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Ok....I'm new to reloading...I've bought some equipment and learning to take measurements and practing that.I am not reloading live ammo yet. So I'm trying to learn how to use the Hornady oal length guage, when I measure the chamber in my Savage 12 LRP, 6.5 CM, and compare that measurement to a factory loaded round using the the same bullet, my measurement is .077 shorter than the factory round , does that sound correct? I'm using the Hornady bullet comparator to take the measurements.
If you are truly measuring OAL of the loaded cartridge, it's not that large of a deal; nor MAY it matter if measuring off the ogive.
Re-read your manuals and understand the theory of operation.
The Creedmoor is a bottleneck case, so headspace is measured from the base of the case to a point roughly mid shoulder. The tips of bullets varies in shape and length, so measuring the total cartridge OAL will always vary some. Measuring off the ogive is what you care about. Factory ammo needs to function in every conceivable gun ever chambered for Creed. That includes short magazines in an AR pattern rifle. Factory and will ALWAYS be minimum spec. You only need to know at what distance every different bullet you use, touches the lands. From touching, you need to back off, making the bullets not jammed. Everyone has magical herbs and spices for the amount of jump to the rifling.
FWIW, I have NEVER found any bullet on the planet that won't shoot with 0.0625" of jump, unless you have a crappy load to begin with.
Cheers
I am measuring from the ogive. I'm comparing the same bullet to a factory round. It just seems odd to me that the factory round is longer than what the gauge is saying it should be.
to use the hornady OLG slide a bullet that you intend to use into the modified case. leave the rod at the rear loose. put the case in the chamber and turn it some to the right to make sure it is seated in the chamber. if you turn it counter clockwise you may unscrew the case.
slide a wooden dowel or a cleaning.rod from the muzzle.
now holding the case tightly into the chamber push the bullet up into the throat and against the lands. tap the rod lightly until you have firm resistance. it is very easy to feel the first resistance of the bullet going into the throat and stop there. still quite a ways to the lands.
now lock the rod with the set screw and remove the tool leaving the bullet in the rifling. check to make sure the cas is still tightly screwed down.
use the dowel or cleaning rod to push the bullet into the.action and place it back in the tool. measure with the calipers and hornady headspace gauges.
this will be a slight jam but should be a repeatable measurement. try it several times until you get consistency.
I have never had much luck with the Hornady oal tool. Measurements were always inconsistent and never inspired confidence.
My recommendation is to make a dummy round (no powder and no primer) that has the bullit loaded long, long enough that you know it will not chamber. remove firing pin and ejector from your bolt.
Now you can incrimenaly seat the bullit deeper until it Chambers without resistance. I have had repeatable results to .001".
This technique is much easier if you have a micrometer bullit seater but can be done without.
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If yours is always shorter then it sounds possible that the two cases are not the same dimensions.. Have you measured the datum points on both modified and factory cases to see if there is any difference between the two?
Try and chamber the modified case to make sure it fits in your chamber.
There is always a possibility your freebore diameter is tight, thus not allowing you to push the bullet all the way to the lands.
If your measurements are correct, this means the factory round would be jamming the bullet into the rifling, making it hard to extract a live round.... Most likely pulling the bullet out of the case and spilling powder all inside the chamber and receiver during extraction.
If it's hard to close the action on a factory round then it's most likely because the bullet is being jammed into the rifling.
And if that's the case, you wold have to send the rifle back to Savage to have it corrected.
If you are not using the same bullet; manufacture /design/weight, you will not be able to make a comparison.
Robinhood is correct.
Same bullet but different lot # will make the measurement different.
Bullet manufacturers adjust and change the shape of the bullets to accommodate different things from their machinery and dies to just making a bullet better overall.
Did you pull the bullet from the factory cartridge and used it to get your chambers measurement ? or did you buy a box of the same bullet as the factory loaded ammo ???
It can be, and has been since before all the (need to have) tools were ever created.Quote:
Originally Posted by Cmgoff
As stated above, load a bullet in an empty unprimed case, leaving the bullet long in the case and then
close the bolt on it to jam seat the bullet. Then keep adjusting the die down till you can barely see the rifleing marks on the bullet.
Smoke the bullet with a match or use a sharpie on the bullet.
Save the final version for a dummy round for that bullet for future die adjustments.
Makes no difference on exact case length trim as the o a l is what your looking for.
No comparator or any other special tools needed, just a case, a bullet, and the gun.
While trimming does not matter to measure oal, sizing does. If you're bumping the shoulder during sizing you're affecting case length.When the shoulder is bumped back say .002" the neck that holds the bullet also travels the same distance. If you're going to compare factory loaded oal to the modified case max oal you need to first establish that your modified case is within the same dimension as the factory loaded case spec. The case head spaces on the case shoulder. If somehow they sold you a modified case that has been sized improperly prior to being drilled and tapped, ie. sized to the point that the shoulder has been set back then when you measure from the base to the bullet it will always come back too short. Or if not FL sized back to SAAMI specs then it will always give you a longer reading. I highly doubt they are using brand new cases to make these modified cases. I have a store bought .223 and .308 modified case. Both are from different manufacturers. That leads me to believe they are not new cases to start with. While that would insure all the cases are to SAAMI specs we all know everything revolves around money so they are possibly using range brass to create these cases and you just never know how they are being or not being sized prior to modification. This is the very reason why I started making my own modified cases.Quote:
Originally Posted by yobuck
Well it would be easy to start another discussion on sizing also.Quote:
Originally Posted by PaddyD
But assuming your full length resizing, it might be both best and necessary to start with a resized case before jamming the bullet home with the bolt.
And for that just follow the simple instructions included with the dies when you set them up in your press.
I'm not so sure it makes any difference in the oal length to the rifleing, but it cant hurt either.
On the other hand if you prefer just neck sizing, than a case fired in the gun would be adequate after resizing the neck.
Otherwise without resizing, the close tolerances of factory chambers might cause the bullet to just slip down into the case. lol
Interesting thread, but I think I'm missing something. How are you measuring your chamber?