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I just got done reloading some 300 BLK and while I was reloading I noticed that the brass was not coming up to the cannelure on some cases and going to far deep on others. Brass was all trimmed to length and I checked that everything was tight on the die. Then I checked the OAL of several in question and they were either over or under the set length. Winchester cases- Trimmed to 1.366 CCI small rifle primers 16.8gr A4100 Hornady 125gr FMJ Set OAL to 2.05  "though the will of the majority is in all cases to prevail, that will to be rightful must be reasonable; that the minority possess their equal rights, which equal law must protect, and to violate would be oppression." ---Thomas Jefferson | ||
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Common problem not noticed by most reloaders; bullet seaters do not care about OAL and they do not touch the tip of the bullets; they act on the ogive. If the bullets are not completely uniform in that area, you get what you got. Brass all the same. Die set the same; but OAL, not. It's the bullets. Ogives not uniform. OTOH, for a 300 blackout it won't matter. | |||
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This^^^^ is exactly what I was thinking. dpcd nailed it IMHO. I've been checking bullet Base To Ogive and Base To Tip and many brands and models vary wildly! Zeke | |||
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Right. More insight; Good; you are getting exactly the same jump from ogive to rifling. Bad; you are getting a different chamber volume for each round; albeit it super small and probably of no consequence. I know of no tests on this phenomenon. In my world it don't matter. Meaning, shooting things with big holes full of lots of powder. Most guys focus on OAL length without considering what is really happening. As above. | |||
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The above comments or probably right but another thing I've found with buying "seconds" is that the cannelure can be in several different locations on some batches. Some high some low, whatever, this happens as they are setting up the bullet making dies for specific runs. | |||
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What dpcd said! I gave up on trying to seat 5 /1000 etc off the lands just due to the fact that there was at least or more variance in the bullet ogives! Hip | |||
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I'm satisfied that the ogive to base of bullet vary bullet to bullet. I've measured "base of bullet" to where my Hornacy Comparator seats (at the ogive, or close to it) and there really are differences. I don't know how important that might be in the real world, but when someone proclaims they seated their bullets some specific distance off the lands, I don't know how they'd determine it. | |||
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Yes it was this. I went back and measured some of the remaining bullets and both the base to tip and base to ogive were all over the place. In the grand scheme of things, it won't matter for the pistol I am loading for but it got me curious how any my other bullets/brands stacked up. Mainly, because this is something I hadn't noticed before and also I had an hour or two to burn while my youngest was taking a nap. So, after spending the better part of an hour measuring my dwindling supply of bullets, I found that (and big surprise here) CEB's were the clear winner with no measurable difference and everything but the cheap hornady and speer's were pretty consistent. "though the will of the majority is in all cases to prevail, that will to be rightful must be reasonable; that the minority possess their equal rights, which equal law must protect, and to violate would be oppression." ---Thomas Jefferson | |||
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These are cheaply made bulk bullets by one of the less, shall we say, "precision" manufacturers. Variations like this are to be expected. Using a seating stem which has the diameter of its inside radius as close as practical to the bullet's full diameter will make the jump to lands more consistent. Too many seating stems have a small inner diameter which places the contact point with the bullet very close to the nose. I've seen the jacket near the nose of hollow points and faux hollow points like Ballistic Tips creased near the nose by too-small seating stems. | |||
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They determine it by using a sample of bullets from the box to measure the jump, and make the assumption that the rest of them are the same. And for 99.9% of uses, they are. Actually it is 100%, but I gave you .1% just to avoid criticism. In reality, in order to have a truly accurate jump value, you would need a seating stem reamed with the same throat reamer that your rifle has. Ain't going to happen in real life. | |||
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CORRECTION: Following applies to head space not OAL. My bad! Bench resters do it by removing the firing pin assy from the bolt and judge how freely (or not) the handle falls down. NRA Benefactor Member US Navy Veteran | |||
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I try to NOT get to anal while reloading HUNTING rounds----If it shoots good, I am good to go! Hip  | |||
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Dpcd's point is good. I was loading Hornady 286gr Interlocks in my 9.3x62 but discovered the second box had a different taper, giving COL problems. Another issue I've had was with the universal shell holder on a Redding case trimmer. If you unwind the handle too far (or not enough), it may grab the case at the wrong step. So, I now check to see nothing more or less than the extraction cannelure disappears in there, on that calibre. This wouldn't change the COL, of course, but it can cause trouble. | |||
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