded rounds in next post....
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