Can somebody explain this huge load difference?

[Doyle]

Barnes and Hornady each provide load data for their all-copper bullets. When I compare Barnes data for a 130gr TTSX or TSX to the Hornady data for a 125gr GMX for a some powders, the starting and max loads are SIGNIFICANTLY different. Yet, for other powders the loads are not too far apart.

For example
Barnes 130gr using H4895
Start 52.5gr / 3071fps Max 55.5 gr / 3276fps
Hornady 125gr using H4985
Start 46.1gr / 2900fps Max 53.2gr / 3200fps

That's over 6 gr difference in starting loads and 2 gr difference in max.

Yet, for other powders (like Varget or IMR 4064) Hornady gives a very similar max load but always a much lower start load.

Do you think that Hornady is just being more conservative? Or, is it that the bullet characteristics of the TTSX are so significantly different from the GMX? Even if it is due to different bullet characteristics, wouldn't that mean a similar start/max difference for all powders rather than just for some?

[Bart B.]

Contact each company then ask what their objectives, conditions and standards are for the data published.

Each company doesn't use the same ones. They're not required to, but it would help customers make better decisions.

[FrankenMauser]

Case brand and COAL are usually big contenders for differences like that.

When bringing Hornady data into the mix, however, you also have to consider whether or not they included other bullets and aggregated the data.

Something else to keep in mind: It is suspected that Barnes doesn't really develop their load data any more. They just get ballistics programs to spit out predictions, test to see if the gun explodes, and publish the data if nothing bad happens. (That's one of the reasons why Barnes has so many listings with unpopular powders - because that was considered the 'most ideal' by a computer simulation ... not by someone with a functioning brain.)

[44 AMP]

You're looking at two different weight bullets, from two different companies, most likely with different alloy jackets and different bearing surfaces, fired from two different barrels, using different components..

and you expect the data to be the same??

[hounddawg]

I blew a primer out using Hogdon data once in a similar situation, the starting load being several grains higher than other sources for similar bullets. Always err on the side of caution no matter what anyone here says. It's your safety that is on the line, companies can and do make mistakes

Case brand and COAL are usually big contenders for differences like that.

6 grains is a hell of lot of difference, almost 15%

just out of curiosity what caliber/cartridge ?

[Doyle]

and you expect the data to be the same??

No, but I wouldn't expect a 15% difference for only a 5gr weight difference in bullets - plus normally the difference is in the opposite direction (with the lighter bullet having higher powder loads).

just out of curiosity what caliber/cartridge ?

30-06

I'm beginning to wonder if Frankenmauser is onto something - i.e. that Barnes isn't using real (tested) numbers - just something produced by a computer simulation.

[hounddawg]

Hogdon list 48.0 to 53.1 for 130 gn bullets. It would be hard to go wrong by starting low at 48 and working your way up. Sometimes you just got to use common sense

[T. O'Heir]

Manuals reflect averages of loads tested using the exact firearm, if there was one, barrel length, rifling twist and atmospheric conditions on the day of the test only. And solid copper bullets do not use the same data as a lead cored bullet.
Keep in mind that you do not need bullet specific data. You need 125 and 130 grain copper bullet data. Who made it doesn't matter. Five grains is close enough not to make much difference, but where your data came from does.

[Doyle]

Hogdon list 48.0 to 53.1 for 130 gn bullets. It would be hard to go wrong by starting low at 48 and working your way up. Sometimes you just got to use common sense

I'm beginning to think this is the right answer. Based the other sources, Barnes idea of 52.5gr as a staring load is sounding a little "maybeish". Now, if I could get up to their max without showing pressure signs then I'd be happy. In searching the internet, I did come up with at least one report of a person very happily using 55gr of H4895 with the 130gr TTSX so Barnes max load doesn't sound totally outrageous.

[hounddawg]

might try loading 2 rounds at 49,50,51,52 and 53. Shoot across a chrono if you can and look for over pressure signs while checking the velocity to see if it is unusually high. Ten sets of components is cheap insurance.

[Unclenick]

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

Originally Posted by Doyle

Hornady 125gr using H4985
Start 46.1gr / 2900fps Max 53.2gr / 3200fps

On page 511 of the #10 Hornady Handbook of Cartridge Reloading, for a 125 grain Hornady SST bullet in .30-06, the H4895 loads given are:

44.5 grains at 2700 fps Minimum
56.9 grains at 3300 fps Maximum

To allow for the GMX, QuickLOAD will give ratios accurately. It suggests 55.5 grains should be the new maximum and 50 grains to start.

Hodgdon, who distributes the powder and uses special data lots of it that are at a true average performance value to develop their load data with, suggests 48 grains to start with the Speer 125-grain HP (not even a solid), and I would be inclined to go there rather than just to 0.9 times Hornady's current number. Hodgdon's maximum is 53.7 grains. I am perfectly comfortable working up somewhat past that and other load manual maximums for technical reasons having to do with how manual authors differ in their use of the SAAMI limits from how an ammo manufacturer uses them. In this case, though, I am suspicious that Hornady got a powder sample that was burning at the low end of the burn rate tolerance range for their non-solid data and I would, therefore, be inclined to stay with Hodgdon's lower maximum if (if, if, if) I had no velocity measuring equipment I trusted. With such equipment, however, I would calculate a velocity difference from 24" for any actual barrel length I was testing, and would consider loading warmer if I had not met the velocity difference I had calculated for my barrel. I would back down if I had exceeded that velocity. I would be watching not only for all the usual pressure signs, but for an accuracy node, of course, and to see if it was better than the last one. if the higher pressure hadn't got me to a new accuracy node, I would back down to the last one I saw. If it had, but it wasn't better accuracy, I would also back down. It's not a competition to see how fast I can shoot a barrel throat out.

I've noticed in the past that Hornady loads could vary from about -1% to as much as -9% below other data sources. I think it has something to do with how they work loads up, something to do with how they lump a bunch of same-weight bullets of different lengths and COL's together, and how they publish loads only for fixed increments of velocity which may or may not happen to coincide with reaching a SAAMI standard pressure reading. However, more recently I notice they've upped their game by adding strain gauge pressure measuring equipment to their standard load workups, so I am expecting more higher numbers to appear in the future. The #10 handbook's numbers for that jacketed bullet may well be among those newer measurements. I'd have to dig out my #7 to compare, and I'm too lazy at the moment.

[Bart B.]

Unclenick,

What's your opinion on most accurate system to measure pressure; strain gage or piezoelectric?

[Doyle]

Thank you Uncle Nick. That's the most comprehensive answer so far. One question though:

I would back down if I had exceeded that velocity.

Why would you back down if you exceed that velocity (assuming that you aren't seeing pressure signs in your brass yet)?

[langenc]

H4895 is the one powder that can be DOWN loaded to 70% of a published load at least for rifle calibers. Check Hodgdons site for 'youth loads'.

Perhaps, just perhaps that is what one of them has done, a little, not 30% for handgun loads. Better check if that applies to handgun loads.

[Unclenick]

Bart,

Some time ago Denton Bramwell concluded the strain gauge had the most reliable repeatability. From his article PRE, CHE, RIP:

σe is a figure of merit for a measurement system. It is the standard deviation of the random error in the system. Smaller is better. In terms of PSI, I have measured or calculated from published data the following σe numbers for a single cartridge test. This provides the simplest way of comparing several systems side by side.

{in decending order of measurment error-prone behavior}

CHE method, 7,500
PRE method, 6,800
Copper crusher method, 1827
Commercial piezoelectric, 1366
PressureTrace™ strain gauge, 667

I read somewhere that Hornady is now using strain gauge gear in their routine testing. If you have access to reference loads, it is probably the most accurate way to work and is certainly more economical than crushers and transducers and, as the table shows, more than 10 times better than the pressure signs on cases that manual authors used back in the day.


Doyle,

I wrote that on the assumption the user wanted to stay within load data pressures. When you don't, you incur shorter barrel life and more fatigue of the gun steel. That can be worthwhile if the gun genuinely shoots more accurately that way or if you have a real need for a faster bullet, but it should be an informed decision.

If I want to stay inside SAAMI pressure numbers, the reasoning behind backing off the load from getting a higher velocity is this: If you load starting with data developed in a pressure test gun and are using the same barrel length, you will most often get lower velocity in a production gun, but occasionally you find one that gets higher velocity. Obviously, If your gun gets lower velocity, your gun is experiencing less pressure from the load than the test gun did. If your gun gets higher velocity, your gun is experiencing more pressure than the test gun did.

In the case of getting lower pressure, increasing the powder charge to match the published velocity (and this assumes you know your chronograph is accurate) will still leave you with lower peak pressure because, with higher powder charge, you are making more gas and therefore a greater portion of your total bullet acceleration is in the barrel after the pressure peak. Thus, your peak pressure is still a little below the published one and that leaves room for going still higher without exceeding the standard limits. But in the reverse case, the opposite is true. Where you get more velocity than the load source publishes, even if you back the charge down to get the same velocity as the load source got, your peak pressure is still higher than the test gun saw because you now have less gas and therefore less post-peak bullet acceleration contributing to the final bullet velocity. Therefore, more of the velocity is being provided by pressure occurring up to the peak value, which therefore must be higher than the test gun saw. In this case you are incurring more throat wear and shortening barrel life as compared to the standard load so your peak velocity should be a little lower than book to avoid that. Probably about as much lower as your initial velocity was too high.

Incidentally, it can simply be your powder lot or different components that make the velocity difference. My main point is that if you match velocity with less powder in the same barrel length, your peak pressure value is higher than the book load produced.

[Don Fischer]

I don't fool with any premium bullet's but have a though. The Barne's TST is supposed to be a pure copper jacket. The Hornady GMX and the Nosler bullet's have the jacket's made from regular guilding metal as found on cup and core type bullet's. Perhap's there is a difference in resistance going down the barrel. If you really want to find out start low with the Barn's bullet and work your way up till you find pressure. I substitute data with cup and core bullet's all the time that way.

[old roper]

This is loading data from Hornady site.

https://www.hornady.com/assets/site/...-125gr-gmx.pdf

They don't list test rifle.