Cleaning method for a sharp square crown

[just country]

morning there r various types of crowns for rifle barrels.
the thing about a crown is to square the bullet with the
lands and grooves as the bullet leaves the barrel. a
barrel crown should b protected by a counter sink
process done by the barrel installer requested by the
rifle owner. different crowns can effect barrel accuracy.
justme gbot tum

 

[Mram10us]

Haha I ain't buying it. It's a conspiracy man!!!

I haven't tested the internal degradation of a barrel based on cleaning. Just regurgitating what I've read .....which is usually a bad thing

 

[DSheetz]

I don't understand not at least breaking the edge of the cut on the crown . It's easy and doesn't take long to do with a good sharp 30 degree counter bore you don't even have to be 100 percent dialed in as it will center it's self and on the outside of the cut an emery board will take the edge off . Just my thoughts

 

[John Klingenberg]

Can bet the reason for the square crown, no need to get bore precisely centered in lathe. Even if not true a tool bit passing across end of barrel will make a perfect 90 degree crown.

Square edge should not be an issue. If a plastic coated cleaning rod is used I see no reason for worrying about rod bumping into the edge. Now pulling a bore brush rearward would be another story.

It looks square but off center is off center, it wont be a perfect 90. That wobble means one side is higher. The lathe cant cut a perfect 90 unless its center

 

[ntsqd]

You are technically correct that if it isn't on-center that it won't cut a perfect 90°, but if I did the trig right if the muzzle of a 20" barrel is .03" eccentric (I'd consider that excessively sloppy work) that is a .086° angle error. Are we really going to notice this?

Biggest issue that I see with a perfectly square crown, even a rebated one as described, is that I would fear it easy to damage in the field. Perhaps if the recess is deep enough to protect the bore to crown transition then it's a non-issue?

EDIT: Meant to add that I don't see how the shape of the crown would dictate any difference in cleaning method. Which isn't the same thing as suggesting that an ideal cleaning method wouldn't damage it while a far less than ideal method could. I think that we can all agree on that, even if we don't agree on what that ideal method IS.

 

[KyCarl]

A mild steel piece turned to about a 60 degree point and a bit of lapping compound
turn it by hand easy and break the corner about .003-.004 just enough so it's not razor sharp. If you want it close indicate the bore and use the tailstock by hand not cranking it.

 

[jpope02]

I don't trust a flat crown on any rifle barrel especially on a hunting barrel. Many times rifles are jammed barrel first into the floorboards of hunting vehicles have filth, dirt, sand, mud, gravel and in some cases metal suufacesl that most certainly can and will damage the crown far more than a plastic bristle bore brush. Look at factory barrels most have provisions to protect the crowns as much as possible.

 

[Mram10us]

I don't trust a flat crown on any rifle barrel especially on a hunting barrel. Many times rifles are jammed barrel first into the floorboards of hunting vehicles have filth, dirt, sand, mud, gravel and in some cases metal suufacesl that most certainly can and will damage the crown far more than a plastic bristle bore brush. Look at factory barrels most have provisions to protect the crowns as much as possible.

I use muzzle brakes on everything so I have a couple I left flat to see if it made a difference. Still shot good. I see your point if it is unprotected though

 

[cmarchand]

Check out this article on barrel crowns, there was another I read a couple years ago
that says the same thing; crowns only affect the poi not the accuracy...take it for what it's worth
https://rifleshooter.com/2018/03/do-rifle-crowns-matter-does-a-crown-effect-accuracy/

 

[J E Custom]

The way I was taught was to protect the crown at all cost. The explanation was that the crown was the last thing the bullet sees and it needs to be taken care of.

There are many ways of doing this and here are some that I know and use.

1= On a fine rifle that is for precision shooting never pull anything backwards through the crown no matter what type of crown you have.
The simple way to do this is take one cleaning rod and ream out the threaded end just enough to slip a standard brush in it with minimum slack for best fit.
Using a throat saver, insert the brush or jag followed by the rod with the brush or jag inserted in it, this way It will function the same way except you will not be able to pull anything back through the crown. It simply falls out when you try to back up and you don't have to buy anything special. Some take the time and trouble to unscrew the brush or jag, but this saves time and the chance of pulling something backwards through the bore.

As to the sharp edge on the crown, There are several different thoughts and opinions about this. The idea is for the bullet and gas to escape uni-formally and without adding any yaw or uneven forces on the bullet. You can achieve this by cutting any crown precisely whether it is 90o, 11o (Actually a 11 degree crown has a 101 degree angle to the bore) this is my personal favorite because the edge is not as fragile. I personally don't chamfer any crowns because of the possibility of inconsistency in the bevel.

Single point with the bore centered is the best way to avoid any burr and only start from the inside and cut out. Some feel that it is Ok to have a burr at first and let the bullet take care of it the first firing. I personally think that if the set up is correct and the tooling is used correctly, a finished crown will be the end results.

Everyone has their favorite way of cutting a crown and as long as it is true and crisp, it should perform well. The durability of the crown depends on the cleaning method.

There was a mention of the bore not being perfectly centered before the crown was cut, And this is very important to produce the best crown possible.

Some rifles have to be cleaned from the crown end and a brass bore guide (Comes with many cleaning rods) should be used if possible to minimize crown wear.

Everything comes out of a barrel towards the muzzle and crown, (Hopefully) so it makes sense (At least to some) that nothing should be pushed the other way down the bore. Each person has to decide if it is important or not.

Just my opinion

J E CUSTOM

 

[DSheetz]

Off subject a little . I had a barrel that was turned off center to the bore so the crown wasn't true to the bore and the bore wasn't true to the outside giving it a thick side so the barrel didn't heat up evenly . The first shot would be left 3 inches the second would be dead on the third would be right 3 inches . The builder said yep it doesn't shoot good at all but if you want to pay me 4000.00 to build you a good rifle instead of having me just put a barrel on one, it will shoot good I never looked back or went to him again .

 

[RYEWSKY25284]

Hope to get some advice here from the experts on cleaning please. I just had a rifle re-barreled and noticed that the crown is razor sharp/square . I have never had a barrel crowned like this before , so thought I would ask how you guys clean your barrels in a way to ensure that this type of crown does not get damaged . I assume plastic brushes only and being careful not to over extend the rod out of the muzzle so as not to drag the rod against the crown . Any other advise would be appreciated . Thanks

sounds like the smith forgot to bevel the crown. it should not be sharp

 

[Mram10us]

sounds like the smith forgot to bevel the crown. it should not be sharp

Bevel and not sharp? Some very good br smiths say after crowning, just touch the crown with 600 grit enough to break the edge in both forward and rear directions on the lathe. No bevel, just enough to knock off any junk. Food for thought

 

[J E Custom]

Off subject a little . I had a barrel that was turned off center to the bore so the crown wasn't true to the bore and the bore wasn't true to the outside giving it a thick side so the barrel didn't heat up evenly . The first shot would be left 3 inches the second would be dead on the third would be right 3 inches . The builder said yep it doesn't shoot good at all but if you want to pay me 4000.00 to build you a good rifle instead of having me just put a barrel on one, it will shoot good I never looked back or went to him again .

This is an old post but important enough to re post on. One of the first things a gunsmith should do is check the barrel blank for bore quality, straightness between centers, And concentricity to the bore. If any of these things are off beyond normal limits (Normally .000 to.003 or .004. It should be sent back to the barrel maker.

Sometimes, if the schedule is tight he may have to re contour to true it up. If this is done the barrel should/will be very forgiven and heat will not change the POI. there is no advantage in truing an action, and then installing a barrel that is not straight and concentric to the bore.

Installing a barrel on an existing rifle should require the same care and precision as a complete build and the only additional cost should be the labor to re contour it or ship it back.

J E CUSTOM