Load Data and OAL

[Howa 9700]

Had a bit of an epiphany the other day. Mentioned it in another thread, but thought it may be worth it's own stand alone discussion.

Tip off came the other day when I was assessing load data for 150 grain Hornady Interlock in 308 Win using Varget powder.

Found 4 or 5 load data sources that listed max powder charge of Varget at 47 to 48 grains.......but with OAL of 2.800 or 2.810......(seating depth of bullet to achieve over all length).

The outlier was the Hornady data (I have developed habit of going to bullet maker data to get their recommendation for powder and OAL). Hornady topped out the powder charge at 44.5 grains......but had bullet seated deeper at 2.735 OAL.

Didn't make the connection at the time, but now occurs to me that OAL is not a trivial thing. It is very much part of the load data recommendation. Seating a bullet deeper (say going from 2.810 to 2.735) would appear to do the same thing as a case with lower internal volume......say a commercial case vs. Lake City brass. Universal recommendation using LC brass is to lower start charge one full grain to account for smaller internal volume and higher pressures that result from it. Seating a bullet deeper would appear to do the same thing.

Cross threading the two.......using higher powder charge from one set of data with deeper seated bullet from another.....would seem to offer good potential for all kinds of problems related to pressure.

Haven't seen that mentioned in print in any of the manuals, but seems to be the case just the same. Something I'm going to pay strict attention to going forward.

 

[Charlie98]

I've paid a lot more attention to OAL measurements the past few years... that lightbulb turned on about 15 years ago when I tooled up for reloading .308 for my M1a... with commercial or military brass.

Many years ago, when I was loading 9mm for my BHP, I had terrible over pressure issues. Back then, being young and indestructible, I ran max loads as a matter of course... and I was blowing primers, and very often the hammer on the BHP would follow the slide back into battery. Much of this was because I disregarded bullet seating depth at max charge in a high pressure cartridge like the 9mm... further, I was shooting 147's back then, further exasperating the issue. Back then, I didn't even measure OAL, except by happenstance to get the rounds to feed... and never really made the connection between pressure, and a deep-seated bullet.

These days, I'm all about OAL...

 

[HowieG]

I've paid a lot more attention to OAL measurements the past few years... that lightbulb turned on about 15 years ago when I tooled up for reloading .308 for my M1a... with commercial or military brass.

Many years ago, when I was loading 9mm for my BHP, I had terrible over pressure issues. Back then, being young and indestructible, I ran max loads as a matter of course... and I was blowing primers, and very often the hammer on the BHP would follow the slide back into battery. Much of this was because I disregarded bullet seating depth at max charge in a high pressure cartridge like the 9mm... further, I was shooting 147's back then, further exasperating the issue. Back then, I didn't even measure OAL, except by happenstance to get the rounds to feed... and never really made the connection between pressure, and a deep-seated bullet.

These days, I'm all about OAL...

And you still have all your body parts?? The Saints must have been smiling on you.

 

[Charlie98]

And you still have all your body parts?? The Saints must have been smiling on you.

I've given any number of angels their wings over the years, for sure... for a while, I was a sure bet.

 

[HowieG]

Had a bit of an epiphany the other day. Mentioned it in another thread, but thought it may be worth it's own stand alone discussion.

Tip off came the other day when I was assessing load data for 150 grain Hornady Interlock in 308 Win using Varget powder.

Found 4 or 5 load data sources that listed max powder charge of Varget at 47 to 48 grains.......but with OAL of 2.800 or 2.810......(seating depth of bullet to achieve over all length).

The outlier was the Hornady data (I have developed habit of going to bullet maker data to get their recommendation for powder and OAL). Hornady topped out the powder charge at 44.5 grains......but had bullet seated deeper at 2.735 OAL.

Didn't make the connection at the time, but now occurs to me that OAL is not a trivial thing. It is very much part of the load data recommendation. Seating a bullet deeper (say going from 2.810 to 2.735) would appear to do the same thing as a case with lower internal volume......say a commercial case vs. Lake City brass. Universal recommendation using LC brass is to lower start charge one full grain to account for smaller internal volume and higher pressures that result from it. Seating a bullet deeper would appear to do the same thing.

Cross threading the two.......using higher powder charge from one set of data with deeper seated bullet from another.....would seem to offer good potential for all kinds of problems related to pressure.

Haven't seen that mentioned in print in any of the manuals, but seems to be the case just the same. Something I'm going to pay strict attention to going forward.

Do you have a 9th edition Nosler manual? Page 69.

 

[Howa 9700]

Another tip off for this came when I finally caught notice of the listed OAL for the above referenced 308 Win load in the Lee Reloading Manual. That wasn't just OAL......it was Minimum OAL.....as in don't seat a bullet any deeper than this. The Hornady OAL would get you deeper......much deeper. Implication is pressure would go up if you did.

Again, light has come on........OAL listed in load data is not a trivial thing. It is there for a purpose.

 

[Howa 9700]

Do you have a 9th edition Nosler manual? Page 69.

No. I often seek out Nosler load data, but get in online for the caliber / bullet I'm loading.

 

[JFrank]

47-48 grains of Varget would be a really hot load under a 155 class projectile, the oal differences listed are perhaps due to the different style bullets.
Those soft points are pretty short

 

[Charlie98]

Again, light has come on........OAL listed in load data is not a trivial thing. It is there for a purpose.

Here's an odd thing... and you are correct to go get specific OAL data from the bullet manufacturer... is things like ogive shape and profile can translate to significant differences in required seating depth...

Here are 3 different .30 bullets... L to R, Winchester 147grn, Prvi 145grn, and the Hornady 150grn. Note the differences in not only the ogive profile, particularly the Hornady with their 'secant' ogive, but the position of the cannelure.

 

[Howa 9700]

Yes.......light came on re: Hornady Interlock and seating depth. When I seat those to 2.800, there is a large gap between case rim and cannelure. If seated to the depth Hornady lists (2.735)....rim hits very outboard edge of cannelure. So their OAL appears to take that into account, and perhaps that is also why they back down the powder charge.

Interesting that in the Hornady book, they go to great lengths to explain that if a bullet is seated too deep, pressure can drop (WT*????)....so is to be avoided. Their reasoning is bullet starts to move too early and has too much jump to lands.....so adequate pressure never builds to get velocity up where it should be. Which of course is in direct violation to their own load data. Also fails to mention if that is with or without a crimp.....which does more than hold bullet in place during handling and cycling. As per Mr. Lee.....a crimp serves same purpose in getting consistent pressure as does loading to just off the lands.

Wish all these guys could get their story straight. It is confusing to us newbs.

 

[JFrank]

I disregard the cannlure position and seat bullets either to magazine length or per optimum seating depth established by incremental testing and a base to ogive comparator, single feed if necessary.

 

[Lennyjoe]

OAL is a recommendation. This is nice to have for rifle. https://www.midwayusa.com/product/1012747079?pid=570611 along with your rifles caliber gauge. It’s always good to document your rifles max OAL for future load development when you want to adjust at the end to increase accuracy.

The ole plunk test is great for auto loader pistols.

 

[HowieG]

I believe that most hand loaders basically learn on their own. I also believe (by personal observation) that the majority of people aren't really fond of reading and some of the nuanced stuff gets by them. It's too easy to just jump online and grab a load. Maybe that grabbed load is from a third-party source rather than from established tested data. Even the established mainstream reloading manuals vary in what they present, and how they present it. One thing the manuals all have in common is that little statement where they tell you that they aren't liable for any of the stupid stuff you do.

On the other hand, I have given a reloading class to a couple of people in which I emphasized many of the little twiddly things that a good hand loader needs to pay attention to if he wishes to avoid trouble. What came of that is the persons I taught decided NOT to take up the hobby. Too many rules, too many tools, and too complex.

 

[HowieG]

I think the best rifle for a neophyte to learn reloading for is a box magazine repeater. It takes a lot of the decision making away. Every round has to be short enough to fit into the magazine. If it fits in the magazine, it will chamber unless you gooned up resizing or something. Loading for a 308? Well 2.81 inches to fit in the mag. All you have to do then is not shorten them up too much.

 

[Charlie98]

Wish all these guys could get their story straight. It is confusing to us newbs.

Actually... that's all true. Sorta. Sometimes. The devil is in the details, including, as you mention, the crimp or lack therof, and the rifle chamber and throat.

Crimp is a tricky subject... some insist on it, some insist against it. I used to be a Crimper, but have since gotten away from it, almost completely. Lee is right... and wrong. You really want to jack up your consistency? Try crimping cartridges with an inconsistent brass length. I am convinced, finally, that as long as you have proper neck tension, that it is far better than introducing the irregularity of a crimp, in most cases.

 

[RealGun]

With Hornady you have to watch case trim length too. They don't hesitate to require a special case to suit one of their greatest-new-thing bullets.

 

[HowieG]

Actually... that's all true. Sorta. Sometimes. The devil is in the details, including, as you mention, the crimp or lack therof, and the rifle chamber and throat.

Crimp is a tricky subject... some insist on it, some insist against it. I used to be a Crimper, but have since gotten away from it, almost completely. Lee is right... and wrong. You really want to jack up your consistency? Try crimping cartridges with an inconsistent brass length. I am convinced, finally, that as long as you have proper neck tension, that it is far better than introducing the irregularity of a crimp, in most cases.

And what's proper neck tension? That depends on what you are doing. Some benchrest shooters prefer minimal or none. The term I would use is 'consistent' neck tension. Make 'em all the same.

 

[GeoDudeFlorida]

I’ve known and said for decades, oal is not the thing to pay attention to; the charge column volume and cartridge chamber volume, determined in part by seating depth and in part by cartridge construction, is the critical component. OAL is what most people measure as an approximation or best guess of seating depth. Measure bullet base to ogive, get an average, measure cartridge base to shoulder, get an average, measure cartridge shoulder to case mouth, get an average. Now calculate a cartridge overall average length from ogive to base that gives a safe average seating depth. It’s not going to be precise but it’s accurate.

 

[denton]

Harold Vaughn did an investigation of pressure vs. seating depth several years ago. The short version is that when the bullet is deeply seated, pressure is high. As the bullet is seated farther out, pressure diminishes. As the bullet is seated yet farther out, proximity to the rifling starts to take over, and as OAL is increased, pressure again increases.

 

[HowieG]

Harold Vaughn did an investigation of pressure vs. seating depth several years ago. The short version is that when the bullet is deeply seated, pressure is high. As the bullet is seated farther out, pressure diminishes. As the bullet is seated yet farther out, proximity to the rifling starts to take over, and as OAL is increased, pressure again increases.

Which makes perfect sense.

 

[HowieG]

I’ve known and said for decades, oal is not the thing to pay attention to; the charge column volume and cartridge chamber volume, determined in part by seating depth and in part by cartridge construction, is the critical component. OAL is what most people measure as an approximation or best guess of seating depth. Measure bullet base to ogive, get an average, measure cartridge base to shoulder, get an average, measure cartridge shoulder to case mouth, get an average. Now calculate a cartridge overall average length from ogive to base that gives a safe average seating depth. It’s not going to be precise but it’s accurate.

I just use a Hornady bullet comparator for whatever caliber bullet I am seating.

 

[BJung]

To answer your statement: yes. Here is a good question to ask other seasoned reloaders that is relevant. You create a set of ladder tests with a recommended COL and you find the best nodes for that powder charge. Then, you adjust the seating depth by .003" with a new set of testloads and find the accuracy node. You will have a certain chamber pressure as a result. Now instead, you randomly pick a load in a table that you think is accurate and first make testloads based on seating depth varied by .003" and look for the node. Finding that, you adjust powder charge to tighten your group. I'd guess it's the two results will be the same.

 

[Charlie98]

And what's proper neck tension? That depends on what you are doing. Some benchrest shooters prefer minimal or none. The term I would use is 'consistent' neck tension. Make 'em all the same.

Benchrest shooters are a completely different ballgame, for a number of different reasons. For the average reloader, it's unlikely they would take the steps (and investment) to prep their handloads like a BR shooter.

I do agree... 'consistent' is a better term, and is actually what I meant. Proper sizing, annealing, and other things like neck turning can get you there.

 

[JFrank]

To answer your statement: yes. Here is a good question to ask other seasoned reloaders that is relevant. You create a set of ladder tests with a recommended COL and you find the best nodes for that powder charge. Then, you adjust the seating depth by .003" with a new set of testloads and find the accuracy node. You will have a certain chamber pressure as a result. Now instead, you randomly pick a load in a table that you think is accurate and first make testloads based on seating depth varied by .003" and look for the node. Finding that, you adjust powder charge to tighten your group. I'd guess it's the two results will be the same.

With seating being a finer/harmonic adjustment it’s tough to see the subtle changes in group tendencies unless you are in a reasonably stable charge window, therefore we as Benchrest shooters typically work powder first with a selected depth from records or personal experience with that bullet.

 

[BJung]

With seating being a finer/harmonic adjustment it’s tough to see the subtle changes in group tendencies unless you are in a reasonably stable charge window, therefore we as Benchrest shooters typically work powder first with a selected depth from records or personal experience with that bullet.

I have been seating my bullets to just touch the lands. If that wasn't possible, I'd seat them at an OAL where the cartridge can fit in the magazine. Would you say that works?