The Barnes #3 manual lists min 57.0 gr/max 62 gr of IMR 4831 with 160 gr X bullet in 7mmRM. So... I've been using what I assumed to be a conservative load of 60 gr IMR4831 behind a 160 gr TSX. I recently purchased their #4 manual with the TSX data, and it lists the min/max for the 160 gr TSX as 52.0/58.0. I'm not totally surprised that the load I'm using is 2 grs. beyond the listed max. What I find strange is that the "book" loads for the TSX are significantly lower than for the X. I thought the whole idea of the TSX grooved projectiles was to reduce contact area with the barrel, thereby reducing friction and pressures, allowing for slightly more powder and consequent increases in velocity... all with the added benefit of decreased copper fouling. What am I missing or miss-reading here?
Barnes numbers...Say what?
- Thread starter icedog
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- The Conservative part of Ontario
Not so much Lawyer proof, but with the advent of better pressure testing equiptment, it has been found certain cartridges exhibit some nasty pressure spike tendancies. 7mm Rem Mag, and 243Win are two of them. The loads reflect what has been found to be a safe margin to keep the pressure spikes within SAAMI specs. A lot of old stand by loads have also been found to be above SAAMI spec pressures, especially with newer lots of powders.
Remember the old original H4831 was a tad slower than the new manufactured stuff. Many powders have had their burn rates change over the years. Keep that one in mind when you try to duplicate something Grand Pappy did to his old rifle years ago.
Lots of things have changed, you cant totally blame it all on Ambulance chasing Lawyers.
BINGO!
If you also compare enough old to new data you will find that in a more than a few cases the maximum loads using some ball powders have actually increased a bit as the test equipment becomes more sophisticated. A lot of the older manuals were actually developed with the technicians reading the fired cases rather than using any pressure testing equipment.
A quote: "Remember the old original H4831 was a tad slower than the new manufactured stuff. Many powders have had their burn rates change over the years."
Not the batches I tested weren't. When the newly manufactured H4831 came out, Hodgdon's stated the same loading data as the old war surplus could be used with the new. I loaded five 270 W with 130 grain bullets and the old powder. Then loaded five more, with everything the same, except the new powder.
The new powder was 100 fps slower than the old war surplus and also had a greater spread, than did the original.
Not the batches I tested weren't. When the newly manufactured H4831 came out, Hodgdon's stated the same loading data as the old war surplus could be used with the new. I loaded five 270 W with 130 grain bullets and the old powder. Then loaded five more, with everything the same, except the new powder.
The new powder was 100 fps slower than the old war surplus and also had a greater spread, than did the original.
Where in the world did you get this bit about, "Technicians reading the fired cases rather than using any pressure testing equipment."
In Hatchers Notebook, he tells about the rifles and ammunition for the 1920 national matches. He states the pressure of their load was 51,335 psi, which gave a muzzle velocity of 2700 fps. to the 170 grain bullet.
That sounds like pretty sophisticated testing to me.
The next year he also refers to the copper crusher method of testing pressure. The book has pictures of both types of testers.
Obviously, du Pont would have state of the art testing methods for use with all their powders, as well, since even the military was using their powders.
After WW2 when Bruce Hodgdon got into the surplus powder business, he built a completely modern lab and they state, pressure tested every load that went out.
It was but that equipment was owned by the American military. Most people who provided reloading data up into the 1960's couldn't afford to access technology like pressure barrels .
