Why the huge discrepancy between load sources?

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LocoGringo

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I'm loading up test rounds for my Bergara B14 in 7mm-08 and I researched my load options with the Hornady 139 grain BTSP. I ended up deciding on trying Varget first since I have quite a bit of it for .308. I decided on 10 test rounds starting at 41.0 grains of powder and ending on 43.0 at .5 grain intervals. Well, it's been a little while since I did that research and I decided to look through my Hornady manual and the MAX load in the Hornady manual is 41.5 grains with that powder! I almost had an extreme bowel movement and wondered where I got my load data from. I just found it on the Hodgden website and their max is 43.5. I'm certain that is the reference I originally used. The Hornady manual max is the second lowest of five test loads. The manual is Hornady 8th edition from 2010.

My question is why is there such a large discrepancy? Did I choose a dangerous max load? Is my manual outdated? I think I might be testing tomorrow, but if it doesn't look safe, that plan may change.
 
Hornady generally has lower charges then other manuals..

One load I was checking out Hornady's max charge was lower then Lee's minimum charge.


When I do test loads I never go to the max.
I start at the minimum and work up the one charge below the max.
 
The only problem I can see with your plan is charge weight. If I'm looking for the gun to tell me it's max I'm not going up in half grain increments unless I'm dealing with a cartridge with 300 or larger in its name. This mainly comes to light as it appears to be your first trip ever with this rifle. If it were me I would build a pressure ladder to run first and then you will know if your good or where to stop.
 
LocoGringo said:
I'm loading up test rounds for my Bergara B14 in 7mm-08 and I researched my load options with the Hornady 139 grain BTSP. I ended up deciding on trying Varget first since I have quite a bit of it for .308. I decided on 10 test rounds starting at 41.0 grains of powder and ending on 43.0 at .5 grain intervals. Well, it's been a little while since I did that research and I decided to look through my Hornady manual and the MAX load in the Hornady manual is 41.5 grains with that powder! I almost had an extreme bowel movement and wondered where I got my load data from. I just found it on the Hodgden website and their max is 43.5. I'm certain that is the reference I originally used. The Hornady manual max is the second lowest of five test loads. The manual is Hornady 8th edition from 2010.

My question is why is there such a large discrepancy? Did I choose a dangerous max load? Is my manual outdated? I think I might be testing tomorrow, but if it doesn't look safe, that plan may change.
Click to expand...

It's all in the details. The OAL may be longer, different brass, primer, not the same bullet. These are just test reports on what they did. Does not mean it's what your going to get. As always start low and work up till you find the node(s) before pressure signs show up.
 
Highland Lofts said:
One load I was checking out Hornady's max charge was lower then Lee's minimum charge.
Click to expand...

I have many Lee products and I'm very satisfied with them. I'm not here to bash Lee. But I consider their reloading manual only good for a door stop. They do not do their own testing, data is compiled from other sources. But what hacks me the most about their manual is that for all the bullet molds they sell very few of them have data in the manual.

When I'm working up a load I go to Lyman, Hornady, Nosler, or Western powders manuals. Make notes of the range of charges they recommend for the powders I have on hand. Then go to the powder manufacturers web sites and again record the ranges. Yes there are wide discrepancies between all. I normally start with the lowest charge loading 5 rounds. For rifle I work up in 0.5 grain increments and stop at about 95% of the maximum load. Normally an accurate load can be found in that range.
 
AJC1 said:
The only problem I can see with your plan is charge weight. If I'm looking for the gun to tell me it's max I'm not going up in half grain increments unless I'm dealing with a cartridge with 300 or larger in its name. This mainly comes to light as it appears to be your first trip ever with this rifle. If it were me I would build a pressure ladder to run first and then you will know if your good or where to stop.
Click to expand...
So Hodgden's website for Varget with this bullet weight in this caliber starts at 40.5 and maxes at 43.5 grains. I'm starting at 41 but stopping at 43, so I'm keeping it in between the extremes. I thought maybe Varget was recently introduced to when the manual was written, but a quick Google search says Varget was first introduced in 1996 which gives Hornady plenty of time to figure out their numbers seem low.

My goal is to try to find an accuracy node, or close to one and then fine tune around that one by .2 grains of powder up and down. I'm not looking for max pressure, just precision. I'm loading a bit long (theoretically between .045 and .050 off the lands and grooves), so that relieves pressure a bit, I think.

Is it a safe assumption that the powder manufacturers know the pressures better than the bullet manufacturers? Which one do you go with?
 
LocoGringo said:
So Hodgden's website for Varget with this bullet weight in this caliber starts at 40.5 and maxes at 43.5 grains. I'm starting at 41 but stopping at 43, so I'm keeping it in between the extremes. I thought maybe Varget was recently introduced to when the manual was written, but a quick Google search says Varget was first introduced in 1996 which gives Hornady plenty of time to figure out their numbers seem low.

My goal is to try to find an accuracy node, or close to one and then fine tune around that one by .2 grains of powder up and down. I'm not looking for max pressure, just precision. I'm loading a bit long (theoretically between .045 and .050 off the lands and grooves), so that relieves pressure a bit, I think.

Is it a safe assumption that the powder manufacturers know the pressures better than the bullet manufacturers? Which one do you go with?
Click to expand...
I'm saying you should be fine but look for the limit. If you get no signs at max then your great. If you get signs a grain early then you know. You should find out what pressure looks like in your gun, so when you go looking for that next higher node you recognize signs you've seen before. Again I'm not saying go over max but I'm saying knock on the door of max and learn your rifle. It's not unheard of to couple this with a ladder test so you get double the data for the same exercise.
 
Hornady bullets get Hornady data for my 308 rifles. Check primers too. I had some pretty severe over pressure signs shooting Hornady bullets at just 0.3 grains over their published max. I was also using CCI #34 primers.
 
My loads are 139 gr. Hornady BTSP, Remington brass, Varget powder ranging from 41 grains to 43 grains by .5 grain increments, and Federal 210M primers assembled to 2.201" oal from the ogive. The mouth of the case is just to the base of the cannelure.
 
BBarn said:
The question comes up rather often. Needs a sticky.

The short answer is that the load particulars of the apparent discrepancy are usually different.
Click to expand...
Yes, absolutely. And so are the testing criteria and testing goals. Hodgdon is telling you where the tests met the maximum allowed pressure based on safety constraints established by the industry. Hornady is telling you where their bullets performed best. Hodgdon publishes a range pressure readings. Hornady publishes a range of velocity readings. The two tests maximum and minimum numbers rarely coincide for a lot of reasons, including the idea that the most accurate loads are rarely at the maximum pressure just before damage to some part of the loading equation occurs - brass, bolt, barrel, chamber, etc.
Anyway, if you read the introductory chapter on testing methods used by each they explain their reasoning.
 
The problem with published data is that pressure can vary a good bit from different bullets of the same weight, and also there is a HUGE variation in case capacities of different batches or brands of brass, so some manuals tend to give you a safe number that will cover most of the bullets in that weight class and case capacities that you might run into so as to keep you on the safe side. They may tell you what the exact bullet and case they used, but they know you're not going to use that same case and bullet anyway so they generalize a bit. Hornady seams to be especially conservative.

Just an example of how much specific components can make a difference, I was loading a wildcat a few years ago that I was making out of 270 winchester cases. I was given about 500 270 cases by a family member, all federal headstamp, and all of it was originally the exact same 150 grain RN load bought from the store. I was getting crazy pressure spreads and eratic groups with my loads and finally noticed that the powder was not filling all the cases to the same level. I started weight sorting my cases and found about 1/4 of them were 155 grains, 1/4 of them were 162 grains, and 1/2 of them were 172 grains! And all the same headstamp and indistinguishable from one another from the outside. That is a huge difference in internal case capacity. I set aside all the light weight cases and my problems went away.
 
The Hodgdon data uses Rem 9 1/2 primers and Rem cases, under the Hornady 139 BTSP. Hodgdon pressure tests all of their loads. We can see on the Hodgdon site, this particular combination is a legacy load, reported in CUP, suggesting there is a bit of age on this data - this might not mean anything, as Varget may not have changed over the elapsed time, or it may mean something.

Hornady also pressure tests all of their loads, despite not reporting it in their manuals. Obviously, the Hornady 8th edition has some age on it as well, but if memory serves, it still would have been published comfortably after the adoption of piezoelectric methods as standard - all of which, again, may mean nothing or may mean something if the formulation of Varget has changed. Of note, however, the Hornady manual also uses Rem 9 1/2 primers, but uses Hornady cases under the 139 BTSP. Something also particularly noteworthy, included in the Hornady 139grn bullet data is the 139 GMX, which is a monometal bullet of a considerably harder alloy - and Monometal bullets are physically larger, infamously requiring reduced loads, often recommended as commensurate with the next weight class UP in bullet weight for a given cartridge. For example, in the case of a 139grn monometal in 7mm-08, load data may be recommended which is more similar to the 150-154grn class of bullets. However, we also see in the Hornady manual that the max load for the 120’s in 7-08 is only 41.8grn Varget.

Personally, I don’t rely solely on manual data. In this instance, while not using 139 Hornady BTSP’s, I HAVE used 42.0grn Varget under a handful of 140grn bullets in 7-08 for many years, so I’d be very comfortable working up from a 41.5 and testing for bolt click and case head expansion as my indicator for maximum pressure in MY rifle, rather than simply following the manuals - given additional confidence in the data by Hodgdon’s info.

And 100% agree, Lee has never pressure tested any of their load data, only receiving their loads from outside sources, so they are never a source upon which I am willing to put above others when alternative data exists.
 
Differences in components, especially the lot # of powder, can produce significant differences in results that account for differences in load data. I would recommend you update your Manual to the current issue.

Hornady's data is not conservative, though may people make that claim. This keeps coming up and it isn't true according to someone who worked on the manuals.

Guy Neill worked in the industry and developed loads for Hornady and Speer. He's very clear that the loads are not conservative. They developed loads right up to the maximum SAAMI pressure limit, without exceeding it.

Check out his comments at these two sources;

https://forums.brianenos.com/topic/302740-book-max-seems-low-for-n320-plated-124gn-9mm/

The reloading manuals, at least those I'm personally familiar with are not conservative. All the maximum loads I hsve developed for manuals have been as close to SAAMI MAP (Maximum Average Pressure) as possible without going over. That's not being conservative.

But, yes, reloading data HAS changed over the years, but not due to being conservative. In the 1950's or so, none of the manuals (that I'm aware of) for load development. They used case head expansion measurements - a very poor means of trying to determine pressure.


https://forums.brianenos.com/topic/41041-44-magnum-they-cant-all-be-right/

I don't know how other manufacturers do it, but at Speer and Hornady, the CYA factor was whatever was built into the SAAMI specs. Both have loading manuals with max loads as close to SAAMI max, without going over as the tests showed. Thus, there was no added CYA factor for those manuals.

Also, no one has come up with a better means of measuring load pressures than using pressure guns. If that is a weird set-up, then so be it. At both Speer and Hornady, the loads are fired from standard guns following the pressure gun work-up, generally to get a real world velocity.

All this does not relieve the shooter/reloader from starting low and working up. His (her?) gun and components are different, and tolerances can stack up in one direction to vary results.



If any of you internet forum experts want to challenge this, please provide the pressure data Hornady used for their loads.
 
jmorris said:
All of the variables involved.

Ask how many miles to the gallon everyone gets here, it would be luck if any two were exactly the same. Why? Also lots of variables.
Click to expand...
I feel for you OP. I tried to figure this out for my powders a while back and for sure it’s the variables in testing methods and goals, minor component changes, minor this & that, and the vintage of the published data itself. It’s dizzying.

But @jmorris your analogy doesn’t always work… for example @Mark_Mark. He drives a Prius and he’d have so many misspellings in his response you couldn’t figure it out anyway.
 
when I've seen discrepencies like that, eventually if I continue to study the differences between data sources usually there is some real indication why there is a variance if you look closely enough at the details long enough and reference as much data as you can get your hands on.
 
Differences from manual to manual? How many differences are there in components and component lots? Different testing equipment (and equipment wear and tear)?. Some use universal receivers and different length barrels, with how many thousands of rounds fired through them? Some use real guns. How many different testing personnel?

I prefer to believe what I read in reliable load manuals and stay away from conspiracy theories like "loaded down for safety" or "lawyer influence, aka CYA". I would question manuals that are 100% exactly the same. (Lee does no testing. Just uses data from other component manufacturers' testing).
 
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