Richard Teague
Active Member
Getting ready to ream a barrel and I notice 4H has two variations, the standard 260 Rem reamer and the 6.5 Smack which is the 260 with a 1.5 degree lead angle. Is one better than the other?
Which 260 Remington reamer
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Canadian Bushman
Well-Known Member
My opinion on lead angle is that it only really correlates with the bullet being used.
Dan Lilja ran a number of test on this topic which i believe are still posted on his site.
riflebarrels.com
His idea was to see if there were accuracy improvements in matching lead angles to the angle of tangency on the ogive of a given bullet.
I believe in recent years, the shallower angles are preferred for less of a pressure spike from lower engraving force and more potential for higher MV's. 1.5 deg is very common these days on most reamers.
Dont quote me but I think Roy Weatherby was one of the pioneers of this, of course coupled with large amounts of free bore and slow twist. He knew early on that speed sells.
Dan Lilja ran a number of test on this topic which i believe are still posted on his site.
A Look at Bullet Ogives and Chamber Throat Angles - Lilja
After ordering a new set of bullet dies recently, I began to wonder how the new ogive shape that I had decided on would compare to the throat angle of my chamber reamer. Typically the reamer makers will grind a one and a half degree angle on the throat (or leade, as it is sometimes... View Article
His idea was to see if there were accuracy improvements in matching lead angles to the angle of tangency on the ogive of a given bullet.
I believe in recent years, the shallower angles are preferred for less of a pressure spike from lower engraving force and more potential for higher MV's. 1.5 deg is very common these days on most reamers.
Dont quote me but I think Roy Weatherby was one of the pioneers of this, of course coupled with large amounts of free bore and slow twist. He knew early on that speed sells.
Richard Teague
Active Member
Interesting link, the math is pretty deep and the formulae long. However "it just works" is good enough for me.
Canadian Bushman
Well-Known Member
Basically you want the bullet to enter the barrel straight.
If the ogive tangency and lead angles match, the bullet will want center up well.
With shallow angles the bullet can get a little crooked as it enters the rifling.
The differences are minor. With straight, concentric, ammo and seating close to the rifling, its a moot point.
If the ogive tangency and lead angles match, the bullet will want center up well.
With shallow angles the bullet can get a little crooked as it enters the rifling.
The differences are minor. With straight, concentric, ammo and seating close to the rifling, its a moot point.
Bob Wright
Well-Known Member
I would at least call the reamer maker and see what bullet styles work best with those 2 reamers. If they have 2 reamers, they should know. Then you could understand reamer/bullet correlation and decide from there. Mainly based on, "I plan on shooting this bullet a whole bunch more than that bullet"
Richard Teague
Active Member
Well I thought the barrel was short chambered but it turns out it chambers factory ammo with just a small amount of resistance. It shoots pretty good also with some very old Remington 140 gr. factory ammo.
