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 ?
Another Head Scratcher
- Thread starter 284winner
- Start date
I fireformed that case before having it threaded to fit the gauge so it's very close if not identical to my cases I load.
Did you load your dummy with the same bullet you used with the gauge? Something has to be out of spec, either your bullet or cases. I am assuming your measurement technique is correct.
Every bullet I use in the OAL gauge shows the same inaccurate measurement. When I load a dummy round with any bullet, that measurement is much less once I load it in the chamber and close the hard to close bolt. It seats the bullet to the "True" measurement to the rifling. I've used these OAL gauges for almost all my rifles and this is the only time I've had this issue. I'll say the rifle shoots great but I'm trying to figure out why its not been firing consistently. Second round misfires are common. Light firing pin strikes but after resetting the firing pin by lifting the bolt and locking it back down, the round fires.
The stop collar on my case gauge is sloppy. I have to compensate for that. You're not pushing the gray plastic rod hard enough to flex it when touching the lands?
Those are both dumb possibilities, I just can't think of anything else.
No. I thought maybe I was jamming the bullets too far but did it numerous times lightly barely hitting the lands and the bullet is barely in the case when seated. Then when chambered and upon bolt closing, it pushes the bullet back several thousandths back into the case. This is just fine as it accomplished what I want but it's a head scratcher for me.
Weird.
Yes that's what I'm going to try now. See if this problem persists using that method. If it does, I'm really gonna be confused. Trying to get that measurement into the lands to load future fire form rounds to see if it cures the misfire issues I'm having. Blow out the case for better in the chamber fit eliminating any play causing the firing pin to move the case forward instead of igniting the primer.
Mulligan
Silver $$ Contributor
How does the case base to shoulder measurement on the stony point case compare with your prepped brass?
CW
The biggest measurement difference is .002 and that is with cases I believe have only been fired once in the chamber. Most are identical. Even the .002 is fractional based on how much the difference is when the actual dummy round is chambered and seats deeper once the bolt closes.
There is a pretty big difference between touch and hard jam closing with your bolt is definitely hard jam pushing the gray plastic rod on the comparator with your finger very lightly would be considered touch
Another way to check headspace is barely start a spent primer in the primer pocket chamber the round and close your bolt remove the round whatever the primer is sticking up would be your head space measurement. as for cartridge base to ogive seat a bullet long color it with a black sharpie chamber the round you will see Marks indicating contact with the rifling re- seat the bullet .001 deeper color bullet again and chamber and look for Marks keep doing this to you see no marks add .001 that is your distance to touch
I though there might be also so I tried both methods. They really weren't much different measurement wise. The difference was so little I couldn't hardly tell visually. I never pounded the rod into the lands just a push till the bullet felt snug. The other method was just a soft slide till a tiny bit of resistance was felt.
I wish there was a ballistic expert that would take the time to explain the whole process while showing what happens as you increase distance into the lands. As lead and brass are softer than steel, it is hard for me to visualize or comprehend the difference between 2 and 15 thousands into the lands.
Push a bullet into the lands and they cut grooves into it. Push it harder, and the grooves get deeper.
Don't get me wrong. I have certainly expermitted with this by finalizing seating depth at the range. What I want to know is why. Is it increased pressure which should increase velocity?
I'm old and stubborn, and it might be that I think too much and should forget about the why and simply concentrate with the results. It's the stubborn part that causes me the most problem. I like to fully understand anything I do.
Push a bullet into the lands and they cut grooves into it. Push it harder, and the grooves get deeper.
Don't get me wrong. I have certainly expermitted with this by finalizing seating depth at the range. What I want to know is why. Is it increased pressure which should increase velocity?
I'm old and stubborn, and it might be that I think too much and should forget about the why and simply concentrate with the results. It's the stubborn part that causes me the most problem. I like to fully understand anything I do.
As do I. Looking at the rifling marks in the bullets, it's apparent that the bullet isn't really very far in them. Too bad they don't make a jacketed bullet that's harder than copper but just softer than steel so the stop would be pronounced. One that mimics the bullet used in a loaded case
Here’s one analogy take a hammer and try to push in a nail then raise a hammer smack it down on the nail it drives much easier this relates to jam or jump with a bullet as well jam does not let the bullet build up speed to hit the rifling and engrave therefore it does raise pressures and then return raise velocity but I am just an old construction worker you may have a much different opinion
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