Tuning 500mm barrel shooting slugs

[Al_Miller]

Are you guys having any luck with slugs out of short barrels? Just got my compact .25 mk3 wildcat. It was shooting 25gr jsb really good and I got the the 34 gr flying at 830 fps and they’re grouping in a ragged hole at 50 yards. I tried a mag of uncleaned slugs just to see if they would shoot. 30 yards 5 shots grouped acceptable but not as good as the pellets. Figured I would have to find tune it. I just cleaned them today but haven’t shot them. They were SUPER dirty holy cow that shocked me . Big lead pieces and turned water dirty instantly. 29.5 gr Nielsen slugs. Also gave em a small squirt of ballistol for lube. Just wanted to know what has worked for guys with short barrels specifically in .25 cal instead of .22. I like to read what you guys are doing! Thanks

 

[Vetmx]

I’m not going to give you any tuning specs but what I can offer is some insight from experience. Don’t try to make your 500mm do what a 600mm will do. You might be able to over the chronograph but it will bite you when striving for accuracy and efficiency. There is no substitute for barrel length. A 600mm guy should set all his tuning velocities one notch below the 700mm guys. You should do the same below the 600mm guys. That is the first step for success.

 

[Long_Gun_Dallas]

My gauges have been all bugged out. I have no idea where my tune is at, lol. I did get new gauges but havnt swapped or had time to shoot more.

I went with the 500mm normal superior liner in my Crown. (still have a 700mm and 380mm barrel) I tested a different 500mm barrel on it before and was seeing 50fpe. PLENTY to sling slugs in .22 caliber. (my gun is tuned, ported, and also has a small hammer weight if I need it.)

Last I was out, I had intended to tune for 25gr projectiles, but I only had 2. Yep, two in my bag of ammo, lol. 21gr it was. 940fps, and clover leafing at 72 yards without touching a thing on the gun. I'll take it, but will still be trying heavier ammo. (I pretty much exclusively shoot griffin slugs, they use pure lead, and have always done well by me)

I did bond my liner with carbon fiber to reduce tune sensitivity.

@vetmx my 700mm barrel likes being shot slow. I think this may be due to it's flimsiness, and length. Using any moderator on it reduces accuracy. It is overall very picky with ammo, and power level. I have not tried bonding the barrel, because the barrel is just too long for any practical use.

 

 

[Vetmx]

Yes 700mm can be a harmonic nightmare but velocity comes very easy. All I was saying is you have to lean on your gun harder with a shorter barrel to achieve what a longer barrel will do easily.

 

[Long_Gun_Dallas]

Ah, ok. This is true. Especially for smaller calibers.

 

[jcote258]

Are you guys having any luck with slugs out of short barrels? Just got my compact .25 mk3 wildcat. It was shooting 25gr jsb really good and I got the the 34 gr flying at 830 fps and they’re grouping in a ragged hole at 50 yards. I tried a mag of uncleaned slugs just to see if they would shoot. 30 yards 5 shots grouped acceptable but not as good as the pellets. Figured I would have to find tune it. I just cleaned them today but haven’t shot them. They were SUPER dirty holy cow that shocked me . Big lead pieces and turned water dirty instantly. 29.5 gr Nielsen slugs. Also gave em a small squirt of ballistol for lube. Just wanted to know what has worked for guys with short barrels specifically in .25 cal instead of .22. I like to read what you guys are doing! Thanks

I'll be starting this journey shortly. I just received my Impact MK2 Compact in 25 Cal and ordered the dual transfer port from 910 Airguns, where Ernest Rowe sells his parts. I agree with Vetmx that you will certainly want to curb your expectations a bit regarding the 500mm barrel. When I ordered the compact from Baker Airguns, the owner told me that all maxed out his compact was shooting the MKII 33 grain pellets at 950. I was impressed, to say the least, but I also don't want to put that kind of wear and tear on my rifle. 

While I'm still in the discovery phase, I hope to shoot 28-33 grain slugs from Griffin and other makers around the 900-930 fps area. What is your max shooting distance? I have about 5 acres where most of it is cleared out, and the furthest I'll probably shoot is around 100 yards, probably more at 30-75 than anything else. 

I'm starting around 145-150 bar on the reg and adjust the hammer spring and valve accordingly. 

What brands of slugs are you testing, and what grains? I see you said NSA 29.5. Those are the .249 slugs, right? I was hoping he had the .250 is a lower grain, but it looks like 33.5 is all he has for a low weight .250 diameter. Griffin has various weights in .250 slug size ranging from 23-44 grains. They can be found on eBay. Another place to check out is AVS slugs. They have slugs in a .2503 diameter with various weights as well. Send me a PM when you get a chance. Maybe we can trade phone numbers and text. It would be nice to work with someone else on the same platform.

 

[Al_Miller]

I’m not going to give you any tuning specs but what I can offer is some insight from experience. Don’t try to make your 500mm do what a 600mm will do. You might be able to over the chronograph but it will bite you when striving for accuracy and efficiency. There is no substitute for barrel length. A 600mm guy should set all his tuning velocities one notch below the 700mm guys. You should do the same below the 600mm guys. That is the first step for success.

Yes I completely understand and this sounds like solid advice. I’ll definitely get more brands and sizes of slugs in the future to try. The neilsen seemed cheap and people like them so I gave them the first go. The 29.5 gr is the .249 diameter. Figured I go in between the jsb king and jsb heavy pellets for the first slug size. Half inch groups at 50 yards should be good enough. Not sure I will going out further than 100 yards unless I get something shooting lights out. If I wanted a long range slug gun I would’ve bought a impact but I wanted my first high end gun to be a compact, maneuverable bull pup. If the wildcat can’t get it done I’ll be plenty happy with pellets for the moment.

 

[Al_Miller]

Ok so I got out to shoot some slugs today. My velocities ranged from 830-875. Couldn’t get more than 875 out of it. 29.5 Nielsen slugs. Unfortunately I couldn’t get a acceptable group at 50 yards. I shot for 2 hours. I had a good group going at 835 but the HST was just light enough to drop velocity to 800 1 out of 5 shots and it killed my consistency. I started to get cold after 2 hours so I put the jsb heavies back in and it just stacked them in one hole at 825. Felt so good after those slugs haha. I wouldn’t say they were shooting bad but they weren’t a 1/2 inch. If they tightened up to that 1/2inch I’d call it good. My biggest take away was I noticed that when I put the pellets back in and pushed the probe forward I felt a small amount of resistance to the pellet being seated. I never felt any resistance while pushing the slugs in. I think I need to get some bigger slugs. I was afraid of getting bigger ones because I figured my velocity wouldn’t be enough. Turns out velocity may be a smaller variable of the slug performance than we think

 

[Long_Gun_Dallas]

I think the largest factor is harmonics in the fx guns that use liners. Seat depth is a factor, as is speed. I'd highly recommend bonding your liner with a carbon fiber tube offered in earnest rowes custom shop 

 

[Al_Miller]

I think the largest factor is harmonics in the fx guns that use liners. Seat depth is a factor, as is speed. I'd highly recommend bonding your liner with a carbon fiber tube offered in earnest rowes custom shop

Figured they would be out of stock but the .25 500mm was not! Had a gift card from Christmas take care of the $40! We’ll see if it helps me out. 

 

[Jayman07770]

I've tried NSA 26.8, 29.5, 33.5, 36.2 and FX Hybrid in my .25 Impact Compact. None of them grouped to my expectations at 30-50 yards. Since this setup is for small game hunting under 60 yards I decide to tune for JSB Hades. The 500mm .25 cal barrel is an awesome pellet shooter. If I plan to hunt pass 60 yards than I'll use slugs with a 600mm or 700mm barrel and a bigger bottle. 

 

[Long_Gun_Dallas]

I think the largest factor is harmonics in the fx guns that use liners. Seat depth is a factor, as is speed. I'd highly recommend bonding your liner with a carbon fiber tube offered in earnest rowes custom shop

Figured they would be out of stock but the .25 500mm was not! Had a gift card from Christmas take care of the $40! We’ll see if it helps me out.

awesome! If it works anywhere near how well it did for me, you'll be fairly tickled.

 

[jcote258]

I've tried NSA 26.8, 29.5, 33.5, 36.2 and FX Hybrid in my .25 Impact Compact. None of them grouped to my expectations at 30-50 yards. Since this setup is for small game hunting under 60 yards I decide to tune for JSB Hades. If I plan to hunt pass 60 yards than I'll use slugs with a 600mm or 700mm barrel and a bigger bottle.

That's disappointing to hear, what speed were you able to get them to leave the barrel? I would have thought the Hybrid slugs would have done at least acceptable along with the .250 diameter slugs from NSA.

 

[Al_Miller]

I think the largest factor is harmonics in the fx guns that use liners. Seat depth is a factor, as is speed. I'd highly recommend bonding your liner with a carbon fiber tube offered in earnest rowes custom shop

Figured they would be out of stock but the .25 500mm was not! Had a gift card from Christmas take care of the $40! We’ll see if it helps me out.

awesome! If it works anywhere near how well it did for me, you'll be fairly tickled.

Figured it wouldn’t hurt anything at the worst and I won’t have to deal with those stupid o rings anymore. If it helps with the slugs it would be totally worth it. Didn’t really buy the gun for slugs but figured I should give them a solid chance before I write them off. 

 

[Jayman07770]

I've tried NSA 26.8, 29.5, 33.5, 36.2 and FX Hybrid in my .25 Impact Compact. None of them grouped to my expectations at 30-50 yards. Since this setup is for small game hunting under 60 yards I decide to tune for JSB Hades. If I plan to hunt pass 60 yards than I'll use slugs with a 600mm or 700mm barrel and a bigger bottle.

That's disappointing to hear, what speed were you able to get them to leave the barrel? I would have thought the Hybrid slugs would have done at least acceptable along with the .250 diameter slugs from NSA.

I think I got the best group with the Hybrids around 930-940. The group started opening up as I went faster. It didn’t make sense for me to use expensive FX slugs at the speed for under 60 yards. It was more cost effective to use the Hades and they did everything I needed within that range. 

 

[Al_Miller]

So I got the NSA 29.5 gr slugs to shoot out of the wildcat compact! The only thing I did different was try shooting them after I indexed my barrel! That’s it! At 50 yards with 10 shots flying at 870 fps they grouped the size of my thumb. Best thing is I didn’t have to rezero my scope. Meaning jsb mk 1 heavies sighted in at 28 yards on power wheel setting 6 is the same as slugs at power wheel 7 sighted at 50 yards. Reg at 150. My “range” we full of sparrows at the time and I shot 11 shots and hit 10 birds lol. The one miss was not knowing the trajectory at the angle and range it was at. The slug pop of hitting birds was extremely loud. And they are definitely devastating even under 900 fps