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Rifle Bore Machining Marks ?
- Thread starter Hylander
- Start date
Looks to me it's identical to many excellent barrels that were reamed to finish bore diameter after gun drilling the barrel (evidence is the micro grooves at right angles to the bore axis across the tops of the lands) then rifled (evidence is the lengthwise tinier micro grooves in the bottom of the lands at groove diameter) such that the rifler didn't take off any metal atop the lands.
I shot many a 7.62 NATO Garand barrels that looked exactly like that. Gun drilled, reamed then broach rifled; all 4 grooves at once. They easily shot no worse than 1/3 MOA at 100 yards, 2/3 MOA at 600 with jacketed bullets. Their bore diameter was .2995" and groove diamter was .3078" to .3079".
If your barrel's groove diameter is a bit smaller than jacketed bullet diameter, it may well drive tiny headed tacks. Shoot that barrel to see how it performs. It looks good to me.
I shot many a 7.62 NATO Garand barrels that looked exactly like that. Gun drilled, reamed then broach rifled; all 4 grooves at once. They easily shot no worse than 1/3 MOA at 100 yards, 2/3 MOA at 600 with jacketed bullets. Their bore diameter was .2995" and groove diamter was .3078" to .3079".
If your barrel's groove diameter is a bit smaller than jacketed bullet diameter, it may well drive tiny headed tacks. Shoot that barrel to see how it performs. It looks good to me.
I've seen worse on big-name barrels.
Yes, it will tend to foul, but probably no worse than a normal factory barrel from any of the big-name rifle makers (RemSavChester, etc).
This is the reason why the best custom barrels are lapped.
Once you start looking down bores with a borescope, you will be amazed at what you see. Furthermore, I've looked down some bores that look absolutely horrible... but shot quite accurately.
Yes, it will tend to foul, but probably no worse than a normal factory barrel from any of the big-name rifle makers (RemSavChester, etc).
This is the reason why the best custom barrels are lapped.
Once you start looking down bores with a borescope, you will be amazed at what you see. Furthermore, I've looked down some bores that look absolutely horrible... but shot quite accurately.
They have a rep for being harder steel than most other barrels. I've never personally used one.
BTW, you can lap your own barrel blank before you chamber and crown it... so if marks in a barrel really bother you, you can do something about it. Start at about 800 grit lapping compound and work your way to finer grits. Takes at most a couple hours.
BTW, you can lap your own barrel blank before you chamber and crown it... so if marks in a barrel really bother you, you can do something about it. Start at about 800 grit lapping compound and work your way to finer grits. Takes at most a couple hours.
http://www.lothar-walther.com/268.php
These are pre-threaded and long chambered,you do not need a chambering reamer unless you "miss"
Careful depth mic work ,rec ring to diaphram,rec ring to bolt face,"go" gage protrusion from the chamber of the bbl,make a sketch.You want a little crush on the end of the barrel,to the diaphram,I shoot for .001 to .002.Others may have advise.
I have depth mics,and the Starret mic you can change the fixed anvil...multi-mic? the kind you can put a pin in for neck thickness.Well,I take the clamp clear off and it becomes a small height mic.Works good to measure the headspace gage protrusion from the chamber.
If you prefer not to just boldly cut to numbers,remember you can use shims or feeler gage like if you use a .005 shim between the bbl end and the diaphram,try the go/nogo.If the go just goes and the no go won't,you have .005 to take off yet.If the nogo goes,take the shim out,gage again.You might be done,etc.
I have one of the Walther 718 contour bbls,very light,about a #2 Douglas.Threads,a fine snug fit,all finish,beautiful.
They are listed at $226,threaded,excellent exterior finish,long chambered.Does not seem expensive to me.
http://www.lothar-walther.com/337.php
I have never used a McGowen barrel,but Harry has been making them a long time,seems 40 years,anyway.I was looking at a .405 WCF blank on his page,he'll custom contour,octagon..
Generally,if you do not make a good product,you won't last 40 years.
These are pre-threaded and long chambered,you do not need a chambering reamer unless you "miss"
Careful depth mic work ,rec ring to diaphram,rec ring to bolt face,"go" gage protrusion from the chamber of the bbl,make a sketch.You want a little crush on the end of the barrel,to the diaphram,I shoot for .001 to .002.Others may have advise.
I have depth mics,and the Starret mic you can change the fixed anvil...multi-mic? the kind you can put a pin in for neck thickness.Well,I take the clamp clear off and it becomes a small height mic.Works good to measure the headspace gage protrusion from the chamber.
If you prefer not to just boldly cut to numbers,remember you can use shims or feeler gage like if you use a .005 shim between the bbl end and the diaphram,try the go/nogo.If the go just goes and the no go won't,you have .005 to take off yet.If the nogo goes,take the shim out,gage again.You might be done,etc.
I have one of the Walther 718 contour bbls,very light,about a #2 Douglas.Threads,a fine snug fit,all finish,beautiful.
They are listed at $226,threaded,excellent exterior finish,long chambered.Does not seem expensive to me.
http://www.lothar-walther.com/337.php
I have never used a McGowen barrel,but Harry has been making them a long time,seems 40 years,anyway.I was looking at a .405 WCF blank on his page,he'll custom contour,octagon..
Generally,if you do not make a good product,you won't last 40 years.
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Harry McGowen sold McGowen Barrels in 2007. The new owners make top quality barrels at reasonable prices.I have never used a McGowen barrel,but Harry has been making them a long time,seems 40 years,anyway.
wyop claims:
Buy an air gauge with its gauging head matched to your bore and groove profile, or, buy a hole micrometer accurate to sub 1/10,000th inch long enough to reach the middle of the bore from either end.
Learn how to use either bore gauge so you get repeatable numbers measuring the same point in the bore.
Learn how to make a lapping head out of some soft metal that matches your bore and groove profile. Then make one.
Learn how to charge that lap with the right compound and use it to best advantage. Got a barrel to use as a training aid to practice with?
Get the feel of lapping the bore and measuring its diameters from breech to muzzle so they're at least as uniform as the original bore. Use that barrel you practiced lapping with.
And finally accept the fact the the lapped bore will have greater bore and groove diameters than it originally did.
Otherwise. . . . you'll probably make that barrel not as good as it was in the beginning. But it will have the smoothest finish on all those hill and valley high and low spots that hurt accuracy.
True, but one needs to do something else first. . . .BTW, you can lap your own barrel blank before you chamber and crown it... so if marks in a barrel really bother you, you can do something about it. Start at about 800 grit lapping compound and work your way to finer grits. Takes at most a couple hours.
Buy an air gauge with its gauging head matched to your bore and groove profile, or, buy a hole micrometer accurate to sub 1/10,000th inch long enough to reach the middle of the bore from either end.
Learn how to use either bore gauge so you get repeatable numbers measuring the same point in the bore.
Learn how to make a lapping head out of some soft metal that matches your bore and groove profile. Then make one.
Learn how to charge that lap with the right compound and use it to best advantage. Got a barrel to use as a training aid to practice with?
Get the feel of lapping the bore and measuring its diameters from breech to muzzle so they're at least as uniform as the original bore. Use that barrel you practiced lapping with.
And finally accept the fact the the lapped bore will have greater bore and groove diameters than it originally did.
Otherwise. . . . you'll probably make that barrel not as good as it was in the beginning. But it will have the smoothest finish on all those hill and valley high and low spots that hurt accuracy.
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As I indicated above, I've seen barrels in a bore scope that looked like a beaver reamed them - and they could shoot well. If someone is worried about reamer or button rifling marks before they've shot a barrel, well then, I don't think they're terribly worried about air gaging the barrel - or shooting to less than a minute.
Someone asked about reamer marks, I told them how to get rid of reamer marks.
If they wanted to not have reamer marks and they wanted the barrel to shoot to maximal accuracy, then they should have had their priorities in a different order.
Someone asked about reamer marks, I told them how to get rid of reamer marks.
If they wanted to not have reamer marks and they wanted the barrel to shoot to maximal accuracy, then they should have had their priorities in a different order.
“Learn how to make a lapping head out of some soft metal that matches your bore and groove profile. Then make one”
Bart B. teach him, show him, some of the equipment you are pushing cost $3,000 and up.
Wyop, as you know anyone that can lap a barrel is not much of a barrel lapper if he needs a micrometer to measure the barrel diameter for consistent diameter, then there is that part where Bart B. says
“Buy an air gauge with its gauging head matched to your bore and groove profile, or, buy a hole micrometer accurate to sub 1/10,000th inch long enough to reach the middle of the bore from either end”
When I slug a barrel the weak pass out and the strong get dizzy,
“Learn how to make a lapping head out of some soft metal that matches your bore and groove profile. Then make one”
I use universal fit all material that matches all bores that automatically adjust to groove profile and bore diameter.
Then there are (us) casters that can roll their own, then there is the Internet, for sale, lapping bullets, not a fan but some swear by the process.
F. Guffey
Bart B. teach him, show him, some of the equipment you are pushing cost $3,000 and up.
Wyop, as you know anyone that can lap a barrel is not much of a barrel lapper if he needs a micrometer to measure the barrel diameter for consistent diameter, then there is that part where Bart B. says
“Buy an air gauge with its gauging head matched to your bore and groove profile, or, buy a hole micrometer accurate to sub 1/10,000th inch long enough to reach the middle of the bore from either end”
When I slug a barrel the weak pass out and the strong get dizzy,
“Learn how to make a lapping head out of some soft metal that matches your bore and groove profile. Then make one”
I use universal fit all material that matches all bores that automatically adjust to groove profile and bore diameter.
Then there are (us) casters that can roll their own, then there is the Internet, for sale, lapping bullets, not a fan but some swear by the process.
F. Guffey
The point I was making was missed, and I'm sorry I caused people to waste time responding. I'll clear this up in excruciating detail right now.
1. When a gunsmith starts showing people what bores actually look like through a borescope, many customers recoil in horror.
Increasingly, I think that a gunsmith showing most customers what barrel bores actually look like is a mistake, unless we're pointing out some specific damage eg, pitting or throat erosion. Showing customers what a new rifled bore actually looks like (as compared to what they perceive from either end of the barrel held up to the light) just seems to invite all manner of obsession by customers.
I've seen bores that looked like what the OP photographed there.... and worse. Much worse. An example: I've got a barrel on an AR-15 that looks like it was reamed by a bionic beaver... and yet it shoots what I would consider pretty well for what it is. BTW, this barrel won't even pass military go/no-go gage requirements, especially the barrel straightness gage. The price was right - dirt cheap. So I slapped it onto a carbine and ran some ammo through it. I figured "OK, it's $50. Let's experiment and see just what a failed barrel looks like on paper."
I can group five rounds from just over 2" to about 2.75" at 100 yards off the bench, depending on how hard I work at it and the variance in the bulk ammo. This isn't bad at all for a carbine length barrel on an AR, with iron sights, with Walmart bulk .223 55gr ammo. Actually, all things considered, I'm quite pleased with those results. A $50 reject barrel, carbine length, iron sights that shoots that well? I lucked out when I bought that barrel, IMO.
It truly does look like hammered crap on the inside. I won't and don't worry about what it looks like - the results on the paper are what I look at. Does it foul? Oh hell yes, does it foul - mostly powder fouling with some copper on top. You can clean it for an hour to get a clean patch.
2. I don't worry too much about what a mass produced barrel looks like until it shows me something is wrong. "Wrong" can be:
- it doesn't group
- it shows me evidence of high chamber pressures
- it fouls very quickly - like gobs of lead or copper in 50 rounds.
Now, if I'm paying a premium for a custom barrel that is supposed to be lapped and very well finished, then I might complain if the bore is rough. I paid for something better.
3. What I was suggesting was that if someone is worried with what a barrel's machining marks look like before they've even shot it, they can cure the "problem" by lapping away the marks. A couple of hours and they have reduced the marks, ergo, no more problem, right? If they haven't shot it yet, they wouldn't notice a difference in accuracy. That was uncharitable of me, for which I apologize.
Starting with 800 grit is actually starting rather fine. Barrel lappers usually start down around 320 to 400.
4. Bart then went into the details of air gaging barrels, which while significant to someone who can shoot as well as Bart, flies over the head of most shooters at about Mach 2. The vast majority of shooters aren't anywhere near as serious a marksman as someone like Bart and are nowhere near as methodical and consistent in their evaluation of contributing factors to rifle accuracy - ie, if you gave them two rifles with variances in the bore diameter or rifling consistency that were identical in all other aspects, would the shooter be able to a) notice the difference in accuracy and b) properly attribute the cause of the difference? I'll bet "no."
If you're in the accuracy game at Bart's level, you're most likely not buying an inexpensive, mass-produced barrel. You're quite picky about your barrels - and your barrel maker(s), and your bullet makers, and your brass, and your primers, etc. And you're most likely not mounting your accuracy barrels on a Mauser - which, as much as I love Mauser actions for hunting rifles, I have to admit that they're not the go-to action for accuracy work.
5. I'll touch briefly on the issue of air gaging.
Air gaging barrels is all very well and nice, and there are lots of barrel manufactures who claim to air gage their barrels... and then the details of what they DO once they've air gaged a barrel start becoming thin.
Do they simply set a criteria for variance along the bore, and reject any/all barrels that exceed these criteria? What are these criteria?
Do they sort/select their barrels into two groups - the barrels that gaged with very high uniformity, and then "most everything else" and reject the worst of them?
Do they lap out the tight spots to obtain more uniform bore diameters?
Or... do they do something else? Like sell their rejects to a customer with a lower quality criteria, which then are sold at a low[er] price with no name attributed to the barrels? This is how I got my AR barrel - it failed acceptance criteria, so it ended up in the aftermarket with a dirt-cheap price on it.
They could do any of these things... but many mass-production barrel manufactures are rather quiet on what they do after they've air gaged their barrels. For guns where I'm really worried about accuracy, I buy barrels from companies that tell me what their criteria are and what they do with the information. This usually means paying a premium for the barrel and waiting a fair bit of time for delivery...
1. When a gunsmith starts showing people what bores actually look like through a borescope, many customers recoil in horror.
Increasingly, I think that a gunsmith showing most customers what barrel bores actually look like is a mistake, unless we're pointing out some specific damage eg, pitting or throat erosion. Showing customers what a new rifled bore actually looks like (as compared to what they perceive from either end of the barrel held up to the light) just seems to invite all manner of obsession by customers.
I've seen bores that looked like what the OP photographed there.... and worse. Much worse. An example: I've got a barrel on an AR-15 that looks like it was reamed by a bionic beaver... and yet it shoots what I would consider pretty well for what it is. BTW, this barrel won't even pass military go/no-go gage requirements, especially the barrel straightness gage. The price was right - dirt cheap. So I slapped it onto a carbine and ran some ammo through it. I figured "OK, it's $50. Let's experiment and see just what a failed barrel looks like on paper."
I can group five rounds from just over 2" to about 2.75" at 100 yards off the bench, depending on how hard I work at it and the variance in the bulk ammo. This isn't bad at all for a carbine length barrel on an AR, with iron sights, with Walmart bulk .223 55gr ammo. Actually, all things considered, I'm quite pleased with those results. A $50 reject barrel, carbine length, iron sights that shoots that well? I lucked out when I bought that barrel, IMO.
It truly does look like hammered crap on the inside. I won't and don't worry about what it looks like - the results on the paper are what I look at. Does it foul? Oh hell yes, does it foul - mostly powder fouling with some copper on top. You can clean it for an hour to get a clean patch.
2. I don't worry too much about what a mass produced barrel looks like until it shows me something is wrong. "Wrong" can be:
- it doesn't group
- it shows me evidence of high chamber pressures
- it fouls very quickly - like gobs of lead or copper in 50 rounds.
Now, if I'm paying a premium for a custom barrel that is supposed to be lapped and very well finished, then I might complain if the bore is rough. I paid for something better.
3. What I was suggesting was that if someone is worried with what a barrel's machining marks look like before they've even shot it, they can cure the "problem" by lapping away the marks. A couple of hours and they have reduced the marks, ergo, no more problem, right? If they haven't shot it yet, they wouldn't notice a difference in accuracy. That was uncharitable of me, for which I apologize.
Starting with 800 grit is actually starting rather fine. Barrel lappers usually start down around 320 to 400.
4. Bart then went into the details of air gaging barrels, which while significant to someone who can shoot as well as Bart, flies over the head of most shooters at about Mach 2. The vast majority of shooters aren't anywhere near as serious a marksman as someone like Bart and are nowhere near as methodical and consistent in their evaluation of contributing factors to rifle accuracy - ie, if you gave them two rifles with variances in the bore diameter or rifling consistency that were identical in all other aspects, would the shooter be able to a) notice the difference in accuracy and b) properly attribute the cause of the difference? I'll bet "no."
If you're in the accuracy game at Bart's level, you're most likely not buying an inexpensive, mass-produced barrel. You're quite picky about your barrels - and your barrel maker(s), and your bullet makers, and your brass, and your primers, etc. And you're most likely not mounting your accuracy barrels on a Mauser - which, as much as I love Mauser actions for hunting rifles, I have to admit that they're not the go-to action for accuracy work.
5. I'll touch briefly on the issue of air gaging.
Air gaging barrels is all very well and nice, and there are lots of barrel manufactures who claim to air gage their barrels... and then the details of what they DO once they've air gaged a barrel start becoming thin.
Do they simply set a criteria for variance along the bore, and reject any/all barrels that exceed these criteria? What are these criteria?
Do they sort/select their barrels into two groups - the barrels that gaged with very high uniformity, and then "most everything else" and reject the worst of them?
Do they lap out the tight spots to obtain more uniform bore diameters?
Or... do they do something else? Like sell their rejects to a customer with a lower quality criteria, which then are sold at a low[er] price with no name attributed to the barrels? This is how I got my AR barrel - it failed acceptance criteria, so it ended up in the aftermarket with a dirt-cheap price on it.
They could do any of these things... but many mass-production barrel manufactures are rather quiet on what they do after they've air gaged their barrels. For guns where I'm really worried about accuracy, I buy barrels from companies that tell me what their criteria are and what they do with the information. This usually means paying a premium for the barrel and waiting a fair bit of time for delivery...