Bad barrel crown?

[Willyp]

How can you tell if a barrel needs recrowned????
I have my son-in-laws 30-30 Marlin-336. I just can't get it to group at 50 yards. At 100 yds. it is a terrible group of 6 to 10 inches!!!!!! I've tried so many different loads and 4 different bullets and different primers! Maybe 2 will come close to each other and then it will shoot 6 to 10 inches some where else!!!!!!!!!
I am useing Jacketed bullets and crimping them. I have tried scrubbing the heck out of the barrel.
The barrel end shows no damage like a dent or ding.

[DougGuy]

Is it scoped? Tried a different scope? Could be the reticle is loose and bouncing around.

[Willyp]

Yep,done that. also new rings and bases!

[Teddy (punchie)]

I tell people to get a small file, like a key file or saw file and dress up the very edge. I get a 10-20 power magnification and look for burr or a bump mark and lightly file it smooth. Sometime you can see it without anything helping you. Sometime you can see them by looking down the bore. I have only found one in and older rifle that looked like it was a barn gun.

I guess if you would slug the barrel there a chance that it may show on the slug as a extra wear mark. Maybe if bad enough the slug would get extra tight at every end of barrel.

[Teddy (punchie)]

On scopes lock tight the mounts and bases to gun and rings to scope, let set for a couple of day or heat to warm with hair dryer and set for over night.

[Love Life]

Have someone else shoot it to see if they have the same issue.

[Willyp]

4 different people shoot it last saturday,with the same results???? This is being shoot from a rest not off hand.

[Blackwater]

You didn't say whether you're using jacketed or cast, or what parameters your loads include, but if you're concerned about your crown, here's a little trick I learned from a country boy "gunsmith" that has turned quite a few rifles locally from poor to so-so shooters into really accurate hunting/shooting tools.

The first time I saw him do this, I nearly swooned, but the results couldn't be denied. I watched him shoot a very surprisingly wide group, and he tried some factorys that were provided by the guy who owned the gun, and some of his handloads he knew to be good, and neither performed worth a darn. He checked the bedding, scope screws for tightness, checked the scope for any signs of having moved or not being tight, and all that was good, so he decided to re-crown the muzzle and try that. It's always a guessing game as to what to do to make a gun shoot, and this was what he was left with. So, he broke out a bullet shaped burr with big ol' "teeth" on it that he'd gotten from work, and put it in his hand drill. Then he eyeballed it to get it aligned very closely with the bore, and spun it a few quick "brrps," and then laid some 600 grit sandpaper over it, folding it like the old flat coffee fileters so it formed a funnel over the burr, and spun that on the muzzle a couple of times, and we went out to try it again. I was shocked at the tools he used, but when we went outside and tried it, it put them all into the same hole at 50 yds.! Despite my shock, seeing is believeing, and I saw him do this a couple more times before I could bring myself to give it a try on any of my own guns.

When I tried it on my own guns, I decided, due to my "finer" sentiments, to use one of those bullet shaped grinding bits instead of a burr like he'd used, and darned if a 10/22 Ruger I had that I couldn't get to shoot went from shooting 1 3/8" at 50 yds. to 3/8"!!! Now THAT will make a believer out of ya'! BIG time! I'd already glass bedded this gun, and done everything else I knew to do, and it turned out to be the crown that really turned that gun into a tack driver.

He and I both, and many others out there, have come to conclude that most factory rifles and other guns don't get really crowned very well. They seem, from what I can see at least, to just cut them and let 'em go as is. I've found that a really good, smooth crown job helps a great many rifles these days. The economy and hostile environment the gun mfgr's work in today makes them HAVE to cut any corners they can, just to stay in business these days, and I understand that. Also, most people just can't shoot very well these days simply from lack of opportunity to do so. It's getting harder and harder to find a PLACE where we can shoot now, that it's really a bit of a miracle we do as well and as much shooting as we do!

Little things like knowing what to do when accuracy is the gun's fault, though, really CAN make a huge difference. When I get a gun that won't shoot well, I do like my buddy did and check the bedding, scope rings and screws, and the scope itself (becuase they CAN, even in better makes, go bad) and the last thing I'll usually do is re-crown the muzzle, but that HAS literally transformed a good many rifles, has never hurt a single one, and even in some decent shooting rifles, has usually proved to provide at least some degree of improvement, and it's been very consistent across the board - so much so that I've taken to doing it before I do even my initial tests these days. Factories just can't afford to do all the fine tuning that makes many guns really shoot like a dream, and still sell them at an affordable price, so knowing a few "tricks" like this CAN often be a huge help.

If it's the crown that really is your problem, then try the little drill and bullet shaped grinding bit with some 400 and 600 grit wet or dry sandpaper over it, and it's doubtful you'll harm it, and very possible you may be able to get much improved accuracy. It's really just doing what needs to be done for the bullet to get a good, clean, consistent exit from the muzzle, and that's important for accuracy.

And incidentally, as to alignment, a prominent benchrester/experimenter once did a test on barrel crowns, and cut a single barrel several times to see what effect the angle of the crown had on a rifle's ability to group. I think he go to an angle of something like 20 degrees off square, and the accuracy remained much the same throughout the several angles he tried, which was a big surprise for everyone, including him, but that's the results he got. I don't recollect how he smoothed the crowns, but however he did it, it obviously worked, given the terribly acute angles he used. I suspect he just got curious as his experiment progressed, and just kept going until he got to a rediculous angle. It was one of those experiments that I've always remembered because it was so startling in the results.

A lot of gunsmiths have propounded the theory that crowns have to be dead flat square, and burr free, but that old experiment tends to indicate that the mainmost thing is that the crown be burr free, which many, many factory guns and some guns that have been used (and thus have a ding on the crown from that use) may well benefit from a very simple re-crown job. Because most people think it must be done by a gunsmith on expensive lathes, etc., they pay big money for a re-crown job, and not without some merit, of course, but this simple do-at-home proceedure has really worked amazingly well in my experience, and I've done at least 40 (probably more) guns like this, and never had anything but positive to VERY positive results from it. You DO have to use care in doing it - good workmanship always shows - but given that, there's no reason this can't be used by most folks here. Idjits can mess up an anvil with a rubber hammer, and some of us just aren't gifted very well with these abilities, but the average person shouldn't mess anything up, and should get positive results, so if you want to try a simple, cheap re-crown, give this a try and see what happens. Crowns DO matter, and a LOT more than most would think. Don't forget all the other things, too, including replacing the scope with another you KNOW is good. I've seen that be the problem more than once, and it's always surprising, but you really have to allow for surprises when dealing with a gun that just won't shoot. Very, very few guns don't have the ability to shoot amazingly well now, but some need a bit of fine tuning or correcting to do it well. Hope this helps.

[Love Life]

Dang. You've eliminated shooter, scope, and ammo.

[John Taylor]

I like to cut crowns in the lathe but some times that is not possible so I bought a crown cutter from Midway that works on 30 cal barrels. I get quite a few Mosin Nagant rifles in to have the barrel shortened and it works great on them ( barrel is very hard to get off for the lathe). I have also used a counter sink for flat head screws for breaking the sharp edge which also works great. The idea of using a round headed brass screw and grinding compound is way to slow when your working by the hour. Basically the crown should be at a right angle to the bore and be even with no burrs. I had a 22 in that would not group at all so I cut 1/4" off the end of the barrel and crowned and now it will put them in the same hole at 25 yards.
http://www.midwayusa.com/product/334892/ptg-muzzle-crown-facing-tool-and-radius-cutter-interchangeable-pilot-m1-garand-1964-pattern?cm_vc=ProductFinding

[pietro]

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I suspect that the rifling @ the front end of the barrel may be worn from years of improper bore cleaning from the muzzle, ILO pulling the bolt & cleaning from the rear.

If that's the case, as an alternative to shortening the barrel, the rifling might need to be removed from the forward 1"-2" of the bore with a drill bit, then re-crowned internally at the new leading edge of the rifling.


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[Willyp]

Blackwater,i've seen what you wrote and i've seen it done also!!!!!! I will try shooting it ,with different loads and bullets once more,before i stone it.
Also,the next to the last sentence says i was using jacketed ammo.
I sold this gun to him,maybe 20 years ago. I shoot it in for him before every season. I take him and my grandson to the range as much as they can make it.[Pappy supplies free ammo!!!!]
Last year,proir to season i shot it and so did he. It seemed to not be up too the way it shot the year before,but i did not say anything to him! He can't shoot for sh*t anyways!!!!!!!!!He missed 2 does last year,but i blamed it on his ability?????

[John Taylor]

I get a lot of old rifles in that are missing the last inch of barrel. This was/is a common way to get an old rifle to shoot strait again. I sometimes get asked to repair these old barrels by adding an inch and installing a liner.

[Jim_P]

Dave Manson Tools has a Military Rifle Crowning Tool Kit for $130.00 Page 16 in the Catalog located here:

https://mansonreamers.files.wordpress.com/2015/06/small-file-july-2015-catalog.pdf

I have one. It's easy to use and works wonderfully. I turned a so-so shooter into a great shooter with a recrown and float job on the barrel and a metal filled Acra Glas bed to the action.

[flounderman]

The end of the barrel isn't bulged by any chance? The ones that are carried muzzle down on the truck floor get sanded out and won't shoot, but cutting them back will cure it. I had to cut a couple back several inches to eliminate problems. One was bent. Some of the military rifles were counter bored to get to good rifling.

[dragonrider]

I use these tools for crowning when needed, they were simple counterbores. I make whatever pilots are needed.
http://img.photobucket.com/albums/0603/PaulGauthier/BARREL%20CROWNING%20TOOL/IMG_0278.jpg (http://smg.photobucket.com/user/PaulGauthier/media/BARREL%20CROWNING%20TOOL/IMG_0278.jpg.html)

[Whiterabbit]

inspect the crown with a magnifying glass or a loupe. Does it look crisp and perfect? next, take a q-tip. stick it down the bore and drag it along the barrel over the crown. did any threads get pulled?

If you get a failure anywhere, take to smith or buy the tool above. I got a nice crown on one rifle just cutting the profile using a reamer like the one above. Maybe lucky, maybe by design.but I found that reamer to be enough to do the muzzle profile and crown both.

[Clark]

I did one tonight.
I cut off the muzzle.
I dial in the chuck with a pin gauge in the bore and a test indicator on the pin gauge.
I cut 11 degree crown.
I cut a 45 degree chamfer on the outside.
I polish by pushing with my thumb on a piece of Scotch brite abrasive scrub pad.

[Half Dog]

When the crowning task is completed, what do you use to protect the metal from the environments?

[Whiterabbit]

gun blue.

[ascast]

got any cerrosafe ? do a muzzle cast of the last 2-3 inches. you will have to clever about knocking it out, maybe remove barrel or install a cleaning rod before the cast in poured. A good cast may show real problems.
Have you every checked your ammo for "ZERO READOUT" before shooting? It could be a good indicator of bad crown.

[Willyp]

I figured it out and it is shooting 1 1/2 inches at 100 yds.

[osteodoc08]

I figured it out and it is shooting 1 1/2 inches at 100 yds.

What was the cause?

[Willyp]

I can't say for sure but i scrubbed the barrel with Isso bore scrub,lapped the crown and took some tension off of the wood forend. It seemed to be pulling the barrel into the barrel clam really tightly??
But it shoots 100% better. I live to far from the range to do one thing at a time and go shoot.