checking barrel crown

[p5200]

what's good to use to clean the target crown on a Savage 10FLP .223 cal. bolt action really good, for close inspection? I thought about JB Bore paste but, I can't find any in the little town I live in. is there anything I could use to polish/lap the crown I tried Hoppes "9 to just clean it but, it seems if it was bright looking I could see it alot better.I'm just not sure about the crown on this rifle which I bought used from a gun shop. Thanks!

[Patrick Aherne]

There's a lap you can get from Brownellshttp://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=855&title=POWER%20CUSTOM%20BR ***%20MUZZLE%20CROWNING%20LAP that you can use with valve grinding compound and a hand-held electric drill. I've used it to put crowns on a few rifles that just needed a little touch up.

Use a magnifying loupe to check for gouges and dings + use a Q-Tip to run around the crown. It will snag on any rough burrs or gouges.

[ar15barrels]

Don't go at it with abrasives or try to polish it.
You will inevitably soften the sharp edge in the process.
Get it clean and go shoot it.
Look for a star pattern to appear on the crown.
A streak will eminate from each groove.
The streaks should be EVEN all the way around, meaning that each streak is just as dark as all the others.
If the presence of the streaks is not even all the way around, then you need to have the crown re-done.

[p5200]

Thanks verry much! I will check into that. Is there much danger of me screwing it up? lol

[p5200]

Don't go at it with abrasives or try to polish it.
You will inevitably soften the sharp edge in the process.
Get it clean and go shoot it.
Look for a star pattern to appear on the crown.
A streak will eminate from each groove.
The streaks should be EVEN all the way around, meaning that each streak is just as dark as all the others.
If the presence of the streaks is not even all the way around, then you need to have the crown re-done.

I'v noticed the pattern you refer to on my new Savage 93r17 hmh-BVSS. but, looking at the crown on the 10 FLP Model .223, I don't see a good distinct pattern and looks like one or two streaks from riffling grove are either real short, or missing. don't see any dings though. Thanks!

[NeoWeird]

I'v noticed the pattern you refer to on my new Savage 93r17 hmh-BVSS. but, looking at the crown on the 10 FLP Model .223, I don't see a good distinct pattern and looks like one or two streaks from riffling grove are either real short, or missing. don't see any dings though. Thanks!

That is most likely caused by a crown that is not perpindicular to the bore. What happens is as the bullet is propelled by the hot gases of the cartridge being fired, the pressure behind it build very rapidly. The moment the bullet's base exits the barrel the high pressure pushes in all directions and vents out the side. The groves of the rifling at the first the open so the streaks seem to burst in a star pattern from the groves. If the crown is perfectly square then the star pattern will be even all around as the bullet leaves the bore/groves at the exact same time on all sides.

Now imagine that your barrel was cut with a 45 degree slant on the front. The bullet will leave the top of the slant first, gases will escape there like normal, but the bottom will still be supported. As the bullet leaves the bottom portion of the barrel the gas pressure behind is nowhere near the pressure it was when the bullet was fully supported. The result is little to no pressure leaking past the bullet as it passes because the pressure is already all gone. This is in essence what is happening with your rifle, except exagerated.

The crown is important because it acts like a launch pad for a rocket; if it's angeled then the force will push more on one side either causing your bullet to drift off center or to tumble in the air as the gas pushes on one side and not the other. The result is like sitting on a swing and having someone push one side of the swing and not the other.....only moving at three times the speed of sound. It may not LOOK like it's slanted, but if the pattern is not even then it is. It may not be much, maybe only .001" but that gets exagerated downrange to the point where your shots may not even stay on the paper.

If it's uneven it needs to be recrowned. There are tools to do it yourself, but if you don't understand how and why a crown works then get someone else to do it or spend some time learning on the subject. You'r be surprised what just touching a crown with emery cloth can do when it's spinning fast enough.

Oh, and NEVER EVER try to do a crown with your hand. Hand tools are a differnt story, but using your finger or palm (I've read people's advice to new shooters to do this) is BAD. Your finger pushes differently at each location so it will never be square and even. Use the proper tool and you will save yourself a lot of time, money, and pain killers for the headaches you will avoid.

[m24armorer]

I haven't been streaking since college........