Question on seating depth of bullet.

Hello All,
First off - what an outstanding site!! I am somewhat new to this hobby and have found many answers to questions I have - and some I didn't even know I had! :rolleyes: - in reading some of the past threads. Thank you guys!
Secondly, I found this thread: http://www.thehighroad.org/showthread.php?t=506678&highlight=Using+an+auto+pistol+barrel+find+MAX+O.A.L+with+your+bullet It seems to have most of the info I was looking for. (I too can't believe it's not a sticky!! :eek: ) Awesome post Walkalong! Thank you!

I initially started reloading because I shoot IDPA and was looking to try to save money/shoot more and fellow shooters who reload said that it was fun as well. (they were right!) Now, being new to this hobby, all my reloads, 9mm, have been conservative (and will continue so) but I wanted to start going for accuracy. After my first couple recipes I worked up, I also found that reloading my own "Makes me look gooooood" on the paper!! :D There was a LARGE improvement in my shoots! I was really tickled! And I "think", if I understand how this works, you can discern why the big difference with the length of cartridge I can use because of the length of my chamber. BTW, I shoot a Walther P-99AS.
Anyway, I made up 3 "dummies" and did all the measuring with FMJ's. They came up with the OAL being 2 @ 1.176, and 1 @ 1.174. (the difference was in the brass) That is the exact measurements without adding anything for "variations". So going by what the books say as 1.169 being max length, I guess I will just use that and not try to get closer to the rifling. But I think getting closer to the rifling is what really helped my accuracy.

And if I may, I was wondering why I did not see many people shooting 147gr. bullets? That is the bullet that seems to shoot best out of my gun. I am using Xtreme FMJ's but want to try cast TC bullets (weighing 150gr.), as soon as I get some Win 231. (right now I only have Titegroup) I was hoping They would work as well as FMJ's and save me a bit of money.
I tried woking up 3 dummies using cast TC's but it was a bit of a hassle so I did the other trick by just dropping in a bullet, measure to it from the muzzle, reassemble it, and measure the full length. I did not need a pencil as I have a mechanical calibers that can do that with the tang that comes out the end. That measurement came out as 1.11. I guess I will go with the published minimum length there. :) The cast TC bullets concern me tho, as I understand they need to be seated deeper.

Thank you all again for the help I have already recieved from the old posts and look forward to learning more from you all in the future.

Welcome to THR and the hobby of reloading!

First off, variations in OAL are because olgive and nose configuration on bullets are inconsistent, as this is what the seating plug makes contact with. Brass really has no effect on OAL.

Second, use the bullet you are intending to load as your dumy round for OAL / seating depth. Different bullets, have different olgive and nose configurations, so using a different bullet won't be an effective method. Even if you were to use two bullets that are both FMJ's, but different manufacturer's, they would have varying points of contact off the nose to seating plug, and olgive to barrel lands.

GS

^ What he said.

Also, whenever you switch bullet types, back your seating die off and sneak up on your OAL again. It's easier to start long and seat deeper with a few twists of the die... than to seat too deep and then have to get out the bullet puller. :)

Variations on OAL are inevitable, even on match grade bullets. You'll see a lot more variation on longer bullets; my 220 grain sierra match kings have +/- .006" OAL with competition seating dies. Just gotta live with it. Makes it tough if you are trying to get the bullet right up on the lands.

Good advice above, nothin I can add other than

WELCOME to thr (the high road)!!!!

The "book" max OAL isn't hard and fast at all. That is merely what SAAMI has laid out there as the max that commercial loads will adhere to and also sets the minimum that a magazine should accept and feed. What you'll find is that in most cases you can comfortably go longer than that in your particular pistol. Your pistol determines the actual max length.

With a pistol load, what you have to really be concerned with is min length, or more correctly the min allowable space behind the bullet in the case. That remaining case volume is the primary determinant of load pressure with a given bullet and powder. That's why you'll see in the Hornady manual, for example, different OALs listed for the various bullets of the same weight. They're seating to a uniform case volume with the various bullet shapes.

As far as why you didn't see anyone shooting 147gn bullets, they recoil too much when loaded to make power factor. More recoil means slower follow-up shots and slower times. I assume that the other bullets shoot "well enough" to get hits making the faster follow-ups the determining factor.

First off, thank you guys for the info and welcoming! I had replied with a good long post of questions and comments, fine tuned it and click.......... hit the wrong da** button!!!!! :what: :fire: :cuss: :banghead: Man these things can frustrate you at times. Especially if you're but a mere "hunt and pecker" like me.
So here's a condensed version. (sorry)

GS, if I'm not mistaken, the brass length did make a difference in making up my dummies. The brass and bullet hit 2 different spots in the chamber. The length of brass was perfectly porportional to the OAL of each dummy. (or am I confused somehow?)

Thanx Helo for the correction on published OAL. Since I am relatively new at this, I guess I am being overly cautious. My guess is that the 115gr. bullets would handle that small amount on an increase in OAL so I will just pay close attention to the charge.

As far as 147's go, what I was taught/told was that a heavier bullet will bring the gun "back" (towards you) as opposed to a lighter bullet will bring the muzzle of the gun "up" (towards the sky). So using a heavier bullet, in therory, a person could get back on target quicker. :confused: I would really like to know if anyone else has anything on that therory. (maybe another topic??) It would be great to know as I was going to stock up on bullets shortly.

There is a min. power floor necessary for shooting IDPA. It escapes me right now what it is. I will look that up and see what I may need to keep in mind. That could make the difference in what I use. Thanx for the heads up!!!!

Thanx again for all the time and info!!

if I'm not mistaken, the brass length did make a difference in making up my dummies.Case length can have no effect on OAL loaded length.

OAL is measured from the case head to the tip of the bullet when using a dial caliper.
Or from the base of the case to the ogive of the bullet when using a comparator & a caliper.

In either method, a short case would not have as much bullet shank inside it as a long case.
But the OAL would measure the same.

Case length does not enter in the OAL measurement at all, and can have no effect on it.

rc

OK, what am I doing wrong here? Am I using the term "OAL" incorrectly? Does that only pertain to a "loaded round"? I'm not totally fluent in all the acronyms and terms yet but, I thought using the acronym "OAL" would work in measuring a "Dummy".
In my original post, I was only referring to "Dummy" rounds without powder and with the spent primer and new bullet. I am familiar that in loading a round that the brass makes no difference because of how it's made - two points of contact. I was only stating the lengths of the three dummies in the original post for reference. Again, if I am correct, when pushing the dummy down into the chamber, the bullet hits the rifling and the case comes to rest on a shoulder in the chamber. Hence you get the maximum length for your gun.
I guess my grasp of the English language is worse than I thought. :banghead: :D :D
(At this rate, I'll never make a great literary figure. :D)

Yes, OAL only pretains to an assembled loaded round. Varying lengths of brass do not change OAL at all. As RC said, the only thing that changes with different lengths of brass is how much of the bullet shank seats into the case.

GS

OAL generally is used to refer to the "Over All Length" of a loaded round.
Measured base to bullet tip in reloading manual specs.

Case length is, just that. An empty case with no bullet in it.

rc

Mr Skulptor -
Welcome aboard !

► OAL, COAL, Cartridge Length... they all refer to the total length, base to tip, loaded or unloaded. We use these terms interchangeably, sorry if it confuses.

► That's great that you're doing your experimenting with unloaded rounds (only an empty case and bullet). I wish more people were that safety conscious.

► Have you ever tried to jump a curb with your car? Which works best: getting a slow rolling start, or nudging up against the curb, then applying the gas? Why getting a slow rolling start is much easier. Well, it's the same thing with bullets, they need a "head start" at jumping into the rifling. So you never want to have the nose of the bullet resting on the start of the rifling. You'll always want to back off at least .005" (maybe more), and then give an extra allowance that accounts for any variation in cartridge length coming off your press. In other words if you aim to make cartridges 1.160", but some in each batch are as long as 1.164", then you need to add that extra .004" (variation) to the .005" (minimum) setback and give a (working) setback of .009". Follow? This simply assures you that even your longest cartridges have .005" clearance.

Hope this helps!

Mr Skulptor -
Welcome aboard !

► OAL, COAL, Cartridge Length... they all refer to the total length, base to tip, loaded or unloaded. We use these terms interchangeably, sorry if it confuses.

► That's great that you're doing your experimenting with unloaded rounds (only an empty case and bullet). I wish more people were that safety conscious.

► Have you ever tried to jump a curb with your car? Which works best: getting a slow rolling start, or nudging up against the curb, then applying the gas? Why getting a slow rolling start is much easier. Well, it's the same thing with bullets, they need a "head start" at jumping into the rifling. So you never want to have the nose of the bullet resting on the start of the rifling. You'll always want to back off at least .005" (maybe more), and then give an extra allowance that accounts for any variation in cartridge length coming off your press. In other words if you aim to make cartridges 1.160", but some in each batch are as long as 1.164", then you need to add that extra .004" (variation) to the .005" (minimum) setback and give a (working) setback of .009". Follow? This simply assures you that even your longest cartridges have .005" clearance.

Hope this helps!

OK, what am I doing wrong here? Am I using the term "OAL" incorrectly? Does that only pertain to a "loaded round"? I'm not totally fluent in all the acronyms and terms yet but, I thought using the acronym "OAL" would work in measuring a "Dummy".
In my original post, I was only referring to "Dummy" rounds without powder and with the spent primer and new bullet. I am familiar that in loading a round that the brass makes no difference because of how it's made - two points of contact. I was only stating the lengths of the three dummies in the original post for reference. Again, if I am correct, when pushing the dummy down into the chamber, the bullet hits the rifling and the case comes to rest on a shoulder in the chamber. Hence you get the maximum length for your gun.
I guess my grasp of the English language is worse than I thought. :banghead: :D :D
(At this rate, I'll never make a great literary figure. :D)
Pretty sure you don't want both to happen. The loaded round headspaces on the case mouth, and the bullet is loaded deep enough that it doesn't hit the lands, but long enough that it doesn't have to travel far once the primer is struck. Are you saying the difference in oal is due to the shorter brass headspacing on the barrel? That does seem to make some sense, since you headspace on the brass, not with the bullet touching the rifling. 380 brass wouldn't work in your 9mm barrel, for example.

But I'm still figuring this out myself.

Thanx again for the Welcoming! But, below are quotes that I would like to be clear on. My feeling was always the same as that of Mr. rfwobbly - that the terms -OAL, COAL, Cartridge Length - refer to ALL rounds - dummy or live. (I have also read that "COL" refers to the same.)
Thanx for the "curb jump" analysis! I do understand that concept.

OAL generally is used to refer to the "Over All Length" of a loaded round.

Yes, OAL only pretains to an assembled loaded round.

► OAL, COAL, Cartridge Length... they all refer to the total length, base to tip, loaded or unloaded

Hardheart, I was doing "The Simple Push Test" that I found on this site. I will see if I can find that post and edit this one with the address so you can see what I am talking about. There is also a "drawing" somewhere on this site that shows how it works.

Here is the quote on how to do the Push Test:
1SOW
Member



Join Date: October 28, 2007
Location: South Texas
Posts: 3,267 I shoot the Zero 125 JHP for comp loads in my 75B

When you load a new bullet, ALWAYS do the bullet push-test to determine the oal that just touches the rifling or shoulder of the bullet. Then subtract about .015" to allow for press or reloader induced variations.

CZ'z have a short chamber which is good and bad. Bullets with a long body and short nose--like FN or HP (especially conical nosed)-- will hit the cone or riflling long before many other pistol makes will. On the other hand, this pistol is very accurate and reliable and much like a custom bbl would be.

I can run 125gr ZERO JHPs at 1.10" oal reliably and have over 20K times with this bullet. Your chamber could be slightly different-but not much. Use the push-test to find YOUR MAX oal for each new bullet you try.

You can find the "Push Test" with a search (see Wobbly's posts) or:

Use a spent "unsized case" that will let you seat a bullet just enough to hlod the the bullet and insert it bt BY HAND into the chamber. Slowly push this ALL THE WAY INTO the chamber until it seats on the casemouth firmly. Dump/EASE the case back out and measure the length. Do this several time with several spent cases. The consistant measurements show an oal that "HITS the rifling/cone. Subtract .015" and you have a usable & reliable MAX oal for that particular bullet in that pistol.

The 125 ZERO JHP is my favorite competition bullet in a 75B and my son's Custom Shadow.



Hope this helps clear things up! Thanx!!!!!!!!!!!!

yep, I also load 125 Zeros for a 75B, and I load to 1.1 because I fnd I can't go longer. I have to load to an even shorter oal with Berry's HPs, even though the bullet itself is about the same length. Since you insert the bullet/brass combo and the bullet hits the rifling first, and then you seat the bullet into the brass so the case mouth can then properly headspace, I see how shorter brass would lead to a shorter oal. The length from the extractor to the shoulder to the rifling isn't going to change on your single barrel, and you want the same distance from the bullet nose to the case mouth to load a given ogive into that barrel. But, the distance from the case mouth to the rim will vary from one brand of brass to another. Like I mentioned, a long enough bullet in a 380 case could possibly properly engage at two areas of the three - you could maybe get the bullet to touch the rifling while the extractor still catches the rim, or get the bullet to touch while the case mouth headspaces, but the brass is too short to sit in the extractor and headspace at the case mouth, no matter how you seat the bullet.

I think you know more then the people giving you advice. Everything you said is correct.

I'd suggest seat the bullet .030" deeper then your shortest one & work up a load.

Thanx King. I appreciate that but I doubt I know more. But I'm learning. :)
I think there was/is a communication problem. I'm not as versed in the English language as I'd like to be and I sometimes think people know what I am talking about. Plus, I don't know all the terms, acronyms, etc. Many of them, but not all. There may also be some mis-reading of my posts as well. Either way, I am grateful for all the help and suggestions. Especially yours and Mr. rfwobbly. He puts down some good posts.
Thanx to all!