Help with SynRod .22: regulated, de-bounced, but not performing

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FlexWagtail

FlexWagtail

Member
Aug 11, 2016
130
24
MD, United States
My goal is to get this modified Marauder shooting 18.1 JSBs at 880 fps as air-efficiently and consistently as possible, but I'm stuck. The gun is now regulated and debounced but I'm limited to shooting 840 fps /28 ft lbs. range with some inconsistencies. I sure could use some help from more experienced hands. The gun is as follows:Huma regulator (gauge block version) is set to 2200 psi.Valve is wide open (4-turns).Gun is equipped with a FFH debouncer from AirTanksForSale.Stock hammer and stock spring.
Shooting lubricated pellets through a Marmot Militia barrel
To max out velocity, the debouncer is tuned to 6.5 turns from full counterclockwise, which is about as far as it will go before coming off the threads. Fewer turns results slower fps, as you would expect -- down to 450 fps at 0 turns ccw.
Before modifications, the 2200 psi level was where I was catching the last 1/3 of my power curve (the knee) at about 880-890 fps, thus the setting of the regulator at that pressure.
The modified set up is giving me about 30 shots on a fill from 3100 psi down to dropping off the regulator. I'm also getting some mysterious shots that are way high (875) and way low (825). The regulator is "broken in" with at least 300 shots over it.
I was wrongly expecting that max spring pressure would put the 18.1's over 900 fps, and I would tune down from there to get to 880/31 ft. lbs.

I'm now considering a stiffer spring and custom hammer, but I'm not ready to go there yet. The other option is to pull the regulator and amp up the pressure.
A curious clue: The FFH debouncer has been problematic. The threaded post that serves as the striker broke. I replaced with a lesser aluminum post I bought at the hardware store and it broke again. Mr. Brancato at AirTanksforSale.com was nice enough to send an extra steel post. It is reinstalled, but I'm not convinced the unit is striking properly every time. For instance, in a tuning test it mysteriously was not unloading the spring as I tuned down. I took it apart, saw no trouble, reinstalled and it worked fine for a while, only to go goofy again. Wierd. Perhaps the threads in the stock hammer are "catching"? Perhaps the nylon/derlin cuff is slipping or not holding steady? I don't know.
Finally, because I'm now regulated, I am tinkering with overfilling up to 3250 psi, on the theory that the regulator now makes me immune to issues like valve lock from overfill. What's the wisdom of pushing this boundary?
Looking forward to advice from the masters.

 
First, I got in a .25 with an FFH and it was also broke. It is a poor design in my opinion. Though it is expensive, the SSG from WAR is a much better solution. Your odd velocities here and there in your string are most likely due to the ffh.

I assume your valve is stock? To get your desired results, you need a modified or aftermarket valve. Also, the Marmot Militia barrels have a very tight choke and do reduce velocity as compared to a stock barrel, or even an aftermarket Lothar Walther barrel.
 
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The ffh is a different design than the ssg. The cap that is used as the striker on the ffh is a weak point. The design I feel allows for periodic drag that cause velocity spikes in a shot string and almost every ffh string I have seen has spikes. If one were to drill out the hammer threads and use a stronger cap than the one I had, it could be a winner. That is why I would recommend the SSG even though it is way expensive. For those DIY types, making an ssg is really easy if you want to save money. Even the really easy ones I made for myself were all stainless hardware and worked great all while costing under $10. The down side to the really simple ones I made, was they protruded out the back of the end cap. I did those so that the gun was easily returned to stock form.
 
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This feedback is much appreciated. I was unaware a .25 valve was interchangeable in the pressure tube. Would any of you care to explain why the upgrade to that valve is recommended? More plenum? Also interesting feedback on ffh debouncer. Based on my experience I agree the threaded post cap is a weak point, since I managed to break 2. I note the ssg is sold in a kit with optional hammer. What are the pluses Vs. Whatevers on that. Why is a different hammer needed? Again, the advice is excellent and I'm thankful to hear from you all. 
 
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The SSG with hammer is sold with a stock hammer that has been pre-drilled so you can just install and tune. As for why I used a .25 valve it was because it has better flow than the stock .22 valve and I didn't want to spend a whole lot a valve.

Do far its worked out well enough, but if I had to do over I'd probably opt for the huma .25 gauge port version reg for even more plenum space. The again my .22 m-rod was picked up to be a test bed for mods before they make it to my .25.
 
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Post-mortem items learned:
1) The Marmot Militia barrel is a real tight choke. Even lubricated, the extra friction reduces velocity. Experienced hands have told me to expect a 30-50 fps reduction in velocity.
2) The FFH debouncer can be problematic. Might want to spend the extra money on the SSG.
3) Regulating the gun is not the simple "drop-in and perform" install I expected. Experienced voices have told me it really requires a better understanding of the main valve and plenum than I have, and modifications to those as well. I really not ready to go there for another 50 fps.

In the end, I got a lot of experience and knowledge out of this process, but not the performance I expected.

Before mods, I was shooting 18.1's at 880-890 for about 15 shots in the heart of my curve.

With regulator, MMbarrel, and no debouncing, I was getting lots of wasted air on bounceback and not great velocity (840-850) and only 20 shots before falling off reg. The shots were consistent in velocity.

With reg, MMbarrell and FFH debouncer, my shot count went up significantly. One string I got 38 at about 840. But I had weird highs and lows in the strings and the debouncer broke, twice. Re-installs of FFH gave me results that were also hard to duplicate despite identical install procedures.

The MMbarrell has been the best purchase, despite the impact on velocity. It tightens up groups as advertised and is worth the dough.

I am considering dropping a little more scratch to change out to the SSG debouncer.

The upside of all the money and time invested is that if I turn down the power into the 730-750 fps range I DO get longer, consistent shot strings. So I've got myself a nice plinker, though probably not a competitive target shooter.

There's plenty of fun in that, but not for the money I've spent.

Like a lot of noobs, I got into this because I'd been goofing around with some rimfire friends on camp outs and whatnot, but going to the range to pursue the hobby more seriously was too much of a pain. So I went to air guns to enjoy shooting more. The fun part for me has been popping away with accuracy and consistency rivaling or bettering my rimfire pals and jawing with them about it. What I was trying to achieve with this gun was to get the power up enough to go out a little farther for reliable beer-bottle busting at 80 to 100yds with less holdover. While I can hit at that range, it could be better, and I'm just not where I thought I might be. I also want the power up after the unfortunate wounding of a squirrel that really should not have had to suffer my slight miss. A more powerful gun would have killed him I think. 

In the end, I think I could have achieved most of my goals by going with the better barrel and staying stock -- accepting that I would have limited shot strings and would be pumping/gassing more frequently to stay in the curve.





 
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