Depth of Bullet

May sound funny but how much of the bullet are you pushing into the case ?
I'm talking about 9MM, I seat mine to .256. So just over 1/4" is into the case. With all the talk about COAL and all.

Did I explain that right

 

What bullet is being used, weight, type, and brand?

With regard to high pressure rimless AL cartridges, 9mm being one of such, you need to know with some certainty what the oal of other bullets of similar profile and weight were tested at. Other wise it's a dangerous crap shoot, one that can very easily end with pressures going through the roof. You certainly can't determine oal by eye balling a cartridge, at least not a 9mm cartridge.

GS

 

IMPORTANT

Seating depth, OAL, and how much bullet is inside the case varies considerably.

Depending on the weight & bullet ogive design.

There simply is No Set Rule to cover every bullet design & weight.

More important is if the loaded round will drop in the chamber of your gun without the bullet hitting the rifling.

Too long and it wont.
Too short and it may not feed.

Start at the Starting load data, make the OAL with the bullet design you are using fit your barrel, then work load data upward from there.

rc

 

The main thing is case volume with the bullet loaded. That's why there are different OAL listed for different bullets. Different bullets have different lengths so when you seat them you get differences in case volume which directly relates to pressure. Just the other day I measured to different .45acp bullets from Berry's and found a .040 difference. So since I load my .45 to the same length 1.250 with these 2 bullets one would have more case volume than the other when seated.

 

Since 9mm has no cannelure how deep the bullet seats is done by OAL.

Most 9mm end up being between 1.10" and a.169" ( 1.169" is max OAL for a 115 FMJ and some as low as 1.06" to pass plunk). To add to what RC was pointing out that OAL for mine are determine by plunk testing with a dummy round ( no primer or powder and crimp as if it were so).


My starting point however may depend on load data of similar or same bullets (as already mentioned) and using load data note the listed OAL and what it refers to closely. FE Alliant Powders may list min OAL for a given powder charge and I would recommend being above it if possible, once again if it plunks it shouldn't flunk with a big if.

On the other hand others may list data as max OAL (once again just a reference point, plunk to confirm). In this case I would keep it under a smidgen (say .010" or so) and plunk to confirm feeding.

 

We really need to hear back from the OP regarding the specifics of his load make up, bullet weight, brand or type, powder and charge, ect.? So what's the deal 2 Horse, do you want some help, or not?

GS

 

Ok guys, I'm looking at 124gr Bullets. The nose design should not make that much difference. The Bullets are .528, .540 and .587 in length, all are plated. None are seated past the ogive.

I do know that depth is related to pressure, that's the reason for the question. Say I have a FN that's has a AOL of 1.060 with .256 in the case and a RN with a AOL of 1.150 and only .187 in the case. Most books list the same charge for both.


Can I push the RN to a AOL of 1.110 if it's not past the ogive? the pressure should not be greater than the FN, right?

 

First question I would have is why the difference in length for the same bullets. I only load Berry's and the bullet OAL is usually the same for all the same type, for example 115gr rn. Now I did load some hornady xtp 115gr and these were a little shorter, and that's why they reccomended a shorter OAL when loaded.

I guess I don't know why you are concerned dimensionally with how much bullet is in the case, as for reloading manuals the only give OAL of the loaded cartridge. I have never seen how much bullet should be inside the case, too many variables and bullet dimensions. If you load let's say a bullet that is shorter to a OAL to 1.125 and then load a bullet that is longer by .060 to the same OAL with the same charge weight you will definaltley have an increase in pressure because of the smaller case volume with the longer bullet. That's why you will see different charge weights with different bullets,usually the shorter bullet can be loaded to a shorter OAL.

 

FN, HP and RN. The FN is set deeper into the case by .060 or so than the RN. Pressure is different, recoil is different, neck tension is affected ( less bullet contacting the case )
velocity should be affected. If it's safe to load one with .250 in the case why not just load them all like that.

 

seating depth & COL

I like to think with images or sketches.
I hope this helps and adds to the replies already given

A constant COL with the same bullet will have a constant case volume, any variance in case length will ride up and down on the bullet.

Yes, the case length variance is exaggerated
The COL from the manuals is used to establish the safe charge weight, not the seating depth.

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What reloading books do you have? Where in those books does it refer to oal as being relevant to how much bullet shank is seated in the case? And even though the amount of bullet shank in the case does have a direct bearing and impact on pressure, it isn't what we work with, and it won't correlate with the data contained in the books. And it's not that I don't understand what your trying to say here, but it just doesn't work that way. So we would not / can not use that as our standard for measuring oal.

If you have two different bullet profiles, say a RN and FN, both of the same weight, the oal you would use is likely not going to vary by a much. This is because oal is directly relevant as to where the olgive contacts the lands, and what fits the magazine, both must clear.

The most common method used to determine safe seating depth (oal) is to find zero to the lands by plunk testing the loaded or dummy cartridge. Once you've determined this, then adjust from there accordingly, as to what will fit your magazine, and feed through your firearm. But this is also used as a comparison to what the bullet / powder manufacturer tested a particular load at, which is also a major factor regarding pressures.

I would strongly recommend you spend some more time reading what ever reloading books you have. IMO, you are either, way over thinking this, or you simply don't grasp how reloading data functions.

GS

 

I guess you could if that gives proper and safe functioning, but that's not how it works and thats not how the info is relayed to the reloader in manuals.. I used to wonder the same thing. But really, that would be hard to measure accurately anyway, it seems for me anyway.

(Assuming we are talking about loading by the measurement of how much shank is to be inside the case-I just sped thru and didnt read everything in the thread)

 

Hornady 9th, page #771 124gr FN part#35567B COL 1.050, XTP part#35571 COL 1.060, FMJ RN part#355771 COL 1.150, now if you have your manual handy look at it. All three styles list the same powder charge. All have a different seating depth ( amount of bullet in the case ). Case volume and pressure are different also.

 

As others have also said how much bullet shank in the case is not what reloading manuals give data for, so I'm still not sure why you want to look at this dimension. But if you want you can load to any length you want with any bullet of your choice. But if you are seating the bullets deeper thus giving you a shorter OAL than the manuals recommend you will be at risk to over pressure. Then you will need to decrease your charge weight and work up your new loads. You need to aware of case volume when you start to change the seating depth, the OAL length in manuals is recommended not mandatory, so when you change things you have to be careful.

 

You hit the nail on the head, OVER PRESSURE. If the FN seated deeper than the others and is still not over pressure how can seating the RN to the same depth give you overpressure. Case volume is what matters

 

Depth of bullet and excessive pressure

http://www.thehighroad.org/attachment.php?attachmentid=198725&stc=1&d=1400880674

As you can see by my drawing, if cases are all same length (between max & min length) and you use different bullets, the case volume changes.
BUT if you remain at or above the MINIMUM BULLET OAL for each load you work up, as supplied by your reloading manual or the powder manufacturers reloading data, you will not get excessive pressure.
In my example, I am working up MAXIMUM WORKING OAL for MY SIG-SAUER 9mm P938 & SIG-SAUER 9mm M11-1A. Find out how to work up MAXIMUM WORKING OAL here: http://www.thehighroad.org/showthread.php?t=506678
Oddly enough, the P938 could have used a longer MAXIMUM WORKING OAL, but I'm going to reload to the MAXIMUM WORKING OAL that works in both.
To get the train back on the track, bullet #1 is a FRONTIER 115gr plated RN .459" long, #2 is a X-TREME 115gr plated RN .5555" long, #3 is a X-TREME 124gr plated RN .5895 long, #4 is a REMINGTON 115gn JRN .5555" long and #5 is a SPEER 100gn JHP .5425 long.
The following data is referenced from MODERN RELOADING 2nd EDITION by RICHARD LEE.
Using ACCURATE #2, the copper plated 115 gr bullets # 1 & #2 MINIMUM OAL is 1.140" (page 507). The #3 124gr plated bullet MINIMUM OAL is 1.060" (page 509). The #4 115gr copper jacketed bullet's MINIMUM OAL is 1.140" (Page 507). I didn't find a MINIMUM OAL for the 115 gr copper jacketed hollow point so used the data for the copper jacketed round nose of 1.077".

All of the MINIMUM OAL's for these loads using these bullets are UNDER MY MAXIMUM WORKING OAL, so I should not have to worry about excessive pressure as the case volume is LARGER THAN published MINIMUM OAL for these bullets with these powder charges.
gamestalker, bds, swampman or any other vastly more experienced reloaders, please jump in here if I am way off base

 

As a hypothetical exercise:
Let us establish that you have cases that are trimmed to be of equal length and your bullet profile is set to the OAL listed in the manual for that bullet.
For argument purposes let us establish that loading to your manuals’ measurements provides maximum safe performance in your firearm.
If you now substitute a bullet that is longer than the original bullet and if you seat that new bullet to the same OAL as the original, you will seat the base of the second bullet deeper into the case, and you will reduce the space available for containing the powder charge and you will raise pressure to a dangerous level! Remember here that in our example your manual OAL is set at maximum for your gun. So, if you seat deeper you must reduce the amount of powder used and if you seat shallower you can increase the amount of powder.

 

RE: As a hypothetical exercise

homatok,
I completely agree with your hypothetical exercise, that the deeper seated a bullet is you must reduce your powder charge or experience excessive pressure and possible injury or death!
I am not trying to shout at you or anyone else with my words that are in bold type, just using bold type to emphasize some of my points.
So, to get on with it
My example of different length bullets seated into equal length cases shows that the volume is reduced with the longer bullets.
The point I was trying to make was that IF you reload to the MAXIMUM WORKING OAL or the MAXIMUM OAL listed in your reloading manuals, SPECIFICALY for the type (shape, weight etc.) of bullet you are using the SEATING DEPTH is not a factor in producing a cartridge that will have excessive pressure.
Examples:
Data from MODERN RELOADING 2nd EDDITION:
BULLET POWDER START LOAD MAX LOAD MIN.OAL
115gr JRN ACCUR #2 3.6gr 4.5gr 1.077"
115gr C plate RN ACCUR #2 3.8gr 4.6gr 1.140"
124gr C plate RN ACCUR #2 3.3gr 4.1gr 1.060"
Data from WESTERN POWDER HAND GUN DATA:
115gr C plate(RAIN)RN ACCUR #2 3.8gr 4.6gr 1.140"
124gr C plate(RAIN)RN ACCUR #2 3.8gr 4.6gr 1.160"
As MY MAXIMUM WORKING OAL is GREATER THAN the MIN. OAL for these BULLET SPECIFIC start and max loads I will not have a problem with excessive pressure.
The problem of excessive pressure enters when the reloader DOES NOT use data for their SPECIFIC bullet/gun powder type.
The OP was concerned with seating depth and a possibility of over-pressure in his loads. If he follows the load data for HIS type of bullet and HIS gun powder, as long as HIS cartridge OAL is over the MIN OAL listed for HIS load, seating depth does not enter as a factor into an over-pressure situation.
Going beyond published data WILL enter into excessive pressure territory.

This is a great discussion, especially for beginning reloaders concerned with safe reloading practices

 

My point is if you load a .528 flat nose to an oal of 1.050 that gives you .228 of the bullet in the case.
A .540 hollow point to an oal of 1.060 gives you .230 of the bullet in the case
A .587 round nose to an oal of 1.150 gives you only .187 of the bullet in the case, now if you load it to 1.107 it will be .230 in the case.
This should not cause any rise in pressure as the case volume is the same, it should also have the same velocity.
Remember I don't care about Max oal, I'm looking at keeping the same performance with different shape bullets. All cases are trimmed to .750, so it has nothing to do with case length. Powder and primers are also the same.

 

heavier bullet= less powder?????

Are all these bullets the same weight?
To move a heavier bullet you need less powder in the same volume of case, as a heaver bullet develops higher pressure with the same charge weight.
a good explanation of this is here:
http://thefiringline.com/forums/showthread.php?t=381828
Please let me know what you think.

 

All are 124gr. Published data is all over the place with oal.

 

case volume vs oal

OK. In your above statement the OAL changes for the LENGTH of your 124gr. bullets, all are plated.

As a general rule the OAL is different for each bullet length because the longer bullets create more drag going down the barrel, they are in the barrel for a longer period of time compared to the shorter bullets of the same weight which raises the pressure.
That is why the longer bullets require MORE case volume than shorter bullets, this higher volume in case reduces the pressure to a safe level.

True, determining MAX WORKABLE OAL for your pistol enters into accuracy, but also affects the ft. per sec velocity you achieve from each different shaped bullet.
Keeping the same performance with different shape/length bullets is what reloading for your specific pistol is all about. Reloading by working up from minimum powder charge in steps with each different shape/length bullet will give you the performance you are seeking.
There are no short cuts like same case volume = same pressure = same performance when using different shape/length bullets of the same weight.
A load that performs well for you in your pistol may not perform the same in mine, as each pistol is slightly different in what loads, bullets, OAL they "like" as YMMV.
Hope this helps, sorry I became so long winded, and I am not trying to talk down to you, just trying to help another reloader produce safe loads.

 

Yes the OAL changes but the part in the case remains the same. I've been reloading for O about close to 40 years. Just seems funny that 9's and 45's are everywhere with OAL unlike others

 

2 Horse,
Good discussion, you have many decades more reloading experience on me, I was reloading for rifles until shoulder problems so switched to pistols not long ago & found many more variables in loading for pistols. But I enjoy my time working up my loads ALMOST as much as sending the bullets down range

A good & safe MEMORIAL DAY to all

 

I haven't tried to analyze everybody's hypotheticals and individual examples, but will comment in general.

Everything is specified in OAL these days because all you have to do is measure it, and with a digital caliper that does not require reading a dial and certainly not a vernier.
Some of Phil Sharpe's 1937 data includes seating depth which, as said, is inversely related to powder space and is really informative as to internal ballistics. But that takes arithmetic to arrive at an OAL to adjust the seating die to, and that might be too much trouble for Modern Math.

The next problem is that there are many interacting variables. Seating depth is adjusted by OAL, but is affected by bullet length and ogive. Chamber pressure is affected by powder space, bullet weight, and rifling engraving force. There are a lot of different bullets and a lot of different chamber throats out there. You have to arrive at a loaded round that will fit the magazine, fit the chamber, and feed from magazine to chamber. I am at present loading a truncated cone 9mm at maximum length for my Colt which is fine in the SA. I have not tried it in the CZ, which is notorious for short chamber throats. I may have to tailor a load for it.

If you do not have the exact combination of components shown in the manual, you have to apply some thought, and go to the boring fine print about "starting loads" and "working up."

"Working up" can be a problem. "Pressure signs" commonly referenced in high intensity rifle calibers do not show up in pistols at half the pressure. I chronograph. I am usually after IDPA Power Floor velocities which can be reached below maximum with most reasonably suitable powders.
For an occasional batch of defense practice loads, I go to a powder that will give high velocity with pressure tested loads. I like Power Pistol. You can get close to +P performance with standard pressure loads and the report and flash make it seem like more.