Accuracy: Crown vs Grooves and Lands

T

troopcom

New member
I have been a long time collector of various types of milsurp rifles. When I look at a barrel for a good shooting milsurp, I look at the lands, grooves, and the crown.
My question is, What is the most important factor to look for, for an accurate shooter?
Lands and Grooves or the Crown?
The particular rifles in question are some Mosin Nagants I'm currently deciding on.
 
Well...
The rifling is critical.
The crown is critical.
You can fix a bad crown.
Can't fix bad/worn/pitted rifling....

I have a 91/30 sporter that has great rifling, and also had a perfect crown.
But, I wanted to see if shortening the barrel would improve accuracy, even though it was already a good shooter. Chopped the barrel to 22", and gave it an 11 degree target crown. Shoots minute of angle now.

Best to have both, but a worn/pitted bore means "pass"...
 
My namesake Mauser's bore looked like old corrugated metal roofing. The lands had been rounded over, had massive pitting, and were is absolutely terrible condition. The grooves were even worse. The pitting and cupro-nickel deposits were incredible. It looked like something you would find in a black powder rifle that had been buried for 60 years. ...Just terrible.

But, the crown was pretty clean.

If you can determine accuracy by the condition of a bore, that rifle should have been printing shotgun patterns at 6".

But, it didn't. It held 2 MoA, or better with surplus ammo. With proper factory ammo, one of my brothers claimed regular .75" groups at 125 yards (iron sights).

And, there are two Mosin Nagants in my family, that have even worse bores, but maintain decent accuracy. (One M44 looks like a cratered smooth bore, and maintains about 2.5 MoA.)

Condition of the lands and grooves doesn't mean a damn thing. It's how far the throat and bore have been erode, that matters.
Started life as a .323" bore, but now it measures .326" in a few places? ...Not likely to be a shooter.
Was once a .311" bore, but you're up to .318" now? ....Not likely to be a shooter.
Started life as a .323" bore, looks like hell, but still comes out to .3235"? ...Probably a winner.


If you want to judge a bore for accuracy, without shooting the rifle... You need to take measurements (slug it). Your eyes tell you how pretty it is; not how accurate it is. ;)
 
All the visual factors have been mentioned. Anything after that is going to require gages.

Barrel diameter can and does vary, especially 8mm Mausers and Nagants. I have a refurbed K98, refurbed by the Yugo's. Shiney new barrel. Bore diameter is not .323, it is something like 327 or .329! Finnish Nagants have bore diameters all over the place from 308 to 311.
 
So are the Finnish nagants bad? i have one that is a reworked M91/30, crown is great, but the lands are a little worn, no pitting. Also how do you "slug" a bore? What kind of tool do I need? How much are they? Is it practical to do it at a gunshow?
 
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