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

CanMike · 2025-09-16T12:14:11-0400

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 · 2025-09-16T14:14:56-0400

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 · 2025-09-16T15:18:26-0400

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 · 2025-09-16T15:32:25-0400

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 · 2025-09-16T16:17:29-0400

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 · 2025-09-16T17:31:22-0400

CanMike said:
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 · 2025-09-16T17:43:13-0400

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 · 2025-09-16T17:49:24-0400

Spencercoc74 said:
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 · 2025-09-16T18:44:56-0400

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

Ex E6 · 2025-09-16T19:44:39-0400

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 .

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

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