Tuning POI shifting on Dreamline

[PlinkForFun]

Hey guys,

so ive been doing lots of tinkering, and i got my gun to shoot great groups with some NSA 24.8s in my superior, but the POI is CONSTANTLY MOVING, but as it moves, the groups stay tight. I literally leave it on a table inside for an hour, and go back to shoot it, and its changed. Go to fill it up, go shoot it again, its changed. Put it in its case overnight, pull it out, and shoot it, guess what? Its changed. But throughout all of this, the groups have stayed very tight, but its really annoying to zero it, as every darn time i go to shoot it, its no longer zeroed, and it also does this with all the other slugs so far too, but not as bad. Anyone ever experience this?


If it helps, im running with no shroud and only a tanto suppressor, reg at 160 bar, HST maxed. I havent measured the velocities yet, but i’d guess theyre in the mid-high 900s.

 

[Sqwirl57]

Are the grub screws for the barrel tight? Are the screws on your rings/mount properly torqued? I had some issues with POI shift with my Dreamline as well when I put my Shogun on. The barrel band fixed that.

 

[PlinkForFun]

Yep both the grub screws for the barrel and TP, and scope mounts are all properly snugged down. If i could, i would use a barrel band, but i have the bottle version, so the shroud isnt able to be properly held secure, so ive been shooting without a shroud. Using no shroud definitely helped with groups though.

 

[Sqwirl57]

Yep both the grub screws for the barrel and TP, and scope mounts are all properly snugged down. If i could, i would use a barrel band, but i have the bottle version, so the shroud isnt able to be properly held secure, so ive been shooting without a shroud. Using no shroud definitely helped with groups though.

I'm at a loss then unfortunately. Good luck. Hope someone has a better answer for you

 

[biohazardman]

I believe you can get hold of a barrel band that fits on the bottle. This could be one of them check it out.

https://ohioairgun.com/products/fx-dreamline-carbon-bottle-barrel-band

 

[Vetmx]

I keep a lot of airgun info close to my chest but it might finally be time to put this out there. This is directly related to FX airguns. Guys for years have been complaining about FX and their POI shifts. The main reason guys get POI shifts, especially with slugs is because you are gradually leading your barrel. My conventional barrels don’t do it but the FX liners, while accurate, have this flaw. My Impact will remain on point for quite a while after a barrel cleaning. But eventually the chase is on. Then it’s time to clean or chase every time I shoot.

 

[PlinkForFun]

I believe you can get hold of a barrel band that fits on the bottle. This could be one of them check it out.

https://ohioairgun.com/products/fx-dreamline-carbon-bottle-barrel-band

Ive heard about this one, ive been tempted to get it, but ive also heard bad stuff about it.



and also about leading, i just went and thoroughly cleaned my superior barrel, and went through about 2-300 slugs in the past several days, and the patches came through as barely even dirty. The first time i used slugs, the patches were dark black every 50 or so shots, and now, it seems to be broken in somewhat. Is there some sort of trick to keep the POI from shifting? Ive heard of polishing, but it seems like fx liners come out pretty good from the factory, and each of mine have a nice mirror finish on the inside.

 

[Stone02]

I keep a lot of airgun info close to my chest but it might finally be time to put this out there. This is directly related to FX airguns. Guys for years have been complaining about FX and their POI shifts. The main reason guys get POI shifts, especially with slugs is because you are gradually leading your barrel. My conventional barrels don’t do it but the FX liners, while accurate, have this flaw. My Impact will remain on point for quite a while after a barrel cleaning. But eventually the chase is on. Then it’s time to clean or chase every time I shoot.



I've always thought that FX POI shift was due to the combination of skinny liners, multiple shrouds, multiple O-rings affecting barrel harmonics plus single screw barrel anchoring.

 

[biohazardman]

I keep a lot of airgun info close to my chest but it might finally be time to put this out there. This is directly related to FX airguns. Guys for years have been complaining about FX and their POI shifts. The main reason guys get POI shifts, especially with slugs is because you are gradually leading your barrel. My conventional barrels don’t do it but the FX liners, while accurate, have this flaw. My Impact will remain on point for quite a while after a barrel cleaning. But eventually the chase is on. Then it’s time to clean or chase every time I shoot.

I have a habit of shooting three to six-hundred rounds, at a time, when I go out to shoot my Impact and have not noticed a POI change while I am shooting. Although I do notice the accuracy starts to degrade at around the six-hundred round point so I clean and it's all good again. That is with the older STX liners I have not shot enough rounds through my Superior liner to notice that as yet.

 

[Vetmx]

I’ve never noticed it while shooting either. But there is a difference between gradual leading and the point where the choke is just plain fouled. There’s also other factors like how tight the slug is, tin content and lube. Because I retired in January, I ran a long experiment over the winter with some of my top guns. They all had my best tunes and lived on bipods in my spare room. Every day I judged their first shot accuracy and monitored reg creep as to not skew the results. I will add for the OP that I have a Dreamline Compact. I don’t shoot slugs but it’s a POI shifter. When it’s on, it’s accurate. I built a barrel for it a while back and recently started using it because it easily lets me shoot 900fps. The gun came with a 380mm so I chopped a 500mm down until the guns max speed was around 940fps for my reg setting. I haven’t shot it enough yet to see if there are going to be POI issues. I’m not sure how the normal Dreamline barrel systems work but I cut mine so with the shroud loose, I could install the barrel, tighten the grub screws, then tighten the shroud into the receiver to put the barrel under tension. I’m hoping this makes the gun more resilient.

 

[Vetmx]

Plink, I would also like to add that if you are shooting with a bare barrel, you have a real wet noodle on your hands. Slugs don’t like wet noodle barrels. Things like temperature changes effect flimsy barrels. You should check to see if you are experiencing the same thing with pellets.

 

[Bobbybeef]

I had the same issue its barrel leading i scrubbed with baristol to no avail patches were clean still nothing 6 passes with a brass brush and hasn't happened again yet people freak when you say brass brush but my accuracy went back like it should 

 

[Stone02]

I had the same issue its barrel leading i scrubbed with baristol to no avail patches were clean still nothing 6 passes with a brass brush and hasn't happened again yet people freak when you say brass brush but my accuracy went back like it should.

+1

In the past I've had to bronze brush a Weihrauch H100 with a heavily choked barrel to remove accumulated lead. Normal cleaning did nothing.

 

[Khornet]

I agree about bronze brush. I do 4-5 passes with a regular .22 rifle brush, then it takes 3 or 4 tight patches pulled through and it's clean. I too think it's the choke where lead really matters, but I'm really still not certain that cleaning matters in my FX liners including Superior standard. I do replace my breech O-ring every time I clean, since the brush can be rough on it.

That said, in my case I think variations in hold are the cause of my POI shifts. I finally marked the positions of my bipod feet, rear bag, and chair feet, and sit so that my chest is just touching the edge of the bench. I place my center dot at 12:00 on the edge of my bull, then press my shoulder against the stock til it's centered. My POI wanders a lot less than before.

Warren Page, in The Accurate Rifle, says that when you're shooting a good card for God's sake don't get up from the bench until you're done. I think that says a lot.

 

[Khornet]

Also, I indexed my liner, and take pains to be sure it hasn't shifted. I don't pull the liner to clean for that reason.

 

[Khornet]

Also, don't forget mirage. It will make your target look higher than it really is, and a little cross wind will make it look higher and to one side. I have had my rifle dead on at 0600, shooting high at noon when the sun is on the grass, and back to dead on at 1900.

 

[FelixS]

What scope are you using and do you,"click"?

I had the same issue early on in my journey; It would shoot lights out, then the following day be off. So, I would re-zero and then the next day again, it was off. This was not a gradual drift, but black and white on one day then off the next. I usually case my guns after shooting, so tried leaving it out to eliminate barrel shift, same thing.

What I found was that my scope would drift overnight. it would hold for a bit while I was shooting, but then eventually settle. It drove me nuts.

 

[Stone02]

What scope are you using and do you,"click"?

I had the same issue early on in my journey; It would shoot lights out, then the following day be off. So, I would re-zero and then the next day again, it was off. This was not a gradual drift, but black and white on one day then off the next. I usually case my guns after shooting, so tried leaving it out to eliminate barrel shift, same thing.

What I found was that my scope would drift overnight. it would hold for a bit while I was shooting, but then eventually settle. It drove me nuts.

+1

Over the years, I've found that some scope reticules suffer lag to adjustments. My solution is to over adjust then back up. So if I need 2 clicks left I'll adjust 5 left followed by 3 right. This seems to correct for sticky reticules.

 

[qball]

Speaking of scope caused POI shift, the parallax can definitely cause this issue. Proper cheek weld is a must but even with that I use to get POI shift with some of my scopes. 

 

[Khornet]

Agree about parallax. I found that I'm not necessarily parallax-free when the target is in sharp focus. When my scope is parallax-free things are slightly blurry.