Help with JSB KO fliers

[dgwren]

I've been working for a while to figure out why I'm getting fliers using JSB KO .217 slugs. I'm shooting an FX Maverick Sniper .22, 135/110 bar front/rear reg settings with Superior barrel and carbon fiber tube over barrel. Velocity is about 923 fps with decent ES of around 10 fps.

The KOs shoot great--like 1-1.5" groups in still conditions and 2" or less in light wind at 100 yds. THEN, one will fly off by 6-10". Usually when that happens, I can hear the slug going through the air. Maybe 1 or 2 more will be wild, then POI goes back and it starts grouping again. I've been through multiple cycles of this, in very still to light wind conditions. It doesn't do this with FX Hybrids or JSB 18.1s. I have shot great 100 yard groups with both. The Hybrids really shoot great from my gun/barrel, but they are so expensive!! The KOs are about half the cost of FX Hybrids.

I've read with interest a thread where Thomasair describes lead deposits that are gradually laid down before being stripped out all at once, causing a big flier. It sounds like a good explanation of what I'm seeing. I have inspected the barrel from both ends, but I can't see anything that looks like a problem. I did a partial polish with JB bore paste, but probably only long enough to clean the barrel thoroughly. I have experimented with pulling Patchworm felt buttons (fit bore tightly) more often for cleaning, but the interval between big fliers is maybe only 20 shots or so. I have tried a single-shot tray, and it does not make a difference. I've tried lubing with FP-10, and it didn't seem to help. I've tried with and without the moderator, with no effect. I've pushed the KOs through the barrel: they slide smoothly down to the choke, and it takes a pretty hard push to get them through. I haven't seen obvious defects on the slugs I've pushed, but I may try again.

What am I missing?! Is it time for a new Superior liner? More thorough polishing? (If I can even get one!) Or....?

 

[Ghostranger169]

dgwren,

It sounds like you have done your due diligence with regards to checking your gun/barrel except for the possiblity of barrel clipping maybe(probably unlikely if you have no issues with 18.1 pellets, tho). I(and I have read of others who) have had similar results with "random" flyers(however mine weren't nearly as frequent or as bad off course) using KO slugs at 50 and 100 yard benchrest shooting using an FX Crown with 700mm Superior and Super Heavy liners. Some have reported better results by changing speed slightly to find the "magic" fps. Others have reported getting better results from a different tin of slugs. Others have reported better results using a different moderator and/or harmonic tuner. I haven't seen where anyone has reported the "magic recipe" to complete eliminate flyers using KO slugs. Shooting outdoors, there is always the possibility of an intermittent "un-noticed" change in atmospheric conditions(especially at 100 yards).

Perhaps ammo imperfections play a part? Slugs can be weighed accurately enough, but it can be difficult to measure/quantify imperfections in their shape. I believe I remember @Thomasair said(in a previous thread) that some slugs measure the correct diameter, but may have concentricity issues(sides not being parallel, or one side being lobed), or something like that and this can be difficult to measure with the normal "drop through a hole" caliber sizers.

I don't know, but I definitely feel your pain. Perhaps someone with experience shooting KOs at 100 yards using a Maverick may have some gun specific info to add.

Good luck

 

[Ranchibi]

Maybe the slugs that are fliers have large imperfections or the slug itself has a different shape (maybe the diameter is too small, most likely scenario) than the others from damage or manufacturing proccess imperfections. When shooting FX hybrids with no fliers I'd guess you barrel is good. You should use a loupe and calipers and go thru the JSB KO's and put aside ones that you deem different, then shoot both the good and bad ones and see if you get fliers. I think it is diameter related as I notice when I shoot slugs through my RAW single shot loading, I notice most load snuggly (these shoot consistently accurately) while a small percentage load too smoothly and these shoot erratically, my barrel is non choked. You could also pull your barrel and slug it with the different size slugs from the same batch. I don't think JSB KO slugs are swagged and most likely are not made with as tight tolerances as the hybrids hence the occasional flier same as the NSA I shoot unless I weed out the smaller diameter ones.

 

[jps2486]

My Crown Saber in .22 doesn't like the .217 dia pellets, but shoots the .216 very well.

This is the story behind my Dreamline Tact Compact in .177. After just over 100 shots, the accuracy went to pot with both pellets and slugs. Pulling the first patch through was very difficult and yielded a lot of lead flakes. After cleaning, it was ok for another 100 or so shots, then the same problem. I cleaned it, then polished the bore with JB for about 200 strokes. I was then able to get maybe 150 pellets before the same problem arose. I slugged the barrel and found that a .178 dia slug came out .173 diameter. That's way too tight! I called FX and talked to a tech and he confirmed that this barrel is defective and would be replaced. You might want to slug your barrel and see how tight it is. I would, however start with using .216 diameter slugs and see how that works. Good luck.

 

[Ghostranger169]

Ranchibi and jps2486,

Excellent point about slugging the barrel/liner! I forgot to mention how important that is. +1 green accuracy point for you!

My Crown 700mm Super Heavy liner prefers .216 KOs also. The 700mm Superior barrel does just ok with either, but does BEST(fewest flyers) with sorted-for-size .216 KOs.

 

[ackc1234]

Could try a push through sizing die to eliminate this as an issue. If you can get them I don't think there too expensive. I have one in .25 caliber. 

 

[dgwren]

Thanks for all of the quick and thoughtful replies! As a result of these replies, I think I'll focus more on the ammo than my barrel and see what I can find out.

I have used a pelletgage to check the sizes, and I did most of one tin that way. Almost every single one went through the 5.53 mm hole (0.2177") with slight resistance. Like, maybe one or two did not. Maybe that's a little big, but the FX Hybrid is the same. The softer lead of the Hybrids may just be more forgiving in the fairly tight choke of my barrel.

As Ghostranger169 pointed out, there may be concentricity issues. I can say that one tin was particularly bad, and I threw them away. One tin was very good, and the one I'm on now is throwing fliers after only 6-8 shots. I guess I'll need go get out my calipers and measure several diameters to see if they are consistent.

As jps2468 said, I can slug the barrel again and measure the slugs after pushing them through. I'm thinking that the harder lead of the KOs may be the issue, along with some imperfections that the Hybrids don't have.

 

[tor47]

I had the same experince with my impact. But for me it was the .216 getting fliers. When I went up to .217 it dissapeared. Maybe your barrel likes the .218 better?