OAL that is listed in reloading data

[copterdrvr]

I know you have to do a "plunk" test and all that good stuff but my question is regarding the "published" OAL for a load in the manuals....

 

Is that the MINIMUM OAL listed by the powder companies to insure that the pressures don't exceed whatever limitation they've decided to use for their data?

 

I'm making two assumptions-if the bullet is seated DEEPER it would increase the pressure and/or it's because the bullet profile wouldn't cycle in a "standard" chamber....

 

Is it really because of the pressure issue?

[Guy Neill]

The published OAL is that that was used in developing the loads.  It does not necessarily represent a minimum or a maximum.  Seating deeper will normally raise the pressure, though that is one of the reasons to start load and work up with charge weights.

If they do not list a firearm it was tested in, it's most likely it was only fired in a pressure gun.  Thereby, function in a firearm must be determined - again, working up.

 

Overall, it is not just because of pressure limitations, but that is obviously a prime concern.  The process of starting low and working up allows the reloader to see what function best in his gun.  If a given load is too long for a cylinder, or to fit in a magazine, it will need to be adjusted.  There are many 38 Super magazines that will not accept a maximum length 38 Super cartridge, though most loading manuals will not test at the maximum OAL.

[copterdrvr]

Thanks for the info-unfortunately, that doesn't explain why the manufacturer picked that particular OAL to use for their load data.  THATS what I'm looking for...............

[ltdmstr]

Other than being within SAAMI specs, they can choose whatever OAL they want.  I have no idea what they go on, but the most logical would be to use a uniform depth for the bullet base in the case, as that would ensure consistent volume and a solid basis for comparing pressure between various combinations of bullets and loads.  Of course, that's assuming OAL is within specs.  If you want a definitive answer, maybe try contacting one of the powder or bullet companies that publish load data and see what they say.

[copterdrvr]

Thanks for the reply's.

 

I guess my question would be why did they pick a particular oal for a bullet..... What was the thought process...

 

As an example, why did they decide that they would use 1.13 oal for a Hornady 147 grn HP for an Alliant SP load......

 

What was their thought criteria and why do ANY of the other powder manufacturers pick a particular oal for a given load?????

 

Thanks for the reply's.....

[Guy Neill]

For those manuals for which I've compiled data, the OAL came from various sources.  Some, when there was also factory ammunition being manufactured, followed the OAL length established for the factory ammunition.  As an example, I used 1.150 for some 9mm Luger loads as that had already been established in the factory ammunition for that company.  The example you mention for the 147gr may have come from the ogive making the deeper seating necessary for function.

 

Some were from p[personal experience.  Some from testing.  

 

Historically the 200 H&G LSWC 45 Auto has been loaded to an OAL of 1.245 - 1.250 and works well.  The Speer 200gr PSWC needed to be a bit longer for good function, so is more like 1.255.  Speer has messed up, using an OAL of 1.275 - which likely doesn't work for much of anyone.

 

Revolvers are fairly easy in that they normally have a cannelure to crimp into.  Thus, the OAL will be something allowing a crimp.

 

As ltdmstr mentioned, SAAMI specifications play a part as well.

 

With rifles it's common with flat base bullets to try to seat the base of the bullet to the base of the neck of the case, but very light or very heavy bullets may make it necessary to seat it differently both for bullet integrity and SAAMI considerations.

 

As reloades, however, it must be understood that the published OAL is not carved in stone.  It shows what the data was developed using.

[copterdrvr]

Thanks for the replies!