Playing with slugs?

In theory you will get good accuracy when you have a good ballance of the reg pressure and hammer tension for a particular pellet or slug.

To find this you need a chrony and writing down speeds.

With the TP on biggest calibre, hammer maxed out, shoot a couple, record speed, then move hammer down a notch, shoot and note speed, repeat through hammer settings. If you were to draw a graph with the speeds, the point where the speed dropped off dramatically is the ballance point. they say that 5% under this point is where you want to be. At this point no more power can be got from the reg and higher hammer tension will only waste air.
Once you've found this point shoot groups adjusting the fine allen screw down to find a point where groups tighten. At this point you are really harmonic tuning.
You should be getting one ragged hole at 25 m hopefully.
You can also adjust the reg a very small amount if you don't find the magic tune. It means that to some extent you need to go through the above adjustments again. Don't think you have to increase power to find accuracy either.
The sound of each shot should sound "sweet" when you have a good tune too. This means that just the right amount of air is being released to push the pellet without waste and the pellet speed will also be consistant.

This is great stuff. Lot of variation to play with.

Paul I was just using the 16 clicks on the hammer spring dial. The “micro” Allen key adjuster is maxed out and I left it there for now.

This evening I tried a few more “tunes”. With the reg still set at 150 bar, I tried the transfer port on the .177/.22 setting and went through a few of the hammer spring settings.
Logically the transfer port should be set at .25/.30 to get the most air through for the biggest push to get the 30gr slugs going as fast as possible out of a 500mm barrel, but I though while I’m into all this testing and tuning let me just see…
And what do u know… at 150bar, TP at .177/.22, and hammer spring at max, a pretty tight 5 shot group at 25m.

Here’s an update on my slug testing…
Spent an hour or two fiddeling around this evening with the 30gr spyda slugs.
Goal no. 1 is to get them grouping tightly, as tight as possible. I don’t care what speed they are doing, as long as they group tightly.
Goal no. 2 is once the slugs have been tuned to perfection, find an easy to set tune for the JSB hades 15.89gr pellets.

I felt the slugs were going too slow out of my 500mm barrel. Reg was set at 125bar, so I slowly turned it up to 150bar for a little more Oomph! They recommend not going past 150bar.
Unfortunately I couldn’t get my chrony to work indoors under the led lights, so I have no idea what speed they are doing out of my 500mm barrel.
I’ve heard that short barrels need a short hare blast of air to get slugs moving, where as a long barrell can use a slower, more gently push of air (and probably get higher speeds too!)
So I set the transfer port to 25/30, which I’m assuming is the largest aperture and will allow the most air into the barrel for a short hard burst of air.
Once I had the reg at 150 bar and the transfer port wide open I started testing different hammer spring settings with 3 shot groups. I got the best results with hammer spring at 5.5 and MAX.
Best group was a 9mm ctc 5 shot group at 25m. See pic. Unfortunately I don’t know how fast they are going.

Tomorrow I will test the transfer port on .177/.22 setting with the various hammer spring settings. I don’t think it will be better then today, but u never know, I might just stumble apon a setting that gives one hole groups 😉
Then re zero the scopes for these new slugs and take it out for some rabbits.

To achieve goal no. 2, I will keep the reg set at 150bar, and try the hades pellets with the transfer port on both the .177/.22 and the LOW settings. Hopefully somewhere in all of that I’ll find a tune that the hades like, and with a bit of luck it will be around the 850fps area.

While setting the reg pressure today (I was using hades pellets for that because they cheaper then the slugs) I happened to stumble across a high power pellet tune that gave a 3 shot, one hole group at 25m. I don’t know what speed they are doing, but with one hole, I’ll take it! I took note of the settings and will come back on it when I get to doing the pellet tunes.

Is that on a Dreamline? Does it have the extra plenum? This makes it easier to produce that extra power.