Load Data Discrepancies .... Why

[kfin]

I used to reload quite a bit and have not for a long time. Had a good mentor back in the day who shot competition so my "load data" was just a copy of his. I have still loaded all of my rifles since then but have always loaded the same bullets/powder combinations. I have definitely been a "if it ain't broke don't fix it" kind of guy. We always used 700X for 45s and seems to me it was either 5.0 or 5.2 grains (been a while) but that is basically irrelevant for my questions. My questions come from respect of what we are actually doing, I know it is safe as long as the guidelines are followed. I also cast my own lead bullets for my pistol, which I now have a few of and also in new calibers.

When looking at the loads in my manuals....I have the hornady book from 1985, a couple of the books that only have a single caliber in them for a huge variety of bullets, the new Lyman manual, the new Lyman cast bullet manual, and have been looking at the load data on the Hodgdon site. What I have found is interesting to me, probably totally old school for you guys but I will ask anyway.

For the same bullet.....why does this collection of sources all have different data for both starting loads AND maximum loads? That just doesn't seem right to me. I was getting my press all set up to do some 9mm tonight with titegroup and looked in the lyman book, starting load for my bullet was 3.3 grains, max load was 3.7 grains. I set the powder measure to do 3.3 grains and was going to load a dozen or so at 3.3, 3.5, and 3.7 to check and see if they all even cycled my Glock 19 and 34 and then go from there.

How does a person know where to start? I would feel pretty comfortable taking load advice on this site, but there are VERY few places that I would take that kind of advice from on the internet....just not going to go there. http://www.brianenos.com/forums/public/style_emoticons/default/smile.png

Secondly...looking at the online Hodgdon data since I have it in front of me, my manuals I forgot and left in the shed...what is the difference in a 125 bullet? I pulled up 125 grain 9mm on the website and get the following loads for Titegroup.
125 gr HDY HAP has a COL of 1.069 with starting load of 2.8 gr / 27,100 psi and a max load of 3.2 gr / 33,700 psi
125 gr SIE FMJ has a COL of 1.090 with starting load of 4.1 gr / 27,300 cup and a max load of 4.4 gr / 30,600 cup
125 gr LCN has a COL of 1.125 with a starting load of 3.6 gr / 22,900 cup and a max load of 4.0 gr / 40,400 cup

I understand that if COL is longer, the pressure goes down assuming all other factors are the same. but are all 125 grain bullets that much different in length? What is causing this big of a discrepancy? Do you need to find a source that has the exact bullet you are using to know that you have a safe starting / ending point?

Again, sorry for such a long post but I just want to make sure that I have a good understanding of using said manuals and am safe before I go load up a couple thousands rounds. Just seems weird to me that for 3 125 gr bullets you can have starting and max loads that far apart.

Thanks for any insights you guys/gals are willing to share to help a guy starting over to be safe while still have good loads.
Keith

[gwpercle]

First, don't overthink it. I mostly reload handgun ammo, so this is how I do say 9 mm or 45 acp. I like to find two , three or four reliable sources. Published data or from powder co. load data site. I prefer using 4 sources.
Look at the loads for your selected powder and take the average for each source. min. + max = avg. Then average all four averages. Now you have a middle of the road load. And this is a good place to start.
OAL...I don't measure doodly-squat , the round has to pass the plunk teast in my barrel , fit into the magazine, and cycle through the action manually. I use a dummy round for testing this ( bullet, no powder, no primer ) I use a factory round as a guide and adjust seating depth until manual function is good. Load up some with average load, shoot and adjust charge up or down. 9 times out of 10, that load's a keeper. Keep the dummy rounds to set dies the next time you reload this bollit. This is a good use for those pesky berdan primed cases .
Gary

[JohnH]

Two things primarily affect load data. Boolits (and bullets) vary particularly bullets. Jacket hardness, thickness, core hardness all affect the pressure required for the bullet to fit itself to the land and grooves of the barrel. The second is barrel condition. Test barrels between bullet and powder makers have different amounts of rounds fired through them, making some smoother than others, some rougher than others. Finally, all barrels are a law unto themselves. Note that the industry practice with pressure test barrels is for the barrels to be machined to SAMMI minimum tolerances. The pressure measured in a chamber is a direct result of chamber volume. The less volume a chamber has (smaller because of tighter tolerances) the higher the pressure will be for any given round fired in that chamber as compared to a chamber of mid-range tolerance. The idea is that any given load which is at maximum pressure in the tight chamber will always produce less pressure when fired in looser chambers. The manufacturers all make this note, load to the recipe, "X" brass, "X" bullet "X" primer. various studies over time have shown that the single biggest changes in a load are produced by changing the bullet from one brand to another. A result of differences in body length, jacket hardness and core hardness.

[tazman]

Most of the differences have to do with the nose profile of the bullet and the material it is made from. Different manufacturers use different designs and materials in their bullets causing different pressures and seating depths.
The third bullet mentioned is a lead conical nose. That data can be used with most cast boolits of the same general type.

[kfin]

Perfect....thanks guys

[runfiverun]

in the 9mm oal DOES make that much difference.

think about that tiny volume and how just a little less of it makes a huge difference in percentage of volume available.
now consider your powder.
titegroup goes from good to boom in about .005"
some powders just do not do well when squeezed in a small space.

[vzerone]

Some very good suggestions here. I too peruse a group of data from different places and then select a load that is inbetween all them. Runfiverun brought a very important point about seating deeper on a case that has a small capacity to start with. The 9mm Luger is the one he mentioned. If you interpolate a load look at the data for the exact bullet you're using and make sure it's not seating deeper then what that data tells you to seat at because you can reach dangerous high pressure in a round that is high pressure to start with.

[kfin]

I understand how COL affects pressure..yes, I will be loading 9mm, but I will also be loading at the longest COL that my work in my gun...passing plunk test, feeding in magazine, and feeding into the chamber.

[RedHawk357Mag]

Can't source this picture so consider that in your decisions. But I think it really puts it in perspective. 159223

[kentuckyshooter]

I second that. The 9mm lugar can be a bugger to find a good load for. Best advice is go with the most concervitive load data and work up. I make 6 rounds of each test charge. 3 rounds fired at 10 and 20 yards to test accracy. While fireing i watch for function and felt recoial. Check your brass after each 3 round string.

[vzerone]

The large variation in brass thickness doesn't help the 9mm any either. Remember the round is made and used around the world.

[kfin]

Can't source this picture so consider that in your decisions. But I think it really puts it in perspective. 159223

I like that....puts it into perspective as far as COL and pressure eh