HDD Testing

[quickster47 †]

There's been lots of discussion about the Hammer Debounce Device (HDD), what it does and mostly, does it work?  Well, I too was skeptical because the first one I installed seemed to yield nothing tangible.  But when I think back on it I installed it on a HPA powered gun and while it did a few things I was not really aware of till now, it mostly appeared not to work.

So after doing some more research on the various forums I decided to conduct another test and this time I would use CO2 powerlets.  After all, the HDD was designed to help shot count when the gun is powered by CO2, and in particular, powerlets.

So why is a HDD necessary?  Well, glad you asked that.  The problem with the Crosman 22xx CO2 guns is hammer bounce (repeatedly hitting the exhaust valve, releasing small burps of CO2) and that wastes gas.  So anything you can do to keep the hammer from repeatedly striking the valve will improve (lessen) the CO2 usage.  Therefore, less CO2 gets wasted when the hammer isn't bouncing into the valve multiple times per trigger pull.  The design of the HDD for Crosman pistols allows the hammer to fly forward without any drag, but as soon as it starts snapping backward the HDD expands against the walls of the bolt bore and brakes it.  This stops the hammer from opening the valve multiple times as it bounces back and forth between the hammer spring and valve spring tension, which obviously just wastes gas.

The HDD fits over the hammer's cocking pin, with the slot/opening facing backward.  The opening/slot is what makes the device expand; the hammer snapping backwards makes the pin attempt to back out of that opening/slot and makes the body expand in the bolt bore, creating friction to slow the hammer.  Forward motion isn't restricted though, so your shot velocity remains unaffected.  You just get way more shots per fill since it isn't re-opening the valve after the pellet's already gone.

It's also worth mentioning that the gun is a lot quieter with the HDD installed.  I actually shot the string with the HDD installed first, and then took it out to shoot the "without HDD" string.  The gun sounded like a cannon after I'd gotten used to the quiet volume of the gun with the HDD.

The gas release due to hammer bounce occurs so late in the firing cycle (because it takes more time to for the hammer to complete the first rebound from the spring than the pellet needs to reach the muzzle), that the pellet is already gone from the barrel.  So that gas has nothing to do with its energy - except make noise.  Hammer bounce actually accounts in this way for most of the muzzle blast of an otherwise efficient airgun.  That's why making that spurious waste of propellant go away by adding an HDD also makes the gun quieter, much, much quieter.

The "other" way to subdue muzzle blast - fitting a LDC - just hides the problem: cuts noise while doing nothing about the underlying cause of the noise (and waste of air).

On the HDD install...  When you install the HDD, be sure to lube it up with some Pellgun oil or non detergent 30 wt. motor oil.  Be sure you don't try to force anything when you install it.

The critical step is mating the receiver to the tube.  Be sure the alignment of the hammer/striker cocking pin is correct and slips into the hole in the HDD.  You don't want to crush the hook at the rear of the HDD.

As with all testing your mileage may vary greatly from mine.  But let me say I'm convinced and will be adding HDDs to my CO2 powered guns and I think you should also.  Look at the data and make up your own mind.  Incidentally, I didn't just run this one time but ran it about six times and the results were all quite similar.

Carl

[airguns100]

hold on. so your getting 86 + shots from one Co2 powerlets using a HDD?

[Stian17722]

What airguns100 said.
That is quite spectacular in terms of economy, think how many shots one would get from a bulk tank with those results, a near 50 percentgain in shots per 12 gram powerlette is nothing short of amazing

[philbert]

actually is it not more than 100% increase in shots 
anyhoo i dont believe your results perhaps you should send me your hdd and ill test it myself 

[eric]

i have heard good and not so good things about these HDDs and if you get 1 that works along with power adjuster you can still do better yet  (best used for plinking and paper punching  )  what caliber were you using for this test ?

[quickster47 †]

The gun I used was a brand spanking new 2240 taken right out of the box, indestructible danged hard plastic package, and used for these tests.  And as I mentioned I ran the test six times and what I published was the best run.  Worst run as 76 shots from a single powerlet.

Carl

[Stian17722]

Philbert, ops,. you are right about that, it is 100 percent more

[airguns100]

That's something that needs to be put on the top five list of up-grades, if there is such a list.
I'm surprised Crosman hasn't factory installed something like this.

[eric]

That's something that needs to be put on the top five list of up-grades, if there is such a list.
I'm surprised Crosman hasn't factory installed something like this.

that would cut into the co2 profits 

[airguns100]

that would cut into the co2 profits  

True. How ever it's made out of "plastic".  

[eric]

here is something from the green from a little while ago from lon and steve   http://www.network54.com/Forum/275684/message/1250518993/I+don%27t+think+anybody+has+done+better+re-++2240-50+shot+count+and+consistency---

[zoned]

Got HDDs in both of my Crosman Co2 guns. Made a believer out of me a long time ago. They DO work.

[mr007s]

I am wondering why the lower velocity at the beginning of the string. Any theories?

[NorthStaR]

Maybe something to do with the co2 stabilising after the initial puncture/release and a temperature shift? Maybe?   

[T191032]

Amazing that a $20 piece of plastic would do that, huh?  LOL