178hpbt load data confusion

[69gen1]

Getting set to start working a 178hpbt load up in my 12fv 308 with varget looking thru the data sources I have they seem to be alot of variance. 1 of my oldest hornady book list 32 to 43.2@2500 newer hornady book 35 to 42.4@2450 with a oal at 2.800 Sierra book says 36.3 to 41.7 @ 2500 with 26" barrel for there 175 hpbt Hodgen load data center list the the sierra 175 at 42 to 45 @2690 I under stand the 178hpbt is not the 175 sierra but the hodgen data seems closer to what I see most people useing trying to narrow down a good start charge to work up.im shooting the 168 amax at 43.5 varget for around 1/2" moa at 100 with the ogive at 1.263 ..thanks to all

[Ted_Feasel]

Getting set to start working a 178hpbt load up in my 12fv 308 with varget looking thru the data sources I have they seem to be alot of variance. 1 of my oldest hornady book list 32 to 43.2@2500 newer hornady book 35 to 42.4@2450 with a oal at 2.800 Sierra book says 36.3 to 41.7 @ 2500 with 26" barrel for there 175 hpbt Hodgen load data center list the the sierra 175 at 42 to 45 @2690 I under stand the 178hpbt is not the 175 sierra but the hodgen data seems closer to what I see most people useing trying to narrow down a good start charge to work up.im shooting the 168 amax at 43.5 varget for around 1/2" moa at 100 with the ogive at 2.263 ..thanks to allI always just use the data as a generic guide, I generally start low side of mid load and work up till I achieve what is needed while looking for signs of overpressure. I load in 1/2 gr increments then when I hit the node I'm looking for I will go back to the nearest .5 below and above loading in .2 gr increments.. maybe a little overkill to some but it has served me very well.

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[69gen1]

I always just use the data as a generic guide, I generally start low side of mid load and work up till I achieve what is needed while looking for signs of overpressure. I load in 1/2 gr increments then when I hit the node I'm looking for I will go back to the nearest .5 below and above loading in .2 gr increments.. maybe a little overkill to some but it has served me very well.

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Thanks Ted that's about what I did with the amax started at 41 with those

[69gen1]

So do I go off of hodgen data starts or stay with the hornady data because there max is virtually sierra and hornady start charges bullit data.

[Ted_Feasel]

So do I go off of hodgen data starts or stay with the hornady data because there max is virtually sierra and hornady start charges bullit data.I would just use what you have always used because if your doing load dev then your going to arrive at the correct node no matter what starting load you use. I typically use hornady and Lyman manuals and I'll cross reference each node till I see a common weight within a couple tenths, but as long as your working up it really doesnt matter. As far as what manual to pick, probably would use the one with latest load data and I have noticed hornady seems to be very conservative on their charges.

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[69gen1]

I would just use what you have always used because if your doing load dev then your going to arrive at the correct node no matter what starting load you use. I typically use hornady and Lyman manuals and I'll cross reference each node till I see a common weight within a couple tenths, but as long as your working up it really doesnt matter. As far as what manual to pick, probably would use the one with latest load data and I have noticed hornady seems to be very conservative on their charges.

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That's my take on the hornady to then I crossed it with sierra data for the 175 they was about the same then hodgen data start was hornady and sierra max got me thinking... I have used hodgen data before

[Ted_Feasel]

That's my take on the hornady to then I crossed it with sierra data for the 175 they was about the same then hodgen data start was hornady and sierra max got me thinking... I have used hodgen data beforeIn that case I would definitely start with the conservative low data just to be safe

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[Robinhood]

Knowing the jump on your bullet can be a factor in presures as well as bearing surface length. That mid 43 area can be a sweet spot.

[69gen1]

Knowing the jump on your bullet can be a factor in presures as well as bearing surface length. That mid 43 area can be a sweet spot.

I agree the 168 amax does real well there in my rifle I'm running it at 2.263 from ogive which gives me the 2.800 up to 2.805 because of the tip on oal.best I can tell I'm jumping .022 from lands with the hornady comparitor and looks like the 178hpbt will be jumping .074 if I set the ogive at 2.130 oal at 2.800 area again tip dependent

[Ted_Feasel]

If I remember correctly, when manufacturers test firearms, they use what is called a proof load and a proof load is a load that will cause catastrophic failure in the firearm within 5 shots and then the saami spec is around 50% power of the proof load, so why am I telling you this?? I have no idea [emoji854][emoji851][emoji3061][emoji4]lmfao

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[69gen1]

If I remember correctly, when manufacturers test firearms, they use what is called a proof load and a proof load is a load that will cause catastrophic failure in the firearm within 5 shots and then the saami spec is around 50% power of the proof load, so why am I telling you this?? I have no idea [emoji854][emoji851][emoji3061][emoji4]lmfao

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Sierra book says they ran there load with a 12vss and 26" barrel for what's that's worth

[Ted_Feasel]

Sierra book says they ran there load with a 12vss and 26" barrel for what's that's wirthI know another thing that gets overlooked alot is bullet brand, 142 gr by x, y and z companies will have different ogives so loading by oal is not necessarily the best way to go unless you are using the exact pill the load data is using.. even then is probably best to use comparator and seat by jump space if your going for precision.. if it's just killing deer then no biggie I recon. Heck even the ogive on a same lot batch of Sierra's or hornady have a pretty crappy variance. I'd like to see a bullet that the ogive breaks at least within a half thou from one to the next.. I couldnt believe the variation on my hornady so I checked sierra and they were just as bad.. over time I checked multiple boxes and they are just consistently inconsistent.

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[69gen1]

I know another thing that gets overlooked alot is bullet brand, 142 gr by x, y and z companies will have different ogives so loading by oal is not necessarily the best way to go unless you are using the exact pill the load data is using.. even then is probably best to use comparator and seat by jump space if your going for precision.. if it's just killing deer then no biggie I recon. Heck even the ogive on a same lot batch of Sierra's or hornady have a pretty crappy variance. I'd like to see a bullet that the ogive breaks at least within a half thou from one to the next.. I couldnt believe the variation on my hornady so I checked sierra and they were just as bad.. over time I checked multiple boxes and they are just consistently inconsistent.

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Yes the ogives do vary not bad on the amax or the hpbt in my lots about 1 or 2 thou

[charlie b]

I usually start with the powder mfg data and then cross ref with bullet mfg data.

I noticed Hornady has an app now so you can get a cartridge load data for $0.99. For those of us who don't load for many cartridges it is a good deal.

And Nosler publishes data on their web site now.

[CFJunkie]

For what it's worth, I use exit time to get a good working node for a new rifle to eliminate the problem of trying to shoot a ladder and figure out what the nodes really are when my shooter induced variations muck up the data.
That approach works great for me and it seems to get me at or very close to the harmonic node within the first couple of tries. I spend more time finding the bullet and jump that works than finding a powder charge that works. All of my best rifles have preferences for bullet shapes, bullet weights, the amount of bullet body that is touching the rifling and, to some degree, for powders.

Your 12 FV with a 26 inch barrel with the standard Savage 3% carbon steel barrel (19,107 fps reflection speed) has a reflection time of 1.361 msec. at the 12th reflection and 1.134 msec. at the 10th reflection.
I have two 12 FVs and have used both reflections in my .223 but only the 12th reflection will stay below PMax on my 6.5mm Creedmoor. I suspect that your .308 will have the same issue with the faster reflection times.
I have published lots of results on the Ammo and Reloading forum the 110 forum for both of my 12 FV rifles using that exit time and I think the data is pretty representative and pretty consistent.

Using Varget and the 178 Hornady BHTP Match, QuickLOAD data that you will be at the 1.361 exit time if you use an O.A.L. of 2.848 with the standard 2.005 trim length with 40.6 grains of Varget. That load with that seating depth yields a muzzle velocity of 2517 fps with a pressure of 47,808 psi - well below the 62,000 psi Pmax so it is just about in the middle of most load tables.
I would work around that charge as the base powder charge.
Every 0.1 grain charge difference will create about an 11 fps change in MV and a 0.004 msec. change in exit time. Higher velocity and lower exit time with more powder and the reverse with lighter charges.

Decreasing seating depth between 0.002 to 0.003 will increase the velocity by 1 fps.
Increasing seating depth decreases the velocity.
Trim length changes of the same amount produce just the opposite effect.
I tune measure trim length and tune seating depth to achieve the desired exit time.
I have found about a 0.1 average group size difference with my 12 FVs results from having the exit time at the chamber versus at the muzzle.


Varget is probably the least temperature insensitive powder made so you shouldn't have to worry about temperature.
If you were using IMR4064 or IMR4895, you would have to adjust for temperature changes to just the right exit time.

[69gen1]

For what it's worth, I use exit time to get a good working node for a new rifle to eliminate the problem of trying to shoot a ladder and figure out what the nodes really are when my shooter induced variations muck up the data.
That approach works great for me and it seems to get me at or very close to the harmonic node within the first couple of tries. I spend more time finding the bullet and jump that works than finding a powder charge that works. All of my best rifles have preferences for bullet shapes, bullet weights, the amount of bullet body that is touching the rifling and, to some degree, for powders.

Your 12 FV with a 26 inch barrel with the standard Savage 3% carbon steel barrel (19,107 fps reflection speed) has a reflection time of 1.361 msec. at the 12th reflection and 1.134 msec. at the 10th reflection.
I have two 12 FVs and have used both reflections in my .223 but only the 12th reflection will stay below PMax on my 6.5mm Creedmoor. I suspect that your .308 will have the same issue with the faster reflection times.
I have published lots of results on the Ammo and Reloading forum the 110 forum for both of my 12 FV rifles using that exit time and I think the data is pretty representative and pretty consistent.

Using Varget and the 178 Hornady BHTP Match, QuickLOAD data that you will be at the 1.361 exit time if you use an O.A.L. of 2.848 with the standard 2.005 trim length with 40.6 grains of Varget. That load with that seating depth yields a muzzle velocity of 2517 fps with a pressure of 47,808 psi - well below the 62,000 psi Pmax so it is just about in the middle of most load tables.
I would work around that charge as the base powder charge.
Every 0.1 grain charge difference will create about an 11 fps change in MV and a 0.004 msec. change in exit time. Higher velocity and lower exit time with more powder and the reverse with lighter charges.

Decreasing seating depth between 0.002 to 0.003 will increase the velocity by 1 fps.
Increasing seating depth decreases the velocity.
Trim length changes of the same amount produce just the opposite effect.
I tune measure trim length and tune seating depth to achieve the desired exit time.
I have found about a 0.1 average group size difference with my 12 FVs results from having the exit time at the chamber versus at the muzzle.


Varget is probably the least temperature insensitive powder made so you shouldn't have to worry about temperature.
If you were using IMR4064 or IMR4895, you would have to adjust for temperature changes to just the right exit time.

Wow that is some serious research and I truly appreciate it.now for me to comprehend it. might take a bit but I do understand for the most part.i also will read thru your other post,and hopefully tighten my loads up some

[bigedp51]

Reloading data between manuals varies because the firearms and reloading components vary and are not the same.

Example if a specific firearm is listed for testing then a strain gauge is glued to the barrel and then calibrated with a cartridge of a known pressure. In the Lyman manual they also use the copper crusher or transducer method with pressure test barrels with chambers and bores at minimum SAAMI dimensions to obtain the highest pressures.

There is a reason why the manuals tell you to start at the suggested start load and work up looking for signs of excess pressure.

Quickload does not know the exact dimensions of your chamber and bore and needs to be calibrated with a chronograph. I have Quickload and even after calibrating it with a chronograph the chamber pressure it outputs is a computer generated guesstimate.

My 30-30 Winchester 94 at the max rated pressure of 38,000 cup or 43,000 always has the primers protruding from the base of the case. This is because the chamber pressure is not great enough to push the base of the case against the bolt face. If you make a workup load starting at the suggested start load you will always see your primers protruding until the approximate midpoint of your loads. And when the primers are flush with the base of the case it means "with that brand of brass" the chamber pressure pushed the case against the bolt face causing the case to stretch.

Below from the Sierra reloading manual.

https://i.imgur.com/QYtojsL.jpg

In the reloading manuals even if you use the exact same components the chamber pressure and velocity can vary from the manual. And why the manuals tell you to start low and work up looking for signs of pressure.

Below the top photo is a button rifled Savage barrel and the bottom photo is a custom made hand lapped barrel. And I wonder how much these two type barrels will effect chamber pressure and velocity. Bottom line firearms and the components used will make the chamber pressure vary and why the manuals data varies. Meaning the manuals are all approximate data and if your primer pockets stretch out of shape after three reloads you are pushing that brand of brass beyond its elastic limits.

https://i.imgur.com/GpTCke2.jpg

https://i.imgur.com/S82Lb6S.jpg

https://i.imgur.com/4kXrGuI.png

[Texas10]

Just wanted to drop a note of thanks to CFjunkie for his fine write up. I'm shooting 168's out of my 26 in Shilen select match barrel in .308 and wanted to try 175's. This information will be a great starting point.

[Ted_Feasel]

Just wanted to drop a note of thanks to CFjunkie for his fine write up. I'm shooting 168's out of my 26 in Shilen select match barrel in .308 and wanted to try 175's. This information will be a great starting point.I got same hole results from 175 smk in my 28" shilen s/s using w748..

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[Ted_Feasel]

I got same hole results from 175 smk in my 28" shilen s/s using w748..

Sent from my SM-N975U using TapatalkSide note.. magnum primers @43gr, LC brass, TL 2.005, OAL 2.800

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