Chasing the lands... how far?

[XTR]

Last yr I shot N550 in one of my F-TR rifles, put a little over 1500 or so rounds down the tube (don't have the log here at my desk). Working up new loads this weekend and found that the distance to the lands has moved about 8 thou from when the barrel was new.

Anyone have any idea how far it will usually go before it craps out? I've scoped it and I really didn't notice anything that looked bad, didn't really see any fire cracking.

 

[searcher]

It can go a lot further. How much further really depends on the bullet you are using and how much seating and neck tension you are left with after continuing to move the bullet further out. As long as you can still effectively seat your bullet, get it to where it needs to be in proximity to the lands and the throat is not too rough to cause drag and shred on your bullet surface - you should only need very minor tune to the load when called for. You barrel will tell you when it is done in terms of accuracy first in most cases.

I have a few 6PPC's in which I shoot the Berger 62 gr. Match bullet. Berger doesn't even provide load data for it in 6PPC because in most 6PPC chambers (as with mine), the bullet is only in the neck about 40% of the way when jambed. Throat erosion is a big, big deal for me using this bullet. If you have only lost .008" or so and shooting obviously much longer bullets used in F-class and "recommended" for the chambering - you are in good shape. I'd say you have thousands of rounds to go, solely on an erosion basis that you are measuring. Unfortunately, the more difficult area to measure is the wear of the lands in that first three inches or so and what the cracking does to your bullets. I've been told by my gunsmith that when that gets "washed out" (or "toasty"), the barrel is toast - regardless of whether you are still making contact with the lands. In a 6PPC, he said that could be in 1,000 rounds or 3,000 rounds. he had set at least one world record on a very high-count barrel. As we know, .223's, .308's, 6BR's, etc. all typically outlast the PPC, some by a very large margin.

 

[ShootDots]

My last 6.5 x 284 barrel went with 87K loss of throat... It had 1700 rounds thru it... 8K is about what you lose in 2 matches... You're in great shape..

 

[XTR]

My last 6.5 x 284 barrel went with 87K loss of throat... It had 1700 rounds thru it... 8K is about what you lose in 2 matches... You're in great shape..

This is a 308, and prior to last yr I'd always run Varget and not really seen erosion happen that "fast" as it were. There is a lot of chatter out there that says double based powder like N550 is harder on the throat, it seems to bear out. I shot that many out of the barrel on my other F-TR rifle yr before last and saw effectively nothing for throat erosion.

I kind of assumed that 8K wasn't much but it's enough that it was pretty clearly there when I measured it.

 

[Shynloco]

0.008" is not much at all...... Must all the life is still left in it !.!.!

What Donovan says. Don't believe all the "chatter" you read and hear, especially about a .308. I've not shot N550 in mine, but used plenty of Varget, IMR4895 and RE15 that has to be harder on a throat than N550. Just my thoughts.