Ads for marauder .25

Cheap DIY Mods for the .25 cal.

This area is dedicated to the .25 caliber Benjamin Marauder by Crosman.

Cheap DIY Mods for the .25 cal.

Postby ackuric » Sat May 20, 2017 6:06 pm

Image

(0$)
1- Throat is increased to have around 10% more air flow than the exit port, with the .06" poppet it achieves just that.
My theory is this. You need your throat to = your average lift * 4 to obtain the most out of it. My lift is roughly .065-.07"...the average lift is unknown but lets roughly say its over .05" and under .065", a safe bet is .055" which .055"*4 = .022, very close to what I ported my throat to...

(.33c)
2- .201" ports are the max I could go in my valve, its a stretch and I would say .190" is safer. .33c Tp wall's are .030"-.040" and made from .250" nylon spacer found at acehardware. The porting was done in steps from .157>.18>.1875>.19>.201

(0$)
3- Bolt probe is restrictive in stock form when going ports this large, tapered to help increase flow @ the opening.
The bolt was dipped in epoxy at the tip to allow for a softer materiel that pushes the pellet.

(0$)
4- Poppet = stem @ .06" which is tiny but I am regulated @ or under 2k psi. Head diameter reduced to .324" from stock .34" to decrease the force that is always on the poppet head.

(15$)
5-Shorter hammer springs to compliment the custom internal ssg, they work great for different power applications.
These were found at mcmaster's website. 11.5 lb spring is good for 20-40 FPE tunes, all I have to do is swap out the ssg as I have two and can easily have a back yard session. The 16 lb spring is good for 40-60 FPE tunes. Same as above for long range/field.

(40$)
6- 42 gr hammer made by Rocker1 - Weight chosen using various formulas for my given desired FPE

(3$)
7- Custom SSG. All internal. Gap adjuster also helps index the adjustment, build instructions may be released. This version doesn't add unnecessary weight to the hammer strike.

(15$)
8- Auxiliary plenum, 20 gr is the new one @ around 25/26 cc. Old was 16 gr @ 18/19 cc. Both fit very well in the stock.
The 20 gr cartridge fits just as good as the 16 gr cartridge with the added benefit of a few extra cc's for plenum. These were drilled out to ".219 along with all the adapters to provide adequate flow.

(0$)
9- Compression spacers supplied with Lane regulator, I decided I wanted a little more preload on my valve spring.
My theory was the spring is a little lazy/slow when not under much preload, more preload = less lazy.

(8$)
10- 6-7 lb Valve spring which was sanded down for 3 coils and closed slightly to match the poppet head @ .324"

(82$)
11- Lane regulator, Gauge port drilled for plenum to flow better, set point personally used = 1600-2000
Highly recommend this regulator as there are very in depth instructions and replacement parts are very easily obtained.

(0$)
12- Dremeled out stock to accommodate the auxiliary plenum
Self explanatory, very easy to do and now my plenum hides right in the stock

(0$)
13- Valve end cap opened to .225". Slots/shortening of the end cap are not needed, would help more if the valve was reamed to .5"

Total cost = 148.33$ if you already have drill bits / dremel, with a cheap 8$ dremel and a few drill bits you're looking at 160$!

Prior to this build I achieved what is in my signature with much less modification. Results from the above mods will be available soon. The mods in my signature were at roughly the same expense as this build. The main difference between the two are throat size (original was .203", new is .219") port size (from .180" to .201"), custom ssg, nylon hammer, and the plenum extension was NOT used in the tune on my signature. My fps capped around 845~/54 fpe with 34gr on the .180" ports @ 2k psi...Going up in ports I was able to squeeze out 56 FPE @ .1875" and 58 FPE with the plenum extension. (@ 2k psi set point). Looking forward to posting new results in the near future with the bigger ports.

-Matt
.25 M-rod

.04" Valve Stem / .212" Ports / Lane Reg / 6.2 # hammer spring
Custom SSG's / 25gr Hammer / Peek Poppet @ .25" / 25cc Plenum Ext.

80 Shots 25.2 FPE
48 Shots @ 41 FPE
32 Shots 53.2 FPE
ackuric
 
Posts: 66
Joined: Mon Aug 22, 2016 11:43 pm

Re: Cheap DIY Mods for the .25 cal.

Postby ackuric » Thu May 25, 2017 3:25 pm

Reduce cost to 140$!

Valve spring @ Ace Hardware Part # = 540437 for 1$

If you do a DIY hammer like I did out of the stock aluminum gauge or use stocker and trim weight off it you further reduce cost to 100$.

The above modifications have only been tested so far @ max preload / plateau of power so efficiency was brutally bad @ 1.1 FPE/CI making 60 FPE (59.55 avg over string). Good for 2 clips @ 800 psi use range and a possible 3rd if finely tuned or power reduced just a hair (1 fpe/877 fps avg). Can't wait to test more but for now I am waiting on good weather and confirming my valve seat / poppet are sealing well as I did get a little closer to the seat than I'd like when going ham with the dremel. (should of used a bit more caution / less angle)
.25 M-rod

.04" Valve Stem / .212" Ports / Lane Reg / 6.2 # hammer spring
Custom SSG's / 25gr Hammer / Peek Poppet @ .25" / 25cc Plenum Ext.

80 Shots 25.2 FPE
48 Shots @ 41 FPE
32 Shots 53.2 FPE
ackuric
 
Posts: 66
Joined: Mon Aug 22, 2016 11:43 pm

Re: Cheap DIY Mods for the .25 cal.

Postby ackuric » Mon May 29, 2017 2:02 pm

All testing complete. I reduced my TP back down to .185" to regain efficiency. Here are the following tunes I have so far achieved. I currently have 4 SSG's (3$ a piece) that retain the tunes with the ** that can be swapped out in minutes

1900/1950 Psi Set point.

**72 Shots @ 20 FPE (1.61 FPE/CI) (jsb 25.4)
**48 Shots @ 36 FPE (1.51 FPE/CI) (jsb 25.4)
**40 Shots @ 47 FPE (1.47 FPE/CI) (jsb 34)
**32 Shots @ 56 FPE (1.35 FPE/CI) (detuned down to 51-52 fpe) (jsb 34)
24 Shots @ 59 FPE (1.2 FPE/CI) (jsb 34) (requires .201" tp and 2k set point)
16 shots @ 60 FPE (1.13 FPE/CI) (jsb 34) (requires .201" tp and 2k set point)


Valve seat / poppet hold air just fine, no leaks over 72 hrs. ES on above tunes are ALL under 1% except the 20 FPE tune as the velocity is really low and es is 2% and that tune is only good for 50 yards max so 2% es is plenty fine.
.25 M-rod

.04" Valve Stem / .212" Ports / Lane Reg / 6.2 # hammer spring
Custom SSG's / 25gr Hammer / Peek Poppet @ .25" / 25cc Plenum Ext.

80 Shots 25.2 FPE
48 Shots @ 41 FPE
32 Shots 53.2 FPE
ackuric
 
Posts: 66
Joined: Mon Aug 22, 2016 11:43 pm

Re: Cheap DIY Mods for the .25 cal.

Postby Skip in WV » Fri Aug 11, 2017 12:33 pm

Do you have a better picture of #3?
Skip in WV
 
Posts: 5
Joined: Sat Jul 15, 2017 6:51 pm

Re: Cheap DIY Mods for the .25 cal.

Postby ackuric » Sat Aug 12, 2017 3:50 pm

Skip in WV wrote:Do you have a better picture of #3?


Of the bolt itself? My method was very crude but worked in a pinch!

Image
.25 M-rod

.04" Valve Stem / .212" Ports / Lane Reg / 6.2 # hammer spring
Custom SSG's / 25gr Hammer / Peek Poppet @ .25" / 25cc Plenum Ext.

80 Shots 25.2 FPE
48 Shots @ 41 FPE
32 Shots 53.2 FPE
ackuric
 
Posts: 66
Joined: Mon Aug 22, 2016 11:43 pm

Re: Cheap DIY Mods for the .25 cal.

Postby Skip in WV » Mon Aug 14, 2017 6:36 pm

It looks like it is cut crosswise on the end in the direction of the airflow?
Skip in WV
 
Posts: 5
Joined: Sat Jul 15, 2017 6:51 pm

Re: Cheap DIY Mods for the .25 cal.

Postby ackuric » Sun Aug 20, 2017 12:31 pm

The area that covers the porting is thinned more.

-Matt
.25 M-rod

.04" Valve Stem / .212" Ports / Lane Reg / 6.2 # hammer spring
Custom SSG's / 25gr Hammer / Peek Poppet @ .25" / 25cc Plenum Ext.

80 Shots 25.2 FPE
48 Shots @ 41 FPE
32 Shots 53.2 FPE
ackuric
 
Posts: 66
Joined: Mon Aug 22, 2016 11:43 pm


Return to .25 Cal Marauders

Who is online

Users browsing this forum: No registered users and 2 guests