Barrel slugging

[DShortt]

I've encountered several centerfire rifle barrels that shot inconsistently. After checking all the usual suspects such as loose hardware, defective scopes and bedding problems I decided to slug the barrel and have been very surprised. A couple wound up being larger at the muzzle by .0015" and .002" and one had constructions at all the dovetails and at the caliber/maker stampings.

So I am curious. I've taken to slugging all my barrels and frankly I've been very surprised by what I've found. I won't drag anyone's name through the mud because the issues were resolved once I pointed them out to the manufacturer but I'm interested.

How many of you slug a barrel before chambering it and why or why not?

Thanks for looking.

 

[Henryrifle]

I have intended to try this out and even purchased slugs in several calibers, but am yet to try it. I only think I know how to do it: lube the slug, drive it into the barrel and as you push it down the bore you should feel a consistent friction from the slug -- maybe you push it back a forth a few times... Is that roughly correct?

Hank

 

[LVLAaron]

I do. Since I learned the basics of it I wish I had some of the barrels I've owned that shot like garbage.

It takes 5 minutes to slug a barrel. I don't generally tell people I do it. If I find one that has what I think is a problem... I'll share... 9 times out of 10 I'd bet that people say "chamber it anyway, it takes 14 months to get a new blank, I'll take my chances"

 

[jackieschmidt]

.0015 to .002 is a HUGE amount in the realm of custom barrel making.

Besides, they should never be looser at the muzzle end.

I have slugger several barrels for myself, but the ones I use feel pretty consistent all the way through.

I don’t think you should feel bad about letting everybody know the name of the manufacturer. Their quality control leaves something to be desired.

 

[DShortt]

.0015 to .002 is a HUGE amount in the realm of custom barrel making.

Besides, they should never be looser at the muzzle end.

I have slugger several barrels for myself, but the ones I use feel pretty consistent all the way through.

I don’t think you should feel bad about letting everybody know the name of the manufacturer. Their quality control leaves something to be desired.

I think everyone makes mistakes occasionally. I know I do. The most important thing is how someone responds once a mistake is identified. Thus far no one has denied a mistake was made. My question is primarily because I'm curious just how many others check for things like this.

 

[DShortt]

I do. Since I learned the basics of it I wish I had some of the barrels I've owned that shot like garbage.

It takes 5 minutes to slug a barrel. I don't generally tell people I do it. If I find one that has what I think is a problem... I'll share... 9 times out of 10 I'd bet that people say "chamber it anyway, it takes 14 months to get a new blank, I'll take my chances"

Interesting. I don't know why someone would take a chance like that but my opinion is just that. My opinion. At least I know someone else is doing this and has noticed problems. I was wondering if it was just me and very poor luck.

 

[DShortt]

I have intended to try this out and even purchased slugs in several calibers, but am yet to try it. I only think I know how to do it: lube the slug, drive it into the barrel and as you push it down the bore you should feel a consistent friction from the slug -- maybe you push it back a forth a few times... Is that roughly correct?

Hank

That's essentially how I do it. I use slugs of dead soft lead an inch long. Hard to detect a rate of twist problem with anything shorter. I don't buy slugs, I use mold blocks I made slightly over diameter for the barrel blank. As with most things, take your time and be careful. Also, I don't use wooden dowels because of the risk of breaking. Personally I use drill rod very near bore diameter. Caution is required.
I slug both ends and measure with a micrometer. Push the slug in an inch or so in the barrel blank to ensure you're away from the end. Just like crowning a barrel, the extreme ends might be oversize a bit. I then push the slug back and forth 3-4 times to check for any abnormalities. It doesn't take long to get a 'feel' for it.

Edit to add - more than once I've had a slug that would become very loose toward the middle and literally fall out of the muzzle if the barrel was slanted that direction. They didn't shoot very well, either. Random, unexplained fliers until slugging was performed.

 

[jackieschmidt]

I think everyone makes mistakes occasionally. I know I do. The most important thing is how someone responds once a mistake is identified. Thus far no one has denied a mistake was made. My question is primarily because I'm curious just how many others check for things like this.

I am in the Machine Shop Buisiness.

True, there can be a mistake in any machining operation. The problem arises when you let it get out the door. If you do, and the faulty part ends up costing large amounts of down time for the customer, my shop can be held responsible for the cost incurred.

I impress upon my men that if they make a mistake on anything, myself or one of my brothers must be informed. Making a mistake is human. Letting it get out the door is unexceptable.

That’s the nature of manufacturing.

Suppose a barrel manufacture lets a barrel out the door that is as bad as yours. You pay a gunsmith up to $600 to chamber it, plus t all the shipping.

Then you spend money on components trying to get the thing to perform at an acceptable level.

The manufacturer says…”no problem, we will send you a new blank”.

Did the manufacture offer to pay your other cost. If he did, then all you are out is your time and good for him.

If he didn’t, then he is just out a barrel that he might have about $100 invested in.

 

[Dusty Stevens]

I am in the Machine Shop Buisiness.

True, there can be a mistake in any machining operation. The problem arises when you let it get out the door. If you do, and the faulty part ends up costing large amounts of down time for the customer, my shop can be held responsible for the cost incurred.

I impress upon my men that if they make a mistake on anything, myself or one of my brothers must be informed. Making a mistake is human. Letting it get out the door is unexceptable.

That’s the nature of manufacturing.

Suppose a barrel manufacture lets a barrel out the door that is as bad as yours. You pay a gunsmith up to $600 to chamber it, plus t all the shipping.

Then you spend money on components trying to get the thing fixed.

The manufacturer says…”no problem, we will send you a new blank”.

Did the manufacture offer to pay your other cost. If he did, then all you are out is your time.

If he didn’t, then he is just out a barrel that he might have about $100 invested in.

Theyre quick to replace a barrel, not so quick to pay for a rechamber/refit

 

[DShortt]

I am in the Machine Shop Buisiness.

True, there can be a mistake in any machining operation. The problem arises when you let it get out the door. If you do, and the faulty part ends up costing large amounts of down time for the customer, my shop can be held responsible for the cost incurred.

I impress upon my men that if they make a mistake on anything, myself or one of my brothers must be informed. Making a mistake is human. Letting it get out the door is unexceptable.

That’s the nature of manufacturing.

Suppose a barrel manufacture lets a barrel out the door that is as bad as yours. You pay a gunsmith up to $600 to chamber it, plus t all the shipping.

Then you spend money on components trying to get the thing to perform at an acceptable level.

The manufacturer says…”no problem, we will send you a new blank”.

Did the manufacture offer to pay your other cost. If he did, then all you are out is your time and good for him.

If he didn’t, then he is just out a barrel that he might have about $100 invested in.

You are absolutely correct. That's why I started slugging blanks. Again, I don't want to drag anyone's name through the mud here because that's not the purpose of this thread. I'm just really curious if anyone else slugs barrels and what they have found. Maybe I just have shit for luck?

 

[whatsupdoc]

Is there a detailed how to document or video?

 

[DShortt]

Is there a detailed how to document or video?

Sending a PM.

 

[hoz53]

Sending a PM.

Gordie Gritters talks about slugging bores in his videos and how he does it and that he always does it. I bought some neco slugs and brass rod to do it but havent yet. i will start though. one thing i wonder if it effects the results is tapping the slug back out. thanks

 

[DShortt]

Gordie Gritters talks about slugging bores in his videos and how he does it and that he always does it. I bought some neco slugs and brass rod to do it but havent yet. i will start though. one thing i wonder if it effects the results is tapping the slug back out. thanks

I don't think so because my experience has been that once they are introduced into the bore it takes little pressure to remove them. Basically just hand pressure unless there is a problem with the bore and *usually* you would need to move them 3" or so to detect a difference. Of course there can always be exceptions.

 

[Dusty Stevens]

If you push them thru a tight spot that is as big as they will get so if youre trying to measure a spot past that you have to bump them back up. They wont re-expand like say if your muzzle is bigger and youre pushing from the chamber end, say the muzzle has .0001 choke your slug will be that size. If youre just feeling for tight spots you gotta bump it back up once you pass that spot or you may miss the next one. One danger is if you call a barrel mfr and tell them you were slugging their barrel and found an issue theyll probably hang up on you. They dont know your skill level and can just envision you beating a slug thru their barrel.

 

[BoydAllen]

A friend casts laps for the same purpose. He has found the sources of numerous potential accuracy problems before starting machining, and diagnosed many rifles' accuracy problems that way. He calls it mapping the bore. Another thing that he uses this procedure for is to measure groove diameter and choke.

 

[LVLAaron]

High-Strength Formable 544 Bearing Bronze​

^ Use that instead of drill rod / tool steel. Get 6 feet of 1/4 and 3/16. Cut to various lengths and you've got all your calibers and barrel lengths covered. I cut some 6 inch pieces to get the slugs started.

 

[rwj]

What degree of variation would one expect from gun drilling a small diameter hole over a relatively long distance?

 

[LVLAaron]

What degree of variation would one expect from gun drilling a small diameter hole over a relatively long distance?

More than you'd expect. Drilling sucks. That's why they hand lap them. When lapping you can feel the tight/loose spots... work the tight spots.

I had a 30 inch FTR barrel that was loose for 9-10 inches in the middle. You could tell just running a patch through it. What matters is that the muzzle end is the smaller diameter

 

[Larryh128]

I've encountered several centerfire rifle barrels that shot inconsistently. After checking all the usual suspects such as loose hardware, defective scopes and bedding problems I decided to slug the barrel and have been very surprised. A couple wound up being larger at the muzzle by .0015" and .002" and one had constructions at all the dovetails and at the caliber/maker stampings.

So I am curious. I've taken to slugging all my barrels and frankly I've been very surprised by what I've found. I won't drag anyone's name through the mud because the issues were resolved once I pointed them out to the manufacturer but I'm interested.

How many of you slug a barrel before chambering it and why or why not?

Thanks for looking.

New lapped barrels are normally going to be looser at both ends, that's why they recommend cutting an inch off both ends. Probably not necessary at the chamber end but definitely necessary on the muzzle end.