Posted: 8/12/2015 6:50:17 PM EDT
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I do not have an OAL length gauge, but is there any reason this would not work for finding where my rifling starts:
Load a dummy cartridge with a very long OAL. LIGHTLY try to close the bolt of the gun on this gun (it should not close since the OAL is too long). Press hte bullet in a few thousands at a time and repeat until the bolt will close on the round. It seems like this would be your max OAL before you engage the rifling. Is there any reason that would not work? |
| Been done that way for years by many many people. I just partially size the neck on a deprimed NO POWDER case and then load long and stick it in there and seat bullet with bolt. If it doesn't come out easily then a very slight tap with a cleaning rod down the bore will pop it free from the rifling. Do it a few times to make sure you have a good reading. |
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It is slightly easier than you make it out.
{ Load an unpowdered unprimed case with a bullet really really long. Chamber bullet and close the bolt. The closing of the bolt will use the lands to push the bullet back into the case. Carefully open the bolt and extract the case. Measure. } Do the bracketed (above) procedure 3 times and average the measurements. |
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Quoted:
I do not have an OAL length gauge, but is there any reason this would not work for finding where my rifling starts: Load a dummy cartridge with a very long OAL. LIGHTLY try to close the bolt of the gun on this gun (it should not close since the OAL is too long). Press hte bullet in a few thousands at a time and repeat until the bolt will close on the round. It seems like this would be your max OAL before you engage the rifling. Is there any reason that would not work? This could work. The difficulty with this measurement is always friction. The wedge effect of those leade angles can have lots of variation with bullet surfaces. The very shallow nature of the surface angle of the bullet and the angle on the leade means there is lots of length difference per unit diameter of engagement. Add the variable of deformation on the bullet with friction, and the length difference on each sample test can drive you nuts. The force available on different neck tensions also means you can get more or less force from the neck just based on how you sized and prepped the case neck. The least amount of variation on the measurement comes from using one of the Stoney Point gages with a carefully selected sample of your bullet. If you were to try and adjust a sample to the exact point of kissing those lands without deforming the bullet, based on the measurement from the gage, you would still find at least a few thousandths of uncertainty. When we track bbl wear, we have some noise in the numbers on the order of less than 0.005" using the gage. Doing it with the dummy cartridge works too, but we usually end up with factors more uncertainty. Try and borrow a gage and also use your method. Just the headspace difference of the case used for the gage adds a few thousandths of bias to the numbers. You can offset the headspace bias, but you will find much less variation in the numbers using the gage. |
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Quoted:
Been done that way for years by many many people. I just partially size the neck on a deprimed NO POWDER case and then load long and stick it in there and seat bullet with bolt. If it doesn't come out easily then a very slight tap with a cleaning rod down the bore will pop it free from the rifling. Do it a few times to make sure you have a good reading. I use a bamboo skewer, find a real straight one, drop it down the muzzle, pops em right out. |
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I split the neck in half on a half dozen cases and pinch the halves of the neck together to hold the bullet. Use a lighter or candle to blacken the neck and bullet if you want a visual cue. Stick the bullet in the case really shallow, run it into the chamber, eject carefully. Now you have the zero jump/zero jam length. Tune from there. No reason to fiddle fart around with jamming a bullet into the lands over and over again trying to get the length right.
The splits down the neck allow you to hold the bullet securely but still allow it to easily glide back in the case without engraving on the rifling. |
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Quoted:
I split the neck in half on a half dozen cases and pinch the halves of the neck together to hold the bullet. Use a lighter or candle to blacken the neck and bullet if you want a visual cue. Stick the bullet in the case really shallow, run it into the chamber, eject carefully. Now you have the zero jump/zero jam length. Tune from there. No reason to fiddle fart around with jamming a bullet into the lands over and over again trying to get the length right. The splits down the neck allow you to hold the bullet securely but still allow it to easily glide back in the case without engraving on the rifling. Excellent tip, sir. Never thought to split the neck. You have both cheap and accurate covered nicely. |