Demystify OAL

[ryan richards]

Hi CBOs.

I'm new, so this one should be easy to explain. I frequently come across "OAL" (over all length) and I would like a better understanding about it.

On one hand, OAL dimensions are according to the industry standard and on the other hand, it appears to be like a chili cookoff with each handloader giving his own recipe within the industry standards.

Question: What negative factors occur when the OAL is longer or shorter than the industry standard for a 380 ACP, 38 Super and a 38 Special?

Question: Should each load be taylor made for best loading and accuracy within the industry standard?

Question: Is this done by trial and error?

Question: What tools are needed to do this?

Thanks for your time and interest.

Sincerely,

Ryan

[heathydee]

There are several factors involved in arriving at an overall length for a cartridge. In a magazine weapon the cartridge must be short enough to fit inside the magazine .
The ideal position for the bullet to be in when a cartridge is chambered is about 20 thou short of touching the rifling for a J word bullet and perhaps lightly seated into the lands for a cast boolit.
Because of the many different lengths and nose profiles available to the handloader often a compromise has to be reached .
If a boolit is light for caliber such as a 100 grain round nose in a 30-06 for instance , it may have to be placed well short of the rifling in order for it to be seated securely in the case neck.
A pointy bullet of about the 150 grain mark seated well out to be just short of the rifling may be too long to fit in the magazine .
Any revolver has to have an overall length shorter than the cylinder to prevent it failing to rotate.

Hope this begins to de-mystify the subject.

[billyb]

oal, bullets pushed to far into the case (to short) can cause over pressure. use calipers to check oal.manuels will show oal for loads listed.most revolver bullets will have a crimp grove. pistol rounds need to fit the clip. use a factory round to set your seating die for cast of like wieghts. Bill

[danski26]

I disagree that "20 thou short of touching the rifling" is THE ideal. First of all "ideal" is subjective. Ideal accuracy? Ideal function? Ideal velocity? Secondly, each cartridge, projectile, powder, primer, case "case prep too" and individual rifle may have an "ideal" OAL. "However you define ideal"

Some statements that tend to be true:

The deeper you seat a projectile the high pressures go.

Small capacity cases, 380acp 38 super 38 special, may have very high pressure with only small OAL variance.

Seating into the lands tends to raise pressure.

Changing any component in the cartridge or rifle could affect "ideal" OAL.

Following OAL sugestions in published manuals SHOULD result in safe handloads.

Also going hand in hand woth OAL is neck tension, having equaly unknown affects until tested.



The only time I play around with OAL is when I have tried the OAL suggestions in the manuals and found my combination does not work well with those recomendations. If it is a match rifle i start with seating into the lands and vary the neck tension until i get the results i'm looking for. If it is a hunting rifle I start at suggested OAL then work closer to the lands until i get the results i'm looking for. I do not seat into the lands for a hunting rifle. For pistol cartridges i stick to sugested OAL.

For actual proceedures for this testing.....I think Glen Zediker covers it best in his book "Handloading For Competition".

[mike in co]

Hi CBOs.

I'm new, so this one should be easy to explain. I frequently come across "OAL" (over all length) and I would like a better understanding about it.

On one hand, OAL dimensions are according to the industry standard and on the other hand, it appears to be like a chili cookoff with each handloader giving his own recipe within the industry standards.

Question: What negative factors occur when the OAL is longer or shorter than the industry standard for a 380 ACP, 38 Super and a 38 Special?

Question: Should each load be taylor made for best loading and accuracy within the industry standard?

Question: Is this done by trial and error?

Question: What tools are needed to do this?

Thanks for your time and interest.

Sincerely,

Ryan

do not mix MAX OAL and the oal listed for a given load.
pistol bullets generally can be measured with simple calipers, jacketed pointed rifle bullets often vary in oal, and thus the distance to the lands is often used by an ammo crafter. specail tools are availble to do this. lots of testing for rifles, typically not much for short distance pistols are shoot at, tho shooting long distance with pistols is possible, and then require more work.

i would suggest you read a couple of relaoding manuals..they will give you a great base to work with.

mike in co

[Bass Ackward]

It's the old bicycle tire, tractor tire scenario. You can pump up a bike tire in 60 seconds to 40 psi, but it will take you much longer to get 12 psi in a tractor tire.

OAL results in a volume figure. A 308 Win and a 30 -378 WBY can be loaded to exactly the same pressure, but the Wby will have substantial more velocity. Volume.

You see this all the time, by loading manuals that tell you not to alter seating depth or switch brands of bullets. And if you do, to start low and work up. But change anything, you start low and work up.

The smaller the capacity of a case is, or the weaker the gun platform, and the more critical this becomes.

[Whitespider]

On one hand, OAL dimensions are according to the industry standard and on the other hand,..... each handloader giving his own recipe.....
By “industry standard” you must mean the maximum cartridge overall length as listed by SAAMI. Not all cartridges (of same caliber) purchased will be the same length, depending on bullet and manufacturer OAL will be different, but all should be equal to or less than SAAMI maximum. There is also minimum chamber dimensions listed by SAAMI, and certain bullets (such as flat nosed type) will be loaded to something well short of maximum allowable SAAMI OAL in order to comply with chamber dimensions. SAAMI dimensions are used (voluntarily) by firearms and ammunition manufactures so when you buy a rifle from Remington and ammunition from Winchester..... well, they fit each other.


Question: What negative factors occur when the OAL is longer or shorter than the industry standard for a 380 ACP, 38 Super and a 38 Special?
As already stated, magazine size and cylinder length will limit OAL. When loading for auto pistols the OAL can, or will, affect reliable feeding and only experimentation will reveal this. But, do not forget, changes in OAL will effect pressures, and typically the smaller the cartridge the greater the effect. The only real “negative” to loading ammunition outside of SAAMI specifications is they are only safe to fire in the particular gun they were developed for! But in all practicality, any handload is only safe to fire in the particular gun(s) they were developed for.


Should each load be taylor made for best loading and accuracy within the industry standard?
As handloaders, we are free to experiment, but it is highly advisable that measurements be taken of your individual chamber to determine the maximum OAL for the particular bullet or boolit you’re using. We are not bound by SAAMI specifications and can exceed them to build ammunition that better “fits” our individual firearm and provides us with the performance we may want.


Is this done by trial and error?
Yup, pretty much.


What tools are needed to do this?
At a bare minimum you’ll need a caliper to measure your cartridge OAL. Other tools, such as gauges to measure and compare chamber to OAL are available from manufactures such as Stoney Point. There are other techniques to determine maximum OAL that do not use special tools, to explain them would require a whole chapter. I would suggest getting one of the many books dedicated to the more advanced reloading techniques, or possibly a Google search would give some insight.

[38 Super Auto]

+1 on WS's summary. Get a Lyman, Dillon, etc. cartridge length gage. Also, it is advisable to verify that your finished rounds chamber in YOUR rig's barrel.

OAL effects cartridge feeding and pressure. For a new bullet, I usually start 20-50 mils under max cartridge length as gaged by my Dillon cartridge length gage and go from there. I tweak the OAL based on feed reliability and performance, for each bullet.

These gages verify correct case diameter, maximum case length, and maximum cartridge length. I have one for each of my auto calibers.