Damaged Crown due to Brass Jag?

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Re: Damaged Crown due to Brass Jag?

Post by Oldbloke » 13 Apr 2021, 9:30 pm

A simple test would be:

Take a small smooth steel bar, such as a shaft and put it in a drill.
While the drill is running at say, 1425rpm, push a piece a brass against the rotating bar. (Bar and brass must be clean) If the jag is the cause of the wear, then within a couple of minutes the brass should create a groove in the bar.

I think 1425rpm for a few minutes would represent many years of cleaning.

Don't lose you fingers doing the test.
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Re: Damaged Crown due to Brass Jag?

Post by JohnV » 04 Jul 2021, 10:12 am

How you clean is the more important thing , going gently and using the correct fitting jags and patches will do no real harm . Ripping the jag back through while the rod is wobbling and the patch is gone is not good . Bad fitting jags that show a lip at the edge of the joint is not good .
Use a rod from the chamber end with a rod guide and never use a pull through unless you are real carful to pull it straight out the muzzle and not against the edges of the crown . I have worn out about 6 barrels from shooting but not one from cleaning damage . Don't work fast work smart and you have less troubles .
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Re: Damaged Crown due to Brass Jag?

Post by Lovey » 04 Jul 2021, 3:45 pm

Unless I've completely misunderstood (it happens a lot) I thought that the point he was trying to make in video was that the difference in the diameter of the jag and the rod, where they join, was what causes the damage.
This difference in diameter caused the jag to 'jump' slightly as it was pulled back into the barrel, which causes chipping. If that is the case, would making the jag the same diameter as the rod, say by turning them on a lathe, alleviate this?
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Re: Damaged Crown due to Brass Jag?

Post by JohnV » 04 Jul 2021, 4:27 pm

Lovey wrote:Unless I've completely misunderstood (it happens a lot) I thought that the point he was trying to make in video was that the difference in the diameter of the jag and the rod, where they join, was what causes the damage.
This difference in diameter caused the jag to 'jump' slightly as it was pulled back into the barrel, which causes chipping. If that is the case, would making the jag the same diameter as the rod, say by turning them on a lathe, alleviate this?

Yes it would fix it . As I said above any bad fitting jag at the joint that has an edge is not good and can bang away at the very edge of the lands after the chamfer . Peoples concept is the jag rips the steel . That's not what happens . The constant contact peens the edge of the lands so they are no longer a sharp neat angle and are ragged . That can affect the consistent release of the bullet . Gently withdrawing instead of ripping it back would also negate any real problems .
Hard scrubbing is generally done with a bronze brush not a jag and patch so much but the joint still has to be neat fitting on both .
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