Another Head Scratcher

[dgeesaman]

Using my stoney point (Hornady) OAL gauge to measure my OAL of a cartridge to load into the rifling, I'm finding this measurement to be false. Once I push the bullet into the rifling and remove the modified case and bullet, I find the measurement to be much longer than what the chamber will actually take once the round is loaded. Once I load a dummy round and chamber it, the bolt will not close without force. Once it closes, the bullet seats much deeper into the case than what the measurement started at. It has me scratching my head at this point. Not that it's a big deal as I use the new measurement of the round after closing the bolt as my "In the rifling" measurement. Just can't understand why the OAL gauge measurement is not accurate. I'm actually gonna start using the Wheeler technique from now on. It certainly is the most accurate. Thoughts ? Experience ?

Accurate relative to what?

Stoney Point setup measures a jammed condition. I find it quick and consistent, especially if I push to a hard jam. It takes a brass rod to push the bullet out. I haven’t spent much time worrying about it but I wouldn’t be surprised if it’s closer to the “square marks” many benchrest guys base upon.

The bolt drop method finely detects the first instant of contact with the lands. It’s not quick but it’s consistent. For someone like Alex who uses this measurement across a variety of actions and chambers, that’s a big advantage.

Choose one, as long as you can get repeatable numbers, you base your load development on it. But if you share your load info in terms of jump or jam, make it clear which method you used.

eta: it seems your tapped brass woudnt seat easily in the chamber. That’s sneaky and annoying. But better in this case then with live rounds.

David

 

[Old Navy]

I don't want to turn this into an indepth discussion on a variant of my problem. It's fairly straight forward as to why I'm trying to get this measurement but as I explained, I'm going to go to the Wheeler method from the Stoney point method after having these difficulties getting a true measurement. I'm simply looking for an explanation or another with the same experience. Once I get the bullet into the lands even if it's by loading long and letting the bolt close method pushing the bullet to the optimum "in the rifling" spot, I'm good with that. Then just dial the micro seater to the jump I want. It's more of a curiousity as to why the measurement are so far off from each other question.

Have you removed the ejector for testing yet?

 

[284winner]

Have you removed the ejector for testing yet?

Yes

 

[284winner]

Accurate relative to what?

Stoney Point setup measures a jammed condition. I find it quick and consistent, especially if I push to a hard jam. It takes a brass rod to push the bullet out. I haven’t spent much time worrying about it but I wouldn’t be surprised if it’s closer to the “square marks” many benchrest guys base upon.

The bolt drop method finely detects the first instant of contact with the lands. It’s not quick but it’s consistent. For someone like Alex who uses this measurement across a variety of actions and chambers, that’s a big advantage.

Choose one, as long as you can get repeatable numbers, you base your load development on it. But if you share your load info in terms of jump or jam, make it clear which method you used.

eta: it seems your tapped brass woudnt seat easily in the chamber. That’s sneaky and annoying. But better in this case then with live rounds.

David

Problem has been solved. My error. I just found a better method that I will use when I need to measure jump more accurately. The OAL tool is ok but doesn't give an accurate reading on touching lands vs in them. The wheeler method is very accurate for determining this. I don't do it with all loading but the ones I do, it will serve me better.