8 replies to this topic

[Air Rifle Hunter]

Hi guys (and gals), Well, I ordered some new springs for my .25 Caliber Benjamin Marauder since the rifle was used and I wanted to see if I could get some better results from replacing it. So I took one of the new springs and per some advice form the MarauderAirRifle.com forum, I baked the spring for 40 to 45 minutes at 450 degrees and then took it out and let it cool naturally on the counter. Once it was completely cooled, I took out the old factory spring and replaced it with the new "Baked" factory spring. I had been advised that it would help to up the FPS of my .25 Marauder. When I first got the rifle (it was used and about a year or so old) the highest velocity I could get it to go was around 848 FPS with an average of around 832 FPS through (16) shots using Benjamin Domed 27.8 grain pellets (the numbers would be much higher if I had tested it using the 25.4 grain JSB Exact Kings). Below are the new results from my latest chrony test after putting in the new spring and tuning the rifle:Starting PSI: 3200Clip #1Shot #1- 840.9, #2- Error, #3- 833.7, #4- 843.7, #5- 838.6, #6- 848.1, #7- 848.3, #8- 857.4Clip #2Shot #9- 860.0, #10- 856.0, #11- 867.6, #12- 860.0, #13- 866.5, #14- 863.4, #15- 865.4, #16- 855.6Clip #3Shot #17- 858.2, #18- 850.9, #19- 851.0, #20- 844.7, #21- 844.7, #22- 836.4, #23- Error, #24- 829.3Ending PSI: 2200The Low was 829.3 FPS, High was 867.6 FPS, Average velocity was 850.9 FPS, Extreme Spread was 38.34 and the Standard Deviation was 11.13. That was a pretty good (24) shot string for a .25 cal Marauder Rifle without a reservior extension or HDD (Hammer Debounce Device). That would give me (24) useable hunting shots with the low FPE being around 42.4, the high FPE being around 46.5 and the average FPE for the 24 shots being 44.7. I can definitely live with those numbers. Now I just have to zero in the scope and get this rifle out hunting.

[havoc]

Those are impressive numbers. I've been itching to try that hammer spring mod myself, but haven't done much shooting lately due to work so busy. I wonder what your string would look like with the jsbs.

[Air Rifle Hunter]

I only have a few of the JSB Exact Kings on hand, but I'll try to do a 24 shot chrony string tomorrow to see what the numbers are. That is as long as I can do it during my lunch time.

[Air Rifle Hunter]

Those are impressive numbers. I've been itching to try that hammer spring mod myself, but haven't done much shooting lately due to work so busy. I wonder what your string would look like with the jsbs.

Ok Havoc, I ran (16) shots over the Chrony with the 25.4 grain JSB Exact Kings. I am a little perplexed by the numbers and how they stay fairly stable for quite a few shots (about 14 shots). I guess because of how I have it tuned for the Benjamin Domed pellets it doesn't have the same curve with the JSB Kings. Anyway, here are the numbers:Staring PSI: 3100+Clip #1Shot #1- 905.3, #2- 903.6, #3- 901.4, #4- 900.8, #5- 901.8, #6- 895.2- #7- 902.7, #8- 900.6Clip #2Shot #9- 899.2, #10- 903.2, #11- 906.1, #12- 898.1, #13- 901.6, #14- 900.7, #15- 888.9, #16- 886.1Ending PSI: 2500+/-Low: 886.1, High: 906.1, Average: 899.6, Extreme Spread: 20.03, Standard Deviation: 5.56 The low velocity would produce 44.3 FPE, the high velocity would produce 46.3 FPE with the average FPE being 45.6. I suppose if I would have had it charged up to 3200 PSI that I would have tried getting a total of (3) clips and it probably wouldn't have started out quite so high on the velocity, but it still only consumed around 600 PSI for those (16) shots. It does seem pretty typical that if I shoot (3) clips that it usually consumes about 1000 or so PSI. If I ever end up switching to the Exact Kings, I'll have to do some tuning to get it to have a bell curve. I'm hoping that when I try out the H & N Baracudas that I get at least an average of 800 FPS, but I'm going to wait to try those out for now.

[havoc]

Interesting results. That string is similar to what I get now with my stock spring after tuning. Thanks for sharing

[Air Rifle Hunter]

I'm thinking that there is a possibility that the transfer port is not aligned properly and possibly an o-ring or seal is interfering with the valve. I think I need to take off the breech again and check it and try realigning it to see if it shoots faster after that. I know it can get more power, but right now I'm kind of tired of continually taking it apart and working on it and would rather just go hunting.

[screwwork]

ARF,A short story about boys & their toys in the early 80'sMy brother was not happy with his 69 Camaro and had been working on it for some time, it just wasn't running well. He placed a for sale sign in the back window and was tired of working with it.Well he was working on the mufflers and had them off just staight pipes coming off the headers.Then he said what the heck just run it down the to the end of the street and get it on. The American Forest guys were getting off work when he lit up the tires and was hauling a$$ down the street. One of the guys from AF stopped by to see how much he wanted for the Camaro and he changed his mind again about selling it after going for a short run down the street.Not really smart when you think about as I am older now but we lived in a area we could do it every now and then without anyone getting really pissed off. Anyways go hunting and shoot some squrrels & rabbiets with your gun and fiddel with it later.

[Air Rifle Hunter]

Exactly! And sometimes if you mess around with them too much, you end up busting an expensive part to replace. For now it shoots pretty hard (for a .25 Marauder) and very accurately, so I'm done messing with the settings and tunings for now.

[Air Rifle Hunter]

I just got some of the 25.4 JSB Exact Kings today and wanted to shoot them over the chrony to get an idea what my distances would be. Keep in mind that I haven't done any major modifications to my .25 Marauder (mine only has a baked factory spring and tuned for max velocity (or close to max)). Here are some Chrony numbers that I just got using a (16) shot string:Temperature: 77 Degrees F.Starting Fill Pressure: 3250 PSI -Clip #1: Shot #1- 903.6, #2- 911.1, #3- Error, #4- 916.3, #5- 913.5, #6- 911.8, #7- 922.8, #8- 923.7Clip #2: Shot #9- 915.7, #10- 914.8, #11- 923.8, #12- 917.9, #13- 914.0, #14- 907.7, #15- Error, #16- 898.8Ending Fill Pressure: 2500 PSILow: 898.8High: 923.8Average: 914Extreme Spread: 24.97Standard Deviation: 7.21 Now let me say this... like I mentioned above, I haven't done anything to my rifle since my last test with the JSB Exact Kings. I havent' adjusted anything other than re-zeroing in my scope earlier today. I just received my two tins of JSB Kings today from PA and decided to Chrony my .25 again so that I could post the results for those of you who are getting ready to tune your .25's. I am very surprised that the velocity seems to have risen. Previously when filling to 3200 PSI I was not getting velocities that were quite this high; close, but about 16 FPS less. It could be because the baked spring has had time to set or many other possible reasons that I haven't yet though of. That being said, at this velocity, the low of 898.8 would produce 45.6 FPE and the high of 923.8 would produce 48.2 FPE with the average velocity of 914 producing an average of 47.1 FPE. I am pleasantly surprised, but stuned as well. In order to even out the (16) shot string I will need to fill to 3300 PSI or turn the velocity metering screw in just a little to see if that give me a more even start and finish. I like the power it's getting, but would exchange that for (24) shots that are closer to what my original chrony test with this pellet was giving me. Originally I was charging to 3200 PSI and getting a starting velocity around 890 or so and it was peaking around 906+ and by shot (24) it was back around 890. That would be plenty fast for me and would give me (8) extra shots that I won't get with my latest chrony test. Oh well, it looks like I can either leave it with the current settings and really lay the smack down on my target animals, or I'll have to do some tinkering and tune it back down to get a little less FPS and some more shots. I think I'm leaning towards leaving the settings where they are and blasting the target with a "take down" velocity shot.