Slugged Avenger Barrel, Now What? (Help)

[EmptyTin_Tim]

Hey guys, I just slugged my Avenger barrel. I have polished and put a crown on it previously using @nervoustrig methods and just now opened the barrel port to 5mm and installed a weaker poppet valve spring and use a heavier hammer spring.

Took some photos of some ammo I have and yes I understand "use whatever gets best groups" but I would like some knowledge from you guys on what the results of slugging my barrel means.

I should have pushed the slugs through til the last bit then backed out and then looked at it vs one that went all the way through for choke but I thought of that after it was re assembled.. Also I pushed two of the same pellet through. You'll notice they look different, and that's because I pushed using my cleaning rod with a pointy jag on it then another go with nothing but the flat threaded end. You can tell especially with the pellets as the skirts got more flared with no jag.

I think maybe the jag wasn't totally centered so that's also why some look odd, they were pushed at a slight angle.

But anyway, overall, what do you think of these? Is there one you think would perform best based solely on the images? Any other insights?

I have FPS readings for these if anyone wants to know, too. 18.13 is my go to pellet but was trying heavier and some slugs recently.

 

[Ranchibi]

H'mmm....from what I am seeing for slugs I think you should push a couple .2155 diameter slugs thru to check contact, NSA makes .2155 in 17.5gr.

 

[EmptyTin_Tim]

Interesting, I thought slugs needed very good contact with the rifling in order to be stabilized and be accurate. You think even the .216 may be too big? Can you please share why that is? I am trying to learn the most I can!
I only just sat down at a bench yesterday and rough sighted in at 30 and then was hitting spinners at 55 yards with the .2165 at 1018.8 fps average is why I am making that comment.
I only had that size with me out there so I unfortunately couldn't compare paper results between the sizes.

 

[manabeknives]

here's a "how to" barrel slugging ..gonna need a micrometer

 

[LDP]

As the video shows the reason for slugging a barrel isnt for visual its so you can measure the bore dimension in order to have a better idea of what size slug will most likely be the most accurate in that barrel. If you dont have a micrometer find a friend that does or buy one. If you dont have access to one and you dont want to spend the money on a decent one then just shoot different slugs until you find the one the barrel likes.

 

[sb327]

If you are pushing a slug through that is under the groove diameter of the barrel, visual appearance is all you can expect to get. Most will claim that you need to slug a barrel but after that, there is no magic formula. So in the end, how precise you can measure it seldom makes a difference, the paper down range will be the best gauge.

Slugging a barrel to feel for barrel inconsistencies is obviously not the same as slugging to measure groove diameter.

Dave

 

[EmptyTin_Tim]

Thank you all for the replies. That's a very detailed video and I'm glad to have watched it. I do not have a micrometer, just digital calipers. But I do have a target and the ammo so I set it up at 30 yards and tested the ammo as suggested.

As shown but just to clarify: top row left to right was NSA 17.5 gr for first three in .216, .2165, and .217 diameter. 4th is FX 25.39gr 5.52mm. Then the 3rd row down is NSA 20.2gr in .216 and 3rd column over is .217. I didn't have .2165 in 20.2 gr that's why I skipped it. All were 10 shots per group and the barrel was cleaned beforehand.

I know the 17.5 gr .2165 is going average of 1018 fps so I think other two 17.5gr are similar. I believe the 25.39gr is about 900 fps and the 20.2 gr is about 950 fps, both based on previous reading but I didn't test this exact time.

So do you guys think the 17.5 gr and 20.2gr in .216 group size difference is because of the speed or that the 20.2 is longer and has more rifling contact?

Any other observations?

Thank you

 

[Scotay42]

Rifling contact. Less slug skirt on the lighter slug so 2165, more contact on the 20.2 so 216. Barrels and liners rely on how much contact is needed to stabilize the slug.

 

[EmptyTin_Tim]

Rifling contact. Less slug skirt on the lighter slug so 2165, more contact on the 20.2 so 216. Barrels and liners rely on how much contact is needed to stabilize the slug.

Makes perfect sense! I ordered some more 20.2 gr in .216 and threw in an order for .2165 just to see if they will work any better. The .217 in 20.2gr is a shotgun pattern so I don't have high hopes for the .2165 20.2 but I'll see.

On a side note I measured the rifling in my Avenger barrel at about 1:18 twist. It seems to still work for those 25.39gr pellets but I know it throws those around if the fps is lower than 900 fps or so. I'm thinking your comment still applies to the pellet since it has lots less contact with the rifling than the slugs but is in 5.52mm so it is tight to the rifling where it touches.