Charge disparities between books

[marksman1941]

Hi all. I've been reloading for years, but generally worked off of a Speer #14 manual and data posted online by mfg's. I ran into a larger disparity than normal in posted data, and was curious how you all approach this situation.

Rifle is a BSA Majestic in .308 win. I believe i's a 12 twist, ultralight little deer rifle (weighs 7 pounds with the optic and 4 rounds in it).
Shoots factory Federal 165gr Trophy Bonds into about 3/4" at 100

I wanted to load up some 165gr sierra TGK for it. IMR 4064 is my go-to 308 powder, although I do have some other options I can switch to if I need.

Here's my conundrum; These are all data posted for 165gr bullets
Speer #14 shows IMR 4064 at 41.0-45.0gr with a velocity range of 2482-2727
My new Hodgdon #11 shows IMR 4064 at 35.1-42.8, with a velocity range of 2100-2600fps
MidsouthShooterSupply has the Sierra load data posted in pdf form, and showing 41.0-42.6 with a velocity range of 2500-2600.

So Hodgdon and the Sierra data both seem to be similar at 42.6-42.8 for 2600 fps, while my Speer book is considerably hotter.

I'm not a velocity chaser (at least in this rifle) so I'll stick with the 41-42 range to start with, but a 2-2.5 gr margin on "max load" seems rather large between books. Are the current publications just lawyered up heavy and reducing charges, or is my Speer book giving me some wishful numbers?

I know the age old response is "start low, work up, see for yourself" but I'm curious if folks have other approaches when they run into disparities like this.

 

[WeiserBucks]

Every MFG uses a test barrel and consults a lawyer. Every test barrel and every lawyer is different.

 

[Mark37082]

It is a bit of a head scratcher to see load data with this much variability. However, it is also true that changing one component can create significant variability. I have found this with brass more than anything else. Being able to identify pressure signs is critical to safe loading.

 

[marksman1941]

It is a bit of a head scratcher to see load data with this much variability. However, it is also true that changing one component can create significant variability. I have found this with brass more than anything else. Being able to identify pressure signs is critical to safe loading.

That's a great point on the brass. Especially with 308 or 5.56 where you can get military brass that often varies In thickness quite a bit from commercial brass. I'll check the books again and see if they list what case they used. I went with federal GMM FC 308 brass as I have a metric pile of it and it's decent enough.

 

[FEENIX]

Hi all. I've been reloading for years, but generally worked off of a Speer #14 manual and data posted online by mfg's. I ran into a larger disparity than normal in posted data, and was curious how you all approach this situation.

Rifle is a BSA Majestic in .308 win. I believe i's a 12 twist, ultralight little deer rifle (weighs 7 pounds with the optic and 4 rounds in it).
Shoots factory Federal 165gr Trophy Bonds into about 3/4" at 100

I wanted to load up some 165gr sierra TGK for it. IMR 4064 is my go-to 308 powder, although I do have some other options I can switch to if I need.

Here's my conundrum; These are all data posted for 165gr bullets
Speer #14 shows IMR 4064 at 41.0-45.0gr with a velocity range of 2482-2727
My new Hodgdon #11 shows IMR 4064 at 35.1-42.8, with a velocity range of 2100-2600fps
MidsouthShooterSupply has the Sierra load data posted in pdf form, and showing 41.0-42.6 with a velocity range of 2500-2600.

So Hodgdon and the Sierra data both seem to be similar at 42.6-42.8 for 2600 fps, while my Speer book is considerably hotter.

I'm not a velocity chaser (at least in this rifle) so I'll stick with the 41-42 range to start with, but a 2-2.5 gr margin on "max load" seems rather large between books. Are the current publications just lawyered up heavy and reducing charges, or is my Speer book giving me some wishful numbers?

I know the age old response is "start low, work up, see for yourself" but I'm curious if folks have other approaches when they run into disparities like this.

I approach it as a guide/reference to ensure safety - always proceed cautiously.

 

[marksman1941]

It is a bit of a head scratcher to see load data with this much variability. However, it is also true that changing one component can create significant variability. I have found this with brass more than anything else. Being able to identify pressure signs is critical to safe loading.

So my Speer book, which is the hottest load, uses IMI brass which is milspec. Milspec .308 is thicker brass than commercial, so you'd think charges would be reduced a grain or two. The Hornady book uses commercial frontier brass, which is slightly thinner. So the mystery continues...

 

[nksmfamjp]

Every MFG uses a test barrel and consults a lawyer. Every test barrel and every lawyer is different.

I think this is a good point.

I'd argue the lawyers are much more similar. No lawyer is going to give you a pass to post over pressure data.

I think there are details of the setup, chamber, throat, rifling dimensions, pressure measuring tools, powder age, powder lot, humidity, primer lot, primer age, action stiffness, etc that all have an impact. There are no industry standards so everyone takes their own "conservative " tested result.

Our job is to put this information into our own rifle specific test regimen and get a load. If I'm not seeing bolt lift force above factory ammo, or other pressure signs, I consider myself ok. I've played with a lot of book data and find it very usable…..almost all of it. Usually max load is just a tad hotter than my rifle likes, but not terrible.

 

[Seabeeken]

I have always found Speer data on the hot side. Maker dont know what conditions, brass, rifle, etc you are using

 

[MagnumManiac]

Simple answer is that all the books are correct with their barrel and components at the time it was tested by that technician. We don't know what fudge factor each company used from their reference ammo either…
If it's published, work up to it…

Cheers.

 

[marksman1941]

well, my answer was found pretty quickly. I loaded 41.0-43.0 using federal brass under 165 TGK and 165 Speer grand slams. The TGK was crunching powder a bit at 41.0, and quite a lot at 43.0. The grand slam started crunching at 42.5. Since the GS are short and stubby, if a person loaded them long (ignore the cannelure, which loads to COAL 2.700") and seats them at the full 2.800" a person may get 45gr in there, but that would be mighty might full. 43.0 was basically at the base of the neck already. I wonder how Speer managed to get 45 grs in a case...

 

[cohunt]

Not all manuals will list actual pressures either. I like to refer to data that has actual chamber pressures to see how close the max charge is to saami psi max.....quite a few "max" charges are several thousand psi lower than max saami pressure-- that will let you know how much the lawyers got involved in the listed max charge.

 

[charlie 7]

Every MFG uses a test barrel and consults a lawyer. Every test barrel and every lawyer is different.

Ha, ha,
very good, quick and smart, should end the discussion right there.

 

[MagnumManiac]

Not all manuals will list actual pressures either. I like to refer to data that has actual chamber pressures to see how close the max charge is to saami psi max.....quite a few "max" charges are several thousand psi lower than max saami pressure-- that will let you know how much the lawyers got involved in the listed max charge.

The reason for them being under is not necessarily lawyer intervention.
Testing over the pressure trace has often shown in many standard cartridges and improved cartridges that a single .5g increase in powder puts the pressure above max, so the load is reduced 3%, normal procedure since SAAMI dropped AVERAGE MAXIMUM PRESSURE. They now base it on ANY load, just ONE, above maximum pressure is to be dropped 3% and that is maximum pressure allowed.

Cheers.

 

[ARlife4me]

Lot numbers, case capacity, throat length, twist, barrel length, bearing surface, coal, trim length, bullet length and how many times the barrel was used/tested. I've seen this across the board even with powder manufacturers having their own data. If they show faster bullets than competitors, it's marketing at its finest!