Test: Double Tap 155 gr Gold Dot vs. Speer 165 gr Gold Dot

[Marcus L.]

sjc,

If you are wanting additional penetration from your .40s, then Double Tap might be the brand for you. I can see it serving a function in large game protection such as black bears. In that case though, you would still be better served using heavier bullets which do better against bone once the bullet has penetrated through thick hide and muscle.

Each caliber/bullet diameter has an expansion threshold which time, and time again has been demonstrated to not expand beyond a certain point. Double Tap advertized their .40S&W loads as expanding to unheard of .75"-plus which just doesn't happen. It looks like their penetration is good, but I also knew a guy who pulled the petals away from the trunk of a load he was testing to make it look good. DT's expansion data by all unbias accounts is false, or done incorrectly. The only reliable, and proven way to improve on your existing caliber of choice is to switch to a larger caliber which has a larger entry hole, and a larger expansion threshold.

[sjc3081]

sjc -- I don't think a tiny change in barrel length or rifling is going to explain the difference between Doctor Roberts's independent controlled test results and the stuff Double Tap is claiming. My opinion, you are off base calling it misleading and dishonest.

The 4006 is very common in CA, as it is the standard issue CHP pistol. On the other hand, Glocks in calibers other than 9mm are not something I am fond of. FWIW, there is minimal difference in velocity between conventional and polygonal rifled pistol barrels--something around 10fps or so. Bottom line, in this test, the DT ammunition offered NO advantages over standard factory ammunition and had the disadvantage of increased flash, blast, and recoil. Pressure testing might be prudent as well.

sjc,

If you are wanting additional penetration from your .40s, then Double Tap might be the brand for you. I can see it serving a function in large game protection such as black bears. In that case though, you would still be better served using heavier bullets which do better against bone once the bullet has penetrated through thick hide and muscle.

Each caliber/bullet diameter has an expansion threshold which time, and time again has been demonstrated to not expand beyond a certain point. Double Tap advertized their .40S&W loads as expanding to unheard of .75"-plus which just doesn't happen. It looks like their penetration is good, but I also knew a guy who pulled the petals away from the trunk of a load he was testing to make it look good. DT's expansion data by all unbias accounts is false, or done incorrectly. The only reliable, and proven way to improve on your existing caliber of choice is to switch to a larger caliber which has a larger entry hole, and a larger expansion threshold.

Ok points well explained. Marcus I thought you were intentionally misleading but I was wrong.

[DocGKR]

Conducting and interpreting gel testing is not hard; there is no reason why manufacturers should not know exactly how what they are selling will perform--I have included a sticky with info here: https://www.m4carbine.net/showthread.php?t=26028

[Marcus L.]

That's a good read, Doc. It makes me wonder if a lot of testers are measuring their expanded bullets incorrectly resulting in exaggerated expansion numbers. It is certainly possible that McNett at Double Tap is just measuring his bullets at their peak expansion point which isn't necessarily being dishonest, but it isn't adhering to the standard. I'll have to go over my old copy of Bullet Penetration and review MacPherson's notes.

[sjc3081]

Why was the definition of diameter changed and why is it acceptable. I'm floored. This seems to add a advantage to heavily constructed slow moving bullets that don't frag.

[DRT]

DocGKR, Thanks for testing these loads! I'm issued 165gr GD that I carry in my P226-40 while on duty. This data just solidifies my belief that, in .40 s&w, you can't do much better than a premium, well-designed 180gr bullet, which is what I carry when it's my choice.

Since everyone is asking about velocities, I had previously chrono'd (prochrono) these loads out of my G27, G22, and G35. I'm going from memory but the velocities I measured were approximately (within 10fps) as follows.

155gr DT = 1180, 1240, 1290 fps, (G27, G22, G35)
165gr GD = 1080, 1170 (G27, G35)

Given the choice, I'd take my G35 with 16 rounds of 180gr HSTs at ~1030fps (~950fps out of my G27). 180gr Ranger T-series would be just as good. 180gr Gold Dot wouldn't be bad as a 3rd option.

[DocGKR]

sjc3081,

"Why was the definition of diameter changed and why is it acceptable. I'm floored."

I am unclear what you mean--the standard accepted calculation for projectile recovered diameter (RD) has been constant since the early 1980's...nothing has changed.

"This seems to add a advantage to heavily constructed slow moving bullets that don't frag."

It is definitely an advantage for handgun bullets that crush more tissue. With handgun bullets, fragmentation is a BAD thing, as bullet mass and surface area is reduced, causing a smaller permanent crush cavity. In addition, most handgun bullet fragments are usually found within 1 cm of the permanent cavity track and do not produce the synergistic effect found with rifle bullet fragmentation and temporary cavity stretch.

[DRT]

A couple more points.

1) The 165gr GD load tested above was the higher-velocity version rated at 1150fps by ATK

2) My P226-40 with a 4.4" conventionally-rifled barrel generally chrono's about 10fps slower than my G22 with a 4.49" polygonally-rifled barrel. Once again, DocGKR is spot on with his assessment.

[sjc3081]

I don't understand why the government would invent a way to measure the actual diameter of a recovered round by not actually measuring the diameter of the round. Than create a testing method by not measuring the actual widest diameter and call the results , a recovered diameter. The more I find out about this jello shooting the more I question the results. It seems like the test method is designed to prove and confirm the testers predetermined expectations. I confused with logic of these testing methods.

[Jim from Houston]

No one "invented" anything...the issue is the following: the EMPTY space between the expanded petals of a round like the HST or DPX rounds does not crush tissue. With such a round, you're trying to find the "diameter" of an object that is not a perfect circle, so you need to do some math...

The projectiles with "petals" may form a differently SHAPED crush cavity, but the VOLUME of said cavity would, in most instances, be nearly the same as similar rounds with a cylindrical profile...

The fact that ATK chooses to willfully ignore these facts in their SALES presentations is a reflection on them, not on the field of terminal ballistics, or researchers within that field...

This is not a matter that is some sort of "debate" between different philosophies...the volume of a crush cavity is something that can be measured, and if certain ammo companies decide to willfully ignore that, well, that's an issue with them...