Diy crown polish?

[Bidwell]

Had some rust down the barrel of my howa superlight 308 and not liking the way the crown is looking after the rust was removed, borescope image below, feels a little rough but I know borescope images exaggerate things. The gunsmiths here are backed up up 2 weeks, or a month, maybe more. Should I wait for a pro, or is polishing a crown something a diyer can safely do well?

My groups seemed to have opened up a bit. I usually tend to get some barely sub moa to 1.5 inch 5-7 shot groups pretty consistently. During my last outing, it was more like 2 inch groupings. With a few 1.5 inch groups. Not exactly catastrophic but annoying. My handloads were sitting in my safe for about 3 months and the humidity was a bit high. Wondering if that could be the reason too. So many variables. Maybe i just had a bad day.

 

[Terrapin]

There’s several piloted crown tools available: midway, brownells, ptg etc.

I wouldn’t recommend trying it with a hand drill, but you can try if you want… if I didn’t have machine tools, I’d probably try it with a tap handle. It’ll take a while & it’s not good for the tool, but it should at least knock down any burrs or defects.

The old school way was with a smooth metal ball with a hand drill & lapping compound. Never tried it.


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[Bidwell]

There’s several piloted crown tools available: midway, brownells, ptg etc.

I wouldn’t recommend trying it with a hand drill, but you can try if you want… if I didn’t have machine tools, I’d probably try it with a tap handle. It’ll take a while & it’s not good for the tool, but it should at least knock down any burrs or defects.

The old school way was with a smooth metal ball with a hand drill & lapping compound. Never tried it.


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Definitely tempting to try myself. I'm not quite sure what angle my crown was cut to, does that matter? I see a lot of the lapping tools use 45 degrees, but I see a lot of people referencing 11 degrees too.

 

[Terrapin]

Definitely tempting to try myself. I'm not quite sure what angle my crown was cut to, does that matter? I see a lot of the lapping tools use 45 degrees, but I see a lot of people referencing 11 degrees too.

There’s lots of opinions, from 45 degrees to zero degrees (recessed target crown)… I’ve never been overly concerned on the angle as long as the crown is even & perfectly perpendicular to the bore. In other words, as the bullet exits it leaves the entire bore at exactly the same time.

Countersinks in general are very grabby and it’s easy to gouge. The pilot will help, but in a hand drill it could get ugly. A drill press would work if you took a lot of time and thought boring soft jaws.

A lap would be way safer. Anything brass with a 45 degree pointed tip or round ball would work. The bigger the ball, the flatter the chamfer so smaller is better so you get below the existing edge.


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[KyleR1985]

I chopped a couple of handi rifle barrels myself, and crowned them with a carriage bolt and valve compound to shape, then a brass cap nut and polishing compound to polish it out.

They both shot as good as they did before the cut/crown.

I think the crown being polished, and the cut/bevel face of it all needs to be perfectly perpendicular to bore, both more important than angle.

But not a gunsmith.

If you’re taking it to a smith eventually anyway, there’s no downside to trying it.

 

[Bidwell]

I chopped a couple of handi rifle barrels myself, and crowned them with a carriage bolt and valve compound to shape, then a brass cap nut and polishing compound to polish it out.

They both shot as good as they did before the cut/crown.

I think the crown being polished, and the cut/bevel face of it all needs to be perfectly perpendicular to bore, both more important than angle.

But not a gunsmith.

If you’re taking it to a smith eventually anyway, there’s no downside to trying it.

Yeah was wondering if I mess this up, should be easy enough for a gunsmith to fix?

 

[Bidwell]

There’s lots of opinions, from 45 degrees to zero degrees (recessed target crown)… I’ve never been overly concerned on the angle as long as the crown is even & perfectly perpendicular to the bore. In other words, as the bullet exits it leaves the entire bore at exactly the same time.

Countersinks in general are very grabby and it’s easy to gouge. The pilot will help, but in a hand drill it could get ugly. A drill press would work if you took a lot of time and thought boring soft jaws.

A lap would be way safer. Anything brass with a 45 degree pointed tip or round ball would work. The bigger the ball, the flatter the chamfer so smaller is better so you get below the existing edge.


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Makes sense, thanks. I've been watching some videos and the hand drill method made me nervous. By hand seems better. I know it's probably hard to say exactly, but very roughly how much time you think would it take to polish?

 

[Wrench]

You can cut it, file it flat and touch off with a brass round head screw with some lapping compound......

But don't expect a huge improvement. I have cut barrels back with my porta band and shot them without work and they shoot to 85% to their potential.

 

[hicountry1]

I bought a kit, and used a hand drill.

The key is rotating the drill in a circular pattern, which makes the cut perfect.

I did it to a pre-64 mod 70 in 264win that was pretty buggered up at the muzzle.

Watched a video on it, and gave it a go. Came out great, perfectly even. Rifle shoots sub .7"

Easy peasy. Just rotate the drill in a circular pattern, and use light pressure.

I wouldn't hesitate to touch up any crown thats dinged up.

 

[Bidwell]

You can cut it, file it flat and touch off with a brass round head screw with some lapping compound......

But don't expect a huge improvement. I have cut barrels back with my porta band and shot them without work and they shoot to 85% to their potential.

Interesting... 15% improvement isn't nothing but cool experiment to see what no crowing work will do. I really hate that let this happen at all, I love this rifle and it was shooting so well. Kills me.

 

[Bidwell]

I bought a kit, and used a hand drill.

The key is rotating the drill in a circular pattern, which makes the cut perfect.

I did it to a pre-64 mod 70 in 264win that was pretty buggered up at the muzzle.

Watched a video on it, and gave it a go. Came out great, perfectly even. Rifle shoots sub .7"

Easy peasy. Just rotate the drill in a circular pattern, and use light pressure.

I wouldn't hesitate to touch up any crown thats dinged up.

Awesome! Just curious, would you be able to send a link to the kit you bought? (if convenient)

 

[Wrench]

Dave Manson has a great crowning kit....but it's not cheap. I have a machine shop and have experimented with lots of crown profiles and I can't shoot the difference 99.9% of the time. I do highly recommend recessed crowns to help protect the crown.

 

[Wrench]

Muzzle Crowning Tool Kit | Manson Precision Reamers https://share.google/tFgbBBoSDUz4vmbDq

 

[Bidwell]

Dave Manson has a great crowning kit....but it's not cheap. I have a machine shop and have experimented with lots of crown profiles and I can't shoot the difference 99.9% of the time. I do highly recommend recessed crowns to help protect the crown.

You weren't kidding! That is pricey

 

[Big_wals]

Also not a gunsmith, but I have cut down a Ruger American barrel with a hacksaw, filed it smooth and crowned it with a round headed brass bolt and lapping compound. Still shot great afterwards. I’d give it a try, you can always take it to a gunsmith if it doesn’t improve.

 

[Big_wals]

Do rifle crowns matter? Does a crown affect accuracy? I find out with the help of my grinder…

Do rifle crowns matter? Does a crown affect accuracy? I think most of use would say yes. It seems intuitive that the crown, the last part of the rifle that touches the bullet before it leaves the…

rifleshooter.com

This article is what convinced me I probably wouldn’t screw things up too bad with my Ruger.

 

[Bidwell]

Do rifle crowns matter? Does a crown affect accuracy? I find out with the help of my grinder…

Do rifle crowns matter? Does a crown affect accuracy? I think most of use would say yes. It seems intuitive that the crown, the last part of the rifle that touches the bullet before it leaves the…

rifleshooter.com

This article is what convinced me I probably wouldn’t screw things up too bad with my Ruger.

Great article, thanks!