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Reloading 9mm cases, fired one time (I did not trim the cases) using 4.3gr Ram Zip powder and Berry's 115gr Plated bullets. The manual lists the "Tested COAL" as 1.130.

I'm getting inconsistent seating depths from 1.126 to 1.132 with my Lee Bullet Seating Die. How much can you deviate from the "Tested COAL" and still be in the safe pressure range for 9mm?
 

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I do not know the perfect answer to your question. You are only talking about a difference of 6/1000 which in my humble opinion ain't a whole lot of difference and will not be enough to spike the pressure to any dangerous level.

I just finished loading a bunch of .30 M1 Carbine cartridges. The listed COAL is 1.680, mine were everywhere from 1.665 to 1.682 and I didn't think twice about the differences. The "point" of every bullet is different, so you would need to have a way to measure the ogive to have each bullet perfectly matched in length. They do make a contraption for those measurements but I personally can't see wasting any money on it!
 

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Depending on your seating stem it's entirely possible/probable they are seated to the same depth, just not the same length. If your stem seats off the ogive, they should be the same depth but, .006 isn't much for bullet tips to be different one from another.
 

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Discussion Starter #4 (Edited by Moderator)
Depending on your seating stem it's entirely possible/probable they are seated to the same depth, just not the same length. If your stem seats off the ogive, they should be the same depth but, .006 isn't much for bullet tips to be different one from another.
Thanks sharps4590...I hadn't thought about the difference between the depth and length...

I do not know the perfect answer to your question. You are only talking about a difference of 6/1000 which in my humble opinion ain't a whole lot of difference and will not be enough to spike the pressure to any dangerous level.

I just finished loading a bunch of .30 M1 Carbine cartridges. The listed COAL is 1.680, mine were everywhere from 1.665 to 1.682 and I didn't think twice about the differences. The "point" of every bullet is different, so you would need to have a way to measure the ogive to have each bullet perfectly matched in length. They do make a contraption for those measurements but I personally can't see wasting any money on it!
Thanks! Appreciate your thoughts on the differences in COAL, very helpful.
 

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Lyman 49th, p41 lengths may vary +/- 0.005. There is a caution of excessive shorter lengths (off of the load data) may cause excessive pressure.
As stated above the secants of the bullets vary, more so on sometimes cheaper bullets. Some times case springback, press flex, etc can be a source.
Progressive can be set up and cycle a single round great. Once you put components into all the positions, the oal may change. So adjusting after all the positions are in use becomes needed sometimes.
Unless you use a single stage and sneak up on the oal using a comparator, don't plan on perfection.
Try to find a mid point load so the variances are not a real concern unless you are trying to get those consistent Ziva shots.
I've had some real cheap bullets that had some of the rounds +/-0.007 off that shot fine and I couldn't tell a difference in feel. But I never load near max. Max loads, or messed up light loads can be more problematic for pressure issues if not careful.
 

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I have asked a similar question in the past and got no definitive answer, so I figgered no one knew. I asked "reducing seating depth can raise pressures, but how much?. How much more pressure will appear with how much deeper seating using XXX powder?", or "is there a formula to find how much does pressure/psi rise with say .005" deeper seating, .010" with XXX powder?". In 4 forums I just got vague answers/warnings but no facts and found nothing in my manuals/texts...
 

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mik, my suspicion is the only real way to know would be with pressure testing equipment, either in a lab or with piezo electric testing equipment. As literally nothing is linear with pressure I don't know how a formula could be devised. I need to note that devising formula's is definitely not my long suit. As drymag noted, Lyman says deeper seating "may", (they mean "might", pressure isn't asking for permission), raise pressures with excessive seating depth. Personally, I don't believe excessive seating depth might raise pressures, I believe it will, at least briefly, until the volume inside the case and chamber is expanded enough by the bullet moving forward. I also believe it's something best avoided.

As an aside, My Freedom Arm Model 97 in 45 Colt has a shorter cylinder than Ruger's or Colt SAA's. When I seat the 255 gr. RCBS, KTSWC for the Freedom I have to taper crimp it on the front driving band rather than in the crimping groove. That is something Keith, Skelton, Jordan, Venturino and others did with regularity with no concerns. With the RCBS bullet that distance can't be .010 and I've experienced no pressure difficulties in any of the above mentioned revolvers when the powder charge was 8 grs.of Unique. Hotter loads, I can't peak to. Methinks a hot 2400, H-110 or other like powder might not be so accommodating.
 

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You'd think some one with a ransom rest properly placed, etc and a solid consistent load was found with best brass, bullets, etc, that testing with rounds seated both sides of the oal would be tried to see if accuracy and velocity varied enough to make a reliable statement of cause/effect.

You know there has to be bullets that checks out great but when cycled thru a semi they get pushed back way past the acceptable reloaders checks and no one notices, or may be it goes bang harsher and the shotting goes, hmmmm, bang, bang, bang.
 

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mik, my suspicion is the only real way to know would be with pressure testing equipment, either in a lab or with piezo electric testing equipment. As literally nothing is linear with pressure I don't know how a formula could be devised. I need to note that devising formula's is definitely not my long suit. As drymag noted, Lyman says deeper seating "may", (they mean "might", pressure isn't asking for permission), raise pressures with excessive seating depth. Personally, I don't believe excessive seating depth might raise pressures, I believe it will, at least briefly, until the volume inside the case and chamber is expanded enough by the bullet moving forward. I also believe it's something best avoided.
When I started reloading 9mm, I read a bunch of warnings sorta like "If you seat deeper than book OAL, the pressures will soar and you'll blow yerself up!". I wanted to know how radical the pressure rise would be, and perhaps a rule of thumb stating something like "If a bullet is seated .020" too deep over Big Bang powder the pressure jumps x,xxx psi.". But I don't think the rise would be linear, and I wasn't able to find any info. Perhaps if I had pressure testing equip., and a lot of time I could chart the pressure jumps vs seating depth, on an individual charge, bullet, seating depth, etc...
 

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I wish I know how to or had the equipment to measure pressure. Whenever I have a bullet that I absolutely know is "pushed into the case too far", I usually just shoot the thing out. None of them have blown me up, yet!!
 

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A friend of mine bought a few coated 124 gr. 9mm bullets of which the shape forced him to load them really short to 1.023".
The usual load he used for this type of bullet was 4.0 grain of Lovex D032 (Shooters world Clean shot or very much like AA #2) at 1.12"
I was hesitant to load them this short so I started low and worked up over a chrono.

The goal was to reach 1050FPS like his usual load @ 1.12" as above.
At 1.023" it took only 3.8 grain to reach 1050fps, at 4.0 grain we got to 1150 fps which is the velocity at max charge according the manual. (@ 4.4 grain)
At this OAL there were no signs over abnormal pressure, velocity is acceptable, no harsh recoil and no weird primers or cases. Feeding however was iffy depending on the gun.

This is just one example but there appears you can play a bit with the OAL before it becomes unsafe as long as you don't load maximum loads.
 

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With bullets that cost $65/1000 you can't expect them to be real consistent.

As said above, pressure values ride on the seating depth, not COAL. The space between bullet and powder is where the pressure is made. Your .006 variance at COAL won't be a concern when talking pressure
 
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