Barrel Crown Evaluation

JP65

Member
Had a conversation today concerning barrels, evaluation and proper crown position.
It was kind of ironic, being that I recently posted a couple of short YouTube video's on the topic.

I told him I would post the links to these video's.....that would make it easier for him to find.

So here you go...... I really enjoyed our conversation today.

Poor Crown:

Proper Crown:

JPatt
 
Your welcome Bill, the results can be surprising.....both good and bad.
Happy New Years to you as well my friend.

JPatt
 
JP -
Can you describe the rod you use to push these through the barrel? are you just removing the head off of a round and pushing it through, where might one get the slug?)

Thanks -
 
Jeff, I understand finding the tightest spot, but how do you determine before cutting the crown, the roundest spot? I would think pushing a slug through the barrel and finding the resistance towards the end of a lapped barrel would indicate the tight spot, but couldn't this also determine the barrel is actually not perfectly round at the same spot?

Do you find a lot of barrels that don't have a round bore?

Geoff
 
Hi Geoff,

quote from your post: "but couldn't this also determine the barrel is actually not perfectly round at the same spot?"

Absolutely
, when you slug the barrel, it's going to tell you a lot of information! The tightest spot for proper crown location as well as whether or not this spot is perfectly round is of paramount information when determining if this particular barrel is going to shoot. At least shoot in the accuracy range that we require.

Once you determine the tightest spot, it depends upon it's location. Does the bore open up immediately after this spot or is the bore straight for several inches after this spot? If it opens up larger, then simply push the slug on out and measure......if it remains tight then sometimes you must ease the slug back out the breech end so that you do not alter the bullet and you can get true measurement of that spot.

It takes practice and time to acquire what the proper bore feels like....but....once you do, the information in invaluable. Sometimes the slug process take me a few minutes.....other times I have to hang it up and start again later (this helps me determine if something I "think" I'm feeling is there or not). I turn the barrel so that I can't see my marks, slug the next day.....if I come to the same conclusions then I'm confident.

Geoff, there's so much to slugging.....if your really interested, I highly recommend reading Calfee's book. He covers it in detail (much better than I). Slugging is NOT just to determine the proper Crown position......much much more.

Thanks
JPatt
 
While evaluating a barrel today....I thought about this thread.
Thought I would add some valuable insight to measuring a lead slug.

As everyone knows, lead is a dead metal and has absolutely no rebound or elasticity.
Therefor when you measure a lead bullet you must be very careful to clean/wipe the slug prior to measuring and then only apply enough pressure on the micrometer jaws to hold the slug in place. I usually have it so loose that it's about to fall out. When measuring down to the tenth of the thousandth (.0000) it's very easy to squeeze lead out of shape.....then you have bad information.

I usually will always measure and then slug again and measure again.....repeat....checking for consistent measurements.

JPatt
 
Thanks for the great info and the videos. Checked a couple of the crowns on a few of my old 22rf military trainers . 2 out of the 3 were real tight. The other pretty much falls out. But rifle still seems to shoot as accurate as the other 2. Just seems to have more noticeable flyers
 
Mtn Boy, may I ask which slug you are using and what are you pushing it through the barrel with? Maybe JP can help with the question asked earlier in the thread. Thank you.
 
Mtn Boy, may I ask which slug you are using and what are you pushing it through the barrel with? Maybe JP can help with the question asked earlier in the thread. Thank you.
Well I used some sk bullets I pulled. And a cleaning rod. I am sure there is a better way but just what I had.
 
Well I used some sk bullets I pulled. And a cleaning rod. I am sure there is a better way but just what I had.
How hard is it to push a slug down a barrel? I know it depends on the barrel, but I don't want the rod to flex and rub the rifling if it's a tight fit. Thanks.
 
JP -
Can you describe the rod you use to push these through the barrel? are you just removing the head off of a round and pushing it through, where might one get the slug?)

Thanks -
Pulling slugs from live rounds is very dangerous, and not recommended! Therefore I will not comment as to how I acquire slugs. Sorry

As for the rod......I use a .187 Ivy cleaning rod, with a brass patch cleaning jag tip that I have rounded off and polished smooth....very smooth.
Always use a slug with a hole in the front tip (like a hollow point round).....this gives the tip of your polished jag something to set into and provides a guide to the front of the rod when pushing the slug back down the bore (muzzle back toward breach).

JPatt
 
Pulling slugs from live rounds is very dangerous, and not recommended! Therefore I will not comment as to how I acquire slugs. Sorry

As for the rod......I use a .187 Ivy cleaning rod, with a brass patch cleaning jag tip that I have rounded off and polished smooth....very smooth.
Always use a slug with a hole in the front tip (like a hollow point round).....this gives the tip of your polished jag something to set into and provides a guide to the front of the rod when pushing the slug back down the bore (muzzle back toward breach).

JPatt
Are the slugs you use bullets?
 
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