Tuning At my wit’s end

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Solo1

Solo1

Member
Nov 22, 2020
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Pa, United States
Ok so i need a little help cause I don’t know what to do from here. My maverick 177 shot great before the last ft match with 12.5 gr nsa slugs at the match it was all over the place but started to come back in the last 1/2 of the match. Came home and could not duplicate my 10 m results at all compared to the day before. Convinced I’ve shot the choke out of the barrel I’ve shipped it off to usa airguns to have a lw barrel installed. To be able to shoot in the mean time i ordered a new barrel kit and installed but it doesn’t like anything other than pellets. As an aside i ordered a 600 22 barrel to replace my 700 on my other maverick. This barrel @10 m shoots 23-27.5 gr nsa lights out 10 shots in a very small single hole. Can someone please tell me what the hell is the difference between 177 and seemingly all other fx barrels for shooting slugs and any thoughts on barrel for slugs as martin thinks i should try a choked lw barrel first. 
 
He hasn’t gotten back to me yet. As for the choke i believe it’s not out from wear but from expansion of the pressed in rifling with a tight slug. If i remember correctly 1 of the south africa guys started shooting 217 slugs and is now shooting 218. I could be ring but? What gets me is it will shoot them so well today but be a mess tomorrow. And even when its a mess with slugs it shoots pellets well. Just put a new barrel on and added cf sleeve and tensioned the barrel and it won’t shoot slugs for nothing. Even spending time indexing. Shoots pellets well?
 
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I had the same problem and I found a slight bur on the crown. Makes no sense to me why pellets would shoot well and slugs would not . This was an cz barrel non choked designed for slugs on a veteran long . Some place on the forum I found a thread on the subject and a fellow shooter trued up the crown and the slugs came on board. I did the same thing and had similar results. It can drive ya nuts. I just carefully lapped the crown. I felt a little ruff spot but can’t say I saw anything. 
 
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Ok so i need a little help cause I don’t know what to do from here. My maverick 177 shot great before the last ft match with 12.5 gr nsa slugs at the match it was all over the place but started to come back in the last 1/2 of the match. Came home and could not duplicate my 10 m results at all compared to the day before. Convinced I’ve shot the choke out of the barrel I’ve shipped it off to usa airguns to have a lw barrel installed. To be able to shoot in the mean time i ordered a new barrel kit and installed but it doesn’t like anything other than pellets. As an aside i ordered a 600 22 barrel to replace my 700 on my other maverick. This barrel @10 m shoots 23-27.5 gr nsa lights out 10 shots in a very small single hole. Can someone please tell me what the hell is the difference between 177 and seemingly all other fx barrels for shooting slugs and any thoughts on barrel for slugs as martin thinks i should try a choked lw barrel first.
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U didn’t mention any crony results? Anytime I have accuracy problems I start shooting over the crony. 
 
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As others have stated probly a leaded barrel. Most any of the FX liners will shoot some slug or other very well, if tuned properly, and not all lead fouled up. I used to shoot slugs, pretty much exclusively in my 700mm .25 slug liner. It was good for about 600 rounds then accuracy started to drop off. After a good cleaning it was back shooting mostly <MOA at 100 yards again.

I have resorted to the bronze brush a number of times when cleaning the lead out of airgun barrels. I seems to do a pretty good job when patches or nylon brushes just don't cut it.
 
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As others have stated probly a leaded barrel. Most any of the FX liners will shoot some slug or other very well, if tuned properly, and not all lead fouled up. I used to shoot slugs, pretty much exclusively in my 700mm .25 slug liner. It was good for about 600 rounds then accuracy started to drop off. After a good cleaning it was back shooting mostly <MOA at 100 yards again.

I have resorted to the bronze brush a number of times when cleaning the lead out of airgun barrels. I seems to do a pretty good job when patches or nylon brushes just don't cut it.
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Nothing at all wrong with using a bronze brush in an air rifle barrel, and it's pure fiction that it will damage the barrel. I've had leading in some barrels that required more aggressive cleaning than possible with a pull-through. As with any barrel, you just need to use the rod properly and avoid banging around the muzzle or breech. 
 
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Ok so I shipped my barrel off to Martin and have received back a poly lw barrel which looks factory except for the weight. He made no comment on my original barrel but I did scrub the poop out of it with a bronze brush and balistol before I sent it to him and it still shot terribly. As for the new barrel it shoots better so far ( only about 100 down the pipe) but will need a bit of tuning. Will report back after I get more lead thru it and it gets a bit warmer
 
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Ok so I’ve shot the new barrel ( which is choked and rifled not a poly barrel as the slip stated) with 12.5 nsa,10 jsb ko,11 griffon, 13.4 jsb ko, and an assortment of pellets all at 10 meters. 10 Pellets of 4.52 shoot a 4.7ish hole. Can’t get the nsa or 10 g Ko’s to shoot consistently. I’ll get 4 or 5 in the same slightly large hole then poi moves. The 13.4 ko’s are looking promising but I can’t understand why the poi shift with the other slugs. Anyone have any thoughts?
 
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Chuck, I think a couple of things might be in play here. First, keep in mind I have no experience with slugs, and know only what I've read about them. I think there is a general opinion that around 30 fpe is needed for slugs to be properly stabilized, which is above the typical power output of .177 rifles. While having no experience with air rifle slugs, I have extensive experience with precision loading and shooting cartridge rifle ammo. Typical diablo pellets have a flexible skirt that obturates under relatively low pressure and fills the grooves in the barrel, which are greater in number but not as deep as most firearm barrels. Since slugs are of a typical bullet design with a solid base, matching the correct groove diameter to the slug is, I believe critical to its stabilization and performance. The lead is not going to flow and fill the grooves under the same pressure as air rifle pellets, so the groove diameter needs to be compatible with the specific slug diameter. In short, I would be surprised if any randomly chosen air rifle barrel would shoot slugs consistently well. Just my thoughts, could be totally wrong. 
 
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Measured the diameter of the 12.5,10,and13.4 slugs the 13.5 and 12.5 measure the same but the 13.5 has a deeper cup in the base Can’t tell the difference in hardness specifically
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What is the diameter of the slugs, and what is the groove diameter of the barrel? In my experience with lead bullet loads for rifles and handguns, most shot best with the bullet at about .001" larger than groove diameter. But again, that relationship might not carry over to air rifle slugs.
 
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Well for anyone following my journey with 177 slugs this will probably be my last entry in this thread. I do believe at this point in time I’ve found the ticket for at least 1 slug to shoot very well and shoot well with pellets too. I can now after all the fiddling around shoot 10 shots in a .180 hole from the bench @ 10 meters and on first try from styx was able to keep 42 out of 50 inside 1 1/8 inch black with many 3&4shot groups@ 3/8” at 40 yds. Only time will tell. Will probably start a post on my field target fun starting next spring. Thanks to all that those to help me on this trip!
 
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