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Hi all,

I've had my Marlin 336C for around 5-6mths and taken it to the range several times. I've tried at least 6 different major factory ammo types but no matter what, I just can't seem to get consistent grouping. I seem to get flyers and rather large groups.

I figured maybe I'd just not found an ammo that this particular rifle likes but recently read (right here on MarlinOwners) that there can be issues with the Rem muzzles and to check them. So I pulled my rifle out of the safe today and was horrified to see a large burr/engraving groove trailing out of the barrel rifling onto the muzzle.

Sorry the pics aren't perfect but hopefully illustrate what I'm trying to describe. My question is, could this have any impact on the problem I'm having with accuracy? Thanks in advance.
 

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I would have that crown fixed. A nick a the edge of the bore has to affect accuracy. A properly cut crown free of nicks or burrs is far better than rough or dinged up crowns. The crown needs to be cut true to the bore at the muzzle no matter what the degree is. My brothers 34 Remington 22 shot bad with all ammo tried. One day we were shooting and he showed me a nick in the crown similar to the crown in the picture. I used fire lapping compound and a brass screw to crown that barrel and it went to shooting very impressive groups and still does. I have crowned a lot of my older Remington bolt actions 22's with the brass screw method and almost all shot better and none shot worse.
 

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+1 on What Bandit said. The Crown could use touching up. If you are not confident in doing it, a Gunsmith will do it for a reasonable price.
 

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I have seen some awful looking crowns that did not affect accuracy how is beyond me, then some crowns that looked ok shot much better after re-crowning. If it were me I would surely have the rifle recrowned and from the looks it needs to be set back at the muzzle enough to get past the burr. That said you could try a brass ball with lapping compound on a drill to see if you can do it yourself, if you can't get the burr removed they make tools to do it by hand, or you could pay a gunsmith or if someone you know has the tools to do it.

Look at the muzzle after a shooting session the burned powder, and residue should have a distinct pattern around the muzzle (this really shows up good on 22rimfire/lead) if any anomalies stand out then it's a good sign that the escaping gasses and bullet is being affected by the damaged crown. I hope this helps, also there is a huge amount of info on the net on crowns, redoing them yourself etc. I prefer a recessed target type crown in my experience it protects the crown better.
 

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Discussion Starter #7
I have seen some awful looking crowns that did not affect accuracy how is beyond me, then some crowns that looked ok shot much better after re-crowning. If it were me I would surely have the rifle recrowned and from the looks it needs to be set back at the muzzle enough to get past the burr. That said you could try a brass ball with lapping compound on a drill to see if you can do it yourself, if you can't get the burr removed they make tools to do it by hand, or you could pay a gunsmith or if someone you know has the tools to do it.

Look at the muzzle after a shooting session the burned powder, and residue should have a distinct pattern around the muzzle (this really shows up good on 22rimfire/lead) if any anomalies stand out then it's a good sign that the escaping gasses and bullet is being affected by the damaged crown. I hope this helps, also there is a huge amount of info on the net on crowns, redoing them yourself etc. I prefer a recessed target type crown in my experience it protects the crown better.
That's an interesting idea. Thanks.

Thanks everyone for your comments. I have to go back to the dealer in a few weeks or so to pick up a new Marlin 17HMR so will take it in and see what they say. I'll come back and let you know how everything turns out.
 

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Well I agree with the others but have to say those are great photos. I would also have a look at that front sight as it looks canted to the left.
 

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How does it shoot? Try that first before doing anything else.
If you are happy with how it shoots leave it alone, and spend money else wheres.

In your case you are not happy with the accuracy so the crown job is the next step. But do a thorough total inspection of the rifle before you do that and check all the screws for appropriate tightness.
Then and only then move on to the the crown.

I am an economizer-- real heavy on the miser part.
 

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Pay a gunsmith $60 to have it re-crowned.
While he's at it, have him look at that front sight that looks canted to the left.
 

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Pictures taken at odd angles can really affect the image, I have seen this before due to the camera held at odd angles to get a picture of an object that makes the sights or receiver or barrel look bent. I suspect that very thing is how all the flat earthers, and fake mooners get most of their fake nasa footage hahaha

If the OP didn't live all the way under the bottom of the world I would be glad to recrown the barrel for free, surely he has some machinist or gunsmith friends that will help out. Unless you know the gunshop people well and they are known for good work be careful letting them touch up the crown what is now a simple job could turn into a headache... That job as of now with correct tools is less than 15 minutes...and a dab of cold blue if you wish
 

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I see a great opertunity to get that barrel choped down to a more manageble length and you can have the crown redone and the front sight straightened while you are at it.
Good luck
 

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Great pics. I have seen worst crowns that still grouped rounds on the target. There are a lot of things that can cause big groups. Before recrowning did you check to see if you have some tension stress caused by a too tight mag tube ? I had a Marlin that the mag tube was sprung onto the forward mounting stud due to the hole in the tube being drilled slightly off. You had to spring it and force it to go onto the stud on the forward end (where the single screw holds it in). This caused my barrel to be stressed and when it got hot it affected accuracy. After I filed the edge of the hole in the mag tube to where it would drop on without being forced that made my rifle shoot tighter groups. Also, if the crown is not "Square" to the bore but was cut slightly at an angle that will cause bad accuracy too.Make sure you have a good clean bore with no built up copper fouling in the grooves.
 
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Almost definitely. That looks deep.
 
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