View Full Version : Barrel slugging

05-23-2011, 08:16 PM
Have any of you fellas ever slugged a barrel to check for tight or loose spots? Does slugging a barrel even tell you anything useful? Whats the proper way to even do such a procedure? I have a 6mm blank here that is pretty long for a ppc barrel. I like to order ,y blanks a little shorter but i bought this new blank second hand. Anyway i need to decide how we are going to cut it this thing. One main factor will be weight of course but i am also curious to know if there is any tight or loose spots in this barrel. Some fellas claim they like to have a tight spot at the muzzle, but i dont know anything about that. So if anyone has any info on slugging a barrel, please share. I dont recall ever reading anything about this here so i thought it might make for a good topic if nothing else. Lee

jackie schmidt
05-23-2011, 10:33 PM
Lee, I suppose every one of us have slugged a barrel, or barrels, at one time or another. A few years back, everybody got all excited about it, Since I had lots of bullet lead for cores I never used, I made slugs, and slugged some.

I talked with Krieger several years ago about their barrels being virtually straight in the groove diameter, and they said that they strived for that because they did not look at a barrel in it's static state. The looked at it when the chamber end is subjected to 50,000 psi. Their opinion was slugging a barrel that was just laying there was a waste of time, because when the chamber end is hit with the high pressure, it actually expands and creates a senarion where, in dynamic use, it actually has a "choke" toward the muzzle. If a shooter insist on lapping choke into a barrel, they are giving it way too much. That is one reason they strive to keep their groove diameters dead straight.

I agree with their synopsis what really happens to a barrel "in use", rather than it a static state. But, many gunsmiths and shooters obviously disagree with Kriegers thoughts on this, as I am sure you are about to find out.....jackie

05-24-2011, 05:23 AM
Lee, you would benefit volumes from contacting Gordy Gritters and inquiring about his next class dates. You can read all the theory you want here but with you not being a machinist or knowing much about it, you're not going to learn much from the words you read. Have you signed up for manual machining classes at the local tech school yet?

05-24-2011, 07:42 AM
My father is a tool and die maker for General Electric, and he is going to be my teacher, along with what i read here and there. I have thought many times about taking gordy's class. It isnt that far away. We also have a junior college here in the town i live in, but i am not sure they offer the kind of classes i would need? i will have to check into this again. I am a pretty sharp fella, and i pick up on things pretty fast. My mind never slows down, so i do have times were i just cant retain all that i wish i could. I am always eager for new knowledge, so maybe a professional class would be ideal. I wish i could get my hands on Gordy's video. I bet it would be very informational. Thanks lee

05-24-2011, 10:07 AM

Gordy has 2 videos out. Both have a lot of good info on them. He also wrote an article on slugging a bore in the Varmint Hunter magazine. I think it was The Nov. 2010 issue.


05-24-2011, 11:36 AM
I have an expensive borescope that will allow the user to see scratches, gouges, tears, throat and crown errosion, copper and carbon and other physical anomolies inside a barrel. The Borescope will not show you variances in bore diameter, tight and loose spots like slugging will. I took a mini course in slugging from Gordy on the telephone and I am in complete agreement that slugging tells one alot about a barrel.

Nat Lambeth

05-24-2011, 01:29 PM
Lee I agree with jackie I fail to see the benifit in slugging I check muzzle and breech if the muzzle is tighter I am good to go. That being said I am not intending to be a smart SOB and I am not taking away from your fathers skills as a tool and die maker .He can show you how to run the machines and perhaps turn you into a machinist . But unless he has the knowledge of what makes a gun shoot well I would see grody . Building guns is not like tool and die work . That career did not prepare me for building rifles .I was fortunate enough to live in and area where several old time gunsmiths had shops and learn from them . I also gathered up all the books and info I could find and I am still gathering after 40 years . Good luck with your endeavers Lee . T.R.

05-24-2011, 04:13 PM
I talk to a lot of different folks at shoots and on the phone all the time, and I am simple amazed or was amazed by the number of fellas that are not machinist nor have any real experience as a machinist, yet they have learned how to chamber barrels. I really don't think there is all that much involved. A little common sense and a little math and the help of an experienced hand, and a little " i want to learn this" and your half way there. I'm not saying it is easy but I just don't think it will be all that hard to do once I get my lathe and watch Gordy's video or take his class. Maybe I am wrong but I really don't think so. There sure are a lot of fellas out there doing it themselves. I also think it helps to be eager to learn or at least passionate. If I want something bad enough I will figure it out. Thanks fellas. Lee

Does anyone have any past issues of varmint hunter magazine? I just joined in march and i have only received one issue. I really enjoyed this magazine. If someone has a couple old issues i would pay the shipping to and from if i could spend a week or so reading them. I would return them in the same condition as i received them of course. Lee

05-24-2011, 08:00 PM
lee, sounds like you have the desire that is important . find a couple different approaches on barreling and your dad can apply some techniques he trusts or that makes sence to him . i use a couple of different techniques in my process that i was taught and have developed on my own . i will check for the magazines if i have them i will contact you with PM . T.R.

05-24-2011, 10:19 PM
While I am certain that the Krieger people know more about barrels than I ever will, it occurs to me that the 50,000 psi occurs behind the bullet. How this would impart an oversize condition in the bore for the bullet to pass through would make for an interesting discussion.

Wayne Shaw
05-25-2011, 08:19 AM
Skeet, first, don't let anyone discourage you from getting a lathe and doing your own work. With your Dad's help, you will learn a lot, and will learn to chamber a barrel very well. This forum has more info in it than anyone's video, but seeing is a good tool for learning. You'll make mistakes, you learn. There are more and more people doing this very thing, and winning matches!

Slugging is a great way to "know" a barrel. Most of the time it's a waste of time doing it with the barrels we have today. But there is always that one time where you should have done it. I have personally found a couple top shelf barrels that had issues, marked the barrel on the outside where the problem was, sent them back, and received phone calls confirming what I found. Replacement was very prompt. It happens to the best.

05-25-2011, 11:14 AM
This is interesting so I thought I would jump in here and relate some info that I have overheard this year. Wade Hull was at the Shamrock sitting across from me, he mentioned in a conversation about barrels, that it seems the hummers that they have produced seemed to be on the larger side of bore diameter. Also, I have heard from several bullet makers this year that it seems smaller bullets are working better (ie: .2428-.243). It was the conclusion of both that bullets in centerfire have so much pressure behind them that they are always trying to fill the bore.

I believe it is understood that you don't want a loose spot right at the crown but other than that, it seems to be all theory.

I'll try to get a hold of a film of a bullet going down a bore of a M40. I believe it was filmed at 140,000 or so frames per second. It looks like your shoving a golf ball down a garden hose....weird.


05-25-2011, 02:12 PM
When I first bought my lathe I decided to practice on rimfires before moving to centerfires. Less pressure, access to cheap blanks, $40 reamer :). Huge mistake. I did learn to do a decent threading job and do a concentric chamber and a nice crown and do a good bedding job but the guns would drive me crazy by shooting decent groups but also throwing a huge flyer at least a couple of times per target. I also got a lesson in turning a blank from 1.25" down to .825 or so. The most miserable chore I have done on my lathe !!!

Then I got a borescope. That showed me that I had work to do to the chamber after the reaming. The borescope also tells you how to clean.

Then I developed a method of slugging the bbls. I then knew where to put the crown [ still on rimfire bbls with choke or taper in the bore ]. I also refined my crown with a tiny radius to give the soft bullets a nice release. Now the bbls that would throw a 5 are now bbls that now shoot 10's and the 9's are me missing the condition change [ although 8 groove rifling also comes into play in this ].

On a centerfire the jacketed bullet covers a lot of errors. The tiny burrs in the throat that kill you on a rimfire get smoothed out/ carried away by the jacketed bullet and 50,000 + psi heat. Same on the crown. A tiny burr that would live there forever on a rf gets taken care of by the bullet, hot gas and the extra brushing a cf gets when compared to the rf.

Get a lathe and have at it. For a newbie the hardest thing is learning to cut good threads so practice this until you are able to do a good job of it. I have seen one job that looked more like a ratchet than a 60 degree thread !

jackie schmidt
05-25-2011, 03:54 PM
Lee, I agree with others, go for it.

I have always said that barrel chambering is something that I would consider any first year apprentice could handle. It is all common sense, and good old sound machine shop practice.

One thing I will instill in you. Learn WHY you do things a certain way, not just HOW to do things. Once you learn the basic tenants, you can apply them to a miriad of different machining operations that guys who do this for a living are faced with on a daily basis.........jackie

05-25-2011, 05:28 PM
We are going to get a lathe. That's almost a done deal. It won't be until fall as we still have a lot of work to do up at the new place. It will come though. In the mean time I can bug you fine fellas for info. Lol thanks guys. Lee

martin zuck
05-25-2011, 10:11 PM
Hovis, Many years ago the barrel maker G.R.Douglas made the same observation as Wade Hull. The larger diameter barrels within the acceptable tolerance range seemed to shoot better. He went so far as to state that he never saw a tight hummer.

05-25-2011, 11:41 PM
There was Rimfire guy who slugged barrels with great success. He has since passed away.