Tuning 177 maverick slug tuning

[Solo1]

Hoping for a little advice on what to look for to try to fix this. Shot a ft match last month with 12.5 gr nsa slugs and thought it was doing pretty good. Shot mostly pellets this month cause i have more of them than slugs. Shot pellets very well. Shot slugs the day before this months match and just blew the first 10 thru as the slugs shoot different after the pellets and shots 11 thru about 17 were good then it threw 1 to 9 oclock 2 or 3 more shots went well then it threw 1 to 6 aclock It did the same thing thru about 25 or 30 more shots! Anyone have an idea what i should look for? Oh and velocity was right on. Ended up shooting pellets in the match and shot my best score so far with the mav

 

[ram2jeep]

What liner and speeds were you shooting with the slugs? Also, at what distance are you shooting the slugs at?

 

[Solo1]

Near as i can tell its the 177 superior 1-18 twist. Shooting 840 fps just under 20 fpe and i was shooting inside at 12 yds. It was throwing the shots about 3/8” first left then low then left again

 

[2L8]

Check out Aim Small's videos on .177 he just put out.

https://www.airgun101.com/component/allvideoshare/video/high-power-177-20ftlb-to-30ftlb-with-500mm-and-600mm-barrel?Itemid=557

Patrick

 

[tor47]

In my lilte experiance with slugs, the diameter has to be correct. I know when I did test the JSB knockouts, the .216 had some flyers, but when I did go up to .217 it went better. Maybe the diameter on the slugs you are using also is just a litle to small?

 

[Rallyshark]

The NSA slugs are .178, so I doubt they are too small per say. The sizing could be contributing though, and likely is. I had a barrel that shot the older 15.5 grain NSAs like a laser when they were .177, but it wouldn't shoot the newer 15 grain .178 nearly as well. You could have a twist issue too, given the low speed. I honestly think a little more twist would work better at the speeds you're shooting. I will say, every accurate .177 slug/barrel combo I've ever had liked speeds of 950+ fps. If you're determined to try and get those slugs to work, then I'd recommend a good cleaning of the barrel, and seasoning it with only those slugs. I good polish with some JB bore paste may help with that as well. The other option would be to try some slugs that aren't .178, like the Griffin slugs for example. That's just my opinion though. Hopefully, the long rumored FX .177 slug liner will come to fruition one of these days!

 

[tor47]

I did try the same NSA slugs in my impact, some days ago, I did not got them to group well. I noticed when I pushed them true the barrel with a rod, not the hole surface of the slug got "scatched" by the barell. By that I mean I could see where the rifling made marks, but inbetween there was area on the slug where the barrel had made no contact. But that might be litle scientific, as it might look differnt after being shot. I do not know if it is the case, as I do not have a bigger one to try. But I did noticed a similiar patern by comparing a .216 and .217 JSB knockout in my .22 barrel. The .217 had barrel marks all around the slug, while the .216 seemed to have some areas untouched. The .216 in my case had some flyers, while they seemed to disapear when using the .217.

But you might be right Rally that the simple reason is that the .177 liners are not tested yet for slugs by FX.

 

[Rallyshark]

That's a little surprising for me. I would have thought the slugs would have made good contact on the FX liner, but I've never played with an FX .177 liner. It sounds like the .177 liner may be a bit over sized by what you're saying on the push through. I know the other liners are choked at the end, even the slug liners. Is there no choke on the .177 liner? Of course, the other option is to machine a non FX barrel in .177 to shoot slugs. The downside is, that's a lot of effort if it turns out not to work, but who knows. I machined an Alfa Precision polygon .177 barrel(16.5" twist) for my Maverick to shoot .177 slugs. It works pretty well, but I only shoot the heavier stuff in the 20-22 grain range in it. I also have another faster twist AP barrel that is a 12 groove(14.6" twist), but I haven't machined it to fit yet. I really do hope FX does come out with a .177 superior heavy liner though, because a non FX barrel can add a lot of weight when you're starting with a 15-16mm OD barrel. I've seen a few people on here say they got decent results with the 12.5 NSAs in the FX liner, but they were shooting much faster.

 

[tor47]

I did a more proper check today. Pushed the .177 NSA slug trough superior liner, while shining with a flashlight on the other end. The slug does seal by shutting of the light, but not until the end of the choke. It rides on the rifling with light gaps on the side, all the way before that. That might be normal for all I know. So If it has to loose fit, or not, I really do not know.

 

[Rallyshark]

Generally, you'd want some rifling engagement prior to the choke. Otherwise, the slug won't always enter the choke at the same angle, which will cause a lot of inconsistency(twist rate aside). In other words, if it is really easy to push through until the choke, then it probably will never be a consistent round As always, there can be some minor manufacturing variations in the barrels, so some FX liners could potentially do better than others.

I was hoping more guys that have shot slugs in their FX liners would chime in on this. I can only speak in generalities, since I have not shot them in an actual FX liner.

 

[Deleted member 33063]

do not even bother trying to shoot slugs out of the impact or any fx. i tried NSA 12,5gr 15gr and jsb knockouts in 10.3 and 13.43 in 4 different riffles. they wont group at all even at 20 meters. the choke is very tight and the 1:18 twist rate pulls them to the right every time .i tried them from 640fps all the way to 1080fps.in the picture is a 15gr pushed throug

h the liner

 

[Rallyshark]

Where did you source the JSB Knockouts in .177??

 

[Deleted member 33063]

Where did you source the JSB Knockouts in .177??

i live in europe..

 

[tor47]

I did manage to get desent groups with the 12.5 grain NSA slugs, after allot of tuning. But this time I used my wildcat mk2, which has a regular smothtwist X-liner, not the superior.

I did as follow: Tried Rallyshark`s advise about doing a proper clean, and leading up the barrel with the slugs only. It seems like a good advise as I personally have been fanatic about keeping the barrel clean when shooting pellets, and cleaning regulary, but it might not be the best thing to do in this case when shooting slugs. I have then shot only theese slugs during the hole prosses, and have not cleaned the barrel at all after probably over 1000 shots.

The first picture is just me leading in the barrel, shooting on 25 m home range. Noticed the velocity jumped probably 80 fps from a newly cleaned barrel and stopped somewhere around 780fps after 2-3 mags. The gun was tuned for a 10 grain JSB pellets, and I did not change anything yet. Did first full 8 shot mags, and then 4 shots in each target, as the wildcat mk2 only has 8 round mags. The first groupings was not good, as I only wanted to lead in the barrel. The last groupings was me increasing the speed up to 800-810 or so, and the grouping got better.

After the first target, I increased the regpressure from 100bar in 5 bar increments, and tried every velocity from 800 in roughly 10-15 fps increments up to max speed on every reg setting. I got some good groupings inbewteen, but fliers ruined it all, and it was not consistent, probably the same as Solo1 also talk about. Took no picture of theese as the results was mainly bad. After probably over 1000 shots I ended with a regpressure at about 125 bar, and a speed of 830-840 fps. Tried the speed up to 890 fps on that regsetting also, which was close to max speed. But 830 seemed better.

Leading in:

And then the final result, where I shot 4 groups in a row where there seemed to be few or no fliers. The best groping measured about 5mm, and the biggest about 9mm.

It is not perfect, but not bad either on 25m. I do not know how the gun will perform longrange in this setting, as 25m is all I have at home. 

 

[Solo1]

Mine shot pretty well i thought at 100yds ( for a 177) but like you id get some good groups and some not so good groups @50 yds and many i was blaming on myself as im not rock solid like i was 10-15 yrs ago

 

[Solo1]

I did a more proper check today. Pushed the .177 NSA slug trough superior liner, while shining with a flashlight on the other end. The slug does seal by shutting of the light, but not until the end of the choke. It rides on the rifling with light gaps on the side, all the way before that. That might be normal for all I know. So If it has to loose fit, or not, I really do not know.

This to me is saying that there is air going past the slug that could disrupt it as it leaves the barrel

 

[tor47]

I did a more proper check today. Pushed the .177 NSA slug trough superior liner, while shining with a flashlight on the other end. The slug does seal by shutting of the light, but not until the end of the choke. It rides on the rifling with light gaps on the side, all the way before that. That might be normal for all I know. So If it has to loose fit, or not, I really do not know.

This to me is saying that there is air going past the slug that could disrupt it as it leaves the barrel

I am no expert, but the cup of the slug might expand out some by the air pressure, engaging the rifling better than when doing a simple push trough. Also by letting the barrel lead in as Rallyshark suggested, the lead buildup might fill up the small gaps, getting a better fit with the barrel. I do not know in my case, if the smooth twist-x actually is a better liner for slugs, than the superior. When I did the test with my impact`s superior liner, I did use lube on the slugs, as I presumed the flyers was because of lead buildup. That might have prevented the lead building up filling the gaps, and actually made it worse? I do not know. But If I should redo the impact tuning, I will probably do the same procedure which work on the wildcat, and not use lube.

 

[Rallyshark]

Where did you source the JSB Knockouts in .177??

i live in europe..

Not fair, lol!

I did a more proper check today. Pushed the .177 NSA slug trough superior liner, while shining with a flashlight on the other end. The slug does seal by shutting of the light, but not until the end of the choke. It rides on the rifling with light gaps on the side, all the way before that. That might be normal for all I know. So If it has to loose fit, or not, I really do not know.

This to me is saying that there is air going past the slug that could disrupt it as it leaves the barrel

I am no expert, but the cup of the slug might expand out some by the air pressure, engaging the rifling better than when doing a simple push trough. Also by letting the barrel lead in as Rallyshark suggested, the lead buildup might fill up the small gaps, getting a better fit with the barrel. I do not know in my case, if the smooth twist-x actually is a better liner for slugs, than the superior. When I did the test with my impact`s superior liner, I did use lube on the slugs, as I presumed the flyers was because of lead buildup. That might have prevented the lead building up filling the gaps, and actually made it worse? I do not know. But If I should redo the impact tuning, I will probably do the same procedure which work on the wildcat, and not use lube.

It is possible Solo1 is correct, but I would be more inclined to think it is a matter of the slugs having some "wobble" on their way out. That wobble can be making them not enter the choke the same all the time. It could be both too. It could also be the twist rate, or all of the above. Of course, I've always believed slugs don't do well in a choked barrel, but FX has proven that isn't necessarily true with their superior heavy liners in other calibers. 

Tor47, it looks like you're definitely making some progress, and they are useable for pesting at 25 yards at the very least! I had groups very similar to this many times on a lot of different barrels when trying to nail down various .177 slug tunes. When NSA went to the .178 sizing, that's what my groups looked like with the 15 grain .178, but the barrel was a laser with the 15.5 with the previous sizing.... I never lubed my NSA slugs, since they do have a minor amount of lube on them from NSA, fwiw. Kudos to you for putting in the effort to try and get them to work, because most people don't! You still may be able to get it better with some more shooting I think, because it isn't bad at all currently. It will either get better or get worse I've been hearing rumors for a while now, that FX is going to release a .177 slug barrel, so hopefully that will happen. If they do, I'd bet money NSA slugs are a part of that development process.

 

[Rallyshark]

I know on the slug A liners, my gun would shoot bad after I cleaned it, until it started to get leaded in a little. After that, I never cleaned an FX liner, unless the accuracy got bad. I just cleaned my superior heavy in .22 the first time, after a few thousand rounds, and it will probably be a lot more until the next cleaning.

 

[tor47]

An update on the tuning: Unfortunatelly the results I got did not hold the when I tried the gun the next day. It was close, but not good enough. Since I did not wanted to leave it there, I spent yesterday, and this evening trying higher pressures. Went up in ca 5 bar increments, testing the same velocity range, and all the way up to 940 fps. I stopped at ca 145-150 bar, and saw no reason to go further. The results did not get any better. But it was worth a try, and I am also running low on slugs. I will probably try the JSB knockouts on my impacts superior liner, in the future, when I can get hold of some.