7mm STW Throat Erosion Measured

[Radman]

7mm STW and 180 gn Berger VLD measured 3.258 CBTO to the lands back in the spring.

After range time and load development I measured yesterday and same bullet CBTO is 3.327

Is this major throat erosion? Now at 3.327 CBTO the bullet is not even fully seated in the neck and I'll have to increase jump.

Do you allow any cooling time between shots?

 

[Marine sniper]

I strongly suspect whatever method you used to measure your throat is the culprit. If you are using the Hornady tool- they are not terribly reliable.

The correct way to do it is to remove your firing pin and extractor- if you did not do that you are going to likely get inaccurate results.

Here is a short video on the correct way to measure what you are looking for:

Videos | wheeleraccuracy

www.wheeleraccuracy.com

Scroll down to "finding your lands"

 

[HRM Johnny]

Tag

 

[Rum River]

Tag

 

[Charlielee]

Berger addresses this exact problem in a separate report on their website: https://bergerbullets.com/vld-making-shoot/.
In fact, they admit that load development could very well wear out the barrel when trying to "touch the lands". This article talks about the sweet spot that could be a jump of up to .150". It recomends a procedure to develope this sweet spot.
If you can look in the barrel check for cracking from heat on the lands. Hopefully the barrel is not ruined.

 

[Lefty7mmstw]

Honestly, I've never worried about enough about erosion to measure it... I simply look down the barrel and if the first couple inches isn't burned flat (or frosty from fire-cracking) and she shoots I'm good. I've fried out a few pipes and none of them gave a hoot about the little measurements until the barrel was about fried out anyway.
You will see movement in the throat, but the wear is not only at the very origin of the rifling so measuring it is really a false comfort. You really need to be able to measure rifling depth for the first few inches to make an educated guess as to what you have left for bore life, so break out the cerrosafe or just eyeball it like I do and let the groups tell you what's up.

 

[General RE LEE]

Honestly, I've never worried about enough about erosion to measure it... I simply look down the barrel and if the first couple inches isn't burned flat (or frosty from fire-cracking) and she shoots I'm good. I've fried out a few pipes and none of them gave a hoot about the little measurements until the barrel was about fried out anyway.
You will see movement in the throat, but the wear is not only at the very origin of the rifling so measuring it is really a false comfort. You really need to be able to measure rifling depth for the first few inches to make an educated guess as to what you have left for bore life, so break out the cerrosafe or just eyeball it like I do and let the groups tell you what's up.

I eye balled bore with a LED light and the rifling is clearly visible starting from the base of the throat.

 

[Lefty7mmstw]

I eye balled bore with a LED light and the rifling is clearly visible starting from the base of the throat.

rock and roll then... shoot her 'till she stops shooting well, then ascertain the issue.