What are your opinions on prefit barrels?

[Alex Wheeler]

Im not commenting on any particular thing here, just some random thoughts on borescopes. When it comes to using a bore scope there is certainly a bit of a learning curve. But if your mapping out the bore and grooves when your dialing in a barrel and then comparing it to what you see when you bore scope the chamber after its done, its not that hard to figure out what your seeing in a throat. I had started a thread about this where I was starting to post some videos of different throats to explain it, but no longer do youtube so no more videos for me. Most of what you see in a throat is the shape of the groove. For example, the "straight belt" looking throat as its was called is showing that the shape of the groove is consistent and its the correct radius for its diameter, as well as the throat being concentric. Yes you absolutely can see a non-concentric throat with a bore scope. I have come to expect this as the norm for a 6mm Krieger. Its the odd one out that doesnt look that way from them. Bartlien and Hawk Hill do this well too and I just cut a Mullerworks that was as good as it gets. Many times a throat will have a curved look to the cut, that usually means the middle of the groove is slightly deeper or shallower than than the edges, I call this radius error. It just means the radius of the groove is not perfect for its diameter. Some times the cut will look slanted, that usually means one side of the groove is deeper than the other. All of that is controlled by the guy grinding the cutter and cutting the grooves. I have had some with oversized grooves, you will see lapping back to the neck on every groove as the reamer wont clean up the groove. Or that can also be a reamer with a small freebore diameter. In one case I had a barrel with one groove .0005" deeper than the other 4. The maker sent out a new one, but since it was in the lathe I chambered it and gave it to a friend, 4 even grooves and one with lapping back to the neck. If your paying attention to the indicator you will know what the throats going to look like before you ever scope it. As a gunsmith I do prefer a very even groove. It makes dialing in a barrel very precisely easy. When you have groove variation you have to get very very picky about where in the groove you indicate. You dont want to dial off the low spot in one groove and the high spot in the opposing groove for example. Most of the minor shapes you see mean nothing, so long as they are consistent groove to groove everything is concentric. You can even get a rough idea if the barrel is on the tight side or loose side if you know your reamers freebore diameter. You could easily spot the difference in 2 barrels with a .0005" groove diameter difference if I pointed out where to look, so long as they were cut with the same reamer. When it comes to buttons, dont expect to see a straight cut in a groove or land its just not how they are shaped. And that does not stop me from using buttons. They just take longer to dial in. But some of my best have been buttons. If you learn to understand what your looking a scope is a good tool, if your ocd and everything gets in your head it may be a problem for you.

 

[urbanrifleman]

Im not commenting on any particular thing here, just some random thoughts on borescopes. When it comes to using a bore scope there is certainly a bit of a learning curve. But if your mapping out the bore and grooves when your dialing in a barrel and then comparing it to what you see when you bore scope the chamber after its done, its not that hard to figure out what your seeing in a throat. I had started a thread about this where I was starting to post some videos of different throats to explain it, but no longer do youtube so no more videos for me. Most of what you see in a throat is the shape of the groove. For example, the "straight belt" looking throat as its was called is showing that the shape of the groove is consistent and its the correct radius for its diameter, as well as the throat being concentric. Yes you absolutely can see a non-concentric throat with a bore scope. I have come to expect this as the norm for a 6mm Krieger. Its the odd one out that doesnt look that way from them. Bartlien and Hawk Hill do this well too and I just cut a Mullerworks that was as good as it gets. Many times a throat will have a curved look to the cut, that usually means the middle of the groove is slightly deeper or shallower than than the edges, I call this radius error. It just means the radius of the groove is not perfect for its diameter. Some times the cut will look slanted, that usually means one side of the groove is deeper than the other. All of that is controlled by the guy grinding the cutter and cutting the grooves. I have had some with oversized grooves, you will see lapping back to the neck on every groove as the reamer wont clean up the groove. Or that can also be a reamer with a small freebore diameter. In one case I had a barrel with one groove .0005" deeper than the other 4. The maker sent out a new one, but since it was in the lathe I chambered it and gave it to a friend, 4 even grooves and one with lapping back to the neck. If your paying attention to the indicator you will know what the throats going to look like before you ever scope it. As a gunsmith I do prefer a very even groove. It makes dialing in a barrel very precisely easy. When you have groove variation you have to get very very picky about where in the groove you indicate. You dont want to dial off the low spot in one groove and the high spot in the opposing groove for example. Most of the minor shapes you see mean nothing, so long as they are consistent groove to groove everything is concentric. You can even get a rough idea if the barrel is on the tight side or loose side if you know your reamers freebore diameter. You could easily spot the difference in 2 barrels with a .0005" groove diameter difference if I pointed out where to look, so long as they were cut with the same reamer. When it comes to buttons, dont expect to see a straight cut in a groove or land its just not how they are shaped. And that does not stop me from using buttons. They just take longer to dial in. But some of best have been buttons. If you learn to understand what your looking a scope is a good tool, if your ocd and everything gets in your head it may be a problem for you.

Yes, I saw the same thing. You could dial in on the lands and grooves and see that they were not perfect.

Still shot great.

Predicting performance is tricky at best. I will just leave it at that.

I am thinking that maybe it would be best if I stop making the videos. It only invites speculations.

Happy customers is a better indicator of performance.



Ps: Alex you really have inspired so many of us. You set the bar very high my friend.

 

[Alex Wheeler]

I have posted many times that much of what your looking at is not predicting performance. I'm only trying to explain what your seeing. I have bore scoped duds and record breakers, many times they look the same. The steel is so critical but we cant tell good steel until we shoot them. I still want to like what I see when I scope them though. None of this is to imply I'm an expert or immune from making mistakes. I'm not.

 

[urbanrifleman]

I have posted many times that much of what your looking at is not predicting performance. I'm only trying to explain what your seeing. I have bore scoped duds and record breakers, many times they look the same. The steel is so critical but we cant tell good steel until we shoot them. I still want to like what I see when I scope them though. None of this is to imply I'm an expert or immune from making mistakes. I'm not.

I understand what you're saying and I was wholeheartedly agreeing with you. That's what I tell my customers when they first get their borescopes and they call me and tell me what they think they see. That was my point once again thank you so much for sharing it's been a great inspiration to me and I think of your recommendations often to my customers. Thank you again

 

[Stan Taylor]

I’m rather enjoying this post ,but I just run out of beer so y’all hold up a little bit I got to go to the store thanks.

 

[Stan Taylor]

Carry on guy’s I got beer.

 

[davidjoe]

Carry on guy’s I got beer.

Ok, I’m game. Barrel customer here, shooter, big fan of the Douglas contribution to the M1A Supermatch, mine being an inseparable asset to the grave, - uncanny, spooky, accuracy, - but not a machinist, at all.

I have always had this question though. How can a reamer that bores the precise chamber, not oversized in any way, not have found the perfect center, when it is stationary and barrel is rotated around it? To my thinking, you could always drill an angled hole into material if the bit was rotating, but you could never spin material around a stationary bit that wasn’t in the center of the material and parallel with the axis of its rotation, without snapping it, right? Or, if not snapping it, at a minimum making the hole bigger than the reamer or bit, which is easily confirmable. But we hear so much about concentricity, even when it seems to me there was no possibility other than perfect concentricity. Do I have it wrong, conceptually?

 

[Dusty Stevens]

Ok, I’m game. Barrel customer here, shooter, big fan of the Douglas contribution to the M1A Supermatch, mine being an inseparable asset to the grave, - uncanny, spooky, accuracy, - but not a machinist, at all.

I have always had this question though. How can a reamer that bores the precise chamber, not oversized in any way, not have found the perfect center, when it is stationary and barrel is rotated around it? To my thinking, you could always drill an angled hole into material if the bit was rotating, but you could never spin material around a stationary bit that wasn’t in the center of the material and parallel with the axis of its rotation, without snapping it, right? Or, if not snapping it, at a minimum making the hole bigger than the reamer or bit, which is easily confirmable. But we hear so much about concentricity, even when it seems to me there was no possibility other than perfect concentricity. Do I have it wrong, conceptually?

Ill fitting bushing, not perfect cutter geometry, hard spots in the metal, tailstock out of alignment, less than rigid setup, too many things to list

 

[Alex Wheeler]

In my opinion the biggest reason a chamber is off is because the barrel was not dialed in as well as it should have been, or the setup moved. Try to picture this in your head, the area the throat is going to end up is dialed in perfectly but 1/2" deeper into the barrel there is .0005" runout. The pilot is going to be in that part of the barrel and will cause the front of the reamer to also run out .0005" meanwhile the part of the barrel that the throat ends up is not running out, so you get a non concentric throat. Thats probably the most common issue in my guess. Even in a rigid setup reamers flex a lot.

 

[redrockranger]

In my opinion the biggest reason a chamber is off is because the barrel was not dialed in as well as it should have been, or the setup moved. Try to picture this in your head, the area the throat is going to end up is dialed in perfectly but 1/2" deeper into the barrel there is .0005" runout. The pilot is going to be in that part of the barrel and will cause the front of the reamer to also run out .0005" meanwhile the part of the barrel that the throat ends up is not running out, so you get a non concentric throat. Thats probably the most common issue in my guess. Even in a rigid setup reamers flex a lot.

How long does it take to dial in a barrel for chambering ? Thanks

 

[Dusty Stevens]

How long does it take to dial in a barrel for chambering ? Thanks

Exactly 13 minutes

 

[tsyarnall]

 

[sdean]

Exactly 13 minutes

Takes me that long to just remember which way to move in or out on my spider.

 

[Alex Wheeler]

How long does it take to dial in a barrel for chambering ? Thanks

Every ones different