What are the symptoms of a bad crown?

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pyscodog

Active member
Anyone experience a bad crown? What are the symptoms? My 700P is giving me a bit of accuracy issues, A guy looked at the crown today and we both noticed that I'm not getting a star pattern at the muzzel. I have 5 marks but was thinking there should be six, like a star. Groups always have at least one flyer if not two. Maybe it just like what I'm feeding it, IDK?? He suggested buying a kit from mid-way to polish the crown. I can't find any "kit" that mid-way offers.
 
you should see one mark for each groove in the rifling.

if you have a 5 groove bore , you'll get 5 marks
6 groove bore, you'll get 6, etc.


if they're evenly spaced, you've got the right amount of marks. if there's one that's missing, or one that's much larger than the others you may have a problem.

generally speaking if your muzzle blast pattern is even and consistent around the bore you probably have an OK crown based on everything i've read on it.
 





if they're evenly spaced, you've got the right amount of marks. if there's one that's missing, or one that's much larger than the others you may have a problem.

Thats what I'm seeing, one is missing.
 
I don't think so. Just looked and mines got 6 grooves with no marks on one groove. The other five have a small dot on the face of the crown. The marks/dots on the crown are different in size also. Watched a few videos on DIY polishing the crown. Some say its good, others say it hype??
 
PSYCHO: Had a 257WBY that had BAD flyers. Took gun to gun smith and had bad erosion on ONE groove; that was my problem. re-barreled to a 7MM RTEM MAG and never looked back. JMHE
 
I had a bad crown once and the result was big groups not fliers. It was fixed with a ball bearing and 800 grit wet/dry paper. It depends on the type of crown if it is a crown that a ball will fit it don't take much to fix it sometimes.
 
Quote:I can't find any "kit" that mid-way offers....You might consider calling the guys at Brownells to see if they have one...Always had helpful experience when I needed something to solve a problem..

If you are shooting reloads, double check the consistency of the rounds before going into the expense of recrowning if visual inspection indicates no probelm,,sometimes the runout, powder charge, or bullet weight can cause an occasional flier...If, out of five rounds, the flier is consistently in the same place, the barrel may be the culprit...

If you have a certified gun smith locally, you might have him recrown it with a 11 degree target crown...Unless the barrel is already short as far as legality, you won't notice a drop in velocity and the accuracy will definitely improve...

You will have the same number of Lands, as you do Grooves and I think the powder pattern comes from the Grooves...Loss of part of the pattern would indicate one of the Lands is damaged and should be noticeable with a magnifying glass..
 
Plenty of barrel,26 inchs. I've seen a star pattern on most of my rifles. This one has dots. Sorta weird, most are small but one is alot larger and one is MIA. I saw a video where they used a brass screw and lapping compound to work the muzzle. Some said it was a waste of time.
 
Re crowning by shade tree efforts may work on occasion (even blind pigs find acorns on occasion), but I would have much more faith with the barrel in a lathe and being cut by a competent smith or machinist...
 
Remember the article in Precision Shooting I think where the guy did a crown test? Stock crown group, then damaged the crown intentionally and shot, then reamed out the muzzle with a carbide bit completely destroying the crown and the rifle shot the same or better each time? Where's catshooter when you need him...
 
Shade tree is it. I am offended. Blind hog indeed. Seriously I know of two good gunsmiths that polish the crown with a bearing. What are you going to find that is rounder. It's not like you might get the bearing sideways. Blind hog,Ha.
 
Originally Posted By: tnshootistShade tree is it. I am offended. Blind hog indeed. Seriously I know of two good gunsmiths that polish the crown with a bearing. What are you going to find that is rounder. It's not like you might get the bearing sideways. Blind hog,Ha.


LOL. Good post!!

I bet there would be a lot of surprised people if they found out how their favorite smith re-crowned/cleaned up the crown on their rifles. If the smith isn't cutting a totally new crown on the end of the barrel, a round fine stone or a bearing and some jeweler's rouge or another similar fine abrasive works wonders in short order.

The comment that, "It's not like you might get the bearing sideways." is a classic on this subject.

Fire away, boys.
 
I can't visually see anything wrong with the crown on my rifle. I used a magnifier that we use at work that is supper strong and see nothing wrong. I drug a cotton swap over the crown, inside the barrel and found no rough spots anywhere. The dots on the crown will not rub off with bore cleaner or an abrasive pad, looks to be something maybe through the coating. I'm beginning to think I just haven't found the "right" load for this rifle. I did paint the crown with some flat black and plan on another trip to the range tomorrow to see if the dots reappear or if I get some sort of star pattern. Never seen dots before and that what was bugging me and started all this. Will update after the trip to the range.
 
You will not see a bad crown with your naked eye...unless of course it is pathetic, and I have seen some come that way from the factory. I think at one time or another Remington tried to train circus chimps to crown rifle barrels wit a dull bit brace!!! Seriously, that crown is very touchy. A very small imperfection can affect accuracy. Generally speaking though the crown wont cause flyers...it will definitely cause the group to open up. The only really proper way to have it checked is to bore scope it. The only proper way to correct this is to recut it on a lathe. The "kit" others were referring to is either a lapping tool or that useless piloted cutter that you turn by hand. Make no mistake, that lap is not a tool that will correct a problem crown. The lapping tool is good for removing a small burr at the very edge after cutting on a lathe. It might save a recrown on a barrel that was scraped by a cleaning rod but that about the extent of it. Under no circumstances do you want to ever use one of those hand tools that "pilot" in the muzzle. The absolute last thing you want to do is stick a piece of hardened heat treated tool steel pilot in the muzzle and rotate it in that bore, especially at the crown where it will do the most maximum damage. It's a bad tool.
 
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