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How to slug a barrel? 🤔

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JungleShooter

JungleShooter

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How to slug a barrel? 🤔 ​


I keep reading how important it is to "slug your barrel" in order to play the slug game..... (And buy correctly sized slugs for the barrel.)

However, two things seem to never get explained in this context:
▪ How to "slug" the barrel
▪ How to measure what you "slugged"

I suspect, to most mechanically minded people these two things are so obvious that they don't require any further explanation.


To me, being less gifted on the mechanical side — I'm a bit lost...

Would you help me out?
Note, that I don't have a lathe in the garage, nor am I a hobby gunsmith, nor do I have a vast variety of tools at my disposal (I do have some).


I have only a made-in-China caliper — and I have no idea how I am supposed to measure the grooves(?) that the rifling put into the slug.... (Now you see just how confused I really am....)

Do I need to go through the hassle of removing the barrel? (More confusion....)


Thanks for any help, 😊

Matthias
 
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Take a lead bullet for your caliber. Set in on a solid surface and give it a light hit with a hammer in the axial direction. Doing this will fatten the bullet just a little. You only need it to increase a few thousands of an inch. Once you have your fattened bullet drive it into the muzzle with a wood dowel . Use short a short length of dowel at first and then progressively longer dowels as you drive the bullet to the breech.

FOR SAFETY DEGAS THE RIFLE FIRST

Use wood dowels so no harm will be done to the steel barrel.

When measuring the bullet once drive through the barrel. The outside diameter is the groove diameter of the barrel. The grooves in the bullet are the lands of the barrel.
 
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Thank you, Loren, for your super quick reply! 👍🏼😊
6 (six!) minutes.... AGN is awesome.


I hope you won't be offended as I use your answer as an example of all the other explanations that I read — and that I have no idea of how to follow them.

● I mentioned I don't have a large variety of tools:
What is a "wooden dowel"....? 🤦🏻‍♂️ (I know, I am mechancially challenged.)
Where can I buy a "wooden dowel"? — no, I currently don't live in the US — what are "wooden dowels" used for? — so I might find the type of store that might sell these.... 😊


● I mentioned I only have a China caliper, with regular thick measurement "arms".
How am I supposed use these to measure the tiny grooves in the slug....? 🤷🏻‍♂️ (Yes, I will need some extra explanation.)


Thanks, guys! I know, I'm lost.... 🤷🏻‍♂️

Matthias
 
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Matthias!
I hope that you are doing well.
A wooden dowel is a round piece of wood commonly used to form joints by drilling holes of corresponding dimension, and gluing the dowel inside that hole to strengthen the joint. Or filling screw holes (short pieces of dowel). They normally come in 2'-3' lengths and Loren's suggestion of using a short piece initially is an excellent choice, otherwise you will likely snap the dowel as it is smaller in diameter that the bore.
A dowel might look like a caged bird perch as a visual. They come in many diameters; you will need one to fit your bore loose enough to allow the pushing of the slugger piece.
As to measuring; It may require a small piece of very thin metal to 'wrap' around at least 180°'s of the slugged piece once you have pushed it into your barrel/liner, this is especially true if your barrel/liner has five lands as the odd number won't allow a direct measurement (if it has an even number of lands, then no thin metal is needed). Measure the very thin piece of metal that you are wrapping first and write that number down.
Wrap the thin metal around at least 180°'s so that now you have a 'flat' surface to measure (five lands can't be measured straight across due to your caliper landing on a land or groove) the diameter. Measure the diameter over the metal wrap and deduct the thickness that you wrote down (x2), giving you the true outside diameter of the slugged piece. The normal groove dimension, as I understand it, is usually .001" added to the now procured overall diameter.
You may wish to use some lubricant while pushing the slugger down your barrel/liner as it will make it easier to force it through.
Of course, if your barrel/liner has a choke, DO NOT PUSH THE SLUGGER into that part as it will not be a true diameter of the barrel. However, as others have now stated subscriber and bigHUN), pushing at least one or two through the choked area can help tell a story.
I hope that this helps!
Have a very Merry Christmas and a Happy New Year!
mike
 
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For driving a slug (or pellet) from the breech, you will need access to the breech. This probably involved removing the barrel from the action. Be careful when reinstalling the barrel, to line up the transfer port, retention screw dimples, and magazine depth clearance. In theory, all of these will coincide when correct.

Do not over tighten the barrel retention grub screws, or you will created bumps inside the bore opposite the screws. Rather make the screws just snug and use Loctite to prevent them from backing out. You can apply Loctite to the screw before "torqueing" it, but consider that a "wet" screw is lubricated, so go easy. Or, you can apply "wicking" Loctite after the screws are installed. See video below.

If you barrel is choked, the right size of slug for shooting might be the groove diameter at the choke, rather than just ahead of the breech. Or 0.001" over that diameter; or under it; depending on caliber, rifling type; "chamber" shape, size and length. You will get a lot of advice about the right size for a slug to shoot well, but it is one of those "it depends" situations. For a start, it depends on how heavy the choke it; or if there is one at all.

You might be slugging the barrel to find the right pellet size to shoot; or best slug size. You could try different pellet sizes and slug sizes, shoot them and determine which work best. Part of that equation is more about consistent projectile diameter, rather than "correct" average diameter - providing the projectile does not rattle down the barrel; or worse, out of the muzzle. Too tight and projectiles may be hard to load, distort on loading, then shoot poorly; or in some cases stick in the barrel. So, any "rule" about best projectile diameter may not always be true.

.22 PCP seem to be more efficient with slugs slightly under groove diameter. Larger caliber PCPs are more like firearms where you want to match the barrel groove diameter, or be slightly larger with your slugs.

You may want to drive some slugs (or pellets) all the way through the barrel; and some short of the choke to get a measure the barrel there. Also, just ahead of the breech by an inch or two.

Just pushing pellets through the bore from breech to muzzle will tell you a lot about the shape of the bore, because it may not be as parallel as we like to think. You can use a cleaning rod for that. If the bore has tight spots, the slug passing through will end up at that size and may drive a choice of an undersize projectile in the future.

Mapping tight spots would be useful, if you plan to lap them out, so the bore is more even down its length - short of the choke. Lapping a barrel bore may be "easy", but it is also an opportunity to turn a mediocre barrel into scrap. As with all activities to make things better; first do no harm.

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For smaller calibers, wood dowels may be too fragile to drive oversize slugs down the barrel. Then use a clean brass rod that is a little below the land diameter at the muzzle, so it does not get stuck when driven from the breech - in case there is a choke.

Forum threads about barrel bore slugging:
 
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You are in Peru if I remember correctly. What measuring system you have there? inches or millimeters.
Buy a micrometer, no need the most expensive but precise you can afford, I got this from amazon the precision is good enough in microns (I am a simple guy living with metric). Amazon or any machine shop supply store you have in your local. I show you this one because easy to read the digits and the cost is on lower end and good enough for home use.
I am pretty much doing a same as described above, push the slug half way into barrel and back it out from other side. I do this with my barrel cleaning CF rod.
I have small zip loc bags I put a sticker on with my notes which caliber / barrel / twist rate / and the measured size.
Also for a fun of it when I am done I push one slug all the way through the barrel through the choke, just to get an insight how much is the choke tighter. Same in a zip loc bag, put a sticker.

20231224_002939.jpg


The value is to document everything. We have a joke in my language : "literate people writing everything down, illiterate remember" ;)
 
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JMO ... In air guns ... if a slug is large enough to contact the Groove it has the potential to be very draggy and smear lead fouling barrel rather quickly.
A lot of shooters have found that so long as the LAND of rifling makes good contact and holds slug true to bore the minimal blow by of a slighter smaller to groove fit is not an issue.
Barrel with not foul as quickly or badly either.

Have found the same !!
Also I try and avoid shooting slugs in choked barrels
 
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Matthias
good to hear something from you.. I was worried about you since I can't remember last when we talked..
so I assume that everyone has their own way of doing it, but from my experience, especially if you don't know if you actually have a choked barrel would be to pull the barrel and go from the breach end.. you likely can just use your cleaning rod and if you are very careful, I have been actually able to measure twist rate with a cleaning swab.. just a mark on the cleaning rod and then watch for a complete revolution and then measure the distance traveled..
you will want to remove a moderator if installed because who knows where the slug will end up.. if you are not sure if it's a choked barrel.. then you can always push the first one through all the way and if it gets tighter when you get to the muzzle, then it's choked and that would give you the choke diameter..
then only go part way in and then push it back out with the cleaning rod and that's the regular bore..
now something came to mind when you were describing the calipers, you possibly have duplicating calipers? I have a few old ones that are basically not able to measure, because they don't have markings.. they are just useful for comparison..
I have all, so just a simple caliper with a dial indicator for down to 0.001 increments, I also have a cheap digital caliper from harbor freight.. China that seems good as any, especially for $25.. then since I do have said lathe and mill, I have a set of micrometers.. 0-6".. I rarely use those as for everything I do currently the digital caliper is good enough.. but I'd be worried about you using the micrometers because they have a spring loaded wheel so you tighten them down basically like a c clamp and the spring loaded wheel makes sure you tighten the same amount..
myself I would use pellets for slugging and no need to hammer them larger.. hopefully they already are and you will be able to easily see the lands and groove.. also they should be a lot easier to push than a tight slug.. now the issue is if you use pellets and they are hollow like most are.. I'm afraid of the micrometers tighten too much and getting bad reading because it crushed in instead of just measuring..
you can always try pushing in from the muzzle if you want to try to avoid pulling the barrel.. just remember if you start out tight and then it gets loose all the way to the breach.. then you have only the choke diameter..
I also assume that choke diameter is important because if it is a tight fit in the chamber or bore, slugs being solid might get stuck in the choke..
so hopefully between everyone you have a good idea of how to accomplish what you want.. please don't hesitate to ask any questions..
yes there those of us who have had experience with most things including machine shop.. but it doesn't make you less smart.. your just starting where we did, no knowledge of it.. and I personally can tell you if it was not for a friend who was a mechanic, welder and machinest.. I wouldn't have half the knowledge I have.. he actually took the time to show me how to do things and learn..
that's a valuable experience.. and while we might not be able to show you hands on, but I expect with the YouTube video and others you can easily learn this..
so if you don't understand anything please ask..
I don't always find these threads again.. yes I could use both help with computer and Internet and also memory for the next day 🤣
it's good to see you around..
also I seem to have disappearing pm messages, so you can just start a new pm if you want to ask me anything..
one more thing.. id use blue locktite for the setscrew on the barrel.. red locktite is too permanent.. I prefer to apply it to the outside thread of the setscrew and then put in.. I also have it in a, well like lipstick tube.. that one is really handy since it doesn't run, doesn't dry out in the tube and doesn't spill..
that kind that was mentioned above that seeps into the thread sounds interesting, I am going to have to check it out, my only concern is if it hardened up in the head of the screw, might be a issue for disassemble next time
Mark Hooper
 
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Motorhead said:
JMO ... In air guns ... if a slug is large enough to contact the Groove it has the potential to be very draggy and smear lead fouling barrel rather quickly.
A lot of shooters have found that so long as the LAND of rifling makes good contact and holds slug true to bore the minimal blow by of a slighter smaller to groove fit is not an issue.
Barrel with not foul as quickly or badly either.

Have found the same !!
Also I try and avoid shooting slugs in choked barrels
Click to expand...
I agree with you about the slugs and choked barrel.. probably not a good idea..
however I would have to wonder if unless the slugs have a small soft skirt to fully engage the rifling, might have a hard time completely sealing the air in?? also I think a skirt would be defeating the purpose of the slugs since I have read that the boat tail slugs are more accurate..
I have also been looking at swaging dies for slugs and I found a company that has a ring making attachments so they can be more like black powder bullets with the shallow groove so you end up with good rifling engaging and yet not full length dragging.. muzzle loader usually put some type of several different choices for lubricant in those grooves.. I think would be fine for PCP but I'd worry about dieseling in a spring gun..
oh PS has anyone heard of dieseling in a PCP, id think it would be possible but I haven't seen anything about it.
Mark
 
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markhooper said:
I agree with you about the slugs and choked barrel.. probably not a good idea..
however I would have to wonder if unless the slugs have a small soft skirt to fully engage the rifling, might have a hard time completely sealing the air in?? also I think a skirt would be defeating the purpose of the slugs since I have read that the boat tail slugs are more accurate..
I have also been looking at swaging dies for slugs and I found a company that has a ring making attachments so they can be more like black powder bullets with the shallow groove so you end up with good rifling engaging and yet not full length dragging.. muzzle loader usually put some type of several different choices for lubricant in those grooves.. I think would be fine for PCP but I'd worry about dieseling in a spring gun..
oh PS has anyone heard of dieseling in a PCP, id think it would be possible but I haven't seen anything about it.
Mark
Click to expand...
The slugs I cast are like that.

Screenshot_20231224-111036.png
 
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DesertSilver said:
The slugs I cast are like that.

View attachment 418600
Click to expand...
nice.. what does it cost to get into that, how do you melt the lead, grandpa used a white gas blowtorch and a ladle for sinkers.. I still have it, but I assume that there's a modern way now.. how many slugs per mold? just wondering how long it takes to make a decent batch..
myself I have not cast anything except babbit bearings and I was working with the supervision of a good old timer, but unfortunately I don't remember all the details.. was probably 15 years ago and only once..
thank you
Mark
 
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markhooper said:
nice.. what does it cost to get into that, how do you melt the lead, grandpa used a white gas blowtorch and a ladle for sinkers.. I still have it, but I assume that there's a modern way now.. how many slugs per mold? just wondering how long it takes to make a decent batch..
myself I have not cast anything except babbit bearings and I was working with the supervision of a good old timer, but unfortunately I don't remember all the details.. was probably 15 years ago and only once..
thank you
Mark
Click to expand...

DesertSilver said:
The slugs I cast are like that.

View attachment 418600
Click to expand...
I also figured that I could get a good barrel and fit it to a avenger X so it would be a straight bore and no choke.. just takes me a long time to get my own projects done..
Mark
 
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markhooper said:
looks like a propane torch and a funnel?
I don't understand about the title for lapping with the pictures.. I assume that it's for casting? any pics of the molds?
thank you
Mark
Click to expand...
When you perform barrel lapping you need to have so called barrel lead lap. You pour melted lead into the bore and that is your mold which produces a negative sculpture of your bore. Then you apply some polishing compound on the lap and you are ready to make your bore as consistent as possible. However, it is a time consuming process and it needs some practice to be done correctly. The funnel is there to make it easier to pour the lead into the bore.

IMG_20230927_195109~2.jpg

You may ask what it has in common with slugging of the bore. When you slug a bore you may notice some loose and tight spots. Lapping is a process to achieve a very consistent bore. So slugging and lapping are correlated. You slug then lap then slug and lap again. It takes a lot of time and patience but it allows you to achieve a perfect bore.
 
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markhooper said:
I also figured that I could get a good barrel and fit it to a avenger X so it would be a straight bore and no choke.. just takes me a long time to get my own projects done..
Mark
Click to expand...
You won't be happy with those slugs in your avenger. It has a very tight .215 groove diameter and the 30 grain BBT can't be sized down that far. The 25 grain slugs work much better after being sized down to .215.
https://noebulletmolds.com/site/shop/bullet-moulds/224/218-25-rf-d6/218-25-rf-d6-rg2-2-cavity/

I have a liberty which uses the same barrel as the Aspen, freedom, and avenger. Not sure about the X but I have a suspicion that it's the same barrel also. My liberty did real well with the 25 grain slug.
 
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