Hi Folks, A mate asked me to re-thread and re-crown his .170 Hornet and re-fit his Moderator. He said there was damage 5mm back from the crown. I honestly could not see what he was seeing but as the customer is always right I cut the thread off and this is what i found.[URL= ] [/URL]

Could this kind damage been caused by a crowning tool or at the rifling stage. Anyone seen this kind of damage.jc

Should never have left the factory this way; I can't imagine what caused it except for a bad reamer at some point. Or really bad crowning pilot. I saw this kind of damage once when a "machinist" crowned a barrel for a guy and he used a deburring tool, which left gouges like yours inside the rifling. He admitted he did it to several barrels and did not realize what he was doing. As for the customer being always right; I find that they are wrong at least 50 percent of the time. Usually more. And we are not allowed to have such things as "moderators" here.

My first reaction was to think that the rifle was fired with some kind of obstruction in the bore, but the damage, while similar, looks a little too uniform for that. It looks more like some kind of pilot was placed in the bore which turned.

quote:

Originally posted by Stonecreek:
My first reaction was to think that the rifle was fired with some kind of obstruction in the bore, but the damage, while similar, looks a little too uniform for that. It looks more like some kind of pilot was placed in the bore which turned.

+1

This was what it looked like before I cut it off. I dont do this type of crown although I have seen them on some heavy varmint barrels. Looks a bit rough to me.jc

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Only the very muzzle edge is important; the rest of a crown can be rough. Of course, good workmanship will dictate that you get it smooth.

If you don't remove muzzle brakes (Moderator?) to clean you can really batter that end. Well, at least the one rifle I own that has a threaded muzzle break gives me grief if I don't take it off -- the cleaning brush with patches doesn't go all the way out. Maybe the crown got bashed by whatever jag or wrap style patch jag was used? Something beat the fool out of that muzzle!

2 cents

Hello folks, Thank you for your comments. Sound moderators are widely used in the U.K. More so in the past 20 years. The advice is to remove them after use. Advice on maintenance varies from each manufacturer. Most new, out of the box rifles, come with a 'factory'thread already cut. This Ruger.170" Hornet rifle, which is quite new, now groups very well with its new crown and the damage removed.
I would be surprised if the damaged was caused by any cleaning operation,I know the fellow who owns it very well and these rifles are made of better stuff. More likely,having thought it out more, whoever cut the crown unfortunatly jammed metal swarf between the cutter pilot and the rifling. Ive never used or even seen this type of tool. Or maybe at the rifling stage.
If it was mine i would have returned it to have it checked out. Who knows how many are just like it. Its a wee bore to see inside without using macro-lens.. jc

quote:

Originally posted by dpcd:
And we are not allowed to have such things as "moderators" here.

You are in most States but it'll cost you $200 for the tax stamp & the time & effort needed to fill in the paperwork & jump through the hoops.