Benjamin Stock 25 Marauder Tune

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Cbourbeau32

Cbourbeau32

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Nov 27, 2020
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Sterling, Kansas USA
Hello, I am curious what fellow 25 caliber Marauder owners are tuning for? I'd like to learn what folks are doing for the following tunes: (using stock components)

Power tune
Shot count tune


What are your hammer spring, hammer stroke and valve metering screw settings
How many shots per fill?
Shot string with fps and pellet brand/weight if you have rhem

Thank you!
 
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Benjamin - 25 caliber Marauder Range Session

Hello, purchased my 25 Marauder back in February but just recently started to mod/shoot it a little bit. I added an 18 lb hammer spring from Jefferson State and a hammer denounce device from AOA. I got the following shot strings in the attached screenshots, using JSB 25.39 and 33.95 with four...
www.airgunnation.com www.airgunnation.com

I am having a serious case of deja vu :unsure:.

Okay, I will play, I do not like the stock arrangment of hammer spring preloading the valve, not at all. I replaced it with either the AGR FFH, the JSAR TSS-SSG or my own home made versions thereof and found improved efficiency and power. And the reason is that the stock hammer and spring preloaded to the valve poppet stem results in hammer bounce (Brr---rrr--rrr-ppp) and wasted air that I could have used to either 1) get more fpe or 2) get more useful shots, but not both. As stated by several in your other thread, you want to tune for a Bell curve string, not a declining string.

My M-Rod based .25 rifles:



An out of the box M-Rod .25 should give 16 shots at about 40 to 44 fpe on a Bell curve with the JSB 25.4 grain pellets.
 
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3Crows said:

Benjamin - 25 caliber Marauder Range Session

Hello, purchased my 25 Marauder back in February but just recently started to mod/shoot it a little bit. I added an 18 lb hammer spring from Jefferson State and a hammer denounce device from AOA. I got the following shot strings in the attached screenshots, using JSB 25.39 and 33.95 with four...
www.airgunnation.com www.airgunnation.com

I am having a serious case of deja vu :unsure:.

Okay, I will play, I do not like the stock arrangment of hammer spring preloading the valve, not at all. I replaced it with either the AGR FFH, the JSAR TSS-SSG or my own home made versions thereof and found improved efficiency and power. And the reason is that the stock hammer and spring preloaded to the valve poppet stem results in hammer bounce (Brr---rrr--rrr-ppp) and wasted air that I could have used to either 1) get more fpe or 2) get more useful shots, but not both. As stated by several in your other thread, you want to tune for a Bell curve string, not a declining string.

My M-Rod based .25 rifles:



An out of the box M-Rod .25 should give 16 shots at about 40 to 44 fpe on a Bell curve with the JSB 25.4 grain pellets.
Click to expand...
Thank you for the reply!

How hard are the hammer denounce devises to make or how much do they cost?
 
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Just put this AGR hybrid tube on my beautiful Gen 1 .25 M-Rod. The tube was custom made. Knocked the weight down and improved the balance.



It also has the AGR FFH assembly and I did some work on the Gen 2 valve (.161 porting), barrel port to .161 and a custom transfer port. Typical string at current tune with the JSB 25.4 pellets:

880 (3000)
890
894
880
882
876
882 (2600)
----------
870
873
870
869
864
858
858
855 (2300)

It will shoot three magazines, 24 shots, the final shot is at 830 fps (38 fpe).

AGR:

www.airgunrevisions.com

Tuned SSG De-Bouncer Hammer Kit for Benjamin Marauder - Airgun Revisions

A complete drop in kit made from Stainless Steel and specifically tuned to give your gun a flatter shot string and up to 80% better shot count. Nylon button on adjusting screw keeps it in place from vibration without harming the threads and galling from a locking screw. Kit is…
www.airgunrevisions.com www.airgunrevisions.com

www.airgunrevisions.com

Marauder Thumb Rest - Airgun Revisions

Add a bit of comfort when cycling your charging handle with this AR exclusive Thumb Rest. Just screw into back of air tube. Rest your thumb on it while grabbing charging handle and squeeze your hand. Aids in smoother cocking as well bringing your index finger lower on bolt handle…
www.airgunrevisions.com www.airgunrevisions.com

The M-Rod in .25 quickly runs into the brick wall reality that is the 210cc reservoir capacity and only 3,000 psi. Just not a lot of air capacity there and when pulling power, well, not going to get many shots.
 
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3Crows said:
Just put this AGR hybrid tube on my beautiful Gen 1 .25 M-Rod. The tube was custom made. Knocked the weight down and improved the balance.



It also has the AGR FFH assembly and I did some work on the Gen 2 valve (.161 porting), barrel port to .161 and a custom transfer port.

www.airgunrevisions.com

Tuned SSG De-Bouncer Hammer Kit for Benjamin Marauder - Airgun Revisions

A complete drop in kit made from Stainless Steel and specifically tuned to give your gun a flatter shot string and up to 80% better shot count. Nylon button on adjusting screw keeps it in place from vibration without harming the threads and galling from a locking screw. Kit is…
www.airgunrevisions.com www.airgunrevisions.com

www.airgunrevisions.com

Marauder Thumb Rest - Airgun Revisions

Add a bit of comfort when cycling your charging handle with this AR exclusive Thumb Rest. Just screw into back of air tube. Rest your thumb on it while grabbing charging handle and squeeze your hand. Aids in smoother cocking as well bringing your index finger lower on bolt handle…
www.airgunrevisions.com www.airgunrevisions.com

The M-Rod in .25 quickly runs into the brick wall reality that is the 210cc reservoir capacity and only 3,000 psi. Just not a lot of air capacity there and when pulling power, well, not going to get many shots.
Click to expand...
Thank you!
 
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This is a FFH where the hammer and the spring are seperate, unlike the AGR product link earlier. The hammer has the striker (PEEK material) cut such that it is threaded in flush and does not protrude into the interior of the hammer. The spring assembly is trapped inside the hammer (nut end)and the end cap (slotted screw) and does allow for adjustable free flight gap. The slotted screw will protrude from the end cap when cocked. The hammer spring adjuster was bored out and shortened so that the slotted screw can pass through. This is not meant to be a how to, this is simply an experiment that did work but the rifle now has a JSAR FFH spring which is very similar but of course professionally made ;).

 
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Cbourbeau32 said:
That's kind of what I was asking.
Click to expand...
This is my bet, grab any assortment of out of the box new Marauder rifles and see what the tune settings are and you will likely find no specific settings. The .25 is tuned from the factory for 16 shots at around 40 to 44 fpe from 3000 to 2000 psi. The reason is that there is likely variation in the spring rates from batch to batch and who ever set the rifle up and did the test shots.

Here are the "alleged" factory settings, YRMV:




For posterity, for those who have a new M-Rod, before adjusting anything shoot the rifle over a darn chronograph please. Guessing does not work. If you do not have a chronograph leave the rifle alone until you do. Then run the hammer tension full in and the same with the striker and transfer screws carefully counting the turns. Now you will know the factory settings for your rifle. Gen 1, Gen 2, no matter, they are mechanically the same for practical purposes of tuning.

Let me interpret the data above for y'all for the .25 caliber rifle. Hammer Tension 5 turns in from minimum, Hammer Stroke 4 turns in from fully seated, Transfer Screw 4 turns in from fully out of path. And BTW, the one M-Rod .25 I purchased (NIB) was not set as above and I have no idea where the card is I recorded the data on as it is no matter to me now. The reason it matters not, well, I have Hammer gap, not Hammer tension, I have my Hammer Striker recessed or face flush to Hammer to facilitate free flight gap with a usefully long spring, Transfer Screw, bah, humbug! I ain't got no stinking Transfer Screw to adjust, what is the point of going up to .161 or larger porting if going to choke it with the TP screw?

There have been a number of threads regarding M-Rod "factory" settings. If they are important to you, why did you not record the settings before undoing what was done by the factory? I guess I am confused because if the initial settings were not good enough such that you decided to mess with them, why go back to what you were not satisfied with?
 
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