Hodgden loading data re 139 vs 140gr 7mm

[bheadboy]

curious, they list the 139 (assume hornaday) with very different powder charges vs the 140sft sp, not sure what that 140 bullet is, not Sierra, nosler, speer,

The grain weight charge difference i would think to be a function of bearing surface bbl contact, thus pressure difference,

Any thoughts? wisdom? experience?

Bob

 

[wapiti25]

I found some of the 6.5-06 loads to be very consevitive. Start low and work up is all I know to do.

 

[bheadboy]

just figured it out t- the 140 is a Swift with a longer bearing surface.

Actually the Sierra 140sbt has a shorter bearing surface than the 139 hor so should be close in data to the 139


Bob

 

[bheadboy]

I just got the following from Hodgden, just as i suspected it is the bearing surface and jacket hardness that causes the 140 data to show lower powder charges.


"There is q difference between a Hornady Spire point bullet and a Swift Soft point. The Swift bullet has a heavier jacket, more bearing surface and higher friction than the Hornady bullet. So, the Swift bullet would generally get a lighter load than the Hornady of similar weight."

So to all reading,be carefull you do not use the same load on light jacket vs heavy jacket long bearing surface as pressure will build --

words for the wise

Bob

 

[Clark]

There are lie, damn lies, and then there are statistics.
There are wimpy published loads, lawyered up loads, and then there are 7mmRemMag published loads.

The 7x57mm Mauser cartridge. with weaker case head and smaller capacity, can be loaded to less than the threshold of long brass life by a reasonable safety margin, and still beat most published loads for the 7mmRemMag.

 

[normmatzen]

Clark,

You tweaked my interest!

I am building a large ring Mauser in 7 X 57. What is a reasonable 140gr load for a military barrel?

I am of the opinion the posted 7 X 57 loads are WAY wimpy due to lawyers and fear of the small ring rifles.
Yes, I will start low,and ladder up to find a good sweet spot, but knowing where to start and what a reasonable range would be would help.

 

[necchi]

can be loaded to less than the threshold of long brass life by a reasonable safety margin,

Wha?? :-\
What on earth does that mean?

 

[bheadboy]

Norm,
The reasonable thing to do is use the published loads for the higher end as a start, then work up .3gr slowly watching for pressure signs, bolt lift, primer extrusion/flatening, expansion ring at case web/body junction growth, (my opinion stop at .001 up from sized case) - you should be working around the .469" area sized on 7x57 +.001 fired. I personally would start jumping .020".

just my experience.

The whole idea of this post is to alert reloades of the danger of using the same max load with bullets of different bearing surface and hardness, some of the readers got off the track of this thought or missed it all together!
Bob