Does anyone know why the DoubleTap Defense - Double Tap can't shoot light loads?

[C0untZer0]

Maybe "can't" is the wrong word, but on DoubleTap Defense's web page they have written

Important: Use the brand of the two fired cases included with your gun first. - For 45 ACP it is 230 grain FMJ standard velocity - For 9mm it is 115 grain FMJ standard velocity The two test fired cases included in your gun were chosen for these reasons. They are usually Remington or Federal .

I thought, being a derringer, it would be able to fire all sorts of cartridges that wouldn't work in a semi-auto, but instead it seems like the most ammo-restrictive firearm in recent production. I can understand not recommending +P ammo, but they're not only specifying bullet weight but they're specifying Remington or Federal and FMJ !

http://www.doubletapdefense.com/

They also have this warning:

- DO NOT USE any brand of so called “low recoil’ type ammunition. -

Does anyone know why low recoil ammunition (like Hornday Lite ?) is causing problems in the Double Tap ?

 

[entropy]

Logically, it would not cock the second hammer on recoil; it probably operates like a single trigger SxS or O/U shotgun, which re-cocks the trigger mechanism with the gun's recoil.

 

[DeepSouth]

It is definitely the most ammo restrictive gun I've ever heard of, at least in modern times.

As for why no low recoil loads, I have no idea other than the last paragraph in the link you provided.

vvv

"The use of frangible ammunition, “low recoil”, or other specialty ammunition is NOT recommended in the DoubleTap pistol. The lighter bullets, higher velocities, different pressure curves and recoil will all contribute to malfunctions, misfires and light strike conditions."

 

[Deus Machina]

If it recocks under recoil, it needs energy to do so.
Without the weight of a slide to provide the inertia, it needs to come from the round itself.
If they built it to function well with light loads, more standard stuff would beat it up.

 

[Zaydok Allen]

Nothing really to add here, but to say that really stinks. I am not a fan of finicky guns. Sorry you are being restricted on ammo choices.

 

[98Redline]

Have you bought this gun yet or are just looking?

Reason I ask is that many who have fired this particular gun mention that it recoils in a very snappy manner.
A lightweight pistol, a thin profile, locked breech configuration, with a full power 9mm or 45acp load is going to be simply unpleasant to shoot. If you go for the ported barrel it is going to be LOUD!

IMHO: There are much better options out there for a deep concealment self defense weapon that offer more than 2 shots and have far fewer restrictions on what loads you can use. I would pick a Ruger LCP over the Double Tap, even given the 380acp vs 9mm or 45acp loadings.

 

[DeepSouth]

For what it's worth 98Redline is right, it is painful to shoot. I've shot mine 4 times in one session, that's double what anyone else has ever shot it, only one friend of mine has shot it twice. Shooting it was described by my brother as holding your right hand up and bracing it with your left behind it then letting someone hit you in the web of your hand with a ballpeen hammer, that's fairly accurate.
I would add, the pistol is also very inaccurate.


And (on topic) it doesn't cock under recoil.

I have shot Remington and Federal ball ammo as well as HST's and Gold Dots in mine, never had any issue, I always fire the top barrel first.

 

[entropy]

After looking at cutaways, and schematics of it, I have no idea; I'd like to hear from anyone who has shot light loads in one and about their experience. Mechanically, I see no reason why they wouldn't work.

 

[C0untZer0]

I was thinking of getting this gun and loading it with soft shooting ammo like the Hornady 100gr Critical Defense Lite, maybe it would be tolerable, but they specifically rule out the whole Hornady Critical Defense line. I'm not sure I want to shoot standard 115gr, out of that beast. You can get a "Training Glove" that slips over the grip portion, but still, I think I'd only want to fire soft shooting loads out of it. Except it seems to have some sort of problems shooting light loads. I've never known a derringer to have problems with bunny fart ammo. They've written that low-recoil ammo contributes to "light strike conditions" If the primers are good (not overly hard) primers to begin with then how does light recoil contribute to "light strike conditions" ? That's controlled by head space. Unless recoil changes the headspacing?

 

[Jim K]

So they make the gun light weight, which means easy carry but brutal recoil, then add gas ports to reduce recoil, then when the recoil is too light to reset the trigger, they find ammo that will give enough recoil to work the gun and tout it as a great feature. (The typical response of an engineer backed into a corner and unable to get out.)

In my days as a software engineer, we used to call that covering one's a** with paperwork. If something didn't work right, it was written up as a feature, and given some silly explanation. (If the printout comes out upside down, the documentation says that "Requiring the user to operate the system while standing on his head promotes flexibility and a healthy body.")

Jim

 

[Deus Machina]

Hmm. Yeah, now that I look at the cutaway, it seems to be double-action with a ratchet system. So the recoil is essentially meaningless unless they rely on it to align parts. Which is what mechanics and machinists everywhere call 'bad engineering'.
But barring severe oddities like that, I see no reason why light loads shouldn't work.

In my days as a software engineer, we used to call that covering one's a** with paperwork.

Yeah, that seems the most likely explanation.

 

[Mizar]

Well, that ugly POS uses simple mechanical ratchet to switch between the barrels:

 

[VA27]

My best guess would be that it locks the action shut. I fired some shotshells through the one I briefly owned and had to pound it open. Low pressure rounds can sometimes have primer 'setback' that will jam against the breechface making it difficult to open the action.

 

[DT Guy]

I'm wondering if there's concern about bullets 'jumping' out of the case during recoil? I'd imagine touching off that second barrel on a cartridge with the powder spread out down the barrel to the projectile could have negative effects...


Larry

 

[C0untZer0]

I'm wondering if there's concern about bullets 'jumping' out of the case during recoil

That could be it, that makes sense.

Arnie Boberg and XR9-S owners worked collaboratively to create lists of ammo that did and didn't work in the Boberg Shorty, but DoubleTap Defense isn't quite doing that, and they're not being very informative of what the problem is...

 

[DT Guy]

That could be it, that makes sense.

Arnie Boberg and XR9-S owners worked collaboratively to create lists of ammo that did and didn't work in the Boberg Shorty, but DoubleTap Defense isn't quite doing that, and they're not being very informative of what the problem is...

It's not that big an issue, I guess, since it's hard to find anyone who's fired one of their guns more than a couple times.

Maybe the ammo makers should start making 'Double-Tap Packs', with four rounds in them.


Larry

 

[Tirod]

Double Tap is hardly the only maker to specify one round, Rohrbaugh did that and may still. There is also the military - they have a very short list of ammo to shoot in weapons, and don't issue bullet weights willy nilly in low, medium, or high powered cartridges.

It is actually the civilian manual action shooters who enjoy the ability to shoot just about any load, and when the practice is then applied to self defense and military weapons we see issues crop up where unintended consequences arise. That is why some makers and the military specify limited lists of acceptable rounds. When your gun has to go bang more than once no matter what, then physics and the laws of probabilities come into affect. You don't get to play around with whatever ammo you like to shoot - if a sure and consistent result is needed.

 

[Acera]

Tirod, Rohrbaugh did not specify one round. They suggest the gold dots, 124 grain being the most popular (some use 115 and 147 as well). They said no +P rounds whoever makes them. They have not said anything about not shooting anything else, not shooting a particular brand, or staying away from lower power rounds. Plenty of folks use HST, Silver Tips, etc. with no issues. Kinda depends on your individual pistol and what it likes to eat. Mine has no issues with WWB for practice and 124 GDs for carry.

Basically, no high pressure rounds and go with what works in your gun.

Here is a link to some tested results.
http://www.acbsystems.com/boards/data/R9-ammo-data.htm

 

[C0untZer0]

I shoot 147gr RA9T out of my Rohrbaugh.