JMH,
AMEN!!!!
beltfed/arnie

I have been following this thread and I have no dog in this fight.
Seems you're a bit one sided to me.
Let sleeping dogs lie.
Aaron

Bullet fit is an interesting subject all its own as it can make a real good barrel into being just the opposite. It serves multiple purposes one being to create a more consistant powder burn and helping to keep the pressure curve in check. Think of it as being a cork in a Champagne bottle and the effects it has on maintaining enough back pressure and long enough for it to go flying across the room. I am a big fan of cylindrical bullets, 1/16 alloy, a real snug fit and a long baseband. A good example is my current 28 bullet the body is 2 thous. over groove and the base 4 and it just seats snuggly and the results are quite remarkable on the target. I used to be of the same school of thought as Frank but after hours of conversations with my good friend Barry Darr on the subject several years back it all finally clicked and for the better by far for my own personal use. 

I might add the leade angle in my throat is also conducive to this snug fit and it might not work for others based on it alone.
JLouis

So with smokeless.006 will have no advantage over .004?

So would a six groove be better than 3?

The basic groove depth, standard for 32/40 is .003 deep and most number 6 to 8 grooves.

My 33 cal has 6 grooves, with narrow land, .330 bore and .337 groove (it also has a felt choke when cleaning it), it ends in 15 twist and can shoot a bullet 1.30 long, with accuracy. Pictured target, shot at 200 yd. The 2 bullets that I have been using in matches are 1.19 & 1.21 long.

Anything you do to a lead bullet, getting it into the rifling, displaces metal. Hopefully, nothing goes off center while doing it. 

A 3 groove, displaces 1/2 the metal that a 6 groove does and that's why I bought that barrel. I don't recommend the 3 groove though, at this time, as I haven't tested it.

Frank

Thanks for your replies so far. I have further questions:

1. Is there any truth in an odd number of grooves having an advantage over even number because a odd groove number means that the groove and lands oppose an there is less bullet deformation? I guess I an referring to the 5R rifling is it better than conventional 6 with it smoother transition?

2. I believe Krieger will alter groove dimensions for a price, if I went down this route, what width of lands would be optimal for a 6 groove barrel?

Thanks

JLouis wrote on Aug 16^th, 2017 at 6:17pm:


You're welcome John.
What is very interesting to me is the way Pope and Schoyen cut their grooves. Pope used a flat cutter and his grooves were cut just deep enough for the center of the cutter to reach the bore diameter. So he was just cutting two corners for each groove. But he left very narrow lands in between each groove. LH twist.
Schoyen's cutters were concentric to the bore contour, and about the same depth as Pope's, and also with narrow lands. RH twist.
So the two masters had very different methods of creating a similar looking rifling, and a very accurate barrel.