Today reader RidgeRunner, begins telling tells us about tuning his .25-caliber Benjamin Armada. If you’d like to write a guest post for this blog, please email me at blogger@pyramydair.com.
Take it away, RidgeRunner.
Tuning my .25-caliber Benjamin Armada: Part One
by RidgeRunner
This report covers:
- Old school
- Getting started
- String two
- String three
- String four
- String five
- Sixth and final string
- Discussion
This is likely to be quite a long blog report series as I learn this air rifle and figure out what I am going to do with it.
Old school
This Benjamin Armada is old school because it is a bolt action instead of side lever action and it is unregulated. What this thing really is, is a .25 Benjamin Marauder dressed up to look like a black rifle. All of the fancy dress-up goodies make this one heavy honker. If I am lucky, the weight will also make it one steady shooter.
To begin, I lugged the rifle out to the shooting bench with my tank and chronograph to see just where it shoots. As this one came to me used, I had no idea how it was adjusted.
Getting started
After setting it up on the bench and setting up the chronograph, I filled it to 3000 PSI, according to the gauge on my tank, and began running .25 caliber 25.39-grain domed FX pellets through it. I was using the single shot tray, but since the magazine holds eight, I broke my shooting strings into that number. Let’s look at some of those strings now.
Shot…………..Vel.
1………………..764
2………………..774
3………………..765
4………………..771
5………………..772
6………………..773
7………………..773
8………………..784
The average for this first string is 772 f.p.s. Keep that in mind as this test progresses. The spread for this string is 20 f.p.s., from a low of 764 to a high of 784 f.p.s. Now I’ll shoot some more.
String two
Shot…………..Vel.
9………………..782
10………………784
11………………784
12………………787
13………………788
14………………792
15………………796
16………………799
The average for this string is 789 f.p.s. Compare that to the first string and we see that the average velocity has increased by 17 f.p.s. The low velocity was 782 and the high was 799 f.p.s. The average velocity is increasing and the velocity spread is decreasing. That means the fill to 3000 psi is probably too high. Of course that depends on what you want to do with the rifle, but keep it in mind. Let’s look at the third string.
String three
Shot…………..Vel.
17………………797
18………………802
19………………805
20………………805
21………………814
22………………815
23………………807
24………………814
The average for this string is 807 f.p.s. and the spread is 18 f.p.s. (797 to 815 f.p.s.). Compared with the average from the first string this one is 35 f.p.s. faster. And the spread has decreased from 20 f.p.s. to 18 f.p.s. For shooting out to 25 yards that probably won’t make much of a difference. But shooting at 100 yards the tighter spread and higher velocity could make a significant difference. Before we determine that, though, let’s note that the intended target must be considered. If the target is a tin can, 35 f.p.s. difference is probably not an issue — even at 100 yards. But if you are shooting at a one-inch target like the kill zone on a small animal, it makes all the difference in the world. Knowing what you want to do is crucial when tuning the rifle.
At this point I checked the air pressure in the rifle’s reservoir using the gauge on my tank. It opened the valve at around 2500 PSI., so that was how much air remained on a 3000 psi fill after 24 shots. I did not fill the reservoir after this check. I just wanted to know how much air remained in the reservoir and the rifle’s gauge is both too small and too simplistic to make that determination.
Armada gauge is too simplistic for precise readouts.
String four
Shot…………..Vel.
25………………809
26………………813
27………………812
28………………811
29………………812
30………………815
31………………812
32………………808
The average for this string is 813 f.p.s. It’s higher than the previous string by 6 f.p.s. That means the power band has flattened out. Since we know that the fill pressure before this string was 2500 f.p.s. we see that Pyramyd Air’s description page that tells you to fill to 2600 psi is probably pretty close to where you want to be. Obviously we are comparing pressures between different gauges, so to be precise we need to use the same gauge each time.
The spread was just 7 f.p.s. (808 to 815 f.p.s.). For an unregulated air rifle that is a pretty tight spread but of course it is only for one shot string of 8 shots.
String five
Shot…………..Vel.
33………………807
34………………810
35………………809
36………………805
37………………801
38………………801
39………………800
40………………797
I do think the rifle is starting to come down from the peak of the power curve, but this string is not too bad. The average for this string is 804 f.p.s. and the extreme spread is 13 f.p.s. (797-810 f.p.s.). After this one it was now time to shoot my sixth and final string of eight.
Sixth and final string
Shot…………..Vel.
41………………793
42………………789
43………………784
44………………782
45………………776
46………………774
47………………767
48………………756
The Armada has most definitely dropped off of the power curve on string six. I checked the pressure and the gauge registered 1800 PSI.
Discussion
The top of the power curve based on today’s test seems to be around 2500 PSI when read from my air tank gauge. The velocities the rifle was shooting at that time put this air rifle at around 37 foot-pounds of energy at that spot, but of course that will differ depending on where you start and end the shot string.
Looking at what we see in today’s test I see 47 good shots if I’m willing to accept a velocity spread of 48 f.p.s. I can tighten that to an 18 f.p.s. spread and still get 25 good shots (shot number 16 went out at 799 f.p.s. and shot 40 was 797 f.p.s.)
I am most definitely going to have to give this some thought. I would like to drop the fill pressure to around 2000 PSI to make the rifle easy to refill, but I would also like to raise the muzzle energy a bit. I will not need a high shot count but power and accuracy will be very important to me. I am most definitely going to need to do my homework to tune this rifle the way I want it.
RR with a black rifle!!!
Where the world is going to?
Regarding the shot count I would take the -3 magazines, shots 16-39- string any day. Although I understand your intention for higher power so I will be eagerly waiting for your next report.
Bill,
I know, I know. The price was right though. I would have preferred a .22, but at the price I bought it, what tha hey.
Like I said, I am doing some research before I pull this “gal” out of her stock and do any tweaking. I would like to have her fill to 2000 PSI and shoot cast/swaged bullets out to one hundred yards with her. If I only get one magazine full out of her, so be it.
8 shots at 50+ fpe for example? You can do it; go for it. We will be there to share your joy.
That would be my goal. We shall see.
RR
That is about as polar opposite from your 1906 sproinger as you can get.
rk
rk,
Not quite, but I am working on it. 😉
You should see the BSA R10 SE that moved into RRHFWA the other day.
RR,
I am looking forward to the guest blogs on the R10.
rk
rk,
It will likely happen, but please do not hold your breath in anticipation. Your will likely pass out. It has not even been shot by me as of yet.
RidgeRunner,
That thing is a beast!
But she’s got some good power and a nice velocity spread for an unregulated PCP.
Will this be for pesting or for long-range target shooting?
Looking forward to Part 2,
Blessings to you,
dave
I love WordPress, I love WordPress, I love WordPress…
Dave,
This thing is a real beast! I am really looking forward to dancing some with this gal. I can honestly say I do not care much for her outfit, but she sure seems to like to dance.
This is the first .25 to show up at RRHFWA. I have a long way to go with this one. I am looking forward to seeing just what I can do with her. It is my eventual goal to use her for long-range shooting. Around here that would be about one hundred yards. I am hoping for about one MOA out of her with cast/swaged bullets (slugs).
I will be thrilled if I can get the fill pressure down to 2000 PSI. If I only get one magazine at that pressure, I will be happy.
We shall see where this little project goes.
“It is my eventual goal to use her for long-range shooting.”
RidgeRunner, that’s cool; it’ll be nice to see how she does at 100 yards! 😉
We shall see.
Ridgerunner
I’m hoping you will get it to closely mimic the Lewis/Clark air rifle for starting fill pressure, shots per fill and maximum fpe. If you succeed then you can work on changing her clothes.
Should be a good series. Thanks.
Deck
LOL! Only in my dreams! This air rifle was never designed to operate at those “low” pressures. I know I can take her down to 2000 PSI, which by today’s standard is pretty low. The trick will be getting at least eight powerful and accurate shots from her.
If I can squeeze that out of her, she will most definitely be getting a new outfit to wear to the ball.
RidgeRunner,
Can I correctly assume that you shot the .25 caliber 25.39-grain domed FX pellets because your previous testing showed that this is the best pellet for accuracy for this gun? Or this was what you had on hand? Then again this first part is done to establish a baseline from which you can start exploring what this rifle is capable of. That’s a nice shot string by the way.
Siraniko
Siraniko,
I had a large tin of these FX pellets on hand. Like you said, I was just establishing a baseline. I was indeed quite impressed with the shot string.
Thanks for the well-done report. That’s a very nice rifle! I am looking forward to seeing what you are able to with it. How does the trigger feel? What type of sights/scope are you planning to use?
Elmer,
We all need to give our thanks to BB. He fluffed out this report a good bit for me.
As for the trigger, it is superb. It is the typical Marauder trigger. If you have never used one, you have no idea what you are missing.
As for the scope on this, I am using a very old UTG 3-12x Compact SWAT that is no longer made. This one does not have illumination. This particular scope used to sit on top of my Gamo CFX.
Yes, of course we need to thank BB. Thanks for the reminder. Thanks BB! We know that you work very hard to provide us with the very best. We are very fortunate to have all of this to share information and learn. So thanks also to Pyramyd Air for hosting it.
He even puts up with me! Sometimes.
RR,
That seems like a reasonable tune out of box (so to speak) doesn’t it? At least as far as I know about the .25 caliber Marauder platform.
I’ll be watching this series. My .22 gen 2 Marauder could use a new tune. Though for my sake I am more interested in your technique than your results. I was using mine for small game hunting, but I’ve been thinking of setting it up for my nephew. He has cerebral palsy, so for him I would need to keep the cocking effort low. Given that, I would be looking for as long shot string as I could get with 40ish yard accuracy. That is all preliminary, I may change my mind as I keep working through the details of getting the gun and the range set up.
CB
CB,
I will probably be going in the opposite direction than you want to go. I will not be concerned at all about shot count. All I am looking for is “low” fill pressure, high power out and long-range accuracy.
Right now I seem to be getting a pretty good shot count. The cocking effort is not too bad, but I am not sure how much lighter yours is and how much lighter you want it to be.
RR,
I understand we are after different objectives. I do want to see your tuning technique and see if it looks like something I can use towards my goal for my nephew. I’m still not sure that a side lever might not be easier for him to operate. I’ve thought about a JTS Airacuda for him too, just for the side lever. All he would have to do is get a hold of it and pull instead of turning and pulling. (In case you aren’t familiar, cerebral palsy, at least in his case, causes loss of fine motor skills. And as a result, or in addition, he isn’t as strong as he should be for 10 years old) But I already have the Marauder, so it’s weighted in that direction. 🙂 So clearly this is not a fully developed plan.
CB
CB,
I understand. I do not think the Marauder bolt will give him any trouble. If you use a lighter spring you will make it easier to pull back and end up using less air per shot as the hammer will not hit the valve as hard. You will likely need to make the transfer port wide open and use lighter pellets for him so as to insure the air rifle operates properly.
I am still digging around to find what information I will need to get this as I want it. If you contact Stephen Archer over at Hard Air Magazine, he may be able to help you set up your Marauder.
RR,
thanks for the tip. I didn’t know that was an option.
CB
RR,
I wish all pressure gauges had similar dials. Hard to figure anything out with that one…
-Y
Yogi,
The gauges on most PCPs are really there for bragging rights. No two gauges are going to read the same. You just have to pick one and stay with it. That is why I use my tank gauge. It is a pretty good one and is most definitely more useful than any I have seen on any PCP.
Does anybody make a digital pressure gauge? Is there a trade association that will certify them?
Seems like a major weak link if PCP’s are going to rule the world? Hopefully you do not have to point the muzzle at your face just to read it?
-Y
Yogi,
There is a company that makes a digital pressure gauge. As far as certifying it, who cares. That will only add more expense to an already expensive thing.
No, What dinky little pressure gauge this thing has is on the bottom. It was designed here in the USA.
Yogi,
The one complaint i typically hear about digital pressure gages is that they change readings when folks just look at them.
I guess that means they feel defrauded…
If i really relied on an on airgun pressure gage i would put narrow pieces of tape on the bezel to mark the min-max and a different colored one for the set point. That is what we did on most of our engine gauges on aircraft to make the scan quicker and easier.
shootski
RidgeRunner and B.B.,
This is part ?
“Tuning my .25-caliber Benjamin Armada:
Part
July 16, 2024 by Tom Gaylord (B.B. Pelletier)”
Looking good so far on the initial Baseline.
I hope to enjoy every PART ( ? ) of this Guest Blog!
Watching…
shootski
shootski,
This is supposed to be part one. I guess he just ran out of room.
Interesting RR, interesting.
The black rifle and .25 caliber is a bit of a surprise (not your usual style) but I to am more flexible/tolerant of “different flavors” these days – if it suits my application.
I’ll be following this series closely as exploring new (to me) platforms peaks my curiosity. All my PCPs are regulated so it’s the lack of a regulator and how you approach the tune that I’m reading for. Lots of details please!
Sounds like you want a high power sniper working off of a low HPA source. Good luck with that, typically high power wants lots of high pressure air.
Still, a good tune and a good valve can do wonders. The high-flow valve on my .22 Panthera is giving me 60ish fpe with a 135 bar reg setting. The “old style” valve on my .22 Impact MK2 is generating around 50 fpe with 140 bar on the reg.
Have fun, and please keep us in the loop!
Hank
Hank,
Yeah, this thing is somewhat new to me also. I have never had a “black rifle” before and have never worked with .25 before.
I have worked with non-regulated PCPs before. They are really not that bad once you understand what the “shot curve” is all about. Right now, this PCP peaks on the shot curve at around 2600 PSI and gives a pretty flat response for about two eight shot magazines. I still have to see what kind of accuracy this is giving me, but very likely this will be the best it can do.
Then I am going to want to move that shot curve to where it peaks at around 2000 PSI and give me at least one magazine at the top. I would like a little more umph out of it, but I will take accuracy over that any day.
Ridgerunner, thanks for the great report. It sounds like your method will work with any unregulated PCP. I have a Discovery in the original box just waiting for me to dip my toe into the dark side.
If your goal is 100 yards, will you eventually switch over to slugs?
But I tested positive for COVID yesterday evening and I feel like truck hit me. I can read the old reports, though, starting with March 2005….
RG,
You do not want that Discovery. Send it to RRHFWA immediately. I am certain we can work something out that you will find most satisfying.
Will I end up shooting “slugs” in this thing? More than likely. I am certain I will at least be trying some.
How many anti Covid shots have you had? I have not had any. A while back I was told I had it. Though I did not feel my best, I survived. The Chinese bioweapon did not get me.
I remember taking the initial jab and just before I was to take the booster, my wife and I got it. It was so bad my wife had to take the monoclonal antbody shots, which cured her quickly. No jabs since then. Wife and kids never got the vaccine. I’m not antivax, just wary about giving my little kids something so new. Apparently, there is now a more traditional vaccine (not mrna) available that is also not made with fetal stem cells.
Had it once more since then and it was much milder, so never went back to get the jab again.
Bad colds and respiratory infections trigger asthma, and COVID did all kinds of weird things to the wife, so I have to be careful not to let it get out of hand.
Are you trying to do a Jedi mind trick on me?
Me?! Jedi mind trick?! Not me! I just know that you will not be happy with that Discovery and I will. 😉
We shall see, my friend.
RG,
You have given me an idea.
*send me the disco, send me the disco, send me the disco, send me the disco…*
Hey, it worked for Obiwan.
The plan for the Disco is to learn about PCPs. I plan to test it, reseal it if needed, and then dance with her. After that, who knows.
Roamin,
… these are not the droids you are looking for.
BB
🙂
Roamin Greco,
Hope you get better quick and no long term COVID 19 variant KP.3 effects.
shootski
RG,
Send it to me before it is too late! You do not want to dance with her! She will steal your very will! You will become obsessed with her! Just ask Fawlty Manuel! He has several Maximus!
Hey RR, congrats on what I assume is a great buy. A Huma regulator seems to work in this rifle. Just curious as to what you are thinking. For a while, I’ve been toying with the idea of another air rifle purchase with a regulator (Avenger, Air Venturi) but now, since I have two Marauders, maybe equipping one with a regulator. More investigation.
Fred formerly of the Demokratik Peeples Republik of NJ now happily in GA
Fred,
Rather than buying one of those Chinese air rifles, you should buy a Huma regulator to drop in one of those Marauders. You might even think about a new barrel. You can probably take one of those Marauders and turn it into an awesome air rifle that anyone would be thrilled to own.
Now, if you are determined to buy one of those Avengers or Avenge-Xs, just send me one of those Marauders and we will work something out.
So you’re recommending to me what I suggested for you. If there’s an airgun show here in the East this October, maybe we can talk about a trade then. That Diana 46 for one of my Marauders? Let’s think about this.
Fred etc.
Pooky! 🙁 I cannot do that. I had given that 46 to my son-in-law. When he died, it became my grandson’s.
There will be an airgun show in Newton, NC November 1 and 2.
https://www.tmacsairgunservice.com/airgunshow.html
I have a few others I would be willing to trade, but I am afraid I can no longer trade off that 46. My grandson does like it.
All is not lost though. I will ask him.
RidgeRunner,
You know me and most “regulators” don’t see eye to eye.
I don’t understand folks thinking they need a regulator for other than to increased shot count at some predetermined MV.
Folks if you are still reading this…it (regulator) WILL NOT make you a better shooter.
RidgeRunner, if as you say you are happy with 8 shots from a fill to about 2,000 PSI and best power possible you actually don’t want a step down regulator.
I have one very stable/repeatable (BIG EXPENSIVE EXTERNAL regulator) i use to step down 4,500 PSI (300 BAR) to a selected set pressure value for developing my first shot (Cold Bore) performance with a particular projectile. That provides a huge tethered supply of air upstream of the regulator and gun’s valve.
(I could also open and close the cylinder valve just like Ton did for his Record shot attempt…he was simply his own external regulator.)
Open that TP all the way which is usually 4.5 turns back from max throttled. Extend the striker/hammer to maximum length. Then fill to 2,100 PSI. Shoot 8 shots over Chronograph. I think you will find a Little work with hammer spring preload will give you what you want. Pellet or bullet (slug) choice will determine the hammer spring preload to muzzle energy and POI to POA match up.
Of course you could go lots of other routes to make for lots of interesting guest blogs.
I’m going out on a limb here but you might see North of 55 FPE
shootski
shootski,
You could very well be on to something there. One of the things that I intended to do with this Armada was to open the transfer port all the way. I was also planning on playing with the length of the hammer/striker some and adjusting the spring tension.
I think my main objective here was to show these folks that you do not need a regulator if you do not have an incredibly high fill pressure. The only purpose of such is to have a regulator to reduce the pressure to a usable level. This is how to have a large number of shots in a small volume.
Not being a target shooter, I am not concerned with having a gazillion shots per fill. With this Armada I have an air rifle that gives me a very small deviation between shots when I am at the top of the “shot curve”.
At present I have a long top on this “shot curve”. I will likely reduce the length of that top, but I hope to also move it closer to 2000 PSI from where it is now at about 2600 PSI. In shortening the top of the “shot curve” I also hope to raise the FPE higher. We shall see what happens.
RidgeRunner,
We certainly will.
I think folks forget that gauges on PCPs are great to let you know approximately where you are in a fill when the shot count grows beyond the fingers on our hands…sometimes, for some of us, even just on one hand.
Folks you don’t need a gauge on the airgun if you keep track of your shots and your fill device has a reliable gauge!
And that leads me to this idea; IF you run out of needed reservoir volume (overhead) you can add quite a few cc in a Marauder by replacing the gauge block with a blank cylinder or a custom NO GAUGE (fewer leaks) tube. You will know of that need if you tether to your cylinder at the tube pressure or with the use of a step down external regulator and your performance improves. The gauge block is still a flow to valve restriction but not by all too much to not still allow the difference it makes.
R.R. you now the performance improvement the Lloyd double tube modification did for the discovery.
Just a thought.
shootski
shootski,
The new 3622 from TCFKAC does not have a gauge. More often than not, the gauge is a waste of usable space and expensive to boot. I more often than not ignore such on PCPs, mostly because they are usually inaccurate.
I do have to admit that for the newbie they can have a benefit to insure they do not overfill the PCP. There are just too many who rely on the accuracy of that gauge. More often than not, those folks are underinflating their PCP reservoirs. At least, that has been my experience over the years.
Fred DPRoNJ,
Why?
Shot Count?
The regulator in a Marauder tube takes up very valuable reservoir volume.
shootski
OK, you’re asking me to explain my reasoning and rationale. This is very dangerous but bear with me. I was initially suggesting RR get a regulator. He responded that I should get one for one of my Marauders instead of buying a regulated out of the box air rifle like an Avenger or Aircuda. I was thinking I needed to reduce the clutter in the closet and perhaps get rid of 4 or 5 rifles and treat myself to a new toy. Now RR has messed up my mind with his Jedi powers and has me leaning towards a regulator and a new rifle and keeping everything I have.
Do you feel a disturbance in “the force”?
Fred etc.
Fred DORoNJ,
Fred i think i detect a disturbance in the finances…the Force remains the Force.
Said plainly: with three you get egg roll.
Airguns are never clutter! Look at all the pain and anguishes your fellow airgunners have suffered, later, when they rushed into lowering their AIR assets.
CHOOSE wisely,
shootski
In reply to your message above, thanks.