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Old 05-12-2016, 10:07 AM
Dr Denby Dr Denby is offline
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Default need OAL cartridge length help

I am just getting started reloading.

I plan to only load 9mm luger, 40s&w, and 45acp

The problem is that I keep finding conflicting OAL cartridge length. Each powder manufacturer each manual all seem to have a different spec for the same cartridge.

Where are you all getting your cartridge lengths data?

What is the proper specs for 9mm jacketed round nose, 40s&w jacketed flat nose, and 45acp jacketed round nose? and what are the +/- tolerances?

The bullet weight shouldn't matter for OAL right? just the tip?

Doc
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Old 05-12-2016, 10:34 AM
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OAL is a result of a bullet/powder combination. It is not a specification! Several manuals show the SAAMI Maximum LOA specification, while their data shows an "as tested" length for their bullet. If loading their maximum load then consider their LOA as a minimum length.

Other than this, don't worry about it!
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Old 05-12-2016, 11:07 AM
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Yes, beginning loaders often get all wrapped around the axle about OAL, mostly because they don't understand what's important.
First, on the back end, the distance from the base of the bullet to the rear of the cartridge determines the size of the available powder cavity, which determines the ballistic expansion ratio. Changing the expansion ratio is what changes the pressure. Two similar bullets seated to give the same expansion ratio will have similar pressures.

Second, on the front end, the bullet must allow the cartridge to fit in the magazine and also allow the loaded cartridge to drop freely into the chamber without sticking in the rifling (the "plunk" test).

So there is a heck of a lot of leeway in OAL, as long as you don't get into trouble on either end. And no, you can't just pick a "magic OAL" and use it for everything, because when you change the length and shape of the bullet, it changes how that particular bullet fits.

For beginning loaders of old favorite cartridges, I always advise STUDYING the technical part of a good reloading manual first. Then pick a medium powder and load in the MIDDLE of the data, checking to be sure the cartridge fits their particular gun. Starting in the middle instead of either end of the data gives a lot more leeway for small changes being safe. Too light a load can stick a bullet; too heavy can go dangerously overpressure. Same with length: too short raises pressure, too long may not feed.
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Old 05-12-2016, 02:17 PM
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That is because OAL is ALWAYS bullet & barrel specific. When I teach my class, I put up 6 diff 9mm/124gr bullets. All are diff styles, all load to diff lengths as they fit YOUR bbl & if mag fed, the mag. It seems to be the most diff thing for newb reloaders to grasp. Regardless of the book data, the bullet must fit your gun. If you never go beyond midrange loads, small variations in OAL between bullets of the same wt won't matter much as to pressures, as long as the bullet isn't wedged into the rifling.
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Old 05-12-2016, 02:53 PM
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Maximum length that will work through the magazine and freely chamber. "Freely chamber" - take the barrel out of the pistol, drop a dummy round in. Very, very slight resistance hurts nothing as long as the cartridge is fully seated in the barrel chamber with nothing protruding.

If the cartridge won't fully seat, either the case is not properly sized, the bullet is seated too far out, or the crimp is insufficient. Try again.

And, if you don't have paper handloading manuals, get at least two or three. All this is explained far better than I can do it. Usually, the maximum OALs listed in the books are about the maximum lengths that will work through magazines. Sometimes, these can be slightly exceeded, but not by much.
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Old 05-12-2016, 07:40 PM
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Google "plunk test". There's a Shooting a Times article that explains it, plus a few YouTube videos. This is probably the best way to determine your OAL for your auto loaders. Remember, these headspace on the cartridge mouth. That's what counts.

Last edited by ChuckS1; 05-12-2016 at 07:45 PM.
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Old 05-12-2016, 07:55 PM
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There is usually a maximum OAL that will work in most auto's.
There are some that need the short loads to feed and eject.

The big problem is the short, "Minimum OAL" for the bullets.....
since this is where the pressure is at its maximum, due to minimum case volume and usually a compressed loading of powder, of a lot of powders.

Just going from a JHP to a FMJ will from the same company will change pressure with the same amount of powder.

You just need to try out the short to long oal of a load in your pistol, to see what it likes.
Just today I shot a long 135gr with a full load of Red Dot at 1.16" and got 1013fps, while the same bullet at 1.12" and a good amount of Unique only hit 1009fps.

You never know what is going to happen with oal and powder amounts.
Later.

ps;
I would post 135gr results from today but.........
I am taking the wife out to dinner, for our 20th Anniversary to the BEST steak house in Reno
in about 16 minutes!!
Later.

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Old 05-12-2016, 08:32 PM
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Thanks guys.

This is some good information that went well to explain why I kept getting conflicting recommended lengths.

Looks like I am gonna need a bullet puller and a lot of experimenting with my guns.

Doc


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I am taking the wife out to dinner, for our 20th Anniversary to the BEST steak house in Reno
in about 16 minutes!!
Later.
Do tell which. So far my favorite is Ruths Chris. Their medium rare ribeye, grilled asparagus, and baked potato dinner is a culinary orgasm. Always open to trying other steakhouses.
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Old 05-12-2016, 08:54 PM
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When using jacketed bullets, I go with the manufacturer's data. Example; for my 9mm reloads with Hornady 124 gr. XTP bullets, the Hornady manual states 1.060" as the recommended OAL for that specific bullet. When I use Nosler bullets I use Nosler's manual data. Sierra bullets, Sierra manual, etc. For new reloaders I suggest using the OAL the bullet manufacturer determined for a specific bullet. After a bit of experience is gained there are methods to determine the OAL for your specific gun/ammo combination. Slugging/making chamber casts, Plunk Test, are a couple. You are prolly looking at different OALs for different bullets, getting "conflicting" dimensions...

I can't see how the powder can make a difference....

Last edited by mikld; 05-12-2016 at 08:56 PM.
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Old 05-13-2016, 12:21 AM
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It's not that important in most cases. Two major COAL considerations for any bullet. First, not too long to fit into the magazine (autopistol), or, if in a revolver, bullet noses not sticking out of the chambers. Second, that the case will fully chamber easily. Especially in an autopistol chamber. I think it's best to have a maximum COAL which fulfills both. COAL with many revolver loads will be influenced by a cannelure (jacketed bullet) or crimping groove (lead bullet). For very light-for-caliber bullets, the COAL will have to be somewhat below maximum SAAMI COAL specs to allow the short bullet to be properly held by the case.

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Old 05-13-2016, 02:44 AM
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Default Plunk Test for a semi-automatic pistol

Quote:
Originally Posted by Dr Denby View Post
I plan to only load 9mm luger, 40s&w, and 45acp...
Where are you all getting your cartridge lengths data?
.

It's best to use the OAL" that works in your pistol's barrel by using the plunk test.


Plunk Test for a semi-automatic pistol:

This is how you do a "plunk test" but for me it's most important, and accurate, how the assembled "test round" sounds, and feels, when you drop it in the barrel's chamber, as much as where the rim is in relation to the hood. (The rim should not extend beyond the end of the hood.)

When you drop the round in the removed barrel's chamber, it should make a nice metal to metal clink, "plunk", sound. -(Make sure you've added a minimal (taper) crimp that's just enough to remove any case flare from the sample round before, otherwise the results are deceiving.)- That's the case mouth hitting the chamber's shoulder, where the cartridge headspaces on. If the bullet is seated out too much (long) then the bullet's ogive hits the rifling & you don't get the same sound, but rather a dull thud. Additionally, if you rotate the round in the chamber it should be nice & smooth (case mouth on chamber shoulder). If it's too long, it'll feel rough because the bullet's ogive is rubbing against the rifling. (Remember, eliminate any flare before checking.)

Initially, seat the bullet out farther than needed & slowly adjust your seating die deeper, doing a plunk test between adjustments until you get the proper results. Then set your final crimp & double check the results before continuing loading. Verify fit in magazine too.

It doesn't take long to get the right adjustment & once you record the OAL", for that specific bullet, you can use that measurement next time & forego the plunk test, if you like. Make sure it's at or below the SAAMI max. OAL" for that cartridge. (I like to load mine as long as possible while still passing the plunk test & not exceeding max. OAL")

Also, different guns have different amounts for freebore/leade (space between the chamber shoulder & the start of the rifling), so one gun's barrel that can handle a max. OAL" assembled cartridge may find it not to be ideal for another's, due to bullet shape, so double check if in doubt.

I've never seen the need for a case gauge (for pistols) as the barrel/chamber already acts as the "custom gauge" that you are trying to match. Also, I have no idea how they could indicate if your particular gun's leade would interfer with the bullet you were loading for. It only takes a minute to remove & use the barrel in question & eliminate any doubts.

.
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Old 05-13-2016, 06:34 AM
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Default Whatever COAL the bullet was tested under...

Or a similar profile/weight/type of construction, If you are near MAX load, do not push the bullet deeper than recommended as pressure rises the deeper the bullet goes in. There isn't as much internal volume to play with as in most revolver cartridges where OAL is more variable. Of course you can make the cartridges longer, if they will fit you gun, as pressure reduces the farther out the bullet is.

I'm finding that compact pistols tend to have short leades and certain bullets get really stuck in the rifling. The gun won't fire because it's slightly out of battery and is very hard to eject because the bullet is jammed in tight. I want all of my ammo to fit all my guns, so besides getting the leads cut back I'm adjusting OALs inward, with care as not to overpressure.
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