OAL = COL ?

FlySubCompact · September 1, 2012, 12:53 AM

I recently bought some Hornady 115 grain 9mm FMJ RN bullets.

My Lyman Pistol manual does not list 115 grain RN's.

I did save a pic of a page from a Hornady manual someone posted here when I was searching for load data on some Hornady 124 XTP HP's In that pic it also listed load data for these 115 gr RN I want to load now. In that data I notice they list a COL for each bullet. My Lyman manual shows OAL.

Are COL and OAL the exact same thing?

Shootest · September 1, 2012, 01:16 AM

Quote:

Are COL and OAL the exact same thing?

Pretty much.
COL = Cartridge Overall Length
OAL = Over All Length

FlySubCompact · September 1, 2012, 01:23 AM

Thanks Shootest. I was thinking it was the same, but thanks for the verification.

New to reloading....I need another brand of manual.

THORN74 · September 1, 2012, 08:56 AM

I made this mistake early on .... each diff bullet type has potentially a diff COL. Its based ion the shape of the bullet. I loaded some jhp 45acp to the same COL as fmjrn and it wouldn't even fit in the magazine let alone into the chamber.

It was easy enough to fix thankfully

Sent from my GT-P7510 using Tapatalk 2

FlySubCompact · September 1, 2012, 10:09 AM

Just curious......

Using the only load data that I had (the picture scan I saved from a previous thread I mentioned earlier) I set OAL as close to 1.105" as I could. That was the COL listed on that page for Hornady 115 FMJ RN. 1.05" with medium charge of 4.7gr of 231 powder, just to be safe.

After loading and checking all the rounds I just made I forgot that I had some WWB factory loads. These are also 115gr FMJ RN bullets. These mic out at a OAL of 1.160"

.055" OAL seems like an unusually large difference in OAL for bullets that supposed to be simular. I know the the FMJ RN bullets that are used in the WWB's may be slightly different, but .055" is alarming to me.

Now I don't know if I can shoot the 50 shells I just made. Can anyone verify if 1.105 OAL is right?

snuffy · September 1, 2012, 10:31 AM

COL= either Cartridge Overall Length, or Case Overall Length. OAL could be anything. The problem is lazy people not wanting to take the time to spell things out. In your problem you're concerned about cartridge overall length.

Since you neglected to give what powder/primer you're loading, we can't give you any advice. That's where COL comes into play, the loads Horandy worked up were for that shorter COL. IF you used the powder they used at that COL, you're safe. IF you used data from some other source at that shorter COL, then you're not safe.

**Mal H** · September 1, 2012, 10:33 AM

Several of the manuals I have suggest an OAL round 1.135" +- .01".

I have some factory Federal 9mm using a 115 gr FMJ that mike out to 1.150" on average. Unless the Hornady bullet is abnormally squat for that weight and style, then 1.105" seems a bit short to me.

(Note - you need to edit your post and correct the first OAL you stated - 1.05".)

steve4102 · September 1, 2012, 11:03 AM

Quote:

I set OAL as close to 1.105" as I could. That was the COL listed on that page for Hornady 115 FMJ RN. 1.05"

Typo, or are you confusing yourself?

Quote:

Can anyone verify if 1.105 OAL is right

No, OAL/COL/COAL is bullet and firearm specific, not manual specific. You need to find the OAL/COL/COAL that fits-feeds-fires in YOUR pistol. Then start low and work up. After all, if it doesn't fit-feed-fire there is no need to worry about pressure is there.

FlySubCompact · September 1, 2012, 11:59 AM

snuffy,

I did mention the powder. It is 231. That .jpg of Hornady load data I used said that 4.7grains of 231 was a low/medium powder charge. I did not mention the primers. CCI 500 smalls.

Steve,

These ones fit nicely in the Glock. Actually, it's that I am just concerned as to if I just made these new bullets too short after comparing them to some factory WWB's that are supposed to be simular.

FlySubCompact · September 1, 2012, 12:02 PM

Mal,

1.105" is what is shown in the .jpg I have. The pic is supposed to be a manual with Hornady load data. That is what I set these to.

FlySubCompact · September 1, 2012, 12:14 PM

This the exact data that is shown on the .jpg scan I saved...seeing how my Lyman book did
not list this bullet.

#3555 FMJ-RN (115 grain bullets page)
Ballistic Coefficient- .140
COL- 1.105"

(in Win 231 collumn)
4.5 grain (1050 fps) ....MIN
4.7grain (1110 fps) ...Load I chose
5.1 grain (1150 fps)
5.5 grains (1200 fps)...MAX

**Mal H** · September 1, 2012, 12:52 PM

FSC - it's not clear if your response to my post was addressing the edit of "1.05 inches" or "1.105 inches seems a bit short to me [for that weight and style bullet]."

FlySubCompact · September 1, 2012, 01:24 PM

1.05" was a typo.

1.105" is the OAL data from the .jpg scan I have. That is also the OAL is set this batch of 50 shells.

I cannot remember where exactly I got the .jpg, but I did load some Hornady XTP HP's last loading session using that same scan. Test rounds from it did not Kaboom or squib.

It just puzzles me how this particular load data makes the OAL so short when compared to factory ammo (WWB 115g RN)of the same bullet weight. .055" " is a lot.

FlySubCompact · September 1, 2012, 01:40 PM

BTW,

I am a new reloader. I only have one manual, the Lyman.
Any of you reading this thread have load data from your other brand of manuals for the following?

CCI 500 small pistols primers.
Medium/low pressure with Win 231 powder.
Hornady 115 grain FMJ RN bullets.

What OAL does your manuals list?

wncchester · September 1, 2012, 06:00 PM

" OAL/COL/COAL is bullet and firearm specific, not manual specific. You need to find the OAL/COL/COAL that fits-feeds-fires in YOUR pistol. Then start low and work up. After all, if it doesn't fit-feed-fire there is no need to worry about pressure is there"

And THAT'S the truth!

Book OAL is what the bookmakers used to develop their data in THEIR firearm - it's interesting to some I suppose but book OAL is no more a law for anyone else than the book maker's powder charges are!

I've been reloading for pushing 50 years now and have never taken a book OAL into account for anything I've ever loaded for; I just find and use the proper OAL for myself and what I'm working with. If we are to be slaves to book data we may as well use factory ammo, the stuff totally made by real 'experts' you know? When I started, few manual makers listed any OAL at all. Then some began listing their OALs, just to help, and I believe it's caused much more angst than help! I've read of guys who couldn't find some specific bullet listed and just had no idea of where/how to seat them or what powder charges they should use! Goodness.

Case length is case length, there's no "over all case length" about it. The term OAL/COAL is for the cartridge, ie, the case and seated bullet and nothing more. Or less.

FlySubCompact · September 1, 2012, 06:54 PM

wncchester,

I guess I have been worrying for nothing. I took a few sample shells out of this new batch (ones that were most out of spec, either up or down on OAL), loaded them in a mag, donned a leather glove on weak hand, put a tree betwixt the gun and my torso and fired them.

No Kaboom. Also ran a mag of WWB's just for comparison. Could tell no difference in recoil, sound, feed or ejection. Cases all looked like they did before I reloaded them. No bulges, primers looked like they were fired from a Glock......which they were.

mrawesome22 · September 2, 2012, 08:48 AM

Book oal is meaningless to a handloader.

I don't know why they even include it in the book.

sudo passwd root

snuffy · September 2, 2012, 10:34 AM

Quote:

Book oal is meaningless to a handloader.

I don't know why they even include it in the book.

sudo passwd root

No it's NOT! It's the overall length of the bullet-case used in their testing---period! If you use a different overall length, then you're not going to duplicate their shown velocity. But more important, you're not going to duplicate their pressure either. In fact, if you go with a shorter bullet seating depth, you'll RAISE the pressure. Sometimes to a dangerous level.

Bullets of the same weight are made with different profiles. That means some are more pointed, or have a truncated cone profile. This makes for different full caliber bullet diameter that actually rides the bore. Some are a cupped bottom, or hollow base profile that pushes the weight forward and results in a longer section that rides the bore. This results in more friction with the bore. Friction and weight are responsible for pressure. That's all figured into the charge weights for the powder.

As some said, I take most manuals as suggestions. As long as the weight is the same, or within 5 grains, I use the suggested starting powder charges as just that, a place to start.

Fly sub was correct to be worried his suggested shorter seating depth might produce higher pressures. But Hornady took the shorter depth into account when testing and publishing the load data.

9mm is a high intensity, high pressure cartridge, it's loading parameters are very narrow. But most guns chambered for it can withstand higher pressure without letting go. Reading pressure from what the fired case looks like is like reading tea leaves. If you've shot your pistol a lot, excessive recoil/muzzle flip will tell you somethings not right. Excessively flat primers or extractor damage to the rims helps identify excess pressure.

Quote:

sudo passwd root

WTH is that? French latin? What does that say, and how does it pertain to reloading?

mrawesome22 · September 2, 2012, 11:38 AM

I use a chronograph and other signs to determine general pressure vincinity.

If I have to decrease oal to achieve desired function: reduce charge and work back up using the chronograph and other signs such as spent shell location as my guide.

I rarely use the exact combo found in the book. I would say 99% of the time, my components differ from theirs in some aspect.

That is regarding auto pistols.

Revolvers using canullured bullets: seat to the cannulure. Pretty simple there.

Rifles: determine ogive touching rifling, back off 30 thou, and start powder work up. Unless the book tells me how long the leade is in their test barrel, the books oal is again meaningless to me. Their velocity data is very helpful however, since I can compare theirs with mine, and use some other tricks, such as bolt lift and such, to give me a general idea of the pressure the load is generating.

sudo passwd root is my Sig using the Tapatalk android app and is inserted automatically. It allows you to change the root account password in a Linux distro, if you have admin privlidges.

sudo passwd root

Jim Watson · September 2, 2012, 11:53 AM

Quote:

Unless the Hornady bullet is abnormally squat for that weight and style, then 1.105" seems a bit short to me.

Hornady XTP bullets ARE "squat" and call for shorter loaded length than many other brands. (So are Sierras) All of the same caliber have the same truncated cone ogive, just different cylindrical bearing surface length in proportion to weight.

Quote:

1.05" was a typo.

1.105" is the OAL data from the .jpg scan I have.

And that is one reason you must be VERY careful about taking load data at the "recipe" level off the internet. Few of us have proofreaders going over what we want to post.

wncchester · September 2, 2012, 08:56 PM

The oft mentioned variables in bullets (or powder lots or primer lots, etc.) that are supposed to be significant in changing book projected pressures pale in comparison to the differences between individual firearms and that can't be helped.

Anyone hoping to 'gage' pressure by observable signs in handgun cases are crusing for a brusing; by the time the most common over pressure signs are evident most handguns will have already come from together.

FlySubCompact · September 3, 2012, 02:48 AM

Quote:

Reading pressure from what the fired case looks like is like reading tea leaves. If you've shot your pistol a lot, excessive recoil/muzzle flip will tell you somethings not right. Excessively flat primers or extractor damage to the rims helps identify excess pressure.

BTW, I did eyeball the few samples I shot from this last lot. Case walls looked good. Primers had the usual "Glock" rectangular imprint on the primers and were not unusually flat. I only bought 100 of these Hornady's just to get my feet wet. My future range bullets will be cheaper Berry's RN FMJ and loaded to medium low.

steve4102 · September 3, 2012, 07:49 AM

Quote:

No it's NOT! It's the overall length of the bullet-case used in their testing---period! If you use a different overall length, then you're not going to duplicate their shown velocity. But more important, you're not going to duplicate their pressure either.

True, But you are not going to Duplicate their pressures by treating their data as a recipe and follow it to the letter either. Unless of course you use the same powder/primer lot number, same lot brass, same temp/altitude and of course the same exact firearm or test barrel.

SL1 · September 3, 2012, 10:08 AM

Today, MOST reloading manuals provide data that was produced using TEST barrels to determine PRESSURE. Some simply report the velocities achieved in those test barrels, while others fire the same loads in an "example" or "test" firearm that is commercially available. The rationale is that the test barrels is carefully made to SAAMI minimum dimension specifications, so it will produce as-high or higher pressure than more sloppy commercial barrels. That helps ensure that the loads developed will not cause excessive pressures in handloaders' guns. But, the more sloppy chambers may produce less pressure, and therefore less velocity. SO, many manuals also report the velocities from the example commercial guns (which may also have different barrel lengths than the standard SAAMI test barrels). That helps handloaders understand what vleocities they can realistically expect to achieve. But, it does provide a half-apples-half-oranges type of data fruit salad for the armchair reloader to try to reconcile in his head from manual to manual. With all the other varibles involved, figuring-out what chamber pressure should equal what velocity in your own gun is generally just not doable without a computer program like QuickLOAD or some acutal pressure testing equipment like NECO sells.

With that in mind, the COL listed in a manual still is VERY important when developing handloads for small, high-pressure cartridges like the 9mm and 40 S&W. If you shorten the COL WITH THE SAME BULLET as used in the data, you will increase the pressure. If you use a DIFFERENT bullet with the same COL, you may change the pressure up or down if the bullet is not the same length as the bullet used to develop the data. That is because the real variable of interest is SEATING DEPTH, which is the sum of bullet length and case length minus the COL. That (and the case's internal volume) is what determines the space remaining for the powder, which is what is needed to determine the pressure (in conjunction with a lot of other variables including the powder, bullet weight, primer, etc).

When you change the seating depth by 0.01" or more from some loading manual data for a specified bullet weight, either by changing the COL or by using a different bullet that has a different length, then you should be addressing the change in pressure. Laboratory tests have shown that changing the seating depth in a 9mm by something like 0.030" CAN change the peak pressure by tens of thousands of psi with particularly sensitive loads. Typically, pressure differences are much smaller than that, but can still be quite significant, especially if you are pushing the max.

SL1

tobnpr · September 3, 2012, 10:54 AM

Yep...
Be careful with OAL...

I recently made up a bunch of match handloads for my son's K-31, chambered in 7.5 x 55....

The Sierra manual specifies an OAL of 3.06"...

So, I loaded up 50 rounds of MatchKings at that length, since the modified case for the bullet comparator had not arrived yet....

He was telling me that he was having trouble closing the bolt...extraction was fine, just hard to close the bolt.

After about ten rounds, I took the rifle from him. Bolt closed fine with no round in the chamber. With no explanation, and not wanting to risk an out-of-battery firing, we put the rifle up.

When the modified case arrived, I put a bullet in it, and chucked it into the chamber. OAL to the lands was 2.845- a far cry from the 3.06 in the manual...

We were jamming the bullet into the rifling by about a quarter inch...not a good thing...The loads weren't hot, and that was likely a good thing.

Turns out that, after some research, Swiss rifles chambered in 7.5 x 55 had ALOT of variations in throat dimensions and length.

Sierra, IMO, should have made that clear in their manual- but they did not.

If you handload, there is no reason not to spend the few bucks on a bullet comparator to develop your loaded lengths. More precision, greater accuracy.
Length to the lands varies not just by bullet weight, but ogive shape.

I realize this may not be as big an issue with handguns, but it should be noted nonetheless.

September 1, 2012, 12:53 AM	#1
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	OAL = COL ? I recently bought some Hornady 115 grain 9mm FMJ RN bullets. My Lyman Pistol manual does not list 115 grain RN's. I did save a pic of a page from a Hornady manual someone posted here when I was searching for load data on some Hornady 124 XTP HP's In that pic it also listed load data for these 115 gr RN I want to load now. In that data I notice they list a COL for each bullet. My Lyman manual shows OAL. Are COL and OAL the exact same thing?

September 1, 2012, 10:31 AM	#6
snuffy Senior Member Join Date: May 20, 2001 Location: Oshkosh wi. Posts: 3,055	COL= either Cartridge Overall Length, or Case Overall Length. OAL could be anything. The problem is lazy people not wanting to take the time to spell things out. In your problem you're concerned about cartridge overall length. Since you neglected to give what powder/primer you're loading, we can't give you any advice. That's where COL comes into play, the loads Horandy worked up were for that shorter COL. IF you used the powder they used at that COL, you're safe. IF you used data from some other source at that shorter COL, then you're not safe. __________________ The more people I meet, the more I love my dog They're going to get their butts kicked over there this election. How come people can't spell and use words correctly?

September 1, 2012, 06:00 PM	#15
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	" OAL/COL/COAL is bullet and firearm specific, not manual specific. You need to find the OAL/COL/COAL that fits-feeds-fires in YOUR pistol. Then start low and work up. After all, if it doesn't fit-feed-fire there is no need to worry about pressure is there" And THAT'S the truth! Book OAL is what the bookmakers used to develop their data in THEIR firearm - it's interesting to some I suppose but book OAL is no more a law for anyone else than the book maker's powder charges are! I've been reloading for pushing 50 years now and have never taken a book OAL into account for anything I've ever loaded for; I just find and use the proper OAL for myself and what I'm working with. If we are to be slaves to book data we may as well use factory ammo, the stuff totally made by real 'experts' you know? When I started, few manual makers listed any OAL at all. Then some began listing their OALs, just to help, and I believe it's caused much more angst than help! I've read of guys who couldn't find some specific bullet listed and just had no idea of where/how to seat them or what powder charges they should use! Goodness. Case length is case length, there's no "over all case length" about it. The term OAL/COAL is for the cartridge, ie, the case and seated bullet and nothing more. Or less. Last edited by wncchester; September 1, 2012 at 06:07 PM.

September 1, 2012, 01:23 AM	#3
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	Thanks Shootest. I was thinking it was the same, but thanks for the verification. New to reloading....I need another brand of manual.

September 1, 2012, 08:56 AM	#4
THORN74 Senior Member Join Date: May 30, 2010 Location: Chicago 'Burbs Posts: 543	I made this mistake early on .... each diff bullet type has potentially a diff COL. Its based ion the shape of the bullet. I loaded some jhp 45acp to the same COL as fmjrn and it wouldn't even fit in the magazine let alone into the chamber. It was easy enough to fix thankfully Sent from my GT-P7510 using Tapatalk 2

September 1, 2012, 10:09 AM	#5
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	Just curious...... Using the only load data that I had (the picture scan I saved from a previous thread I mentioned earlier) I set OAL as close to 1.105" as I could. That was the COL listed on that page for Hornady 115 FMJ RN. 1.05" with medium charge of 4.7gr of 231 powder, just to be safe. After loading and checking all the rounds I just made I forgot that I had some WWB factory loads. These are also 115gr FMJ RN bullets. These mic out at a OAL of 1.160" .055" OAL seems like an unusually large difference in OAL for bullets that supposed to be simular. I know the the FMJ RN bullets that are used in the WWB's may be slightly different, but .055" is alarming to me. Now I don't know if I can shoot the 50 shells I just made. Can anyone verify if 1.105 OAL is right?

September 1, 2012, 10:33 AM	#7
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	Several of the manuals I have suggest an OAL round 1.135" +- .01". I have some factory Federal 9mm using a 115 gr FMJ that mike out to 1.150" on average. Unless the Hornady bullet is abnormally squat for that weight and style, then 1.105" seems a bit short to me. (Note - you need to edit your post and correct the first OAL you stated - 1.05".)

September 1, 2012, 11:59 AM	#9
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	snuffy, I did mention the powder. It is 231. That .jpg of Hornady load data I used said that 4.7grains of 231 was a low/medium powder charge. I did not mention the primers. CCI 500 smalls. Steve, These ones fit nicely in the Glock. Actually, it's that I am just concerned as to if I just made these new bullets too short after comparing them to some factory WWB's that are supposed to be simular.

September 1, 2012, 12:02 PM	#10
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	Mal, 1.105" is what is shown in the .jpg I have. The pic is supposed to be a manual with Hornady load data. That is what I set these to.

September 1, 2012, 12:14 PM	#11
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	This the exact data that is shown on the .jpg scan I saved...seeing how my Lyman book did not list this bullet. #3555 FMJ-RN (115 grain bullets page) Ballistic Coefficient- .140 COL- 1.105" (in Win 231 collumn) 4.5 grain (1050 fps) ....MIN 4.7grain (1110 fps) ...Load I chose 5.1 grain (1150 fps) 5.5 grains (1200 fps)...MAX

September 1, 2012, 12:52 PM	#12
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	FSC - it's not clear if your response to my post was addressing the edit of "1.05 inches" or "1.105 inches seems a bit short to me [for that weight and style bullet]."

September 1, 2012, 01:24 PM	#13
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	1.05" was a typo. 1.105" is the OAL data from the .jpg scan I have. That is also the OAL is set this batch of 50 shells. I cannot remember where exactly I got the .jpg, but I did load some Hornady XTP HP's last loading session using that same scan. Test rounds from it did not Kaboom or squib. It just puzzles me how this particular load data makes the OAL so short when compared to factory ammo (WWB 115g RN)of the same bullet weight. .055" " is a lot.

September 1, 2012, 01:40 PM	#14
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	BTW, I am a new reloader. I only have one manual, the Lyman. Any of you reading this thread have load data from your other brand of manuals for the following? CCI 500 small pistols primers. Medium/low pressure with Win 231 powder. Hornady 115 grain FMJ RN bullets. What OAL does your manuals list?

September 1, 2012, 06:54 PM	#16
FlySubCompact Senior Member Join Date: February 16, 2012 Posts: 306	wncchester, I guess I have been worrying for nothing. I took a few sample shells out of this new batch (ones that were most out of spec, either up or down on OAL), loaded them in a mag, donned a leather glove on weak hand, put a tree betwixt the gun and my torso and fired them. No Kaboom. Also ran a mag of WWB's just for comparison. Could tell no difference in recoil, sound, feed or ejection. Cases all looked like they did before I reloaded them. No bulges, primers looked like they were fired from a Glock......which they were.

September 2, 2012, 08:48 AM	#17
mrawesome22 Senior Member Join Date: November 9, 2005 Location: Ohio, Appalachia's foothills. Posts: 3,779	Book oal is meaningless to a handloader. I don't know why they even include it in the book. sudo passwd root

September 2, 2012, 11:38 AM	#19
mrawesome22 Senior Member Join Date: November 9, 2005 Location: Ohio, Appalachia's foothills. Posts: 3,779	I use a chronograph and other signs to determine general pressure vincinity. If I have to decrease oal to achieve desired function: reduce charge and work back up using the chronograph and other signs such as spent shell location as my guide. I rarely use the exact combo found in the book. I would say 99% of the time, my components differ from theirs in some aspect. That is regarding auto pistols. Revolvers using canullured bullets: seat to the cannulure. Pretty simple there. Rifles: determine ogive touching rifling, back off 30 thou, and start powder work up. Unless the book tells me how long the leade is in their test barrel, the books oal is again meaningless to me. Their velocity data is very helpful however, since I can compare theirs with mine, and use some other tricks, such as bolt lift and such, to give me a general idea of the pressure the load is generating. sudo passwd root is my Sig using the Tapatalk android app and is inserted automatically. It allows you to change the root account password in a Linux distro, if you have admin privlidges. sudo passwd root

September 2, 2012, 08:56 PM	#21
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	The oft mentioned variables in bullets (or powder lots or primer lots, etc.) that are supposed to be significant in changing book projected pressures pale in comparison to the differences between individual firearms and that can't be helped. Anyone hoping to 'gage' pressure by observable signs in handgun cases are crusing for a brusing; by the time the most common over pressure signs are evident most handguns will have already come from together.

September 3, 2012, 10:08 AM	#24
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Today, MOST reloading manuals provide data that was produced using TEST barrels to determine PRESSURE. Some simply report the velocities achieved in those test barrels, while others fire the same loads in an "example" or "test" firearm that is commercially available. The rationale is that the test barrels is carefully made to SAAMI minimum dimension specifications, so it will produce as-high or higher pressure than more sloppy commercial barrels. That helps ensure that the loads developed will not cause excessive pressures in handloaders' guns. But, the more sloppy chambers may produce less pressure, and therefore less velocity. SO, many manuals also report the velocities from the example commercial guns (which may also have different barrel lengths than the standard SAAMI test barrels). That helps handloaders understand what vleocities they can realistically expect to achieve. But, it does provide a half-apples-half-oranges type of data fruit salad for the armchair reloader to try to reconcile in his head from manual to manual. With all the other varibles involved, figuring-out what chamber pressure should equal what velocity in your own gun is generally just not doable without a computer program like QuickLOAD or some acutal pressure testing equipment like NECO sells. With that in mind, the COL listed in a manual still is VERY important when developing handloads for small, high-pressure cartridges like the 9mm and 40 S&W. If you shorten the COL WITH THE SAME BULLET as used in the data, you will increase the pressure. If you use a DIFFERENT bullet with the same COL, you may change the pressure up or down if the bullet is not the same length as the bullet used to develop the data. That is because the real variable of interest is SEATING DEPTH, which is the sum of bullet length and case length minus the COL. That (and the case's internal volume) is what determines the space remaining for the powder, which is what is needed to determine the pressure (in conjunction with a lot of other variables including the powder, bullet weight, primer, etc). When you change the seating depth by 0.01" or more from some loading manual data for a specified bullet weight, either by changing the COL or by using a different bullet that has a different length, then you should be addressing the change in pressure. Laboratory tests have shown that changing the seating depth in a 9mm by something like 0.030" CAN change the peak pressure by tens of thousands of psi with particularly sensitive loads. Typically, pressure differences are much smaller than that, but can still be quite significant, especially if you are pushing the max. SL1

September 3, 2012, 10:54 AM	#25
tobnpr Senior Member Join Date: August 1, 2010 Location: Tampa Bay Posts: 4,556	Yep... Be careful with OAL... I recently made up a bunch of match handloads for my son's K-31, chambered in 7.5 x 55.... The Sierra manual specifies an OAL of 3.06"... So, I loaded up 50 rounds of MatchKings at that length, since the modified case for the bullet comparator had not arrived yet.... He was telling me that he was having trouble closing the bolt...extraction was fine, just hard to close the bolt. After about ten rounds, I took the rifle from him. Bolt closed fine with no round in the chamber. With no explanation, and not wanting to risk an out-of-battery firing, we put the rifle up. When the modified case arrived, I put a bullet in it, and chucked it into the chamber. OAL to the lands was 2.845- a far cry from the 3.06 in the manual... We were jamming the bullet into the rifling by about a quarter inch...not a good thing...The loads weren't hot, and that was likely a good thing. Turns out that, after some research, Swiss rifles chambered in 7.5 x 55 had ALOT of variations in throat dimensions and length. Sierra, IMO, should have made that clear in their manual- but they did not. If you handload, there is no reason not to spend the few bucks on a bullet comparator to develop your loaded lengths. More precision, greater accuracy. Length to the lands varies not just by bullet weight, but ogive shape. I realize this may not be as big an issue with handguns, but it should be noted nonetheless.