OAL is different for reloads than commercial - why?

[Jim K III]

[Edited: I'm reloading for a Springfield Hellcat 9mm]

Questions about OAL. I use the 49th Edition of the Lyman Reloading Handbook. For 9mm, the OAL ranges from:

1.005 95gr FMJ -to-
1.115 147gr TMJ

But, the OAL for commercial rounds is greater than those. Here are several brands I have:

OAL Brand
1.152 Hornady 147gr XTP
1.158 Wolf 115gr FMJ
1.154 Magtech 115gr FMJ
1.128 Remington 115gr FMJ
1.152 Speer 115gr FMJ

Why are the OALs in the reloading manual much shorter than any of the commercial rounds?

I've been real anal about following the reloading handbook, but do I really need to be?

 

[Varminterror]

Learn how to plunk test your barrels and you’ll never look at book OAL’s ever again.

I’ve said it a bunch on this forum today, but this is another thread which is diving headlong into empty weeds, praying to find a rabbit for supper. Much ado about nuthin’…

Different brands of shoes fit different feet differently. Learn how to try on shoes and you’ll live happy with shoes that fit your feet. If you ever take up work making lasts, then you’ll have to worry about why different shoes fit differently. Today likely ain’t that day.

 

[Jim K III]

Learn how to plunk test your barrels and you’ll never look at book OAL’s ever again.

I’ve said it a bunch on this forum today, but this is another thread which is diving headlong into empty weeds, praying to find a rabbit for supper. Much ado about nuthin’…

Different brands of shoes fit different feet differently. Learn how to try on shoes and you’ll live happy with shoes that fit your feet. If you ever take up work making lasts, then you’ll have to worry about why different shoes fit differently. Today likely ain’t that day.

I like it - short and simple. Cheers!

 

[rfwobbly]

Welcome ! OAL is set by how your bullet fits into your barrel.... NOT the OAL listed in the loading manual.
► You did not tell us your gun, so no one here can advise you on OAL.
► The OAL in the manual is the OAL they used in their gun. Their "handgun" looks like this....

• The manual publisher is merely REPORTING the OAL they used during their testing. They are not making a recommendation.
• You'll need to measure how your bullet interfaces with your barrel and then make reasonable adjustments and plans based on your experience with the cartridge and pistol. Each bullet-to-barrel interplay is totally different/ unique/ discrete/ distinct/ individual.
• Understand that ALL auto pistol cartridges allow a RANGE of OAL to be used. There are PHYSICAL limits used by the shooting industry, and then typically further restricting those are the LOAD limits set by Your gun and Your load recipe.

The following cartoon shows/ explains this better....

► On the outside we have the SAAMI Physical limits for 9x19 Luger. Longer than ~1.169" won't fit inside the mag; shorter than 1.000" won't feed well.
► Typically, further restricting those are the additional limits of reality. You don't want to go shorter than the Reported OAL in the recipe, to prevent chamber pressure spikes. You do not want to go longer than what the barrel will accept, due to fears of creating a cartridge that has the physical ability to create an Out Of Battery accident. Every bullet is different; every barrel is different. No one here can advise you on this number... you have to measure it for yourself.

► ► Between those 4 Limits is a "zone" or range of OALs that is safe to use. This part is the Science of Reloading. Then, based on your past experience with your handgun, within that range is an OAL that will allow your handgun to feed well and deliver the desired accuracy. This part is the Art of Reloading. Welcome to Reloading !

Hope this helps.

 

[fxvr5]

OAL can be a little complicated sometimes. The link below has some useful information. Scroll down to the section titled "Nose Shape and Cartridge Overall Length". It's about half way down the page. It will explain some stuff that can help you understand what's going on.

Bullet Design and Feeding Reliability

 

[fxvr5]

For information on the plunk test, see this link:

Reloading Tips: The Plunk Test - Shooting Times

The plunk test. It's a funny name, but it's very important to use when you're reloading. The

www.shootingtimes.com

 

[OFFGRID]

Obviously the biggest factor besides if the round will chamber properly or not is if it fits the magazine and feeds properly, something i overlook sometimes. I was doing a ladder test on a 300 win today and as always im pushing closer to the lands trying to reduce dispersion (as if that tiny detail makes a huge difference in my backwoods reloading) I found the rounds were too long for the magazine. Luckly i found this out quickly and seated the whole ladder to spec to fit the mag and then was able to do the test without effecting any of the results.

Still i find myself wondering about the coal and pressure relationship. Does seating to spec coal vs slightly longer give different pressures because of higher case volume? Does the increase in volume allow more powder charge before pressure signs are noticeable and therefore higher velocity? Does pressure increase when the bullet is closer to resistance(the lands) ? Get too close to the lands and cause pressure spikes as well?


Maybe KISSIT and just go by the book? One of my tightest loads was 80k or 100k off the lands when seated to specified COAL in the data with a light bullet.

 

[Carl N. Brown]

9mm Luger OAL handload length in my old Hornady manual varies by bullet weight and style.
I suspect it also varied by cartridge feed from the magazine of their test gun (S&W Model 39).