Load Data Conundrums.

Greetings All,
While I was trawling through some of the Hodgdons load data for the 7mm Remington Magnum the other day I spotted some odd data. The loads for the 150 grain Barnes TTSX BT were considerably higher than those for the 150 grain Nosler Partition. Due to the extra length and hardness of the Barnes you would expect it to be the other way around. A conundrum if you like. The 7mm Rem Mag came out in the 1960's, loaded with a powder not available to handloaders so there were some pretty spicy loads listed when people were trying to match the claimed factory loads in the days when few handloading manuals. But this data was recent and had pressure data with it, a conundrum if you like. Being the OCD type of chap that I am I just had to make sense of it.
First the data for the Hodgdon/ ADI powders and the Nosler projectile was old with pressure in CUP (Copper Units of Pressure). At the time that pressure started to be measured in PSI it was found that the old copper crusher system was understating the pressure. Further it was not picking up variations in pressure in some cartridges, the 7mm Rem Mag being one. Loads were reduced for some cartridges around 1990 so the load data for these powders could be on the light side.
Next I compared the Barnes and Hodgdon data for the Barnes 150 grain TTSX BT. The Barnes max loads were roughly the same as the Hodgdon start loads for the 4 powders powders in common. Further Hodgdons got around 100 fps less velocity than Barnes with the same load. So the Hodgdons barrel was slower.
So there we have it. A combination of old soft data and higher pressure data in a slow barrel. One thing that did not change as much was velocity. Hodgdons only got from 80 to 120 fps more velocity for all that powder so working up to a velocity rather than a charge weight has a lot of merit, something I have been doing for some time. Velocity is a better measure of pressure than anything else available to the handloader.
Regards Grandpamac.

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Originally Posted by grandpamac

Greetings All,
While I was trawling through some of the Hodgdons load data for the 7mm Remington Magnum the other day I spotted some odd data. The loads for the 150 grain Barnes TTSX BT were considerably higher than those for the 150 grain Nosler Partition. Due to the extra length and hardness of the Barnes you would expect it to be the other way around. A conundrum if you like. The 7mm Rem Mag came out in the 1960's, loaded with a powder not available to handloaders so there were some pretty spicy loads listed when people were trying to match the claimed factory loads in the days when few handloading manuals. But this data was recent and had pressure data with it, a conundrum if you like. Being the OCD type of chap that I am I just had to make sense of it.
First the data for the Hodgdon/ ADI powders and the Nosler projectile was old with pressure in CUP (Copper Units of Pressure). At the time that pressure started to be measured in PSI it was found that the old copper crusher system was understating the pressure. Further it was not picking up variations in pressure in some cartridges, the 7mm Rem Mag being one. Loads were reduced for some cartridges around 1990 so the load data for these powders could be on the light side.
Next I compared the Barnes and Hodgdon data for the Barnes 150 grain TTSX BT. The Barnes max loads were roughly the same as the Hodgdon start loads for the 4 powders powders in common. Further Hodgdons got around 100 fps less velocity than Barnes with the same load. So the Hodgdons barrel was slower.
So there we have it. A combination of old soft data and higher pressure data in a slow barrel. One thing that did not change as much was velocity. Hodgdons only got from 80 to 120 fps more velocity for all that powder so working up to a velocity rather than a charge weight has a lot of merit, something I have been doing for some time. Velocity is a better measure of pressure than anything else available to the handloader.
Regards Grandpamac.

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I work up loads to find the sweet spot of acceptable velocity combined with a desired level of accuracy. I establish this by shooting a brass / ascending powder charge / bullet combination that initially showed potential. This sometimes fails and I go back to square one. But once a very good load is achieved I often find that with a different powder and bullet accuracy will be best in that same velocity area so long as bullet weight is the same. Other common factors are loads having a full case or nearly full case of powder and velocities being in the upper region of max while not necessarily exceeding the "safe" max load.
The only pressure indicators I have are post shot bolt lift and brass condition. Also, rarely, a blown primer indicating excessive pressure.

and as I said in other thread..the ttsx was changed from older barnes projectiles to have more groove n less land.pluss boat tail.so its bearing surface is less/pressure lower...

Greetings All, @Micky Duck you are correct that the grooves reduce engraving resistance but they are still harder and longer than cup and core projectiles due to the solid copper construction. They also need to be seated much further from the rifling as detailed by Barnes in their load data which reduces peak pressure some.
We had a thunderstorm last night and it was wet out this morning. Did not feel much like outside work so I did a little research. I was looking for Ken Waters second Pet Load report which I found and additionally a Propellant Profiles report on H1000. This was done by Sam Fadala in 1989 just after H1000 was released. I was interested to see how this differed from later data currently published by Hodgdon. It certainly did. A single load was listed for the 160/162 grain projectiles with the start load being higher than the max load shown in current data, even for the hotter 162 grain Hornady BTSP projectile. Current max pressure for the 7mm Rem mag is 52,000 CUP or 61,000 PSI and this data went to 55,500 CUP. Crikey!
Since this data was produced two things have happened. First the powder industry has moved to electronic measurement of pressure (PSI). This is more sensitive and accurate and showed wider pressure swings, with some cartridges, than expected. Additionally H1000 (AR2217) production was moved to Australia from Scotland around 2,000. One of the thing I have found helps understanding different load data sets is to plot them on a graph. This was done for the 160/ 162 grain data plus the 162 grain Hornady BTSP and 160 grain Nosler Partition data. Extending the line for the 162 grain BTSP projectile showed that it was close to the hot 160-162 data. The latter data gave a little more velocity for a little less pressure at the same load level.
So here is the conundrum. Would I push on a little from the current data toward the older data. The .300 Win Mag has a max pressure of 64,000 PSI and my little 7mm SAUM max is 65,000 PSI. Frankly I don't know. No doubt there are those that do but likely not me.
Regards Grandpamac.

I believe I poked up data with similar abnomaly in it just the other day..out of an ADI manual the heavier projectile had considerably higher charge listed than one 2grns lighter..... this is where the plot on graph shows up things well....now me,no way would I push up n above the line shown by graph....

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Originally Posted by Micky Duck

I believe I poked up data with similar abnomaly in it just the other day..out of an ADI manual the heavier projectile had considerably higher charge listed than one 2grns lighter..... this is where the plot on graph shows up things well....now me,no way would I push up n above the line shown by graph....

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Greetings,
Those were the two projectiles I graphed, along with the old Hodgdon Data. The interesting thing was that the 160 grain partition was gaining pressure much faster than the 162 Hornady BTSP and would have got to 52,000 CUP well before the heavier projectile. I will certainly not be fiddling with high pressure loads in a 7mm Rem Mag as I don't have one. The 7mm SAUM I do have has data up to 65,000 PSI max rather than the 61,000 PSI max for the Rem Mag. The job for winter is to sort out loads for that and my heavy barrelled .223 for next seasons F Class shooting.
Regards Grandpamac.

Greetings All,
Looked out the window, raining again, a good day to sort out my data for the 7mm Rem SAUM. I remembered an article in Handloader around 2005 so dug into the appropriate banana box to find it. Also in the box was Ken Waters third Pet Loads report from 1998. In it he listed a load of 70 grains of H1000 behind the Nosler Ballistic Tip projectile developing 3,070 fps. This is 2 grains above the current Hodgdons max. More conundrums.
Back to the 7mm SAUM. My initial test loads using the Remington 150 grain Corelokt and AR2213SC gave velocities lower than expected back in 2004 gave velocities less than expected in spite of the 26 inch barrel. Looking back the Hodgdons data was for the 150 grain Scirocco projectile which has a very heavy jacket, a little like the Nosler LRAB. Recent chronographing with the latter showed it gave significantly more velocity, and I assume pressure, than the same weight interlock. I think some more graphs will be needed. Will keep you posted.
Regards Grandpamac.

A quick question GPM. You're a bit of a reloading guru.

If you reload, do you have to chronograph your hand loads?? or is that just a 'nice to have' part of reloading.

The simpleton in me thinks that if the round is accurate, doesn't show pressure signs then all is ok?? AS LONG as you DONT exceed the max load data.??

K

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Originally Posted by tac a1

A quick question GPM. You're a bit of a reloading guru.

If you reload, do you have to chronograph your hand loads?? or is that just a 'nice to have' part of reloading.

The simpleton in me thinks that if the round is accurate, doesn't show pressure signs then all is ok?? AS LONG as you DONT exceed the max load data.??

K

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Greetings @tac a1,
A lot can be said for either option. If you just want to reload cartridges for hunting and stick to the standard cartridges which have plenty of modern pressure tested data then you can probably do without one. This is especially so if you can get a friend to chronograph your favoured load to make sure your velocity is in the Goldilocks zone. The difficulty is relying on pressure signs. Most of these only show up when you have already gone too far and the chronograph is your best measure of pressure. For us handloaders the regard the loading as just as much a pastime as hunting and possibly more as we age then the chronograph is as essential. This is especially so for long range target shooters where trajectory is important.
I am afraid that is a long winded reply to a yes no question but what I suggest is that you find someone local, with a chronograph, that can test the odd load for you. Don't be offended if the prefer to shoot the loads themselves as a decent chronograph is expensive and far from bullet proof. Also get someone with handloading knowledge to run their eye over your loads or make suggestions. I would be happy to help with that. You will decide over time if you need a chronograph but you can definitely do without one.
Hope that helps.
Regards Grandpamac.

Yep cool thank you. I'm not a 'push the boundaries' sort of person when it comes to firearms and ammunition.

Greetings All,
Research is under way for the 1,000 yard loads. The rifle is a Remington 700 Sendero with a 26 inch fluted stainless barrel purchased new in 2004. A Bushnell Match Pro 6-24x50 scope, mounted on a 20 MoA base, was added earlier this year. The rifle has fired about 50 rounds and the load will be developed with 162 grain AMax projectiles, ADI AR2217 powder and Federal 125 primers. All of these are in the cupboards plus AR2213SC powder and Federal 210 primers if needed.
Two conundrums have shown up already. Initial chronographing in 2004 and 2005 using 150 grain Remington Corelokt projectiles, AR2213SC powder and Winchester WLR primers gave disappointing velocities, about 100 fps below the Hodgdon data in spite of the longer barrel. A switch to AR2217 powder got closer with max loads but was still behind the factory rounds that chronographed around 3,060 fps. At the time I put the differences down to the WLR primers and was likely half right. I failed to appreciate how much difference the harder 150 grain Sirocco projectiles made in the Hodgdon data.
About this time the Sendero entered an extended period of safe curing with only occasional trips to the range and a couple of hunts.
Fast forward to 2023 and the limited data available has been collected. The Hodgdon data developed 20 years ago, for the 7mm Rem SAUM remains unchanged but I also found an article by John Haviland in Handloader from 2005. John tested the 150 grain Scirocco plus the Sierra 150 grain HPBT Match projectiles with the 68 grain Hodgdon max load. The Sierra projectile produced around 50 fps more velocity. With AR2213SC the boot was on the other foot. In the Hodgdon data the same 67 grain max load of AR2217 was tested with the 160 grain Nosler partition, 162 grain Hornady SPBT and the 168 grain Sierra HPBT. Velocities were as you would expect but the Nosler developed the highest pressure and the Hornady the least. Another conundrum. The Hornady 162 grain SPBT data should be a good match for my AMax projectiles.
Next job is to load some rounds for my next trip to the range. I do check zeroing here at home but restrict that to a few rounds with my less noisy rifles. Load development will need to be done on the range, likely at Taupo.
Regards Grandpamac.