Boyd Allen
Active member
I am under the impression that barrel makers commonly use aluminum oxide to lap their barrels. Do any of you have any information or experience in this area that you can share?
Type of abrasive used to lap barrels?
- Thread starter Boyd Allen
- Start date
G
Gordy Gritters
Guest
Boyd, I lap a lot of barrels both in my shop and in my classes, and I know at least some of the barrel makers use similar methods/abrasives since this is where I learned some of my techniques for doing this. It's amazing just how much this will help a lot of barrels.
I generally use 150 grit aluminum oxide powder mixed with a thin grease to dress the lap when I have to lap a factory barrel and even up varying dimensions in a bore. Then after getting the bore where I want it with the 150 I use some 180 aluminum oxide to lay down the final finish end-to-end.
If I just need to smooth up a generally good factory barrel surface, correct minor bore dimension issues in a custom barrel blank, clean up smeared lands in a throat caused by someone chambering a barrel with a dull reamer, or just have to correct some minor bore damage, I'll usually use just 180 aluminum oxide.
I have also used 220 silicon carbide on occasion and got along fine, but I do prefer the aluminum oxide since it breaks down into a nice slurry and isn't too agressive. I do keep adding a thin oil to the lap after charging it with abrasive to keep it wet and help develop the slurry. Also, no matter what you use, you better figure on re-crowning the barrel in most cases.
Good luck!
Gordy Gritters
www.ExtremeAccuracyInstitute.com
I generally use 150 grit aluminum oxide powder mixed with a thin grease to dress the lap when I have to lap a factory barrel and even up varying dimensions in a bore. Then after getting the bore where I want it with the 150 I use some 180 aluminum oxide to lay down the final finish end-to-end.
If I just need to smooth up a generally good factory barrel surface, correct minor bore dimension issues in a custom barrel blank, clean up smeared lands in a throat caused by someone chambering a barrel with a dull reamer, or just have to correct some minor bore damage, I'll usually use just 180 aluminum oxide.
I have also used 220 silicon carbide on occasion and got along fine, but I do prefer the aluminum oxide since it breaks down into a nice slurry and isn't too agressive. I do keep adding a thin oil to the lap after charging it with abrasive to keep it wet and help develop the slurry. Also, no matter what you use, you better figure on re-crowning the barrel in most cases.
Good luck!
Gordy Gritters
www.ExtremeAccuracyInstitute.com
Boyd Allen
Active member
Gordy,
Thanks for the help. Like you, my friend has found that he can do a lot to help some barrels by doing some lapping, although it is still a work in progress, he has already gotten some interesting results.
Boyd
Thanks for the help. Like you, my friend has found that he can do a lot to help some barrels by doing some lapping, although it is still a work in progress, he has already gotten some interesting results.
Boyd
Ive used my friends kit from Brownells. I don't think what I do is lapping maybe just polishing but it has really helped on some of the barrels Ive tried it on. Check their website, I think the grit goes from 220 to 1000. He taught me to use a Parker/Hale jag and a tight patch and coat it with the paste and give it 25 strokes and clean it real well then go to a smaller grit and start over with that grit till you get to the 1000. Use a stop on the rod so that it just comes out the muzzle a little.
Boyd Allen
Active member
Thanks, my friend is using poured laps, and is able to remove tight spots and put a little choke at the muzzle, providing he has a small enough groove diameter to work with. What he needs now is to be able to come up with a finish that breaks in fairly easily to minimize jacket fouling. If he manages to do that, a little better, he will be there.
Gordy,
I seem to remember something about a lapping DVD. Is that still in the works?
Boyd
Gordy,
I seem to remember something about a lapping DVD. Is that still in the works?
Boyd
J
JRB
Guest
For those who have not yet slugged a barrel
What do you use for lead? Do you cast it?
How is this done?
Thanks
Jim
What do you use for lead? Do you cast it?
How is this done?
Thanks
Jim
For 22lr I pull a bullet from the actual cartridges that I will be using in competition. This way you can closely inspect the bullet under magnification after it has passed down the bore. You can use the same bullet more than once while you are learning the process of slugging. For a 'push rod' I use a piece of carbon fiber tubing left over from my RC airplane days.
D
doc gordon
Guest
lapping a bbl
i'm amazed you use 180-220 grit . I used neco kit years ago and now I know why it took so many passes ! I started with 400 and went up to 1200 however I wond up with some good shooting rem 700s and easy to clean.
i'm amazed you use 180-220 grit . I used neco kit years ago and now I know why it took so many passes ! I started with 400 and went up to 1200 however I wond up with some good shooting rem 700s and easy to clean.
G
Gordy Gritters
Guest
I know that 150 grit for the main lap and finishing up with 180 grit sounded like it would be too coarse to me also the first time I had one of the top barrel makers show me how they lapped barrels. But this is aluminum oxide on a poured lead lap, and then flooded with a light oil so it breaks down into a very fine slurry as you use it. When you're done and inspect the barrel with a borescope, it looks exactly like any of the top custom barrels inside, and works very well.
JRB, it works best to use pure lead in all bores, especially 22 cal and smaller. But it works OK to mix some wheel weights with pure lead on larger bores. In a nutshell, I melt the lead in a bottom pour lead pot, and pour it into the barrel to cast it over a cleaning rod jag, making a 2"-4" long lap, then use the rod to push and pull the lap through the bore.
An advantage of hand-lapping over fire-lapping is it is completely controllable and does not erode the throat forward like fire lapping does. I show and explain this in my upcoming DVD on hand-lapping rifle bores, which Boyd asked about.
Boyd, I had to put my Hand-Lapping instructional DVD project on the back burner for the past couple years when I moved from Iowa down to Kansas City. I recently got back to work on it, have most of the re-filming done I needed to do, and am in the final stages editing getting it ready to finish. I am so busy in my shop I haven't been able to devote the time needed to finish this DVD, which is taking way more time than I thought it would, but I am getting there - I promise!!
This subject of hand-lapping rifle bores for accuracy is something there is just not much good instructional information out there on, so that is why I teach it in my classes and why I am putting this DVD together to show anyone who is interested exactly how to do this themselves. I'll be sure to let everyone know when I do get it finished.
Gordy Gritters
www.ExtremeAccuracyInstitute.com
JRB, it works best to use pure lead in all bores, especially 22 cal and smaller. But it works OK to mix some wheel weights with pure lead on larger bores. In a nutshell, I melt the lead in a bottom pour lead pot, and pour it into the barrel to cast it over a cleaning rod jag, making a 2"-4" long lap, then use the rod to push and pull the lap through the bore.
An advantage of hand-lapping over fire-lapping is it is completely controllable and does not erode the throat forward like fire lapping does. I show and explain this in my upcoming DVD on hand-lapping rifle bores, which Boyd asked about.
Boyd, I had to put my Hand-Lapping instructional DVD project on the back burner for the past couple years when I moved from Iowa down to Kansas City. I recently got back to work on it, have most of the re-filming done I needed to do, and am in the final stages editing getting it ready to finish. I am so busy in my shop I haven't been able to devote the time needed to finish this DVD, which is taking way more time than I thought it would, but I am getting there - I promise!!
This subject of hand-lapping rifle bores for accuracy is something there is just not much good instructional information out there on, so that is why I teach it in my classes and why I am putting this DVD together to show anyone who is interested exactly how to do this themselves. I'll be sure to let everyone know when I do get it finished.
Gordy Gritters
www.ExtremeAccuracyInstitute.com
Last edited by a moderator:
J
JRB
Guest
Gordy, thanks for the reply.
Do you lap all your barrels, or only if you can see an imperfection or if it does not shoot to your expectations?
I have a new rimfire barrel and I can see some scratches in the bore in two different spots, can you make any recommendations
In both cases the marks are across one of the lands, they do not look to deep but are definitely a indent
Jim
Do you lap all your barrels, or only if you can see an imperfection or if it does not shoot to your expectations?
I have a new rimfire barrel and I can see some scratches in the bore in two different spots, can you make any recommendations
In both cases the marks are across one of the lands, they do not look to deep but are definitely a indent
Jim
G
Gordy Gritters
Guest
JRB, I only lap them if I need to - generally by what I can see in the borescope and especially what I can feel when slugging them. Slugging is integral to lapping since you can tell exactly what's going on in most cases when you slug a bore.
In your case, it depends on what the scratches look like, but if the bore dimensions feel OK when it is slugged, and you cannot feel anything at all when the slug passes over the scratches, and the scratch has not picked up copper or lead fouling (as seen in the borescope), I generally won't lap it.
If I can feel it even the tiniest bit with a slug or if it is picking up some copper or lead, I will lap it lightly and re-slug it until it's smooth and I can no longer feel it with the slug. If you can't feel the scratches with a slug, it means the scratch is below the surface and has not raised any metal above the surface, so the bullet will in most cases slide right over it without problems. To remove the scratch, you would have to lap the whole bore larger, which is often not good or even necessary.
Another integral part of slugging/lapping is accurately measuring the slugs so you know exactly what the bore diameter is. This can be done after pushing a slug all the way through (measures the tightest spot wherever it is in the bore), and then by pushing a slug in each end and then back out (measures bore dimension at each end to find taper and especially to make sure the crown end is the same or slightly tighter than the rest of the bore). If it's already too large diameter, you won't want to lap very much at all since it will just get larger. But if it's smaller and not oversize already, then you definitely have some room to work with and have more options on lapping problems out.
Hope this helps!
Gordy Gritters
www.ExtremeAccuracyInstitute.com
In your case, it depends on what the scratches look like, but if the bore dimensions feel OK when it is slugged, and you cannot feel anything at all when the slug passes over the scratches, and the scratch has not picked up copper or lead fouling (as seen in the borescope), I generally won't lap it.
If I can feel it even the tiniest bit with a slug or if it is picking up some copper or lead, I will lap it lightly and re-slug it until it's smooth and I can no longer feel it with the slug. If you can't feel the scratches with a slug, it means the scratch is below the surface and has not raised any metal above the surface, so the bullet will in most cases slide right over it without problems. To remove the scratch, you would have to lap the whole bore larger, which is often not good or even necessary.
Another integral part of slugging/lapping is accurately measuring the slugs so you know exactly what the bore diameter is. This can be done after pushing a slug all the way through (measures the tightest spot wherever it is in the bore), and then by pushing a slug in each end and then back out (measures bore dimension at each end to find taper and especially to make sure the crown end is the same or slightly tighter than the rest of the bore). If it's already too large diameter, you won't want to lap very much at all since it will just get larger. But if it's smaller and not oversize already, then you definitely have some room to work with and have more options on lapping problems out.
Hope this helps!
Gordy Gritters
www.ExtremeAccuracyInstitute.com
Mr. Gritters (believe we met at the 2005 Nationals at Pella, Iowa):
As you might have encountered, one thing that can happen to a barrel after around 1,000 rounds is what feels like a slight constriction 4-5 inches up the bore from the breech.
Such barrels can still shoot pretty good, but sometimes that wining edge seems gone. Have you ever tried lapping an older barrel with just this issue to try & restore it?
TIA
As you might have encountered, one thing that can happen to a barrel after around 1,000 rounds is what feels like a slight constriction 4-5 inches up the bore from the breech.
Such barrels can still shoot pretty good, but sometimes that wining edge seems gone. Have you ever tried lapping an older barrel with just this issue to try & restore it?
TIA
G
Gordy Gritters
Guest
Charles, yes I sure do remember meeting you at the Nationals - great time!
I have lightly lapped the first 6-8" or so of barrels a number of times to smooth up erosion and sometimes to quickly remove a buildup of fouling that someone has let get away from them, but have not done any lapping for that specific problem on a known accuracy barrel with that many rounds on it to see if it's original accuracy level would come back. I think it's a great idea that would definitely have some merit for some testing to see if the accuracy and/or barrel life on barrels like this would consistently improve/extend for a while longer. This is one of those things that I do think would help a worn barrel, but like most things like this, doing some actual testing with a number of known barrels to find out what really happens would tell us the real story here.
I definitely have felt the constriction you are talking about when slugging a worn barrel, but I believe this is more often roughness/surface friction from erosion than an actual bore constriction. In fact, when you measure the slugs to determine internal bore diameter, you will often find that on a worn-out barrel a slug will measure larger right ahead of the throat than the rest of the bore, even though it feels "tighter" on a slug. This is because the metal in the bore at this end has eroded away making the bore larger here (erosion goes much farther down the barrel than just the throat even though everyone always calls it "throat erosion"), but since the surface of the bore at this end is now rougher from the erosion, it feels with a slug like it's smaller/tighter.
I have felt this many times on a slug even when a barrel has only 100-200 rounds, and used to think it was caused by the bore being tight at the breech end. So one of the first times I felt this on my own barrel at the time, I lapped it lightly until it got smooth and even, then continued shooting (it continued to shoot great), but after 100-200 more rounds the tightness was back - hmmm?! What just happened - and why? There is definitely something to be learned here!
So I cleaned it agressively to make sure it wasn't powder fouling, which it wasn't, and then after seeing this happen on number of barrels I came to realize that it was not a bad barrel or a barrel-maker problem, but just that the surface friction of the bore was changing due to bore erosion.
So, Charles - I do think the barrel life will probably be extended a while, but since the bore is eroding away I'm not sure how much it can be extended. Testing by doing this to a number of barrels that the accuracy is starting to go away on will be the best way to determine just how much we will gain by doing this. It will be interesting......!
Gordy Gritters
www.ExtremeAccuracyInstitute.com
I have lightly lapped the first 6-8" or so of barrels a number of times to smooth up erosion and sometimes to quickly remove a buildup of fouling that someone has let get away from them, but have not done any lapping for that specific problem on a known accuracy barrel with that many rounds on it to see if it's original accuracy level would come back. I think it's a great idea that would definitely have some merit for some testing to see if the accuracy and/or barrel life on barrels like this would consistently improve/extend for a while longer. This is one of those things that I do think would help a worn barrel, but like most things like this, doing some actual testing with a number of known barrels to find out what really happens would tell us the real story here.
I definitely have felt the constriction you are talking about when slugging a worn barrel, but I believe this is more often roughness/surface friction from erosion than an actual bore constriction. In fact, when you measure the slugs to determine internal bore diameter, you will often find that on a worn-out barrel a slug will measure larger right ahead of the throat than the rest of the bore, even though it feels "tighter" on a slug. This is because the metal in the bore at this end has eroded away making the bore larger here (erosion goes much farther down the barrel than just the throat even though everyone always calls it "throat erosion"), but since the surface of the bore at this end is now rougher from the erosion, it feels with a slug like it's smaller/tighter.
I have felt this many times on a slug even when a barrel has only 100-200 rounds, and used to think it was caused by the bore being tight at the breech end. So one of the first times I felt this on my own barrel at the time, I lapped it lightly until it got smooth and even, then continued shooting (it continued to shoot great), but after 100-200 more rounds the tightness was back - hmmm?! What just happened - and why? There is definitely something to be learned here!
So I cleaned it agressively to make sure it wasn't powder fouling, which it wasn't, and then after seeing this happen on number of barrels I came to realize that it was not a bad barrel or a barrel-maker problem, but just that the surface friction of the bore was changing due to bore erosion.
So, Charles - I do think the barrel life will probably be extended a while, but since the bore is eroding away I'm not sure how much it can be extended. Testing by doing this to a number of barrels that the accuracy is starting to go away on will be the best way to determine just how much we will gain by doing this. It will be interesting......!
Gordy Gritters
www.ExtremeAccuracyInstitute.com
Boyd Allen
Active member
It is not just roughness that will make a tight patch push a little harder. Recently, I was working with some metal polish (Flitz) and found to my dismay that it polished the part of the bore that I was concentrating on rather quickly to a finish that was brighter than I wanted, and that this created more drag. Being concerned with getting more jacket fouling from too smooth of a finish, I reworked the bore with something slightly coarser, and the uniformity was restored. I was using the felt pellets. This barrel will probably show a little color, due to this experiment, that left it smoother than is ideal, but it seems to shoot well, and the color does not become extreme. The felt pellets are an interesting tool, but one needs to be cautious when using them in combination with cleaning abrasives due to the greater pressure that they exert on the bore. I have more testing to do using them with various solvents. One supplier has the German jags that secure two felts with a tiny nut. I think that this may be an advantage for some applications. Have any of you tried the VFG products? They are different from what we are used to, but interesting.
http://www.vfg.de/fileadmin/VFG/Broschüren/VFG_Waffenpflege_englisch.pdf
http://www.vfg.de/fileadmin/VFG/Broschüren/VFG_Waffenpflege_englisch.pdf
C
Crow99
Guest
Vfg
Boyd, where do you get these products? I've heard something like this mentioned in the past for use on newly reamed chamber throats to remove the initial toolmarks. I'm not sure how that would work out (maybe you've got some experience there) but it sounds interesting.
Boyd, where do you get these products? I've heard something like this mentioned in the past for use on newly reamed chamber throats to remove the initial toolmarks. I'm not sure how that would work out (maybe you've got some experience there) but it sounds interesting.
Boyd Allen
Active member
I've read where some folks feel that the "roughness" and/or "constriction" ahead of the throat may be attributed to firecracking??? That the cause is that the edges of the firecracked sections curl up like the playa slabs on a dry lake bed....
Anyone else remember this testing? Some was in articles and some was reported here on BRC.
al
Great thread BTW thanks Boyd and Gordy!!!
Anyone else remember this testing? Some was in articles and some was reported here on BRC.
al
Great thread BTW thanks Boyd and Gordy!!!
Boyd Allen
Active member
Thanks, what sort of abrasive do you polish throats with, and do you use the regular or heavy duty felts?
J
JRB
Guest
So why does a barrel quit shooting
Please ignore this is off topic, will start another thread.
I can see that making a bore uniform by lapping will improve accuracy, so what makes them quit shooting?
Jim
Please ignore this is off topic, will start another thread.
I can see that making a bore uniform by lapping will improve accuracy, so what makes them quit shooting?
Jim
Last edited by a moderator: