Hornady modified case questions and concerns

[cslamar]

Hello all!
I picked up a modified case from Hornady (.308 win) and was gathering my materials for my first rifle reloading endeavor. I measured all my once fired brass with the Hornady headspace comparator (all measured around 1.616”), then measured the modified case and it measured at 1.625”. Should I be concerned that the modified case is almost 0.010” longer than the fire formed brass? I’ve read that some brass need a few firings to “stretch to really match the rifle’s chamber, but this much of a jump seems to me to be concerning... like I said this is my first venture into rifle reloading, and don’t feel like screwing up Any insight would be greatly appreciated.

Thanks!

 

[spife7980]

Take the difference from your modified case and your once fired brass and add that to your measured seating depth to account for the difference in length from the lands to the bolt face between your brass.

Then verify it with the wheeler method if you can.

 

[Cascade Hemi]

Hello all!
I picked up a modified case from Hornady (.308 win) and was gathering my materials for my first rifle reloading endeavor. I measured all my once fired brass with the Hornady headspace comparator (all measured around 1.616”), then measured the modified case and it measured at 1.625”. Should I be concerned that the modified case is almost 0.010” longer than the fire formed brass? I’ve read that some brass need a few firings to “stretch to really match the rifle’s chamber, but this much of a jump seems to me to be concerning... like I said this is my first venture into rifle reloading, and don’t feel like screwing up Any insight would be greatly appreciated.

Thanks!

As long as the modified case fits in the chamber, just subtract or add the difference. The COAL gage is only measuring the distance from the case shoulder to the lands with a specific bullet.

If you have a bushing die, or oversized neck mandrel, you can make your own modified case with your fired brass. The drill bit and tap are available on Amazon or McMaster Carr.

 

[MarinePMI]

If you have a bushing die, or oversized neck mandrel, you can make your own modified case with your fired brass. The drill bit and tap are available on Amazon or McMaster Carr.

This. 5/16-36 tap, and Letter "L" drill bit. It's best done on the lathe, but can be done by hand as well.

 

[Howland]

Just because your brass is once fired in your chamber doesn't mean it is actually fully expanded. That could take several firings.

If your modified case is longer than your once fired, don't subtract the difference right away. First chamber the modified case with the extractor removed and see if you can feel any resistance closing the bolt or use the method in the video posted by @spife7980 or other videos out there. There is another good video by a guy demonstrating Redding Competition Shell Holders. It's possible that neither your once fired nor the modified case are long enough.

The thing to understand about the OAL gauge is that your contact points are the shoulder and the lands while you really need to know the relationship between three datum points; boltface, shoulder and lands.

The modified case shoulder should be less than SAAMI minimum chamber headspace but that is still 0.004" less than SAAMI maximum cartridge headspace. You need to know headspace (boltface to shoulder) and the distance of lands from boltface. Knowing shoulder to lands without knowing boltface to shoulder isn't enough.

 

[Bradu]

Seems like some of you are sweating the small stuff like worrying about a few thousandths. I don't see most people capable of shooting the difference and a lot of people do seating tests anyway. It would be different if we were shooting benchrest.