260 AI range report and learnings

elkhuntr

elkhuntr

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Kamloops, BC
Hi all. I have 600 rounds now through a McGowen 1-8, 28" barrel. I have been running 142s at 2850 fps. I decided to measure freebore/throat change from new, and confirmed a 0.050 change (now approaching the mystic 2.9" OAL range). This is well outside of the 0.010 jam I have been using for the SMKs.

I made some necessary adjustments, then trodded off to the range for some practice. Got back from a wonderful late range day and found some interesting things to share. Accuracy remains excellent. I shot 500m at a steel gong and had 5 shots cover a 3" stickie. Sorry, no photos, just the experience burned into my soul on a windless evening :)

I had not measured OAL since new, so my learning for today is to continuously measure OAL during the life of the barrel. It seems to me the OAL should be checked at least every 100 rounds for the 260 AI. From your experiences, what kind of barrel erosion changes in OAL have you seen from your precision rigs in the hotter 6.5 calibre chamberings?
 
Obviously you are measuring oal off the bullet tip, not the ogive. It will show a general trend, but it is definitely not an accurate means of measuring throat wear - especially with SMK's.

My plain 260 with Berger 140's and going 2875's is up to 760 rounds. seating depth has grown by about 8 thou. The important thing is that I can load 100 rounds with the same seating depth and they work.

My last 6.5-284 eroded between 5 and 10 thou every 100 rounds. I had to add 5 thou to the seating depth every 50 rounds to keep in land contact. It was done at 750 rounds.
It is an accurate cartridge, but ridiculous for barrel life.
 
Thanks for your input Obtunded. Please note I had measured the OAL from the ogive using a comparitor, and by using the same bullet in the original measurement.

I wonder if I had a rough leade from the beginining which has smoothened out from my original measurement. Guess I'll never know. Regardless, it has taught me to keep a vigilent eye on changes in the barrel over time.

By the way, what length of barrels do you run in your rigs?
 
Windless night - BAH :)

Glad you had a great evening testing.

Yes, keeping up with the lands is a never ending battle and you are doing all the right things.

For my load set up, I didn't chase the lands too much and it worked just fine. I found that the rifling itself got thinner, eventually disappearing for quite a ways. Ironically, there was a tab of rifling where the leade would be so it would still indicate the throat had not moved.

I guess that is how the flame comes out of the neck ?????

Anyways, since you are running a milder load than I did, odds are the bore will last longer. However, I would not want to enter a match with 1000rds down the pipe JUST IN CASE.

Been there, done that - you can only swear in so many languages.

With the present rate of useage and the Farky a few months out, do consider prepping another barrel- Hint, hint, hint....

Glad you are enjoying the barrel. Pity you didn't make the Sierra match. I think you would have done very well.

Enjoy...

Jerry
 
As is normal in life, family duties take president over trigger time. Yes...I know....excuses excuses. Thanks for the info guys.

I have a Sav MkII TR with my ol Tasco for some 100m 22LR practice. This will augment the full bore barrel burning for the summer and should prolong barrel needs for this year anyway. See you in the fall.
Elky...
 
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