My experience and test results with an SSG, and FFH Hammer De-Bouncing Devices (HDD) on a Stock Marauder.

There has been a lot of talk recently about de-bouncing the hammer on a Marauder (and other PCP Airguns) to increase shot efficiency and/or increase power.  At past shooting events, and recently with a customer’s Marauder, instead of a nice clean “bing” or sharp “pop” report, I have heard the tell-tale “Bbraaaattt”.   This “Bbraaaattt” report is a sign of hammer-bounce, where the hammer continues to strike and re-strike the valve, (after it initially strikes the valve to propel the pellet).   Any strike to the hammer after the initial strike is a waste of air. This wasted air could have been used to either increase shot count, increase pellet velocity, or a combination of both.

What does one do to prevent or reduce hammer bounce?   I tested 2 HDD devices, quite different in design, appearance and installation, and offer the un-biased test results to you. 

Note that both, regulated, and non-regulated PCP airguns with hammer bounce will benefit from an HDD, but this particular example is with a stock un-regulated, Marauder.   I then installed each HDD device, without any other modification to the rifle. No tuning for that specific HDD was made, as the idea was to see how a “drop-in” HDD performed.

Mini-lesson on self-regulating rifles:

Most un-regulated PCP Airguns have what is called a “Sweet Spot”.  This is the pressure range at which an individual PCP Airgun shoots a pellet somewhat consistently at relatively the same velocity, even though the pressure is decreasing with each shot. This is called self-regulating (as opposed to a “Regulated PCP Airgun” that has an actual regulator installed into it). 

One needs a proper amount of air to consistently shoot a pellet at a satisfactory speed. The proper pressure to fill will be defined as the “Fill-To Pressure”.  Obviously too little air pressure will result in a slower than intended pellet.    BUT, too much air pressure will also make an un-regulated PCP Airgun shoot slower.  This may seem counter-intuitive, but it is true.  If filled higher than the “Fill-To Pressure”, the increased force on the valve (resulting from the higher pressure exerted on the valve from the airtube) will close the valve quicker, resulting in less air for propulsion and a SLOWER pellet.  Each resulting shot will slightly speed up.   Eventually the pellet hits a peak velocity at a particular pressure, and each subsequent shot results in a slightly slower pellet as the pressure continues to decrease.  Eventually the pellet is so slow, the airgun needs to be refilled. Many airguns tend to be refilled at around 2000 PSI, but others can vary dramatically.  I define this as the “Re-Fill At pressure”.  The range of pressure between when one starts to fill the PCP Airgun (Re-Fill At Pressure) to when one stops filling (Fill-To Pressure) is called the “Sweet Spot”.

One example is of my un-regulated Air Arms S310 shown in Chart 1.

Chart 1

Sample Shot String for AA S310 w/16 Grn JSB

Chart 1 shows that if one wanted to shoot within 20 F/S of the peak velocity, shots #2-#30 would fit this criterion.  Looking to the 4^th column from the left, one can see the “Sweet Spot” for shots #2-#30 would range from 198-144 BAR = about 2900 PSI “Fill-To” and “Re-Fill At” of 2100 PSI.  If one doesn’t have a rifle equipped with a gauge, they would simply fill to 2900, and count 29 shots (yes, 29, not 28)*

My Testing Method:

1) I first tested the stock Marauder with my helper, Ricky. I connected my Great White Tank to the Marauder, and I intentionally over-filed the Marauder to 3200 PSI, so that it would definitely be above the “Fill-To” pressure.  This ensured we got all the preliminary data prior to entering the “Sweet Spot”.  If I had tested at an initially lower pressure, we could have already been in the sweet spot and lost critical data.  (Note: this was for testing purposes. NEVER over-fill ANY PCP Airgun). 

2) We closed the valve at 3200 PSI on the Great White tank, but DID NOT BLEED the valve and hose.  This would allow the check valve in the Marauder to remain open and the Main Gauge on the Great White would indicate the pressure in the Marauder.  We used the Great White Gauge instead of the Marauder’s for 2 reasons. A) the gauge on the Marauders are often off by 500 PSI, vs. the 1% accuracy for the Wika gauge on my Great White tank and 2) the Marauder gauge is too tiny and doesn’t have the hash-marks to interpolate the minute pressure differences .  Even with a large 2.5” gauge on the Great White, we were splitting hairs and it was difficult to interpolate some pressures. 

Photo 1 - Wika 2.5” Gauge, 1% Accuracy

3) Rick and I would measure the pressure prior to each shot, and then enter the velocity from the Chrony. If we missed a shot, we’d re-fill all over again. This got old fast, but we did it.  F/S was measured to 0.1 F/S.  Chart 2 shows the stock Marauder’s shot string with a JSB 25.4 grain pellet.  

Parameters for judging shot efficiency

When judging shot count efficiency, all three measurements, a) “Fill-To” and “Re-Fill At” pressures, b) Velocity/energy for a given pellet and c) Shot Count, need to be viewed as a system to evaluate the stock Marauder with HDD, vs. the stock Marauder without.  While obviously one wants to a) increase the number of shots, as well as possibly b) increasing the Energy per shot, one also wants to c) lower the “Fill-To” pressure and d) reduce the difference between the “Fill-To” and “Re-Fill At” pressures.  Accomplishing c) and d) results in a more air efficient PCP airgun, hence less “topping off” with an air tank would be necessary.

(Chart 2)

http://www.airtanksforsale.com/HDD/StockMrod.txt

(Click link above for Chart 2 – Excel Data for shot string of stock Marauder with a JSB 25.4 grain pellet)

1) Number of Shots per Fill:  a total of 22 shots (#4-#25) met our criterion of being within 20 F/S of the peak (From 795 F/S down to about 773-774 F/S).

Using the fill calculator on my website, 62.9 Fills x 22 Shots = 1384 total shots per Great White with this particular un-modified Marauder.

 2) Velocity:  V-Peak was 795 F/S.  Energy (795 F/S) =  35.7 FPE

3) Fill Pressure:  For this particular un-modified Marauder PCP Air Rifle we measured the “Fill-To” pressure to be 3100 PSI and the “Re-Fill At” pressure at 2130 PSI.  This is a difference of 930 PSI of air used. The unusually high fill pressure (many work best between 2900-3000 PSI) may be attributed to the       hammer bouncing. This requirement will also decrease the number of fills from a Great White from the “normal” 62.9 to 61.6.  Later, we will compare this number of fills to the Marauder with each HDD installed.

3) Report:  For this particular un-modified Marauder PCP Air Rifle we measured the highly technical JoeB Ear-o-meter. Basically everyone in the shop could hear the tell-tale “Bbraaaattt” in the Marauder’s report, signaling it had massive hammer bounce (as many do).

4) Shots per tank: 61.6 Fills x 22 Shots = 1,355 total shots per Great White with for this particular stock Marauder.

Conclusion for Stock:  As with most Marauders, it got about 20 shots (22 to be exact) that I consider usable.  

SSG, FFH, they’re all HDD!

I will briefly describe each HDD, its parts, and installation.

SSG

On the left is the unmodified End-Cap, spring and hammer.   The SSG kit (on the right) contains all the pieces below (From top on the right: Modified End-Cap, Guide Rod, new Spring, Modified Hammer etc.).     I opted for the modified hammer, instead of modifying my own. I was quite impressed with the quality of the components.  Installation was straightforward.  The SSG was installed without changing any pre-set spring tension, etc.. The energy for each shot can be adjusted by a locknut on the Guide Rod, varying the distance between the guide and the screw in the End-Cap.  The SSG is available for Gen I & Gen II Marauders.

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Photo 2 - SSG

Chart 3 shows the results using the SSG.  This time Ron was my helper.  Similar to the un-modified Marauder, we hooked up the Great White tank and didn’t bleed it so we could monitor the pressure before each shot.   I’d shoot and Ron would enter the data on the Excel spreadsheet.  We were both amazed at how little the air pressure dropped in between shots (resulting in more shots). 

(Chart 3)

http://www.airtanksforsale.com/SSG.txt

(Click link above for Chart 3 – Excel Data for shot string of Marauder with SSG, w/JSB 25.4 grain pellet)

Results: Remember, all three measurements, Fill pressure, Velocity (F/S for a given pellet or energy) and shot count, need to be viewed as a system to evaluate the stock Marauder with SSG, vs. the stock Marauder without.

1) Number of Shots per Fill:  a total of 34 shots (#30-#63) met our criterion of being within 20 F/S of the peak (From 815 F/S down to about 795-794 F/S). This was a 54% increase in usable shots from stock.

2) Velocity:  V-Peak was 815 F/S = 37.5 FPE with SSG vs 795 F/s and 35.7 FPE without. This too could have been greatly improved, but we wanted to start with a completely un-modified SSG (i.e. we didn’t tweak it at all). Subsequent to these tests, we may re-install it and re-test to a higher velocity and see how  increasing the velocity affects the number of shots and Fill Pressures.

3) Fill Pressure:  We measured the “Fill-To” pressure to be 2685 PSI and the “Re-Fill At” pressure at 1915 PSI.  This is a difference of only 670 PSI of air used vs. 930 PSI for the un-modified!  This is a very dramatic improvement.  Using the fill calculator on my website this means that one would get 103.5 fills with the FFH installed vs 61.6 in our test gun. (a 68% increase in fills!)

4) Shots per tank: 103.5 Fills x 34 Shots = 3,519 total shots per Great White with SSG installed AND a modest bump up in FPE!  This is an amazing improvement of more than TRIPLE the number of shots per Great White!

Conclusion for SSG:  The SSG was a SIGNIFICANT improvement!  Remember, all three variables need to be viewed as a whole and the shot count went up to 34 shots with the SSG installed, versus 22 shots uninstalled. This is a 54.5% % improvement while ALSO increasing the maximum Energy to 37.5 FPE with the HDD installed, vs. not. And lastly, (and just as important if you are concerned about the number of tank fills one will get) the “Fill-To” pressure decreased to just under 2685 PSI, while the “Re-Fill At” pressure was only 1915 (a difference of 970 PSI).  Using these numbers, one can see that the number of fills increased to 98.8 vs the stock 61.6!  I had to do a double take on that calculation!  Yes, installing the SSG resulted in a 60% increase in the number of usable fills one would get from a Great White (or any) 4500PSI air tank.  Coupling the 60% increase in number of fills with a 54% increase in shot count provides a total of 2.46 (let’s call it 2.5) times more shots from this Marauder from a 4500 PSI Tank!  That is GREAT NEWS for everyone, especially those that drive long distances to get their tanks filled..

FFH

The FFH is a very simple item.  The package contains the items at the bottom of the picture, as well as a few extra pieces not necessary with the stock spring.  The stock Hammer (top left), stock sprig, and end-cap (top-right) are re-used, and hence not included..  It was the lack of parts that made me wonder how it would work.   Installation was doable. It took me a couple of tries to get all the parts properly put together, but once one I had done it, it would be simple to do a second time.  The FFH is installed using the stock spring that came with the Marauder.  The energy for each shot can externally adjusted by a locknut on the end-cap, varying the distance between the stock plug in the end-cap, and the new screw. No tear-down is required to change velocity.
Note: I did a mistake, that may have made the data erratic, and that I used some lube on the hammer (thinking it would help). I’m wondering if the lube caused “stiction”, and made the data a bit “choppy”.

Photo 3 – FFH

Chart 4 shows the results using the FFH.  I had to do this alone over the weekend instead of the weekday, due to workload.  Similar to the un-modified Marauder, I hooked up the Great White tank and didn’t bleed it so I could monitor the pressure before each shot.  My first observation that even despite using the same hammer spring, the velocity (and hence FPE) went up dramatically with the FFH vs Stock. 

(Chart 4)

http://www.airtanksforsale.com/HDD/FFH.txt

Chart 4 - Shot string of stock Marauder with FFH, and JSB 25.4 grain pellet.

(Click link above for text values in Excel)

Results: Remember, all three measurements, Fill pressure, Velocity (F/S for a given pellet or energy) and shot count, need to be viewed as a system to evaluate the stock Marauder with FFH, vs. the stock Marauder without.

1) Number of Shots per Fill:  a total of 32-33 shots (#1-#32) closely, but not exactly met our criterion of being within 20 F/S of the peak (From 852 F/S down to about 826-828 F/S). This was almost a 45% increase in usable shots vs. stock.

IMPORTANT NOTE: As per my EXACT specification of being within 20 F/S of Vax (854 F/S), only shots #3-24 fit this criterion, yielding only 22 shots. But to be a fair, that in my opinion, the data was so close, and so sporadic, one could have used 10 extra shots not exactly meeting my criterion. Whereas the stock Marauder (and SSG installed) Marauder tests dropped like a stone on either side of the shots that were 20 F/S slower than Vmax, (signaling the edge of the “Sweet Spot”) the FFH modified Marauder was still pretty flat outside for a number of  shots. To me, this indicated it was still in the “Sweet Spot” for these extra “Graced” shots.   In fact, it is my opinion that the Fill-to pressure of 3200 PSI quite in or near the beginning of the “Sweet Spot” and additional data (and possibly good shots) are missing.  In the attempt to publish the review before I get inundated with work, I will publish the data (in all its entirety for all to see), and at a later date attempt to re-do a data string for the FFH starting at 3350 PSI.

2) Velocity & Energy:  V-Peak was 854 F/S = 41.1 FPE with FFH vs 795 F/s and 35.7 FPE without.  This is a 15% increase in FPE with stock spring.   The power can be easily changed up or down to suit one’s need without disassembling the Marauder.  

2) Fill Pressure:  We measured the “Fill-To” pressure to be at least 3200 PSI and the “Re-Fill At” pressure at 2135 PSI (if we use the data for 33 shots).  This is a difference of 1065 PSI of air used vs. 930 PSI for the un-modified. 

3) Report:  Everyone in the shop agreed the report was MUCH quieter than stock.  In addition, no longer could one hear any sign of the tell-tale “Bbraaaattt”.  It may have been a TINY bit louder than the SSG modified Marauder, but this could probably be attributed to the increased FPE. 

4) Shots per tank: 51.2 Tank Fills x 33 Shots = 1689 total shots per Great White with FFH installed (an increase of 25%) modfied vs. with without.  And that increased shot count is with a VERY significant power increase.

Conclusion for FFH: The FFH was a MAJOR improvement over the stock Marauder. Remember, all three variables need to be viewed as a whole.  The shot count went up to 32 shots with the SSG installed, versus 22 shots uninstalled (45% improvement) while ALSO SIGNIFICANTLY increasing the maximum Energy to 41.1 FPE with the FFH installed vs. 35.7 FPE. not (another improvement of 15%).     And lastly, the “Fill-To” pressure increased to 3200 PSI, while the “Re-Fill At” pressure remained the same at about 2135 PSI (a difference of 1065 PSI).  Using these numbers, one can see that the number of fills one could get from a Great White went to 51.2 vs the stock 61.6, while the number of shots increased 45%. 

Overall Conclusion: 

1.       The SSG and FFH each performed remarkably well

2.       As a former Physiciist, I could turn  this into a real science experiment. For an “Apples to Apples” comparison, the overall test could be better performed by either decreasing the velocity with the FFH to match that of the SSG, or the SSG increased to match that of the FFH.  I don’t think this is totally necessary (but it would be nice to do) because of point 3)

3.       It is my opinion that both devices removed the hammer bounce (probably completely).  With that accomplished, the only difference in the tests is that they were performed with different hammer springs set to different energy levels.  Both devices are exceptional in their results and hence perform their task.

Should you have any questions, or wish to purchase one, have an HDD installed, or purchase a Marauder with one installed, please call one of the following:

http://www.airtanksforsale.com/  at 714-907-007

http://experthpa.com/cart/cart.php?m=product_list&c=69 Purchase online

http://www.topgun-airguns.com/  at 602-674-5309