Why does OAL case length vary?

[Jumping Frog]

I am loading .45 ACP with Accurate #7 powder. The Accurate Powder website has a standard loading guide for .45 ACP that lists different cartridge lengths for different bullets weights and types.

For example:

170 gr LSWC - 1.130"
200 gr LSWC - 1.190"
230 gr LRN - 1.230"

Why do the lengths vary?

How critical is this dimension?

For example, if I was loading 200 gr LSWC where some of the rounds were longer than 1.190" (say 1.200") but still well short of 1.230", what impact would that have? Would it not feed? Affect accuracy? Be a safety issue? What?

 

[ranger335v]

It's not critical. The OAL listed in the manuals is much like the charges they show; it's just the length they used to develop the load, not something engraved in stone. I wish they would mention that in the books.

YOU can experiment with OAL as you wish but reduce the load a little if you change a previously developed max load. The simplist way to go is to seat your bullet to the crimping groove and develop your load at that depth.

If it's too long or short for your firearm you will know it by failures to feed but it's unlikely to make a lot of difference if you just seat to the groove.

 

[Ol` Joe]

The listed OAL is usually a lenght that the load will fit the magazine of any factory gun chambered for the cartridge. If it is listed in the header as SAAMI max this is its normal purpose.
The OAL also affects feed and function of the cartridge/firearm, and in some cases is a lenght that should be adhered to for safety reasons. If each bullet in the data has a specific OAL this is an important part of the load.
The VihtaVuori manual makes note of specific bullet/OAL. The book explains the pressures of the loads are affected by the chamber volume and the OAL controls the amount of volume as the cartridge is a part of the chamber when in it. The 9mm is used as a example by VV, showing altering seating deeper by 2 mm increased pressures by ~40 MPa (5801 psi) with a load useing 3N37 power in their lab.
The smaller the case the more pressure is affected by seating depth. The Lee manual shows not only a max cartridge lenght but a min that one shouldn`t seat shorter then in their data.
The contents of the data is there for a reason in most cases, and should be followed as close as possible especially when nearing max listed powder charges.

 

[The Bushmaster]

Ol' Joe wins...+1

 

[Virginian]

Also, with cast bullets, the exact location of your crimping groove may produce a different OAL than they got with the same weight, and than can affect pressures, and you need to know that.

 

[ranger335v]

"...the exact location of your crimping groove may produce a different OAL than they got with the same weight, and than can affect pressures, and you need to know that."

My point is that IF you seat where you want the bullet to be and develop your load at that depth it doesn't matter what the OAL is. Seating to the crimping groove is a rational length - it lets you crimp without damage to the bullet - and that length rarely, if ever, causes any problems feeding.

OAL questions were a rare issue until fairly recently. I think the newer manuals are trying to help with their OAL suggestions but have created massive confusion instead. Anyway, there has been a flood of questions about it the last two years from people who obviously want to do things "right" but find the book OAL doesn't always work out! It would almost seem that those of us who reloaded years ago - using common sense to set our seating depth - should have been killed. We weren't!

 

[Jumping Frog]

I think the newer manuals are trying to help with their OAL suggestions but have created massive confusion instead. . . . from people who obviously want to do things "right" but find the book OAL doesn't always work out!

Amen to that. I am just trying to figure out how to reload and do it "right".

 

[Bullet]

ranger335v
The simplist way to go is to seat your bullet to the crimping groove and develop your load at that depth.

Does 45ACP have a crimp groove?


In handguns reducing OAL always increases pressure, if nothing else is changed.

 

[Walkalong]

No, the .45 ACP bullets do not have a crimp groove. Post what bullet you are using and I bet someone here is shooting it and can give good O.A.L. suggestions.

It has to be short enough to fit in the mag, but after that it's fair game. Load them to the O.A.L. that feeds well. Use starting to midrange data for this. Then work up your load using that O.A.L.

 

[Jumping Frog]

Here is a picture of 4 rounds, loaded to different overall lengths.

The Accurate Powder loading guide lists 1.190" for 200 grain Lead SWC bullets (which is what I am loading).

At 1.190", the bullet is seated below the case rim. The 1.209" round has a barely perceptible case rim above the bullet shoulder -- I can "click it" with my fingernail.

The 1.225" round is seated so the bullet shoulder is just above the case rim. I can just detect a lip with my fingernail.



Look at the picture. The loading guide says 1.190" but that clearly does not look right to me. The best looking fit is 1.225", but that is 0.035" longer than the suggested maximum.

Again, I'll emphasize that these are the first rounds I have ever loaded in my life -- as ranger335v mentions, I am simply trying to do this "right", but have no clue as to what "right" means in this case.

Thanks for your help with this.

 

[Walkalong]

The 1.225 round is about minimum for O.A.L. with that bullet. Looks good actually. You don't want the bullet down in the case like in the first three.

The best looking fit is 1.225", but that is 0.035" longer than the suggested maximum.

Where do you see a max O.A.L. listed that short for the .45 ? 1.275 max is more like it.

I load 200 Gr SWC's at 1.260 to 1.265 usually.

 

[rcmodel]

Have you checked your case length before seating the bullets?

If they are over the .898" standard, the OAL may leave some case sticking out past the bullet shoulder at a specified OAL.

It is also well to keep in mind that all 200 grain lead SWC bullets are not the exact same length & shape.

Alliant doesn't specify the pedigree of the 200 grain bullet they used to get the 1.190" OAL.

For instance, Lyman lists an OAL of 1.161" with the #452460 200 gr. semi-wadcutter.

Then they list an OAL of 1.235" with the #452630 200 gr. Semi-wadcutter, which looks an awful lot like yours.

rcmodel

 

[jfh]

Jumping Frog, that is a really nice picture to illustrate your question.

What people have said so far generally makes sense--here's another way to think about this issue.

1. AA's reccommended LOA is very unusual--and probably an error. "Typical" 200-gr. LSWCs in .45ACP load up about like Walkalong says--from about 1.23+ to 1.275

2. Unless you are doing MAX loads (which I doubt you are and which you shouldn't be at that stage), the LOA of this case-bullet combination should be determined by what feeds reliably in your semi-auto. These bullets are associated with accuracy / bullseye shooting, and therefore usually loaded to a lower velocity, with related lower pressures. So, you don't need to worry about the changes in pressures with varying LOAs--yet.

3. You need to test your cartridge's physical assembly to sort out all the parameters.
Build about six "dummies"--it appears you are doing that--and check the dimensions and note them.

Try filling your magazine and see if the rightmost (1.225) cartridge feeds reliably when you close the slide. Try closing the slide with a "slingshot" release and with a slide stop drop. See if they drop cleanly into your pistols chamber, or check them in your MAX cart gauge. These tests should sort out the physical dimensions for you.

Now load up about twenty rounds at a lower level / start load and try shooting them.

For your first shot, simply load one cartridge, drop the slide and fire, and confirm all went well. The main thing here is the pistol "function"--did the slide close cleanly when loading, then did the case eject "nicely" and the slide lock back? If so, then

Load one magazine (at least five rounds) and shoot those, again noting function. If they all shoot reliably, you're good to go for load development to find the "sweet spot" recipe.

If you are getting incomplete cycling, you may have too weak a charge to cycle your semiauto--that can simply mean increasing your minimum-type load by perhaps .2 gr. and trying again, or you could put in a lower-rated recoil spring.

Jim H.

 

[Jumping Frog]

Have you checked your case length before seating the bullets? If they are over the .898" standard,. . .

I checked them and they are roughly 0.010 under max length.

What people have said so far generally makes sense--here's another way to think about this issue.

1. AA's reccommended LOA is very unusual--and probably an error. "Typical" 200-gr. LSWCs in .45ACP load up about like Walkalong says--from about 1.23+ to 1.275

It started me thinking that maybe their guide is listing minimum overall lengths, not maximum or nominal. If I read it as do not go under 1.190" and do not go over the 1.275" maximum standard length, then that seems to make more sense. Then I can just find a value in the middle that seems to seat well, feed well, and shoot well. I sent an email to the Accurate tech support group asking them to confirm if their guide means minimum length.

BTW, you are right on the money about usage. I intend to use this for target practice and IDPA, so I am looking at reduced, accurate, loads.

3. You need to test your cartridge's physical assembly to sort out all the parameters.
Build about six "dummies"--it appears you are doing that--and check the dimensions and note them.

Try filling your magazine and see if the rightmost (1.225) cartridge feeds reliably when you close the slide. Try closing the slide with a "slingshot" release and with a slide stop drop. See if they drop cleanly into your pistols chamber, or check them in your MAX cart gauge. These tests should sort out the physical dimensions for you.

Now load up about twenty rounds at a lower level / start load and try shooting them.

For your first shot, simply load one cartridge, drop the slide and fire, and confirm all went well. The main thing here is the pistol "function"--did the slide close cleanly when loading, then did the case eject "nicely" and the slide lock back? If so, then

Load one magazine (at least five rounds) and shoot those, again noting function. If they all shoot reliably, you're good to go for load development to find the "sweet spot" recipe.

Well, maybe I need to be more cautious. I just took 75 rounds to the range yesterday and shot 'em all.

They all fired. That is a good thing! Accuracy seemed in the ballpark -- no attempt at fine tuning that yet.

I had failure to feed issues with roughly 15-20 of the 75 rounds. Usually, the difficulty was either the first round in the magazine, either "slingshotted" or using the slide release, or it was the 2nd to last round in the magazine.

So I'll make up some dummy rounds in varying lengths and explore what length feeds the best.

In general with 1911's and SWC, are longer cartridges going to feed better than shorter ones? The short cartridges seemed like they were trying feed one heck of an acute angle when they were jammed.

 

[ranger335v]

"Does 45ACP have a crimp groove?"

Some don't. Mine do.