Barrel Rifling

[boondockcrain]

I'm looking at a Thompson Center rifle in 204 ruger. My concern is that the rifling looks shallow (compared to a Remington 700). Is this normal or does this mean that the barrel is shot out?

 

[chris in va]

IIRC Thompson Center uses what's called '5R rifling' where the groove shoulder is more of a 60 degree angle than a hard 90 degree cut, so it may appear less aggressive.

My M&P 15 Sport also uses that form of rifling and it does look somewhat shallow in comparison.

 

[warbirdlover]

chris beat me to the answer. When I was shopping for a new rifle this fall I compared them (new guns) and that is what I noticed.

 

[Scorch]

The firearms industry (at the behest of the War Department in the interwar period) standardized bore and groove for the common calibers in order to eliminate confusion and variations from one maker to the next. The result is very little variation between makers, the whole idea of standardization. Different barrel makers have developed other rifling designs, like 5r, Microgroove, polygonal rifling, etc, that vary from the traditional pattern, and these may look deeper or shallower, but they are usually within the same bore/groove specs as the older styles. No matter what, rifling is only a few thousandths of an inch deep.

 

[Hawg]

The shallower the rifling the less bullet deformity and better accuracy. The draw back is faster accuracy loss. Krieger makes some of the most accurate barrels there are because they use shallow rifling.

 

[tim s]

Uh...no that is absolutely not the case and I use/have used Kreiger,Bartlein, Hart, & Shilen barrels on my BR guns and Varmit guns. Kreiger makes a fine barrel because of uniformity, cut rifling consistancy but not really anything to do with depth of rifling which is about the same as any other match barrel maker. I've never seen anything about depth of lands having anything to do with much other than maybe some wind drift issues and that's been lagely speculation.