Why would OACL Change?

[Long Hunter]

I am shooting a 30-06 with 200gn Sierra Matchking's at an oacl of 3.290in which is .010in off the lands. Started to experience problems with rounds chambering and I found that in order to get the rounds to chamber properly in needed to change my oacl to 3.260in and to keep the round .010 off the lands my new ocal is 3.250in. What is the reason for needing a shorter ocal for my rounds to chamber? My chamber is clean, all resized brass is trimmed to 2.484in and fits in chamber with no problem, but when I load my brass to 3.290in with matchking's it don't chamber till I shorten my oacl to 3.250 then it chambers fine. I have about 800 rounds through the gun with these rounds loaded to 3.290in but I just started loading a new batch of bullets for me so could this be due to the bullets being slightly longer or larger in diameter?

 

[sp6x6]

It could how are you measuring length , off the tip. Or off the ogive with a comparator.

 

[Long Hunter]

Measuring off the tip. Currently don't have a comparator

 

[BountyHunter]

If you do not have a comparator you are just chasing your tail and getting frustrated. IMO you have no way to accurately measure where you are on the lands. You have to learn how to measure the bulls AND have the tools to do it first.
Plus IF it is a magazine gun load to Max COAL for the magazine and work from there.
FWIW I have seen .017 variance in ogive one box of bullets before Sierra started new procedures. Measuring tips could easily account for what you are seeing.
I just toured their factory in September and now only one operator and one machine make each lot. They have upped the QC bigtime.

Slow down get a comparator and remeasure everything.

 

[NW Hunter]

+1 on what BountyHunter says,

 

[nosualc]

Your new lot of bullets is longer to the ogive than your old.

As others mention, you need to measure to the ogive using a comparator.

Even in the same lot, there will be some variance between bullets. This is why some competitors will sort their bullets by length (to ogive).

Some manufacturers are better than others. It sounds like sierra is taking steps to increase their consistency (which is a good thing).

-nosualc