280AI barrel life, if....

[Greyfox]

IMO, this is one of the toughest questions given all the factors effecting barrel life. With one of the slower burners like H1000, Retumbo, R26, etc, and the shooting regime you describe, I would "estimate" 1500 rounds, +/- 20% when you will experience groups opening up +.5MOA, an increase in ES, and/or fire-cracking into the lands. After initial break-in, take a picture, or observe the condition of the throat with your Lyman bore-scope. Also, keep a bullet for which you have an accurate measurement of the seating depth to the lands. Give both a check every 300-500 rounds fired along with noting any major change in average group size or ES.

 

[keithcandler]

Greyfox's answer is right on.

Here is the fly in the ointment:

280 AI's are throated differently, so when you ask a generic question about barrel life, the answer is tied to two things:

a. how long is your magazine

b. how much freebore was on the reamer used when the barrels were chambered?

When you work up an accurate load with your rifle for hunting, and you have to use the magazine, you can chase the lands as leade grows. You will get only so far before the bullet is out of the "sweet spot" that it likes for the accuracy node. At this point, you are reduced to seating a bullet at the sweet spot that will be too long to fit in the magazine box, then the rest of the rounds in the mag box will be less accurate.

 

[Bob Wright]

IMO, this is one of the toughest questions given all the factors effecting barrel life. With one of the slower burners like H1000, Retumbo, R26, etc, and the shooting regime you describe, I would "estimate" 1500 rounds, +/- 20% when you will experience groups opening up +.5MOA, an increase in ES, and/or fire-cracking into the lands. After initial break-in, take a picture, or observe the condition of the throat with your Lyman bore-scope. Also, keep a bullet for which you have an accurate measurement of the seating depth to the lands. Give both a check every 300-500 rounds fired along with noting any major change in average group size or ES.

This is a good idea. Keep that same bullet for the Hornady tool I have for a permanent reference point. At least I can monitor that forward creep over time. We discussed at the gunsmith, that I was going to work with 150-168 class bullets and he agreed he had a reamer to put me in that window. I will see if he has the throat dimensions from his reamer drawing for reference.

 

[Bob Wright]

Greyfox's answer is right on.

Here is the fly in the ointment:

280 AI's are throated differently, so when you ask a generic question about barrel life, the answer is tied to two things:

a. how long is your magazine

b. how much freebore was on the reamer used when the barrels were chambered?

When you work up an accurate load with your rifle for hunting, and you have to use the magazine, you can chase the lands as leade grows. You will get only so far before the bullet is out of the "sweet spot" that it likes for the accuracy node. At this point, you are reduced to seating a bullet at the sweet spot that will be too long to fit in the magazine box, then the rest of the rounds in the mag box will be less accurate.

The donor rifle was a R700, 7RM, all factory bottom metal. The magnum case visually is almost the same OAL as the 280AI case, but did not measure.
My plan is to get this into a mid range performer and not press for ultimate speed, but hopefully find a node that is accurate to 600 with the necessary velocity required in that chosen bullet to expand properly.
I'm looking at 150gr.+ Hammers or Barnes for lead free hunts in Kaibab, AZ, and 168 Nosler LRAB for target and pack in hunts elsewhere. The Hammers may be the right choice for all. We'll see. Borescope is next on my list as they are on sale. I'll keep good records, hopefully to share with all, down this road.