Gunsmith leaves burr on crown??

uncledillers

uncledillers

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So I had gunsmith who has a sub forum on CGN cut threads onto the muzzle of my shilen prefit barrel. The turn around was quik and when it came back everything look good. But a couple days latter I noticed a burr around the bore where it meets the crown. As I looked closer it appears the gunsmith re crowned the barrel, the face of the lands are shinny and the barrel seems a tad shorted ( Iam only 80% sure on this. I had it marked in quickload as a 24" barrel, is 23, 7/8 ish)

I am worried about the burr. It is very noticeable by running a finger nail over it, even more noticeable on the on the lands. That all being said the burr is on the "outside" of the bore.

in2U3fj.jpg

You can see in the picture that the lands seem to be "pushed" into the surrounding steel at the bore.


Is this something I should be worried about?
What course of action should I be expecting the gunsmith to take?

I have sent him a email, but still now response.
 
Wouldn't be worried as stated. Many smiths will chamfer slightly there with a 60 degree centre reamer so you would not see these burrs and leave a nice finish.

As for the barrel being a bit shorter might be because of the method of threading the barrel. If done between centers you definitely have to re-crown because you have to run a live center in the bore, generally chamfered with a 60 degree reamer before hand for concentricity.

Talk to your smith I am sure he can explain the way he does it.

GST
 
I have always considered a crown left 'flat' like that to be unfinished and easily damaged. I have for about 50 years now finished my crowns using a 60 degree piloted chamfer reamer. No need to shoot a rough burr off...

Titanium_700_crown.jpg


60_degree_reamer.jpg
 
I have always considered a crown left 'flat' like that to be unfinished and easily damaged. I have for about 50 years now finished my crowns using a 60 degree piloted chamfer reamer. No need to shoot a rough burr off...
Click to expand...

Thanks for the clarification and the pictures.

GST
 
Bloberglawp said:
So basically you can hide what your client is inevitably going to do himself. 1/16" further into the barrel?
Click to expand...

Nope. Making a small investment in time and equipment, to prevent the customer from wondering if he got his moneys worth, or if something was missed.

It's in the details, as the saying goes.

I'd be happy enough to crown a barrel for myself that looked more or less as the OP's does, but if I opened a parcel and found it looking unfinished, I like as not would ponder too.

Pretty hard to bang the crown itself, against anything but a pointy rock, with the recess like that anyway. Some guys seem to prefer a dead square muzzle, some want a (insert number of degrees here according to the flavor of the day) 'target' crown, and others take what comes without looking.

I think all it would have taken the OP's smith would have been a couple seconds with some fine paper to deburr and it would never have been questioned, but it does look a little .. under-done, to me.

Confidence plays a huge part in the owner's happiness. case in point here.

Cheers
Trev
 
If the material is indeed pushed into the surrounding metal I would guess your Smith pushed a live centre into the muzzle when he did the threading job and should have recrowned the barrel enough to remove the damage. As for blowing off a sharp edge with a bullet no doubt this has been done countless times but electron microscope shows it rips the steel when this happens...
 
Randy B said:
If the material is indeed pushed into the surrounding metal I would guess your Smith pushed a live centre into the muzzle when he did the threading job and should have recrowned the barrel enough to remove the damage. As for blowing off a sharp edge with a bullet no doubt this has been done countless times but electron microscope shows it rips the steel when this happens...
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I sent a sample of the way I finish a crown to a Centerfire Benchrest Shooter in the US who had access to an Electron Microscope for a while... he told me the reamer left the smoothest finish of all... Far smoother than 'left flat' and sanded crowns. He confirmed what I have felt for years. He had several photos of crowns in various conditions.
 
Should have said 60 deg live centre. Personally don't have a problem with piloted tools though they are Very far from the norm in the bench rest game. Most common is a straight flat crown no recess as the rifles just don't normally encounter any abuse.Flat is preferred over any angle as it simply is the easiest to make perfect. If the bore is not concentric with the angle you develope an elipise. Gas can then escape from one position before the other. Splitting hairs I know. Rare to see other than flat but they are produced.
 
Bloberglawp said:
So basically you can hide what your client is inevitably going to do himself. 1/16" further into the barrel?
Click to expand...
The OP's barrel is fine and will clean up after a few shots. The barrel that Guntech posted is what the OP should have received back. Whether a lack of professional workmanship or lack of equipment is the difference.
 
Randy B said:
Should have said 60 deg live centre. Personally don't have a problem with piloted tools though they are Very far from the norm in the bench rest game. Most common is a straight flat crown no recess as the rifles just don't normally encounter any abuse.Flat is preferred over any angle as it simply is the easiest to make perfect. If the bore is not concentric with the angle you develope an elipise. Gas can then escape from one position before the other. Splitting hairs I know. Rare to see other than flat but they are produced.
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There are a few in the Benchrest Game that are reluctant to make changes for sure... but no one has been able to demonstrate the traditional 'flat' crown is any more accurate than finishing the crown with a piloted chamfer reamer... but that little sharp edged traditional crown is more susceptible to damage while cleaning compared to the piloted 60 degree chamfer. (which is also concentric to the bore)
 
I agree.. Concentric within the confines of the clearance on the pilot.. Sharing knowledge is the hallmark of the game.. Driving aggs lower every year. Most go with what works. You would require an awful lot of different size pilots to chamfer every different bore size to bench rest standards of today all in .0001 increments. Now think in hunting calibre sizes and you need a rather large wallet..
 
Randy B said:
I agree.. Concentric within the confines of the clearance on the pilot.. Sharing knowledge is the hallmark of the game.. Driving aggs lower every year. Most go with what works. You would require an awful lot of different size pilots to chamfer every different bore size to bench rest standards of today all in .0001 increments.
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You mean to say there are shooters other than the 6mm guys? I thought everyone used the well proven 6mm PPC in as many classes as they can... lol.
 
I lightly chamfer mine while in the lathe, melin 60° countersink, no pilot.
I'd consider that unfinished... and a little chattery...
 
This looks like it was cut with an endmill or piloted cutter? Slightly dull/dry, and the blades rolled the work-hardened layers at the bottom of the grooves? Either that or dull carbide rammed in hard, but the regularity and rotation of the chatter looks like a cutter to my eyes.

Asking, not debating.
 
Dogfish858 said:
This looks like it was cut with an endmill or piloted cutter? Slightly dull/dry, and the blades rolled the work-hardened layers at the bottom of the grooves? Either that or dull carbide rammed in hard, but the regularity and rotation of the chatter looks like a cutter to my eyes.

Asking, not debating.
Click to expand...

It was done in a lathe, with a not very sharp, not very rigid tool.

The pattern in the lines in the pictures looks like the tool was chattering a fair bit. Could have been from not being sharp, could have been chipped, maybe a bad relief angle...Lots of ways to get a lousy finish with chatter. Unless you are trying to repeat it, in which case, never the same twice! :)

Cheers
Trev
 
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