Question about load range in different books

[skeeter 20i]

I've got a total noob question here but it's still a question that has me scratching my head so I figured I would ask.  First off let me start preface my question with A) I know I am asking about different bullet designs B) I am totally on board with the start low and build to upper end of the load data as necessary C) I understand there may be other powders that work better/worse for this rifle.

1) Rifle is a Tikka T3 Lite
2) Round in question 139-140gr 7mmRM, Powder IMR 4350
3) In the Nosler 7th data for the AB 140gr it's showing that the upper range is 65gr max
4) In the Hornady data 139gr SST it's showing the upper range is 61.9gr max



Sooo how come so much difference in the max range from the two manf.  is it something in the bullet design that negates one from having as much powder behind it or is it simply more caution being exhibited by one manf vs. the other?  It's all pretty confusing sometimes to know when you are getting into a range of "pushing" things.  For example from just looking at the Nosler I wouldn't have begun to be concerned at 62gr, but if I would have read the Hrndy book first I would have thought 62gr was maxed out.

For testing I used the Nosler info and walked my rifle up to the 63gr mark with the SST's and AB's and the clouds parted and the angles sang.  Then I get the Hrndy book and thought "holy cow" did I just get lucky or is everything going to be fine?

Thanks for the insight.
Jason

[JimmyHoffa]

Could be the bullet length and seating depths.  Not as much about how much the bullet weighs, but how much of the actual case is occupied by the bullet.  You could have a bit less air volume or even be in the compressed load range.  As an extreme example, take barnes tsx (or really any of the all coppers).  To get the same weight, you have to have real long bullets.  Then when you seat them, the bullet goes way inside the case and eats up volume throwing the powder/air ratio off if loading just off bullet weight.  So, the powder is reduced on those bullets or they have higher COAL.

[AWS]

There isn't one testing facillity for all company loads.  Each powder and bullet company has there own testing equipment each barrel and chamber are a little different as they are on even on individual rifles from the same manufactures, different brass and primers plus when you throw in different types of the same weight bullet the will come up with different highs and lows .  that's why it is best to start low and and work up a load, not only will you start out with a safe load you will find the sweet spot for your individual rifle. 

[Kittman]

Cartridge overall length probably dictates that more of the Hornady bullet will be seated further into the case, so they probably back off the powder charge recommendation to keep pressures within specification would be my guess.  Combine that with primers used, different cases, testing equipment, altitudes, temperatures any other variables others on here have mentioned and that possibly explains the difference.

[mazama]

The answer is simple,it is called liability,every gun is different,loose chamber long throat,tight chamber short throat,i have a couple of guns that I have pushed way over max.

[Jonnyjammer]

lol i typed that very statement in before the site went down earlier.  liability is the reason for a lot of discrepancies in lots of diff. situations hahah. 

[Stein]

It looks like you have data for two different bullets.  They are close to the same weight, but they could have dramatically different shapes and lengths.

Even for the exact same bullet, books can have different data.  Don't think of it as data, think of it as a recipe.  Check at least two books and always start low.  I haven't came across a handload yet that shoots best near the max so it usually isn't an issue.  Check the neck and primer and work your way up and you'll be fine.

[Caseknife]

The other thing about homogenous bullets, Barnes and GMX, which you aren't loading, is that the lead core bullets actually compress more when engaging the rifling, thus less pressure.

[Jonnyjammer]

It looks like you have data for two different bullets.  They are close to the same weight, but they could have dramatically different shapes and lengths.

Even for the exact same bullet, books can have different data.  Don't think of it as data, think of it as a recipe.  Check at least two books and always start low.  I haven't came across a handload yet that shoots best near the max so it usually isn't an issue.  Check the neck and primer and work your way up and you'll be fine.

max is a relative term in this instance,Like I said earlier,If you are giving it a longer COAL most times you can be beyond max powder from a books load but no where near cup pressure max.Just to get it close to the right speed for the given cartridge.Not meaning anything in what i said to get the fastest speed possible. 

[skeeter 20i]

Thanks for the info guys, this one had me scratching my head until I kept digging in some more.  It seems that Hornady is consistently around 4% lower than other published max loads, which had me thinking about liability.  Then I cross ref'd another pretty common cartridge the 30.06 in the 165 gr and they fall right in line with a long established "norm" of 57gr.  max.  I would think that if Hornady's testing procedures were different and netted a 4% lower max loading I would see that variance across all their loads so the 30.06 numbers are throwing me a bit.

So I dunno I'm kinda concerned that I'm over the 61.2 max of the Hornady book but all the signs point to it'll be ok.  I had pushed it to 65 ish at one point as indicated by another book and still didn't see anything to indicate I was over pressure or reaching a "critical" level other than the groups opened up the farther up the scale I went heck I even read one book that said the max was 66 (can't remember which one).

Then again sometimes I think I over think things and I should just settle in with the crappy groups 63 gets me.  LOL did I mention I love this Tikka?

One more quick question regarding pulling rounds apart and reloading them.  Do you guys re-size after pulling them apart.  I had some rounds that weren't even in the running when working up the load so rather than waste them I pulled them apart and was going to reuse them and it got me thinking about resizing them to "reset" neck tension is that correct or could I have just pulled them and reloaded them without resizing them again?

Thanks again guys I appreciate your help.
Jason