Reloading: Differences in Reloading Data


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beartooth91
May 24, 2010, 10:08 PM
Hi Everyone,

After 25 years of being out of shooting & reloading; I've dived back in, purchasing a 243 and a 7mm-08 (both Savages). I have a few different bullet weights and two powders (H380 and IMR-4064), but, am confused about differences in powder charges - for the same powder and bullet weight - between different manufacturers. All other things being equal; is there a difference in pressure - with the same powder - between a 140 gr Nosler and a 140 gr Sierra ? Or is it just different data because each test rifle is different and how do you all handle this ?

Thanks

Mark

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JimKirk
May 24, 2010, 10:37 PM
Yes ...could be a difference of jacket hardness, total bore bearing area, hardness of lead core and that just the bullets. Add in the rifles and all their differences and there can be major differences in data. Add test equipment, powder lot, tempertures....

Jimmy K

Walkalong
May 24, 2010, 10:41 PM
Welcome to THR beartooth91.

Like the man with two watches who never knows what time it is, the reloader with two data sources will always wonder which one.

Yes, differences in barrels, differences in pressure equipment, etc.

The old standby warning..."start low and work up"...applies here.

For two 140 Gr bullets with the same powder charge there will not be much difference in pressures if they are similarly constucted with a similar amount of bearing surface. Same jacket thickness, lead hardness etc. There will be some difference for sure.

An example is the Speer manuals where in some cases they show 2 to 4 bullets of the same weight and give data intended for any of them.

sig220mw
May 24, 2010, 11:18 PM
I called hodgdon and asked them about their manual. It's the 26th edition so it is fairly old. Anyway it doesn't list bullet types, only weights. The tech I talked to said that all of their data is derived by using the "worst bullet for caliber" scenario. In other words the lowest quality bullet in that weight. So anything better should perform better theoretically.

You will see different loads and results because the different companies aren't all located in the same region of the country. Atmosphere, climate and their relation to sea level all have effect on the ballistics.

Like some one said earlier, start at the bottom and keep an eye on your brass as you try your loads.

HOWARD J
May 24, 2010, 11:33 PM
Another thing you will find is--loads from many manuals ( 20 years & older ) for certain cartridges have reduced their powder charges in their new manuals.
Many people say--" Oh the testing equipment is much better today"
I say---they found that certain guns were shooting loose from the max loads of the older data---so they toned it down..................

Clark
May 25, 2010, 12:06 AM
IN 16 years, 357 mag max went below 38 Special:

"Speer 6" 1964 38 s&w special 160 gr. soft point 11 gr. 2400

Midway "Load map" 1999 357 mag Speer 160 gr. soft point 10.9 gr. 2400

beartooth91
May 27, 2010, 12:19 PM
Ok, I'm loading up my very 1st loads for my new 243 with the Sierra 70 gr HPBT Matchking with H380.
The Sierra manual specifies 39.6 to a max of 42.0 grains of powder for this bullet, along with the 70 gr Blitzking and 75 gr HP.
The Hodgdon data specifies a starting charge of 42.0 grains and a max of 46 grains, admittedly for the Speer 70 gr HP.
The Lee data looks to be an exact copy of the Hodgdon data but doesn't specify bullet style or manufacturer (mostly). Instead, it says "Jacketed Bullet".
The Nosler data specifies 40.0-44.0 grains for the 70 gr BT.
And the Speer data specifies 41.0-45.0 grains of powder for the 70 gr TNT HP.
Saftey is paramount and I'm not and never was a person who starts out at or just below max load. It does seem, however, the current Sierra data is a bit below the others. In my old Sierra manual, volume 2, as I recall; one could load up the 60 gr HP to almost 4000 fps. But my 43 year-old memory isn't as good as it used to be.
Anyone shooting this bullet/powder combo? If so, what are you're loads? Just curious; I'll probably start at 40.0 grains.

Mark

MachIVshooter
May 27, 2010, 01:31 PM
Yes ...could be a difference of jacket hardness, total bore bearing area, hardness of lead core and that just the bullets. Add in the rifles and all their differences and there can be major differences in data. Add test equipment, powder lot, tempertures....

All of this.

However, the data errs on the side of caution and is always* well within SAAMI specs. If I'm going for max, I find the book with the heaviest listed charge

*There have been a handful of instances where overpressure loads were printed. Warnings/corrections are issued by the company that authored the manual.

qajaq59
May 27, 2010, 01:52 PM
I just look at all the loads in the manuals as "suggestions" for where to start. They used a different gun, plus a different batch of powder and primers. Consequently, the only way to do it is to start at the bottom and work up until you hit the accurate load for your gun. There are just so many variables that even the manuals can't say which is exactly the right load for safety and accuracy.

ranger335v
May 27, 2010, 02:23 PM
" Or is it just different data because each test rifle is different and how do you all handle this ?"

The book differences are indeed largely due to differences in the arms used.

We "handle" the differences from any reason by starting low and only moving up to book max unless/until we see signs of excess pressure.

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