Barrel "slugging"

[liseo]

Hi


As I have no experience in making the lead barrel slug, I thought of using the bushings(tight fit) at the end of the cleaning rod and gently pushing through the barrel to feel any point that offered more resistance. The barrel was well lubricated with thick oil.
I decided to do this and noticed that at some points (every 3 inches)the cleaning rod was heavier to pass through the barrel.
It can be considered a valid method for checking uniformity?

what do you think?

Thanks

***A posted this on another forum, but seems nobody will answer...hope I have more luck here....

 

[jds holler]

I've slugged a lot of barrels to determine what diameter to size my cast bullets, but as a check for uniformity --- I dunno.

I have also felt what seems to be tight spots, but it may just be a characteristic of the lubrication, galling of the slug, or actual inconsistency in land or groove diameter -- rifling twist -- ??

I wonder if a nylon plug of appropriate diameter might be a better plug to use. Whatever you use, the barrel would have to be immaculately clean. jd

 

[Ggmac]

I've never pushed anything HARD down my barrels . The reason for lead is it will not harm your barrel and it's dead , it will not spring back . Once it's compressed at the bores tightest point it'll push easy till it hit something tighter . Usually slug from each end and Mark the rod and transpose to the barrel . Measure the slug after a complete pass . Use another slug to push up to but not thru or past the tight spot and measure . Measure one just pushed into the bore about an inch and push out from other direction , these will be your large bore measurement and the slugs driven completely thru will be your smallest .
I hope this makes sense.
I use double O buck shot or any LEAD black powder bullet or ball .

 

[liseo]

Thank you guys.

I understand the best way is with lead slug. Do you think the best barrel will have zero hight spots. 0r some tighter points are tolerable?

Or another way, your best shooting barrel is the more uniform? Or the´res no relation?

***sorry for language errors

 

[Alex Wheeler]

I lap barrels at times and when you pour a lap you can cut off 1/4" and save it for slugging. Or you can use any piece of lead about that size. Get it started in the bore and use a copper rod to bump it up to a tight fit. Use a cleaning rod to push it down the bore. A light grease in the bore helps. Once you get to the other end, bump it up again and go the other way. You can use this slug many times. I prefer as even a feel as possible, and you dont want the barrel to get looser toward the muzzle. I did have a barrel that was not stress relieved properly and the bore matched the out side contour. It was a #5 or so and as the barrel tapered down the id of the bore grew. Surprisingly it turned out to be a .5 moa barrel. It was from a newer maker and cheap, so the guy was pretty happy.

 

[DaveTooley]

Easiest way to make slug is make a ring with a hole a thousandths over bullet diameter about 3/8" high. Place lead in the hole and flatten with a punch to fill the void. Take a center punch or another flat punch the appropriate diameter and make a dimple in the middle to center your rod. On new blanks remove any burr at the bore, tap in the slug. I use a brass rod and tap the slug in an inch or so then get a short stiff cleaning rod and proceed with the investigation. I only check barrels from new, suspect manufacturers. Soon I'll have chambered 6,000 Bartliens and have never had a reason to slug one. Any of us that use button rifled barrels and are paying attention know that many times they will get slightly larger at the muzzle. Obviously not enough to affect performance but it's there. I don't question many barrel manufacturers. As with many things people agonize over, just because you question something, doesn't mean it will show up on the target. It's always a good practice to look, learn and shoot to determine what does and doesn't affect performance. YMMV

 

[Someoldguy]

Easiest way to make slug is make a ring with a hole a thousandths over bullet diameter about 3/8" high. Place lead in the hole and flatten with a punch to fill the void. Take a center punch or another flat punch the appropriate diameter and make a dimple in the middle to center your rod. On new blanks remove any burr at the bore, tap in the slug. I use a brass rod and tap the slug in an inch or so then get a short stiff cleaning rod and proceed with the investigation. I only check barrels from new, suspect manufacturers. Soon I'll have chambered 6,000 Bartliens and have never had a reason to slug one. Any of us that use button rifled barrels and are paying attention know that many times they will get slightly larger at the muzzle. Obviously not enough to affect performance but it's there. I don't question many barrel manufacturers. As with many things people agonize over, just because you question something, doesn't mean it will show up on the target. It's always a good practice to look, learn and shoot to determine what does and doesn't affect performance. YMMV

I found a factory button rifled barrel that was .0015" oversize at the muzzle. As was stated earlier in the post, the bore diameter matched the outside taper. Best way I can describe on range performance is consistently inconsistent. I blamed it on the bore diameter, but I was wondering, does .0015" sound excessive to you or about average for a factory button rifled barrel?

 

[DaveTooley]

I found a factory button rifled barrel that was .0015" oversize at the muzzle. As was stated earlier in the post, the bore diameter matched the outside taper. Best way I can describe on range performance is consistently inconsistent. I blamed it on the bore diameter, but I was wondering, does .0015" sound excessive to you or about average for a factory button rifled barrel?

That wouldn't surprise me in a factory barrel. I don't check factory barrels. I have better things to do than confirm what we already know. That is they are making them just as fast and cheaply as possible.

 

[Someoldguy]

That wouldn't surprise me in a factory barrel. I don't check factory barrels. I have better things to do than confirm what we already know. That is they are making them just as fast and cheaply as possible.

Good point. I've been told before that trying to determine the cause of inaccuracy in factory barrels is time better spent elsewhere. I can't help it. I just like to know the 'why'.

 

[DaveTooley]

This where I get curious. I chambered up three hammer forged 1.250" straight blanks for a customer. The finish was fine, dimensionally they weren't bad, slugged OK and they shot fair. Now the customer will start the process of turning them into the finished profile and see where accuracy really falls off and where in the process the problems arise.

 

[Someoldguy]

This where I get curious. I chambered up three hammer forged 1.250" straight blanks for a customer. The finish was fine, dimensionally they weren't bad, slugged OK and they shot fair. Now the customer will start the process of turning them into the finished profile and see where accuracy really falls off and where in the process the problems arise.

That's a process I'd like to be able to follow as well. I envy your position.

 

[Will Henry]

I have slugged a lot of barrels to check for size and uniformity. I use a lead ball, a piece of lead wire or whatever will fit the bore. Ill bump it up with two rods (one from each end of the barrel). Pushed through, the slug will measure the smallest point. If one is careful, he can measure either side of the tight spot. Of course, a loose spot cannot be measured with a slug unless said loose spot happens to occur at either end. I think all barrels are likely to have some variation but, in most cases, it is so minor as to be impossible to measure.
I also think many factory barrels get a bad rap. Some of the finest barrels I've seen have been hammer forged Winchester match barrels. Also some Hammerli barrels which were nothing short of superb. Some standard factory barrels are beyond acceptable and many are excellent.
I have re-contoured all kinds of factory barrels and, generally speaking, results have been just fine. These included barrels which were cut, buttoned, and hammer-forged. WH

 

[Someoldguy]

I have slugged a lot of barrels to check for size and uniformity. I use a lead ball, a piece of lead wire or whatever will fit the bore. Ill bump it up with two rods (one from each end of the barrel). Pushed through, the slug will measure the smallest point. If one is careful, he can measure either side of the tight spot. Of course, a loose spot cannot be measured with a slug unless said loose spot happens to occur at either end. I think all barrels are likely to have some variation but, in most cases, it is so minor as to be impossible to measure.
I also think many factory barrels get a bad rap. Some of the finest barrels I've seen have been hammer forged Winchester match barrels. Also some Hammerli barrels which were nothing short of superb. Some standard factory barrels are beyond acceptable and many are excellent.
I have re-contoured all kinds of factory barrels and, generally speaking, results have been just fine. These included barrels which were cut, buttoned, and hammer-forged. WH

If you would be so kind, what material do you use to 'bump up' the slug? Brass? Tape wrapped steel? something else?
I'm about to embark on a barrel slugging/lapping expedition, and so I'd appreciate any information you'd care to share. PM me if you prefer. I'm either going to break some new, (for me) ground, or I'm about to make several 'tomato stakes'. Either way, I'll learn a whole lot.
And thank you.

 

[rayjay]

My first experience with slugging was to find the tight spot in the choked section at the muzzle on the cheap Anschutz match bbls that Numrich has. These are actually very nice bbls internally. Fully polished and totally uniform from the chamber end all the way to the choked section. It was easy to determine where the tightest spot was. Once the slug is engraved it pushes down the bore with just about zero resistance and then the choke has just a bit of additional drag and then some looseness just before the slug leaves the bore. I was using 22 LR bullets that I carefully removed from live rounds.

Current state of the art RF bbls are constantly tapering and the slug takes a good bit of pressure to push. The relative few that I've slugged maintained a consistent resistance all the way down the bore.

 

[lloydx2]

I use (Neco) pure lead slugs, they come in different calibers. I normally cut them in half.
I have brass rods that are sized for each caliber. I buy these from MSC,Travers, ect.
I have a wood handle (dowel) that has a hole in it that I put over the rod to push with. I start with
shorter sections of rod to get the slug going. Using lots of oil. Sometimes if you use a rod that's to small in diameter,
it will want to expand the slug as you push it through (not good). Most Krieger barrels I have done always have
a tight spot about 1/2 inch from the breech end. I think this is something they are doing when profiling.
I am not really sure. But I have seen it with 4 of the last 6 I have done. Not much about .0002-3
It feels like a wall when your pushing slug in from the muzzle end. Other than that they are almost perfect.
I have never measured or felt any taper in the cut rifle barrels I have done. You can learn a lot from slugging.

 

[rayjay]

Eye openers for me :

I chambered up on of those Numrich Anschutz bbls and left it the full 1.25" dia. Later I turned it down to .825. I had run quite a few slugs down it before turning. After turning I could feel the torque shoulder just ahead of the threads. This was on a Remington 40X with their large threads. I ordered a PacNor nut and turned off the torque shoulder and extended the threads.

Another time I had a new bbl I was slugging and I had it mounted in my bench vise clamped between 2 hardwood blocks with a hole bored in them. I had the vise tight enough not to have to worry about the bbl slipping but not cranked down excessively. The first slug I pushed down showed a tight spot in the middle of the bbl. I pushed it back the other way. Yep, tight spot. Oh, wait a minute. The tight spot was the section at the wood blocks. Remove the bbl from the vise and no more tight spot.

 

[gunsandgunsmithing]

Slugging a barrel can point out problems but it can't guarantee a good barrel. I've done some slugging as well as some lapping. Most all premium barrels are lapped before shipping. Lapping can help(or hurt) a barrel but I don't think CF is nearly as critical as RF when it comes to "choke" in a barrel. But you do want a good and smooth feel to the slug while pushing. Actual bore dimensions and choke are not that important to me as long as it shoots. Reason being, there is so much pressure with cf that the barrels swells every time you fire the gun and the bullet simply obturates to fit the bore under pressure, with a "natural" choke due to pressure dropping as the bullet travels down the barrel.

Actual bore dimensions can help with controlling starting pressures...and pressures in general, much the same as using "fat" or "skinny" bullets.

When possible, I have made laps in the cut off from the barrel. I prefer the lap to be 2.5-3" long.

 

[Macropod]

On the subject of putting a choke in a barrel...

This is a modified ER32 collet chuck fitted to a 308 medium Palma barrel turned to 20mm for 40mm from the muzzle. The objective was to add weight to the end of the barrel and provide some choke effect. It appears to work as first time out it shot 0.15 - 0.18moa groups at 100m. That was the best it had ever achieved. This barrel had 2800 rounds down it at this point. Definitely can feel the constriction pushing a patch or slug at the last 40mm to the muzzle. The things we do...

 

[langenc]

Thank you guys.

I understand the best way is with lead slug. Do you think the best barrel will have zero hight spots. 0r some tighter points are tolerable?

Or another way, your best shooting barrel is the more uniform? Or the´res no relation?

***sorry for language errors

Tightest spot should be the last few inches in the barrel.

Get some of Bill Calfees writings on the subject. He wrote for Precision shooting for quite a while. He has a book about rimfire rifle building. He switched to RF from CF many yrs ago.

 

[RW]

I also use the same method as lloydx2 I read a article that Gordy Gritters wrote about lapping a barrel and he used Neco lead slugs with brass rods of different length brass rods to push them thru and a socket in a handle to start the slugs. If the slug gets a little loose you use a brass rod from apposing directions to tighten it up! I talked to Gordy and he talked me thru it. I think he has finally made a video om how he doe's it. RW