Help me understand this vastly different reloading data from similar class bullets

[CanMike]

I am a little stumped here.. I am comparing the Burger 144 Hybrids compared to the new Lapua 144 Hybrid Targets.. The reloading data is VASTLY different but the bullets are relatively similar.. Obviously not the same but close... Why is there a 3 grain difference in max load and the Lapua bullet is listed as a compressed load even though its 3 grains less then the Berger which is not listed as Compressed..

I am looking at N555 here but its pretty much same for all the powders listed.. I am very confused. Is this more based on bullet intended speed or pressure?

Mike

 

[RegionRat]

Aside from the possibility that there were different test barrels involved from two different time periods, the length of the bullets and seating depths play a large roll in the case volume and fill, which in turn creates a different pressure curve.

I know folks get upset when seeing load recipes that vary from within different sources or as in this case what is seemingly from the same labs, but load recipes, ammo batches, cases, test barrels, etc.., all have some natural variation and cause dispersion in internal and external ballistics.

Another reminder that if you don't have a strong background, try to gather as many different sources as possible for a perspective. Play it safe and work up. Ask more experienced competitors and loaders for help, and as a last resort ask here too.

 

[acourvil]

Brass, chamber, powder lot, seating depth and bearing surface can all affect the load data. If the testing wasn’t done at the same time with the same components then differences might be exaggerated.

 

[Herb Stoner]

Good input above but I would add that it could simply be that one source is more conservative in load recommendations than another. Different case capacity could be a factor as well (though I wouldn't think it would drive a 3 grain difference). As always, start low and work up.

 

[CanMike]

Thanks for the input. I get the seating depth but even weirder is the Lapua is seated 20 thousands further out according to their spec so you would think that would at least offset and bullet length differences.

Mike

 

[RegionRat]

Thanks for the input. I get the seating depth but even weirder is the Lapua is seated 20 thousands further out according to their spec so you would think that would at least offset and bullet length differences.

Mike

I don't want to give you the impression that the data you shared wasn't a very odd example because it is.

That Lapua bullet has not been around long enough for me to give you any better advice. The dimensions on the Berger are published in detail, but not for the Lapua. Still, I agree they appear to be very similar.

I have a feeling that once folks who use the same gun or test bbl with both bullets start to share their experience, we may all have a better idea of what is going on. Till then, keep doing the homework as you have, and play it safe.

 

[Spencercoc74]

I am a very black and white kinda guy. When I noticed there was a difference in load data between the bullet and powder manufacturers my view became very gray. I decided to follow the power manufacturers data. My logic is the powder manufacturers know where their recipe should be, where it actually is, and how to adjust to proved the most accurate data.

I’m not absolutely correct and I’m not wrong but this is how I’m going about my reloading.

 

[Rocketmandb]

I am a very black and white kinda guy. When I noticed there was a difference in load data between the bullet and powder manufacturers my view became very gray. I decided to follow the power manufacturers data. My logic is the powder manufacturers know where their recipe should be, where it actually is, and how to adjust to proved the most accurate data.

I’m not absolutely correct and I’m not wrong but this is how I’m going about my reloading.

One significant contributor to this _may_ be different materials in the bullets. A softer bullet, for example, will fill the rifling more quickly, which in turn leads to faster, and hence higher, pressure build due to less gas blow-by (gastro-intestinal jokes are welcome now).

 

[Rocketmandb]

@RegionRat now I know where your head is...

 

[Ex E6]

Some times some loads will be reduced , " IF " a ballistician has an excessive pressure spike using a variation of components ,which could be no more than say 0.020" off the lands . Shape of bullet tail as well as construction regardless of jacket integrity can also play a role in pressure . Lapua BC- G1 .670 - BC - G7 0.335 and Berger which is very very close at , BC- G1 .665 BC G7 0.336 . Berger list all of it's measurements ,Not certain if Lapua does or not ?. Best advice is start reduced work up ,compressed or not and note any obvious pressure signs and see where it puts You .

 

[RegionRat]

@RegionRat now I know where your head is...

I'm still lurking and waiting for the gas blow-by jokes to roll in....

Okay, I found one...

A man has a habit of starting every morning by breaking wind.​

Of course, his wife finds this habit disgusting, and even as she asks him to stop, he only snickers, continuing the habit every morning.

After one of the husband's daily bouts of morning flatulence, the woman tells him that if he continues to fart every morning, his intestines will come out of his ass. Of course, he does not believe her claim, and he gets up, as every day before. Enraged, the woman thinks of a solution.

Later that day, the woman saves the intestines from the turkey that she has cooked, preparing to give her husband a proper scare. When he's fallen asleep, she puts the turkey intestines in his underwear, and when he wakes up, after delivering his usual sour flatuosity, he is horrified to feel what he presumes to be his own innards in his underwear.

As the man rushes to the bathroom, holding his behind all the way, his wife smiles content, asking: "I told you that would happen!"

As she hears a grunt and a slopping sound, her husband comes out of the bathroom, a satisfied grin on his face. "Yes," he says, "but thanks to God's grace and these two fingers, all is back where it should be." YMMV

 

[CanMike]

I got this answer from lapua.

Hello Mike,



The difference between Lapua and Berger bullets is on their toughness; Lapua has significantly “harder” jackets/cores, than most other bullet manufacturers.

 

[Rocketmandb]

I got this answer from lapua.

Hello Mike,



The difference between Lapua and Berger bullets is on their toughness; Lapua has significantly “harder” jackets/cores, than most other bullet manufacturers.

Which makes total sense - harder bullet => later sealing of the bore => more blowby => lower pressure => higher possible powder charge

 

[Rocketmandb]

So, now the question is:

Which delivers more consistent results? Sealing the bore early with a softer jacket/core or later with a harder jacket/core?



EDIT: I'll try to find the answer in Ammunition Demystified. I believe Jeff Siewert mentioned this at some point in his book.

 

[Fig]

I have a dozen reloading books from the '60s and '70s, and when I pull them out and compare the recipes someone who just started reloading would look at them think that they were trying to murder people. This is especially true of the handgun loads, and even among the fast powders.

I don't know if it's better pressure reading equipment, too many of them were reading Elmer Keith, or what, but back in the day max loads would be extreme hot loads by todays measure. Internet people would freak out if they saw the data.

All that said, most of us who have been doing it for our whole lives consider all reloading data as starting places and rough guides, not as dictums. I believe the results from shooting, not what some table tells me to expect. Most of the guys here don't push anything, because barrels are expensive and we want our straight shooting rifles to keep doing that for as long as possible... That said, I've found sweet spots above the maximums, and have absolutely no fear of loading them that way when there are zero signs of excessive pressure.