I had long ago bought a few AR-15 replacement barrels for a particular .20 Practical rifle that were made and chambered by a well-known, quality manufacturer. Time just came for the need of the last replacement. While I should have done this when I first bought the barrels, I just bore-scoped it, readying it for installation. The bullet entry slope on the lands has very uneven lateral machine lines across the top of the lands, which continue all the way up the slope. I realize the bullet will ultimately be compressed beyond the the slope as the bullet reaches the full height of the lands. I can't help but feel I am running the bullet over a cheese grater and that jacket damage will be inflicted before the bullet even gets going down the bore. So- what to do? I don't really have time to send the barrel back - and, given the length of time since I bought it, I feel hesitant to do so. Is there anything I can do myself to smooth this sucker out? I don't own a lathe. Or should I even be concerned? The rest of the barrel itself scoped out great. Guessing there was a bit of chatter at the end of the chambering process. There is no visible chatter in the chamber.
NEED GUNSMITH ADVICE
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1raggedhole
Silver $$ Contributor
Call John at White Oak and get one of his barrels. Best I’ve ever had.
RegionRat
Gold $$ Contributor
Not exactly what you are asking, but what I would like if it were me that did that chamber and you had a concern before you tried anything.
If you still have a good relationship with the folks who chambered the barrel, I would seek their council before I went very far. It is fair to them (and to you) since you would otherwise have to risk sending it back.
Send them the best photos of the issue you are concerned about and write them a note, then follow up with a ring and see what they advise.
If you still have a good relationship with the folks who chambered the barrel, I would seek their council before I went very far. It is fair to them (and to you) since you would otherwise have to risk sending it back.
Send them the best photos of the issue you are concerned about and write them a note, then follow up with a ring and see what they advise.
Deleted member fkimble@charter.net
Did you scope the previous barrels? They may have looked the same way. They will probably tell you to shoot it first before sending it back
Frank
Frank
Use Iosso bore paste on a stiff brush with a patch wrapped around it. This is going to be tough on a 20 caliber I know but it’s better than shooting it out at first. I lengthened my free bore on several of my rifles and the reamer left what I believe is the same thing you have. I believe if the manufacturer had lapped the barrel after chambering, you wouldn’t have these “burrs”. It’s similar to the burr that’s left when they drill the gas port but because it’s the whole circumference of the bore it appears really ugly. I had great results using the bore paste, it removed all the burrs and it helped set in the dimension of the bullet to lands. My polishing moved the bullet to lands measurement .007 from reamed to lapped and after about 200 rounds the measurement only moved another .002. All this is in a 223 bolt gun.
I have never tried to actually remove metal with the likes of Iosso, as these cuts are likely deeper than what a heavy polish will remove. I guess worse case - the bullets go over a somewhat smoothed out surface. I'm trying to find a hard felt polishing cone I can run in there with some lapping compound - but I think we both are thinking the same direction. Thanks
If you have the bore paste already, try it. I was surprised at what it did on mine. It might have been more of the action of passing over it in both directions bent the burrs back and forth and broke them off then the polish just prettied it up.
I'll give it a shot. I have some JB on hand - Iosso on the way. Do you feel the Iosso is more or less abrasive than the JB paste?
I only have Iosso. I was going to buy some JB but haven’t yet. I think they’re probably about the same though.
urbanrifleman
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That doesn't really mean anything. Just go shoot it.
jepp2
Gold $$ Contributor
You do realize that bore scopes tend to highlight things that might not be problems. The steps I would take are:
1. contact the barrel provider with good clear pictures that show what you believe might be a problem, to advise them of the potential issue.
2. mount the barrel, break it in, and shoot it. It might be the best accuracy barrel you have ever had and there may be no indication of any issues.
3. if it works fine, go on with life
4. if it has an issue followup with the barrel provider and update them on the situation.
But be prepared to hear from the barrel provider that the number of complaints they get from folks after bore scoping their barrels has to be seen to be believed. So many mis-calls on issues.
As others have alluded to, this sounds like the bite of the $50 borescopes. I mean, every bbl has these machining marks to some degree. Some are worse than others. Several factors as to why but you simply can't put a cutter to steel without some degree of tooling marks. If it shoots good and with minimal fouling..shoot it and don't worry about it. These inexpensive borescopes are great tools so long as we don't let things bother us that have been there all along...we just didn't look at them until now, nearly as much. To put the marks into perspective, which I think helps with not letting it eat at us from a psychological perspective...the lands are about .004" tall, which is about what the average human hair measures. That's the total height of that HUGE looking land under borescope magnification. Now think about the depth of those tooling marks as a percentage of that .004 tall land.
I have a reamer that makes an ugly throat in a barrel. It was that way when new. It has won a few national championship aggs, though. It's actually gotten better with a few chambers cut on it but no matter what I did, that particular reamer made an ugly throat. You could see the problem using a borescope to inspect the reamer. Under that much magnification, the dang thing looked like a serrated steak knife compared to other reamers. I needed it and kept it. For a while, I used a throating reamer to carefully lengthen the freebore about .010 to clean them up but the last several that that reamer has cut actually look pretty good.
FWIW, this area is where 90% of copper fouling down the bore of a barrel comes from but it typically gets better with break in and shooting, over a little time. JB or similar can make a notable improvement too. It's a subject for a different thread but fouling is virtually never because of a bad barrel. That copper fouling likely came from the throat and got deposited along the bore as temp and pressures fall as the bullet traverses the bore. That "copper wash" near the muzzle...came from the bullet passing over the throat, for the most part.
Shoot it and see how it does. Don't let the borescope get between your ears and your eyeballs. The target is what matters as long as fouling is minimal after a few rounds. Oh, and do not polish that bbl to a mirror finish. Too smooth will create more copper fouling than just about anything.
I have a reamer that makes an ugly throat in a barrel. It was that way when new. It has won a few national championship aggs, though. It's actually gotten better with a few chambers cut on it but no matter what I did, that particular reamer made an ugly throat. You could see the problem using a borescope to inspect the reamer. Under that much magnification, the dang thing looked like a serrated steak knife compared to other reamers. I needed it and kept it. For a while, I used a throating reamer to carefully lengthen the freebore about .010 to clean them up but the last several that that reamer has cut actually look pretty good.
FWIW, this area is where 90% of copper fouling down the bore of a barrel comes from but it typically gets better with break in and shooting, over a little time. JB or similar can make a notable improvement too. It's a subject for a different thread but fouling is virtually never because of a bad barrel. That copper fouling likely came from the throat and got deposited along the bore as temp and pressures fall as the bullet traverses the bore. That "copper wash" near the muzzle...came from the bullet passing over the throat, for the most part.
Shoot it and see how it does. Don't let the borescope get between your ears and your eyeballs. The target is what matters as long as fouling is minimal after a few rounds. Oh, and do not polish that bbl to a mirror finish. Too smooth will create more copper fouling than just about anything.
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I appreciate what you say, though I don't use a cheap borescope - and have scoped scores of barrels - both good and bad. I have just never seen one this rough on entry. I know the effects of borescopes in magnifying things that often don't matter. But this is one of those things that is definitely going to grate the bullet unnecessarily. I've already installed the barrel and will shoot it to see what it does - which I was going to do anyway. It is one of those things, like seeing big burrs on the outer feed lips in just the most critical spot- and you just know it isn't good. I'm going to polish it out the best I can, then shoot it. As you say, one never knows. I have a Ruger factory barrel that one would swear wouldn't shoot. But I shot a sub-.10 group with it using V-Maxes. Miracles never cease.....
Yeah - I'm not going to bicker with the barrel maker over this. I bought this thing a few years ago (bought several at the same time - and this is the last of the batch). What really does matter is whether it shoots - and it may shoot great. I'm just wanting to smooth it out regardless. I shoot thin-jacket varmint bullets at some high velocities. I want to minimize anything that I think might cause jacket problems. This is fixable - even though not shown to be necessary. Just looking for the best approach. Thanks
Yes, I should not have made that assumption about the cheap borescopes. It's just very common since they have come onto the scene is all. Post some pics. It'd be interesting to see how bad it is. Ultimately, it'll probably come down to how it shoots and copper fouls, I think. I would do a proper break in for at least 20 rounds and see if it cleans up inside of those, if it even fouls much anyway. If it's as bad as it sounds, I suspect it will foul but I'd give it a little break in time to see what happens. I had a bunch of photos get lost a while back when a phone crapped out on me. I had some pics of throats left by the reamer I mentioned earlier. It took a bit of work but they all eventually smoothed out and all those barrels shot fine afterward but it's also not worth a lot of time and components to get it there not knowing too. I wish I could post those pics. I was pretty upset with the reamer maker at the time but alls well that ends well and like I said, surprisingly, it got better after a few chambers. But those were ugly at first! Hopefully it won't be bad and it shoots lights out quickly for ya.
With nothing to lose, you can get pretty aggressive with it. I've lapped a few barrels into shape that I had given up for dead using 240 grit aluminum oxide paste then moving to finer grit. Just don't try for a mirror finish. It'll do more harm than good, IME.
I have a ruger mpr. Bore looks terrible with tooling marks all over compared to my custom barrels, tikkas, and cz. Stupid thing can shoot .4 pretty consistent from a stable table and my dumbass loading for it and driving it. If I would have scoped it before shooting id probably have declared it garbage and not even put a round down the bore. Glad I shot it first.
Are you wearing out 20p barrels shooting gophers? Are you running lead -free?
I run mostly leaded - but yes, I do wear them out. Probably half gophers and half larger ground squirrels further South. I see no difference in wear between leaded and unleaded. Once the tubes get around 7,000 rounds, the first inch of rifling is gone, and they lose their sharp accuracy just enough to want to replace them for fear it will go to hell in the middle of a hunt where I might shoot as much as 1,000 rounds of pre-loaded ammo out of each rifle I take. The rest of the barrel is not too bad, going 5" up the tube, but no longer sharp lands. I run Accurate LT32 almost exclusively, so can't really compare the wear from different powders. I run mostly 38 BK's, 32 V-Max (leaded and lead-free) and 40 V-Max mostly. I really do think these barrels would last far longer if I weren't getting them pretty warm. Terrific caliber. With my .223 tubes, I do run different powders and have one tube that has shot nothing but W748 since the first shot. It is the best looking .223 tube I have seen with an over-5,000 round count.
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