Please define the purpose of OAL

[amboy49]

I'm now making the change over from 115 gr. Copper Clad bullets to 147 gr. cast lead bullets with a BRN of 13 to shoot in my S.A. 5.25 in IDPA and USPSA events. The OAL for the copper clad bullets is published to be 1.125. The OAL for the 147 gr. lead is 1.145 for a multitude of powders according to my Modern Reloading book by Richard Lee (Second Edition). Upon a recommmendation from a friend I decided to try Tite Group. I was given the powder charge of 2.5 to 2.8 grains and an OAL of 1.058.

It seems apparent there is quite a difference in the OAL required by (1) powder charge/type and/or (2) bullet type. When I used to load for centerfire rifles I would seat the bullet just short of the lands to maximize accuracy. I have not read anything about this theory in reloading for a pistol. I am using my barrel as a go-no go gauge to make sure the bullets will chamber. What are the factors that I should consider to determine the OAL ? If I use less powder do I have to seat the bullet deeper - as it seems for the the 2.5 grains of Tite Group ?

Can I create a dangerous situation if the bullets are not seated correctly to result in the correct OAL ? Is there a critical difference in having the cartridge OAL too short or too long ? Is the primary concern excessive chamber pressure ? If so, does the OAL contribute to chamber pressure as a result of the bullet seating depth ? I do plan to chronograph the loads as I work up the different powder and charge weights.

Thanks in advance.

 

[IndyGlockMan]

You can create a dangerous situation if your OAL is too short and the pressure gets too high.
If you go too long, you could have feeding issues with your magazine.
1.058 seems pretty darn short for a 147gr bullet but 2.5-2.8 is a very small amount of powder.
I just load 9mm for range practice ammo so I go with powder charges toward the lower end, and keep the OAL toward the high end (1.125 to 1.140), but that's with Alliant Power Pistol.
TiteGroup is a different animal and is more sensitive.
If you do seat those 147's to 1.058, I would load some at 2.5 & 2.6 and test it before going up to 2.8

 

[atalon]

I don't know much about the competitions but I believe from the gr. weights you are talking about a 9MM pistol. If so in pistols OverAll Length (OAL) is mostly about reliability of feeding the particular bullet you have in your cartridge. There is a secondary concern that depending on the powder that if it is filled up close to the bullet, too short will compress the powder and cause higher pressures. I am sure some of the more experienced guys can chime in with a little better detail.

 

[SSGSAD]

Amboy, the 147 gr., is probably LONGER, than either a 115, or a 125, so you will have more bullet, "sticking out" the end of your case. YES, seating a bullet .060 DEEPER, can DOUBLE the pressure.....

 

[vwfred69]

I'm fairly new but my understanding is chamber pressures go up dramatically when oal is short. I loaded some 147gr @ 1.155oal and 4.35gr power pistol and it worked well in my M&P.

 

[Broom_jm]

I'm now making the change over from 115 gr. Copper Clad bullets to 147 gr. cast lead bullets with a BRN of 13 to shoot in my S.A. 5.25 in IDPA and USPSA events. The OAL for the copper clad bullets is published to be 1.125. The OAL for the 147 gr. lead is 1.145 for a multitude of powders according to my Modern Reloading book by Richard Lee (Second Edition). Upon a recommendation from a friend I decided to try Tite Group. I was given the powder charge of 2.5 to 2.8 grains and an OAL of 1.058.

It seems apparent there is quite a difference in the OAL required by (1) powder charge/type and/or (2) bullet type. When I used to load for centerfire rifles I would seat the bullet just short of the lands to maximize accuracy. I have not read anything about this theory in reloading for a pistol. I am using my barrel as a go-no go gauge to make sure the bullets will chamber. What are the factors that I should consider to determine the OAL ? If I use less powder do I have to seat the bullet deeper - as it seems for the the 2.5 grains of Tite Group ?

Can I create a dangerous situation if the bullets are not seated correctly to result in the correct OAL ? Is there a critical difference in having the cartridge OAL too short or too long ? Is the primary concern excessive chamber pressure ? If so, does the OAL contribute to chamber pressure as a result of the bullet seating depth ? I do plan to chronograph the loads as I work up the different powder and charge weights.

Thanks in advance.

For small-capacity, high-pressure rounds like the 9x19 Parabellum, OAL is absolutely critical. Many reloading manuals go out of their way to warn folks about seating a bullet too deep, as it will drive pressure up to dangerous levels very quickly. No disrespect to your buddy, but you have one reputable source of data and one undocumented source. There is no question in my mind which one I would go with.

All other things being equal, heavier bullets in a given cartridge will require a longer OAL than lighter bullets. The very longest a 9mm round should be is about 1.169", but many folks go shorter than that to fit either their magazine or their actual chamber. You say you're using your chamber as a go/no-go gauge, but I'm guessing you don't fully understand the notion of that particular tool. When a gunsmith uses a set of go/no-go gauges he is setting the headspace on the chamber. If an action will close on a "go" gauge, but not on the "no-go" gauge, the headspace is set correctly. He's basically making sure the longest case length specified by SAAMI for that cartridge will "go" in that chamber, but something longer will not.

When guys do the "plunk" test in their pistol barrels, all they're really doing is making sure the case is not too long...they aren't doing anything meaningful in determining whether or not a case is too short. You could leave out the powder and seat a bullet as far down as it will go and still pass the plunk test.

So, why is OAL important? Well, seating a bullet deeper than the load recipe specified drives pressures up dramatically. In the examples you give above, going from 1.145 down to 1.058 takes the pressure from ~21,500 to over 35,000 psi, which exceeds SAAMI specifications! (So much for your buddy's recommendation?)

The bottom line is this: When a reloading manual gives you a load recipe, it's not just the powder charge or bullet weight that matters. The brand of case used, the primer used, and in very small cartridges, the OAL is absolutely critical. If you're going to adjust the OAL, the only safe way to do so is to increase the length, while still keeping it short enough to cycle properly and avoid putting it into the lands. (This is where the plunk test is actually helpful.) Stick to the OAL given by a reputable source, or slightly longer, but don't go to a shorter length unless you really know what you're doing.

I will also add that Titegroup is a "suitable" powder for 9mm, but it is the fastest-burning powder listed from most sources. That means you can use the least amount of powder per case. Maybe you save a penny or two (literally) per round over something like W231, AA #7 or Power Pistol. It also means if you go over a tenth of a grain or two, things can get real scary, real fast. Even worse, it means that you CAN double-charge, depending on the bullet used. I've been doing this for 25 years and still have all of my body parts where they belong. When it comes to loading 9mm rounds, I think I'll leave Titegroup to the "pros".

 

[amboy49]

OAL

For small-capacity, high-pressure rounds like the 9x19 Parabellum, OAL is absolutely critical. Many reloading manuals go out of their way to warn folks about seating a bullet too deep, as it will drive pressure up to dangerous levels very quickly. No disrespect to your buddy, but you have one reputable source of data and one undocumented source. There is no question in my mind which one I would go with.

All other things being equal, heavier bullets in a given cartridge will require a longer OAL than lighter bullets. The very longest a 9mm round should be is about 1.169", but many folks go shorter than that to fit either their magazine or their actual chamber. You say you're using your chamber as a go/no-go gauge, but I'm guessing you don't fully understand the notion of that particular tool. When a gunsmith uses a set of go/no-go gauges he is setting the headspace on the chamber. If an action will close on a "go" gauge, but not on the "no-go" gauge, the headspace is set correctly. He's basically making sure the longest case length specified by SAAMI for that cartridge will "go" in that chamber, but something longer will not.

When guys do the "plunk" test in their pistol barrels, all they're really doing is making sure the case is not too long...they aren't doing anything meaningful in determining whether or not a case is too short. You could leave out the powder and seat a bullet as far down as it will go and still pass the plunk test.

So, why is OAL important? Well, seating a bullet deeper than the load recipe specified drives pressures up dramatically. In the examples you give above, going from 1.145 down to 1.058 takes the pressure from ~21,500 to over 35,000 psi, which exceeds SAAMI specifications! (So much for your buddy's recommendation?)

The bottom line is this: When a reloading manual gives you a load recipe, it's not just the powder charge or bullet weight that matters. The brand of case used, the primer used, and in very small cartridges, the OAL is absolutely critical. If you're going to adjust the OAL, the only safe way to do so is to increase the length, while still keeping it short enough to cycle properly and avoid putting it into the lands. (This is where the plunk test is actually helpful.) Stick to the OAL given by a reputable source, or slightly longer, but don't go to a shorter length unless you really know what you're doing.

I will also add that Titegroup is a "suitable" powder for 9mm, but it is the fastest-burning powder listed from most sources. That means you can use the least amount of powder per case. Maybe you save a penny or two (literally) per round over something like W231, AA #7 or Power Pistol. It also means if you go over a tenth of a grain or two, things can get real scary, real fast. Even worse, it means that you CAN double-charge, depending on the bullet used. I've been doing this for 25 years and still have all of my body parts where they belong. When it comes to loading 9mm rounds, I think I'll leave Titegroup to the "pros".

Thanks for the informative feedback. Just to clarify the OAL recommendation of 1.058 - the information was extracted from a loading manual at an Indy shop. I did not personally read it - I asked the for the recipe when I purchased 147 gr. bullets and received that response. I, too, questioned the minimal powder charge of 2.8 grs as one that could easily vary to an excessive level. I test fired 30 rounds last evening ( still have all my digits ) and the load is definitely soft shooting. I also have a COP die to maintain a visual check on the powder level. All this being said, I think you're admonishment re: using this very small amount f Tite Group could result in an over pressure incident occuring is probably spot on. I was attempting to get the least recoil load to enable me to bring the sights back to target - but it doesn't sound like using Tite Group to accomplish this is the best way to go about it.

I have W231 and Power Pistol. I think I'll give them a try. . . . and seat the bullets out to a more standard OAL.

Again, thanks for the response.

 

[ashby koss]

All the above for safety as well as feeding issues. If your reloading for Revolver these become less of an issue in that anything that fits within the chamber will spin.

 

[rvb]

These for IDPA?
For your 147gr load, load it to 1.150" max and use 3.1-3.4gr of TG (depending on barrel length), chrono to verify PF and be done. Your "friend" is looking to get your ammo ruled not legal at a major match w/ just 2.5-2.8gr; I'd be shocked if that made 125PF (edit: maybe w/ a cast lead load it would make it, but you need to verify). I've loaded around 120,000 147s w/ 3.3gr TG for IDPA/IPSC. Makes about 132PF depending on gun. Still soft shooting but gives you plenty of room for chrono/atmosphere/etc differences.

Longer bullets (the 147s are longer than the 115s) need longer oal to keep the volume the same inside the cartidge.

Sometimes, small variations in oal can make a drastic difference in the consistency of the round. I had a 230gr ball .45 load once that was showing 100fps std. dev. on the chrono. I shortened the oal by 0.010" and the load went to ~12 fps std. dev. That little extra pressure and freespace to the throat made a big difference.....

If you don't have a chrono that should be your next gun-related purchase.

As for TG filling < 1/2 the case.... well, pay attention to what you're doing, make sure the powder level looks right on EVERY round before you put a bullet on top, and you'll be fine. It's all I've ever used for 9mm. Loaded on a 550B.

As always: start low and work up to your intended powder load.

-rvb

 

[Snizz1911]

I believe this friends data was taken from the Lyman cast book, correct? It sounds very similar as I seen that load recommendation before and was a little puzzled, then I seen the short OAL. Like rvp, I've extended my OAL to 1.150 and throw a very similar charge of titegroup.

 

[michaeladkins]

Like others have said, safety! It is about the amount of pressure built up in the case.

I have never chrono'd a shorter round, but I would imagine you are going to gain quite a bit of speed from a shorter round. That is a situation where just a little goes a long way or wrong way!

Mike

 

[amboy49]

I have been measuring the OAL of the rounds I've loaded using the 147 gr cast lead bullets and Tite Group powder. The bullets have a 13 Brinnel Hardness. I am finding the OAL for the rounds are varying from 1.058 to 1.171. I am going to stop loading the rounds to the 1.058 length - even attempting to seat the bullets to an OAL of 1.150 have resulting in wide variations.

I have not found this to be an issue with the copper clad bullets I have been loading. I checked the dimension(s) of the bullets and they are .667 in length plus or minus .001. I can't figure out what is causing the variation. My only guess is the bullets are soft enough that the bullet seating die will not force the bullet into the case.

Is this possible ?

 

[Broom_jm]

That is a HUGE variation in OAL...from too short (with the charge you're using) to too long to cycle through some actions. You need to run down the cause for that discrepancy before you go any further. (My 200gr lead loads in 44/40 vary by +/- .005".)

What kind of press are you using? Do you have the correct stem in your seating die? They make different stems for round-nose and flat-pointed bullets.

 

[XtremeVel]

I am finding the OAL for the rounds are varying from 1.058 to 1.171.

First, check your calipers for repeatabilty... I have seen some pretty bad inconsistency in bullet profiles that might cause .005, maybe even as much as .010 difference in OAL before, but never anything even remotely close to .110 + you speak of..... With that much error, I'd think you could watch the case go in the die and see what is happening...

Also, describe your variations... If the OAL is initially correct, but you find the bullet is slowly being seated deeper as you go, check in the die for accumulated bullet lube... Messy lube on cast bullets can build up on the seater plug, thus slowly increasing the depth of the seated bullet... Now, if your variations are running back and forth, it wouldn't be lube building up on the seating plug/stem.

I don't think your concern about soft bullets is the cause... Obviously they are going into the case, just inconsistent depths... If you are actually deforming them due to force, you'd surely see very obvious evidence of this by looking at them, especially if your readings are correct... .110 is a HUGE difference.

 

[Newhoosier]

Oh ya .110 is extreame. I allow +.003 and no more than -.002 . I have had some of my sloppy self cast boolets load up my seeting die but never like what your talking about.