Synrod with Hill mods 24 shots ES 2.7% 833 fps avg

[jruther2]

I'm getting a little more comfortable making adjustments to the the synrod.   I would have preferred a slightly lower fill pressure and will make some more adjustments and compromises but wanted to post this string as I believe it to be pretty good for a beginner like me.

The modifications from stock are as follows:
Hill modified valve
Hill modified transfer port
Hill de-pinger
12.5# spring

Hammer spring tension:  0
Hammer strike: 0
Velocity meter screw: 4.125ccw

Pellet: .25cal JSB Exact King 25.39gr    1---820      9---833    17--838
Shots: 24                                                      2---825     10--834    18--843
Starting fill pressure: 3100psi                  3---825     11--839    19--837
Ending pressure: 2000psi                        4---825     12--839    20--832
Max vel: 843                                                5---828     13--843    21--836
Min vel: 820                                                 6---832     14--840    22--827
Avg vel: 833                                                 7---834     15--840    23--825
ES: 2.7%                                                       8---832     16--829    24--823

What do you guys think?  I think its pretty good.  As I mentioned, I would prefer a lower fill pressure but my previous attempts to achieve it were not good at all.  I don't pump anymore so low fill pressure is not a deal breaker but even a nitrogen tank runs down eventually. (I've already depleted the 530cf nitrogen tank down from 6000psi to 4500 psi in just over a month!  )

FYI, at these adjustments, starting at 3200psi and going down to 1900psi gives a 32 shot string with an average velocity of 825 (843 max and 802 min) ES of 4.9%

Any suggestions on getting a 24 shot count and ES below 3%  with velocity average at 800 or above?  I know hill posted a string that does exactly that but I'm just not that good yet...

[FuzzyGrub]

Looks good to me.   

[rsterne]

A quick efficiency calculation shows 39.1 FPE x 24 = 938 FPE total from 1100/14.5 = 76 bar of air x 13 CI = 986 CI total which is 0.95 FPE/CI.... It is actually a bit better than that because of the reservoir volume taken up by the depinger.... That's OK, but not stellar, certainly pretty good as a atarting point.... I'm not familiar enough with an MRod to suggest how to improve it....

Bob

[HillGSA]

I'm getting a little more comfortable making adjustments to the the synrod.   I would have preferred a slightly lower fill pressure and will make some more adjustments and compromises but wanted to post this string as I believe it to be pretty good for a beginner like me.

The modifications from stock are as follows:
Hill modified valve
Hill modified transfer port
Hill de-pinger
12.5# spring

Hammer spring tension:  0
Hammer strike: 0
Velocity meter screw: 4.125ccw

Pellet: .25cal JSB Exact King 25.39gr    1---820      9---833    17--838
Shots: 24                                                      2---825     10--834    18--843
Starting fill pressure: 3100psi                  3---825     11--839    19--837
Ending pressure: 2000psi                        4---825     12--839    20--832
Max vel: 843                                                5---828     13--843    21--836
Min vel: 820                                                 6---832     14--840    22--827
Avg vel: 833                                                 7---834     15--840    23--825
ES: 2.7%                                                       8---832     16--829    24--823

What do you guys think?  I think its pretty good.  As I mentioned, I would prefer a lower fill pressure but my previous attempts to achieve it were not good at all.  I don't pump anymore so low fill pressure is not a deal breaker but even a nitrogen tank runs down eventually. (I've already depleted the 530cf nitrogen tank down from 6000psi to 4500 psi in just over a month!  )

FYI, at these adjustments, starting at 3200psi and going down to 1900psi gives a 32 shot string with an average velocity of 825 (843 max and 802 min) ES of 4.9%

Any suggestions on getting a 24 shot count and ES below 3%  with velocity average at 800 or above?  I know hill posted a string that does exactly that but I'm just not that good yet...

I preset the valve meter screw at 5 CCW, I would sugest setting it back there and you may be able to start at a lower fill pressure.
Also, it should help a little with air flow and add a little more air space inside the pressure tube, if you add the modified gauge block.

I think a lot of Marauder fans would like that shot string too, especially for a drop in "set it and forget it" kit 

Nice work 

[jeffharper47]

   to me this doesn't seem quite right. i get 50+ shots with my .22 Srod. the first 30-35 are between 800fps and 810fps. then i get 20-25 shots between 825fps and 835fps. then it slowly decreases fps. thats with the 18.1 jsb's. with crossman domes the shot string is the exact same but with 100fps more.

[HillGSA]

   to me this doesn't seem quite right. i get 50+ shots with my .22 Srod. the first 30-35 are between 800fps and 810fps. then i get 20-25 shots between 825fps and 835fps. then it slowly decreases fps. thats with the 18.1 jsb's. with crossman domes the shot string is the exact same but with 100fps more.

What dosen't seem right ?
Maybe this will help.

.25 cal. rifle = 25.39 GR. AV 833 FPS = 39 FPE

.22 cal. rifle = 18.13 GR. 820 FPS = 27 FPE

.177 will/should get even more shots than the .22

More air is needed to produce more power.
Your E.S. is higher too.



Edit; for a .22 cal. comparison, check out this thread;

http://www.gatewaytoairguns.org/GTA/index.php?topic=69160.0

[jruther2]

I preset the valve meter screw at 5 CCW, I would sugest setting it back there and you may be able to start at a lower fill pressure.
Also, it should help a little with air flow and add a little more air space inside the pressure tube, if you add the modified gauge block.

I think a lot of Marauder fans would like that shot string too, especially for a drop in "set it and forget it" kit 

Nice work 

Here ya go Hill.  I filled to 3000 just in case... I'm glad I did as it nailed the bell curve.
Spring and strike at 0, velocity screw at 5ccw.
24 shots from 3000 down to about 2200
Max 834 Min 814 Average 823.7 ES 2.4%

815
816
823
821
824
827
824
829
834
828
832
830
834
832
833
828
834
829
829
825
822
819
819
814

I'm thinking for the lower fill pressure I may have to turn the striker a bit...  I know the goal is drop in and forget it but looks like the only way for that to happen is if I throw in a modified gauge block.  Thoughts?

[HillGSA]

I preset the valve meter screw at 5 CCW, I would suggest setting it back there and you may be able to start at a lower fill pressure.
Also, it should help a little with air flow and add a little more air space inside the pressure tube, if you add the modified gauge block.

I think a lot of Marauder fans would like that shot string too, especially for a drop in "set it and forget it" kit 

Nice work 

Here ya go Hill.  I filled to 3000 just in case... I'm glad I did as it nailed the bell curve.
Spring and strike at 0, velocity screw at 5ccw.
24 shots from 3000 down to about 2200
Max 834 Min 814 Average 823.7 ES 2.4%

815
816
823
821
824
827
824
829
834
828
832
830
834
832
833
828
834
829
829
825
822
819
819
814

I'm thinking for the lower fill pressure I may have to turn the striker a bit...  I know the goal is drop in and forget it but looks like the only way for that to happen is if I throw in a modified gauge block.  Thoughts?

FPE CU/IN = 1.28
AVG FPE PER SHOT = 38.3
AVG PSI USED PER SHOT = 33

The efficiency is very good  ( saving on nitrogen  )

It may be possible the gauge is reading is a little high ?

Other than installing the modified gauge block, I would leave it as is.  But, you can always put the HT setting back to 0 if you want to 

[Rdsail]

This is what I was able to achieve with my mrod .25. I think I found the perfect balance between all the ports.

I'm also using a 12.5# spring. I use 1.25 turns on the hammer spring. Hammer travel is set to max and also the Velocity screw (5.5 turns CCW)

30 shots
44.8 fpe
3.70% ES
Average Effeciecy of 1.3
This is with JSB Kings. I actually get a much higher efficiency with heavier pellets but they don't group well.

I never shot 30 shots. I fill to 2800psi shot 16 shots and refill. This give me a 1% ES

Full power with EJ35 63fpe - EJ40 68fpe

For more information read this post: http://www.gatewaytoairguns.org/GTA/index.php?topic=58837

[Rdsail]

One thing.

If you want want your efficiency to go up open the velocity screw wide open. If you choke the valve the efficiency goes down with it. What happens is that the valve stays open for longer and it wasts air. When ever I mod valve, I try hard to make the valve deliver as much air possible in the shortest amount of time. The velocity screw generate pressure right after the poppet. This slows the valve from closing. It acts as a cushion and the back pressure does not close the valve fast enough.

[HillGSA]

It's great that some air gun enthusiast have the time, machinery, tools, and other resources available to modify their own air guns.

Though this idea is about making available to anyone, who want's more from their Marauder rifle; a ready to install modification kit. A kit that contains components that have already been properly machined, tested, and proven to work well together. No worries about, buying expensive tools or ruining parts. Plus they can still have the good feeling of a job well done, by installing the parts themselves.


Tim

[Rdsail]

Tim,

Completely agree with you. I love working on air guns. I always make a my finding available to everyone here at the forum. If it can help one person, I'm very happy. I get joy from modifying the guns and then shooting them.

My tools are limited to a drill press, dremel tool, files and sandpaper. I make all my mods with that. that does not mean that some days I wish I had a lathe and mill. But I can't have everything.

Daniel

[Bullfrog]

A quick efficiency calculation shows 39.1 FPE x 24 = 938 FPE total from 1100/14.5 = 76 bar of air x 13 CI = 986 CI total which is 0.95 FPE/CI.... It is actually a bit better than that because of the reservoir volume taken up by the depinger.... That's OK, but not stellar, certainly pretty good as a atarting point.... I'm not familiar enough with an MRod to suggest how to improve it....

Bob

I'm thinking the transfer port on the barrel intake is probably smaller than the output on the valve itself and the transfer port. I didn't start getting 1.2 and 1.4 efficiency at 60fpe until I made all of my ports the exact size. However that requires drill work, and that might be something jurther2 doesn't want to do. Also, making your ports too big seems to hamper accuracy at higher fill pressures.

[rsterne]

I have not found enlarging the fill ports affects the accuracy, unless you create a loading problem in the barrel port by either making it too large (75% of caliber is a good maximum) or have a burr on the inside that is damaging the pellet on loading.... If the larger ports push the pellet too fast, then that can cause accuracy issues, of course....

Bob

[Bullfrog]

I have not found enlarging the fill ports affects the accuracy, unless you create a loading problem in the barrel port by either making it too large (75% of caliber is a good maximum) or have a burr on the inside that is damaging the pellet on loading.... If the larger ports push the pellet too fast, then that can cause accuracy issues, of course....

Bo

Here's the thread where I discussed this months ago: http://www.gatewaytoairguns.org/GTA/index.php?topic=61429.40

There never was a consensus as to what exactly the problem was, there just seemed to be a pattern where filling to 3200 caused inaccuracy, while filling below 3000psi maintained accuracy. Velocity was not the issue, as low velocities above 3000psi were just as inaccurate as high velocities above 3000psi. Conversely, high velocities at low PSI were accurate. This pattern held over 2 different barrels. A couple of other modders reported similar results to varying degrees. Someone suggested that the high, unrestrained blast might be deforming the pellets. I never did test it further once I figured out the gun shot just fine at lower fills. On a 2700psi fill I can push Kings at 1050fps and Barracudas at 960fps with good accuracy. Conversely, on a 3200psi fill my groups open up even at sub 850fps speeds. Don't know why. It just is.

My ports are .18 on a .25 caliber. That's pretty close to the 75% max.

[HillGSA]

Did you make certain the pellet was chambering deep enough into the barrel? By opening up the barrel port, the pellets skirt may have been over the barrels port too far, allowing the blast of air to bend the pellets skirt, before the pellet started moving down the barrel.

[Bullfrog]

Did you make certain the pellet was chambering deep enough into the barrel? By opening up the barrel port, the pellets skirt may have been over the barrels port too far, allowing the blast of air to bend the pellets skirt, before the pellet started moving down the barrel.

No I did not. That may have been what rsterne was referring to but I didn't understand what he meant. What would be the best way to check that? Load a pellet and then take the breach off and have a look?

[rsterne]

That is the correct method to check the probe length.... If the pellet skirt is partly across the port it may indeed be getting bent at higher pressures but not at lower....

Bob

[jruther2]

FPE CU/IN = 1.28
AVG FPE PER SHOT = 38.3
AVG PSI USED PER SHOT = 33

The efficiency is very good  ( saving on nitrogen  )

It may be possible the gauge is reading is a little high ?

Other than installing the modified gauge block, I would leave it as is.  But, you can always put the HT setting back to 0 if you want to 

Yeah, saving on nitrogen is a good thing.  Who knew that big ole tank wouldn't last forever? 

I'm sure the gauge is off, I just try to be consistent with recording what it reads and do the best I can.  I think I may invest in one of those fancy schmancy SSI digital gauges.  Any complaints with yours? Does it only go up to 3000psi?

I shot a couple of strings, both with spring tension left at zero and velocity screw at 5ccw but striker at 0.5cw and 1cw.  I may post them later if anyone is interested. Not a lot changed in terms of usable shots or fill range.

This is what I was able to achieve with my mrod .25. I think I found the perfect balance between all the ports.

I'm also using a 12.5# spring. I use 1.25 turns on the hammer spring. Hammer travel is set to max and also the Velocity screw (5.5 turns CCW)

30 shots
44.8 fpe
3.70% ES
Average Effeciecy of 1.3
This is with JSB Kings. I actually get a much higher efficiency with heavier pellets but they don't group well.

I never shot 30 shots. I fill to 2800psi shot 16 shots and refill. This give me a 1% ES

Full power with EJ35 63fpe - EJ40 68fpe

For more information read this post: http://www.gatewaytoairguns.org/GTA/index.php?topic=58837

Thanks for the info Rdsail, I have admired your work for a while! Those are some very impressive results you have achieved there.

It's great that some air gun enthusiast have the time, machinery, tools, and other resources available to modify their own air guns.

Though this idea is about making available to anyone, who want's more from their Marauder rifle; a ready to install modification kit. A kit that contains components that have already been properly machined, tested, and proven to work well together. No worries about, buying expensive tools or ruining parts. Plus they can still have the good feeling of a job well done, by installing the parts themselves.


Tim

Tim,

Completely agree with you. I love working on air guns. I always make a my finding available to everyone here at the forum. If it can help one person, I'm very happy. I get joy from modifying the guns and then shooting them.

My tools are limited to a drill press, dremel tool, files and sandpaper. I make all my mods with that. that does not mean that some days I wish I had a lathe and mill. But I can't have everything.

Daniel

I'm thinking the transfer port on the barrel intake is probably smaller than the output on the valve itself and the transfer port. I didn't start getting 1.2 and 1.4 efficiency at 60fpe until I made all of my ports the exact size. However that requires drill work, and that might be something jurther2 doesn't want to do. Also, making your ports too big seems to hamper accuracy at higher fill pressures.

I don't mind doing the work, and probably will eventually.  I find that I enjoy the work on and testing of equipment as much as if not more than using it.  It was the same way in my only other hobby which is picking locks.  It wasn't long before I found that I enjoyed making lock picks more than picking locks. (No, I'm not a criminal. I only pick locks that I own or have been given permission to pick by the owner.  A lock is a puzzle to be solved.  Find and use to your advantage the manufacturing tolerances and CLICK! the lock opens  )

For now, I have started down this road of testing "drop in" mods and so I think I'm gonna ride it all the way out before I break out the pliers and blow torch.  There must be at least one or two people out there who would like to see what can be achieved with minimal mod effort on their part.  The next couple of weeks are pretty busy for me so maybe by then I'll have me a modified gauge block to drop in and see how the total Hill package performs.  After that I may test with just one drop in component at a time just to satisfy my own curiosity.  Its been a few years since I sat in fluid dynamics and differential equations class so my memory needs to be jogged in reference to issues relating to air flow.  After that, fire up the drill press and dremel and let the real damage begin! (HA, weird!  It says "let the damage begin"  I typed c.a.r.n.a.g.e. )

[HillGSA]

jruther2
"I'm sure the gauge is off, I just try to be consistent with recording what it reads and do the best I can.  I think I may invest in one of those fancy schmancy SSI digital gauges.  Any complaints with yours? Does it only go up to 3000psi?"




-----------------

First off, I feel the need to say that I mean no offense to anyone.
I tried using analogue gauges, a drill press, etc. - and for the hobbiest, that's probably ok. But since I also supply components to others, as well as myself, I feel a duty to keep the tightest tolerances and/or standards, possible. That's why I switched from testing with an analog gauge to a digital gauge for pressure readings, and to a mill, and lathe (CNC when possible), for making/modifying the components - which usually helps me to stay within +/- 0.001 from each part to the next.

Ok, with that being said…
I purchased the pictured digital gauge from McMaster-Carr in November of 2013, ( http://www.mcmaster.com/#atmospheric-pressure-gauges/=sd2bqv - or -  http://www.mcmaster.com/#3834K18).
This gauge's accuracy is rated at +/- 1% and it measures pressure up to 5000psi. I have found this gauge to reliable, accurate, and have not had to change the battery since I started using it.


Tim