Author Topic: Barrel Rifling (Read 527 times)

Pookee · « **on:** August 15, 2004, 04:16:14 AM »

Did TC use different rifling in the same calibre barrels?
I have noticed some barrels have a sharp step where the rifling starts at the chamber, and others that have a tapered (smooth transition) at the chamber.
What are the differences?
How do you seat the bullet if the barrel has the taper type?
Is accuracy better with one type versus the other?

bgjohn · « **Reply #1 on:** August 15, 2004, 04:28:55 AM »

I've seen some with R.H. twist or L.H. twist in the same caliber.
JM

Pookee · « **Reply #2 on:** August 15, 2004, 04:38:09 AM »

The RH twist was manufactured for the Southern Hemisphere. :wink:
Although there might be some truth to that.

Gavinator · « **Reply #3 on:** August 15, 2004, 05:36:25 AM »

1) Yes, .30 cal. is the best example of this
2) The steep angle makes it harder to accelerate the bullet, causing higher pressure in the chamber, which could help a factory rifle round in a pistol length bbl..
3) Same as any other, find the over-all length that touches the lands, then seat the bullet deeper by .005" to as much as .03" . The closer the bullet is to max OAL most shooters say it's more accurate. The closer the bullet starts to the lands of the rifling, the higher the pressure will be.
4) The shallow taper.
X) The tighter rifling twist bbls. will cause higher pressure & have slower velocity. The weight of the bullet or length, needs to be taken into consideration, as demonstrated by JDJ's 300 Whisper a 1 turn in 8" twist bbl will stabilize a 220gr bullet, while T/C's 1 turn in 10" will not.

Catfish · « **Reply #4 on:** August 16, 2004, 04:29:46 AM »

Seating the bullet into the land by by .005 to .03 is a real bad idea for most people. For one thing all of the data in the reloading manualy would be way over presure. Your presure curve would spike real early limting the amount of powder you could burn and your velosity. Roy Weatherby when the other way with his rifles. He used alot of free bore so the bullet could get a jump in velosity befor it hit the lands alowing him to get more velosity from his rounds. That practice did hurt his accuracy though. There is alot of different oppenions on what is the best bullet jump, if any. Most bench rest shooter load their ammo so that it has some jump to the lands, usually between .005 and .015. There are some that load touching the lands, but I don`t know of any jaming the bullet into the lands by .030.

cbagman · « **Reply #5 on:** August 16, 2004, 04:12:06 PM »

I believe I would vote with Catfish here. I was shooting some 120 Sierras in a 7-30 Bullberry barrel and some 130 grainers with higher ogive and the 130 bullets touched the lands and were showing pressure signs badly..Flat primer. I was seating them same oal. The load was not max.. cbagman

Gavinator · « **Reply #6 on:** August 28, 2004, 07:11:59 AM »

I'm sorry I didn't make that crystal clear, but most reloaders seat their bullets into the cartridge case, not the bbl.. So after you have found the length that touches the rifling lands, seat the bullet further into the case by .005" to .030" .