Tuning Velocity Anomalies

[$p00kygH0ST]

Trying to perfect a tune.
I've been pesting every week heavily and accuracy is outstanding. I've said it in other posts and I'll say it again for the sake of relevance to post.

Shooting a Dreamline Tac 25/600 w 290cc Tube. I'm currently set at 108bar on the reg, 17 on the wheel, about 1.75 turns on the HST internal screw. Getting 857-863 with an EXTREME spread of 12. But mainly between 855-862. I notice when I rechrono to confirm same tune my first shot Will be slightly low (847-850) then back to.the sweet spot for the rest of the mag. Then I'll get a few 837-841-829- then back to 860 for a few. I know if velocity drops after first shots it's too little HST but.. its so consistent and always goes back to the sweet spot. Does anyone have any ideas?

I'm getting Altoids/Dimes at 50- quarters at 100. I'm using the same exact pellets... I'm an over perfectionist and hand weigh the pellets to the .001, inspect all skirts, and place the best 100 out of every can skirt down in empty FX Hybrid Slug blocks to protect them. It's not weight variance or gas bypass from deformed pellets.

 

[Scotay42]

Reg creep sir. Reg valve is bypassing a bit while on rest, so your hammer setting is too low for initial pressure.

 

[$p00kygH0ST]

Reg creep sir. Reg valve is bypassing a bit while on rest, so your hammer setting is too low for initial pressure.

I confirm zero on paper at 45... you'd think a velocity drop of 30fps would cause a flyer. One small jagged hole.

If it's what you say and I gave her another quarter or half turn or dropped er to maybe 105bar could that remedy?

 

[Vetmx]

If a velocity drop of 30fps would cause a flier then an unregulated PCP would never exist. My advice is if all your pellets are on the money at the distances you are trying to kill animals, don’t sweat an issue that isn’t sweating your accuracy. If you just can’t live with yourself if you don’t try something then don’t touch your wheel. Get out your tiny allen wrench and just bump up your strike a little. Then test after the gun sits. If it’s still slow, you can try again. For me, if I’m +10 or -10fps on my first cold shot, I don’t keep poking the gun with a stick. I go hunting with confidence.

 

[$p00kygH0ST]

If a velocity drop of 30fps would cause a flier then an unregulated PCP would never exist. My advice is if all your pellets are on the money at the distances you are trying to kill animals, don’t sweat an issue that isn’t sweating your accuracy. If you just can’t live with yourself if you

I stated that accuracy was great. And I wasn't referring to a "half or quarter turn" of the power/HS cam wheel, as a 6-13 position adjustment would've been over 100-220fps. However I like to if possible, remedy or identify issues before they become a problem. I'm new to this gun and have never had an FX, or regulated pcp before. And the power curve did require holdover adjustments on unregulated guns. To me, consistency and accuracy is one hole. A flyer, to me qualifies as an impact more than .25mil@50 outside of the impact grouping my zero's POA/POI has held, not caused by a user error or atmospheric effect.

 

[Airgun-Revisions]

I confirm zero on paper at 45... you'd think a velocity drop of 30fps would cause a flyer. One small jagged hole.

If it's what you say and I gave her another quarter or half turn or dropped er to maybe 105bar could that remedy?

It will not cause a flyer. People are way under the misconception of that.

 

[$p00kygH0ST]

It will not cause a flyer. People are way under the misconception of that.

At 100 a 30fps drop is .5mil difference in drop. I'd call 1.8" off a flier. In terms of hunting... that's still near 1"@50...the difference between hiting or missing a house sparrow, heart shot or low gut shot on a starling, or braining a squirrel or just removing its jaw.

 

[Vetmx]

Like I said in the second part of my response that you didn’t quote, you can address the slow first shot with the tiny hammer screw, not the wheel. But your weird velocity fluctuations off and on has me scratching my head. The fact that you sort and weigh pellets eliminates that. I guess I would look at how your hammer is lubed and then possibly a reg that is not always consistent with its recovery. How far do you have the gun set below the peak speed at 108b? If your hammer spring is set right, it shouldn’t matter if your reg is reading 106b or 110b when you squeeze the trigger. With a 860fps tune, you should never be in the 830’s with scrutinized pellets. I understand your concern with this anomaly.

 

[$p00kygH0ST]

Like I said in the second part of my response that you didn’t quote, you can address the slow first shot with the tiny hammer screw, not the wheel. But your weird velocity fluctuations off and on has me scratching my head. The fact that you sort and weigh pellets eliminates that. I guess I would look at how your hammer is lubed and then possibly a reg that is not always consistent with its recovery. How far do you have the gun set below the peak speed at 108b? If your hammer spring is set right, it shouldn’t matter if your reg is reading 106b or 110b when you squeeze the trigger. With a 860fps tune, you should never be in the 830’s with scrutinized pellets. I understand your concern with this anomaly.

I did quote it. For some reason the comment that quotes the whole one was caught by the auto Moderator in the "needs to be approved by mod" status and I deleted it.. it wasn't rude, nor crass so I don't understand why.

"1.75 turns on the INTERNAL HST" means on that very screw.

On max position on the power cam wheel its about 930-940 at 110. I've seen no need in going higher in pressure as I enjoy 60 shots per fill on my tube 230-140. I asked "maybe a quarter or half turn" referring to that very "tiny screw". It doesn't make sense. I don't mind the +/-10 on the very first shot of the day.


Is it possibly a chrono issue. Since I'm having very satisfactory accuracy and I'm more than happy with 860fps 6 turns on the external hammer wheel down from max. Position 1 is roughly 530fps, max nears 940

 

[$p00kygH0ST]

Like I said in the second part of my response that you didn’t quote, you can address the slow first shot with the tiny hammer screw, not the wheel. But your weird velocity fluctuations off and on has me scratching my head. The fact that you sort and weigh pellets eliminates that. I guess I would look at how your hammer is lubed and then possibly a reg that is not always consistent with its recovery. How far do you have the gun set below the peak speed at 108b? If your hammer spring is set right, it shouldn’t matter if your reg is reading 106b or 110b when you squeeze the trigger. With a 860fps tune, you should never be in the 830’s with scrutinized pellets. I understand your concern with this anomaly.

I think it was just a very slight internal hs adjustment one tiny 1/16th or maybe 6-8⁰ turn did it. I am content with this....
No more extreme jumps. 48 shots and this is how much I have to spare from 230

 

[Vetmx]

Looks like you’re in business.