New Syn Mrod .25 - Let the mods Begin

[Rdsail]

I repentantly had a discussing in the korean gate about this. I was glad I chose the mrod. I was not surprise on the groups it generated and the vertical elevation. One of the this that the crosman guns are great for are if you like to make modifications. That its he case for me, the part are relative in expensive. I'm very happy with my turn out.

[FuzzyGrub]

Interesting.  From your earlier stats, I would have thought if you brought the power down a little, could get a nice flat 4 mag string. 

[Rdsail]

I would have thought the same thing. I'm going to power it up and see what happens.

[Bullfrog]

I went through 3 factory valves (I kept stripping the velocity port screw) before I installed my custom valve. My last factory was unusual for a factory valve in that in let me get up to 60fpe with Eunjins for a full clip. The odd thing about it is that if I turned the power down I still got roughly the same air usage per shot even if I turned the power down to 40fpe. My custom valve is similar in that regard. My efficiency goes down dramatically if I detune it. Lots of air gets wasted per shot. I'm better off jacking my power to max and enjoying 8-10 shots above 70fpe than 10-12 shots at 60fpe for the same air usage. I've tried both heavy and light springs as well as oring buffers. The efficiency stays pretty consistent. I can expect .8 thereabouts for 40-50fpe, 1.1-1.2 for 60fpe, and .9-.98 for 70fpe. It looks like every valve has a sweet spot for efficiency. Yours appears to be 50fpe.

[Rdsail]

A small update:

I ordered from MSC a new spring that is about 12.5# instead of the 10# spring. I was looking to use less preload.

I tune the gun to 16 shots with JSB kings (I get more that by i wanted s tight spread).

Fill pressure 3000 psi
End pressure 2400 psi
high: 905
low: 893
Spread: 12 (1.3% spread)
SD: 3
Average Speed: 900
Average FPE: 45.7
Efficiency: 1.35

Here is a relative picture of accuracy. There are about 75 shots in those holes maybe more. All shot from 40 yards and I have not zeroed the scope or was shooting carefully either.  They are also shot at all kinds of different speeds ranging from 930 to 850 fps. This is just crony work aim roughly to the center and a quick shot. 






 

[Rdsail]

Update on accuracy:

I had a very frustrating day today gut it ended up well. I started sighting in my scope and found that my POI kept changing. So I started shooting without make adjustment to the scope. I found that I had had two ½ in groups through the shots string which made in impossible to zero the scope. Finally after tons of pellets I brought out the crony. I though the different POIs where caused by different air pressures but soon found out that that was not the case. I found that all shots over 897-895 would shot high to the left and all shots under those numbers would shot low to the right. Both sets grouping very well. Then I incrust the power of the 16 shot string to 920-910 and that did it all shots on the same POI.

I have never experience this before and wonder if any one here has. I can't see the pellet path to see if the pellets are spiraling at certain power levels. I thought my hawke eclipse was had broken but that was not the case.

Tomorrow I'll be doing some more accuracy test. I'm not posting any pictures yet because you will see my frustration on the paper.

[Rdsail]

So once I sorted out the accuracy problem, I decided to increase the power to Average of 911 fps with kings. I'm using a 12.5# spring with 2.5 turns of preload here are the results. The gun is much louder and my efficiency went down a lot but I don't really care too much about that it is a hunting gun. Getting 16 shots at 2% spread is mostly my goal.

Here are the numbers for the KINGs. Average: 912 fps : 46.9 fpe



Then I tried at the same Setting with HN cudas 31g  Average: 839 fps : 48.5 fpe



Also did Shot the cudas at maximum power with my current set up. The results where a high of 925fps at 2800psi that would equal to 58.9 FPE. I could easily reach 60 fpe by just increasing the t port and barrel port size or by adding a little more hammer. My porting is still conservative.

I'm not sure if the lost of efficiency was do to the combination of the heavier spring and increase power. I it is surprising how much louder the gun in from 895 setting to 910 which is the biggest sign of wasted air. I could have reduced the power but my curve gets larger. I'll be happy when my LCD comes in.

Now for accuracy:

All groups from 40 yards.

This would be my average group of 5 with the magazine: (never mind the shots on the upper left Those where the cudas. They do not group as well)


One of the better groups of 5 with one flyer with the magazine


This is my best group so far this is a group of 3 @ 40 yards. I did not shot more because I did not want to mess it up.

[sshewins]

Sweet

[jamaicajed]

Looks good.  what type of fome did you use?  How does it effect the feel.  I was thinking about the wood stock.  what made you go with the synth? 

[sawtoothscream]

wish I had the knowledge to mod my guns,  would need a drill press also.

[Sfttailrdr46]

So once I sorted out the accuracy problem, I decided to increase the power to Average of 911 fps with kings.
This is my best group so far this is a group of 3 @ 40 yards. I did not shot more because I did not want to mess it up.

Coward a brave man would have gone for a 5 or 10 shot group   
Really nice shooting

[Blaster6]

Great thread.  New MROD owner here, used one, stock supposedly.  I'm diving in and trying to learn as much as I can.  I've got about 100 shots through her and can tell it's an air hog and that the trigger is mushy in the second stage.  Gonna play with her for a while and then work to tighten her up.  Thanks for all the info!

[moorepower]

Robert, have you shot the King heavy with this tune yet, and if so, what was the fps and accuracy?