how can you tell if your rifle has a bad crown

[Laker_Taker]

Guys,
I was at the gun range the last weekend and watched a guy shoot a 30-06 bolt. He was shooting at a 3 inch circle at 100 yards. he could hit it about 2 out of three times and the miss shot was about 12 inches off. thinking it was him. I offered my gun vice and the same results. I told him to check all the screws and he did saying they were fine. I said there has to be something going on with your scope. he said it was his crown. does anybody know if there is a way to determine if a crown is bad. this was a older gun. Probably from the 80's and was beat up. Out of my own curiosity I would like to know how to tell if a crown was bad?


thanks LT

 

[DrMike]

Visual inspection can reveal a problem. Alternatively, if a burr is thought to be the cause, running a Q=Tip over the crown will reveal the burr. In many instances, there is neither a burr nor an obvious flaw. If all other issues have been addressed and the problem appears to be down to imprecise crowning, recrowning requires only a matter of seconds with a hand-tool.

 

[FOTIS]

running a Q=Tip over the crown will reveal the burr

Roger that

 

[Mortis]

Not sure this applies here...but I'd feel remissed if I didn't mention it.

NOTE: DrMike and Fotis are on the money....+1

Anyway, I recently got to test Dave Manson's Crowning Kit. One of the barrels we tested it on was a take-off. A Remington 22-250 Varmint barrel. Unfired. It was taken off the action cause the owner was building an wildcat and only needed tha action.

So....just as I started to recrown I noticed several things odd with the muzzle end.

1st........ it had zero crown. None what so ever.

2nd........the muzzle end was not smooth, but had major tooling marks.

3rd.........as I set the squaring tool in place, it was not square to the muzzle, even tho the tool guide provided in the kit will in fact set the tool square to the bore.

Using a protractor, I discovered that the muzzle was 5 degrees out of square.

Now as a machinist, I am puzzled how this could be so messed up and still sold as a quality piece of hunting equipment.

There is no way a muzzle in such a condition from the factory would ever shoot properly.

As I squared the muzzle, it became even more obvious how bad this muzzle was. I had to take nearly .060 off the end before it cleaned up and ready to crown.

Sometimes the problem is not easy to see unless you know what you are looking for. I was not especially looking for anyting wrong, but the eye told the brain to dig deeper.

Before Chamfering.....

After Chamfering......

 

[Oldtrader3]

What is bothering me on this issue is the two shots in group and one out. Usually if the crown is bad, you do not get any repeatable small groups for any shots. Sounds to me without any more information, like a bad scope or bedding problem?

 

[Dr. Vette]

What is bothering me on this issue is the two shots in group and one out. Usually if the crown is bad, you do not get any repeatable small groups for any shots. Sounds to me without any more information, like a bad scope or bedding problem?

I agree.

I would also suspect loose or improperly tightened screw, bad mounts, bad scope or he's shooting them too quickly and the barrel heats up. Alternately he may not have cleaned it since the 80s either and by the 3rd shot it's done.

3 shots at least 5 minutes apart should tell the story if it's heat or similar. A few moments with a FAT wrench and a Q-tip will evaluate the fasteners and the crown.

 

[PJGunner]

What is bothering me on this issue is the two shots in group and one out. Usually if the crown is bad, you do not get any repeatable small groups for any shots. Sounds to me without any more information, like a bad scope or bedding problem?

I'm inclined to agree although I'm thinking if the two close ones and then the one way out of the group is on the last of the three shots the problem might more likely be bedding. If it's random, then possibly the problem is the scope.
I have a Winchester M70 Featherweight that I bought from a friend who said the gun was very accurate. I'd bought from him before and he's never represented a gun before so when this 7x57 shot patterns rather than groups I had to start digging. checked all the screwsand they were OK. Took it to my gunsmith who glas bedded the gun, free floated the barrel and did a fantastic trigger job. No help, the gun still shot patterns. I was thinking, "Naw, it couldn't be the scope. brand new Leupold bad?" Well I put another scope on the gun and went to the range. My friend hadn't lied about that rifle. After getting it on the paper, I shot a .75" group. Not three shots but five. One load it absolutely loves is the 170 gr. Sierra round nose at 2400 FPS using W760. groups run from .375" to .50" depending on how well I'm shooting on that day.
It sure does torque my jaws that Sierra discontinued that bullet and when my meager supply rins out, well they'll just be gone. I've done some work with Hornady's 175 gr. bullet but so far .75 to one inch is the best I've gotten from that bullet.
I sent the bad scope back to Leupold and they had it back in about a week totally repaired. That's fine fast service in my book.
Paul B.

 

[Oldtrader3]

Paul, I have gotten some really good groups from the 160 AccuBond in my .280 Rem. The 140 Partitions shot really well in my .280 Rem as well. The AB's are not too expensive, especially if you can get some from SPS. The 140 BT's are very accurate to and probably cost about the same as the Sierra's.