It seems that all I have is questions....Anyway maybe someone can steer me true.

I am preparing to load for my new .458 Lott.
I have been comparing source material and found a discrepancy. I realize that loads depend on many variables (rifle,case,etc) however, these are usually a grain or three differences. This is a difference of over ten grains.

This involves some logic inference, so I'll try to make my point as clear as possible.
We all know the Lott has a higher case capacity than the W/M.
It would stand to reason that this being the case a load for the Lott using the same components would be able to take more powder. At the very least the same amount .
(For brevity the primer type is held constant.)

In Lyman�s reloading manual the max charge for a W/M w/500 grain JSP is IMR 4320 at 75gr. < !--color--> .

In the Lee book the same load (510gr bullet) shows a max of 74 grains of IMR 4320 < !--color--> - one grain less due to 10extra bullet grains.

In the Hornady manual the Lott < !--color--> shows a maximum load as being IMR 4320 at 73.6gr < !--color-->

First red light. How can the Lott load be less than the W/M max load for the same weight bullet?
It gets worse.
I have source material from Mr. Ray Atkinson who is a trustworthy fellow, and from Steves pages-a forum contributor and one other source (lost their specific info) Cross researching this material they indicate that a safe working zone with this load would be IMR 4320 73.3gr up to 84 gr < !--color--> Their load data coincides with the logic that the Lott could handle more powder all other components remaining constant.

Why is the load data from Hornady listing the max safe load as 73.6 for the lott and everyone else are at least 10 grains higher????
There are three possibilities;
1. Misprint
2. Hornady is terrified of the Lott
3. If I load per the other info I am going to blow up.

Additional information and experienced suggestions appreciated.

Reloading manuals are gudielines. The publisher has liability concerns & diff. firearms/test bbl. are used vs. your particular firearm. Also the Lott is fairly new to the reloading manual world, where rounds like the .270/.30-06 & even the .458Winmag have been around for quite awhile.
I just started loading for my .404 jeffery & there is little to no data. So I am using starting loads for the .416Rem. & data from knowledgable guys like Ray A.

.44

An article by Ross Seyfried in the Nov.-Dec. "Rifle" magazine addresses this very thing.

"You can see the complete load workup from the Hornady lab. The ballistician tells me he worked to a maximum of 62,000 psi (electronic piezo) and that the barrel was a Wiseman and nearly identical to the company's .458 Winchester pressure barrel. Th elargest surprise was that he was only able to wring 2,250 fps out of the Lott with one powder, Winchester # 748. Maximum data for several other powders is within a few tens of a grain of their maximum for the .458 Winchester. The Lott case should have much more internal capacity than the Winchester, and therefore, it should take significantly more of the same powder to acheive the same balisstics. We also see the maximum load of 4320 being 73.6 graisn where historical data went almost 13 grains higher. I knew the old published loads of 4320 were a bit hot, but only by a few grains. Accounting for the next 9 grains,between proven working loads and Hornady's maximum, is difficult. Last but not least, Reloader 15 is shown with a 76.6 grain maximum load and only 2,150 fps. Two things about this confuse me. First RL-15 is usually quite close to WW748 in charge weights. Second, the load is far behind that for the .416 Remiongton, a reasonably similar cartridge where RL-15 is the hands down favorite. How could all this be possible?
I believe wecan point our figers at a few possibilities. First there is the common syndrom of wildcats, even established wildcats, being over loaded by modern scientific pressure standards. Next, there is the PROBABILITY (my emphasis) that the Hornady pressure barrel is not only extra tight , but also it may have an unrealistically short throat. The combination would result in excess pressure with very normal loads. Also, the cases are Hordady manufacture, a brand that has never been used before in the Lott. THis is a big wild card because the case capacity may be different than the historic cases we are used to."

Now it's just me talking......So you see, the Hornady data is circumspect in my opinion. I have been using 93 grains of WW 748 with the old 500 grain Hornadys for years in not only my own rifle but 3 others that we keep in Ethiopia. This is usually in hot humid conditions. This is with cases fireformed from Winchester .375 H&H brass as well as some of the old A Square brass. Never had any problems or signs of excess pressure. I never chrono'd the load because I didn't have one at the time. Can't convince myself it's important enough to do it now I do know of a case where a fellow blew his rifle up with 97 grains of the same powder, though!

Rich Elliott

Rich,



Excellent points. Personally, I would say that the two primary parameters are:



1.) Commercial reamer (chamber specifications) much tighter with significantly less throat than wildcat reamers. This is a well known and documented phenomena.



2.) The tendency of handloaders to over-load a wildcat. Primarily because they have no sophicated instrumentation to measure actual pressure so they resort to using the classical indications, head expansion, primer flattening, etc.



With regard to item #2 above. It takes well over 70,000 psi to expand the case head on 375 H&H belted magnum cases. To blow a primer one must first expand the case's head since it is the case head which supports the primer.



In my simulation software, your load of 93gr of W748 is well above 62000 psi.



The Lott has on average a 13% increase in case capacity over the 458 Winchester magnum. So when loaded to the same pressure with the same 500 gr bullet, one would expect the Lott to beat the Winchester by about 60-70 fps. This assumes that the burn efficiency has not changed with the larger case. This is seldom the case; however, and typically if the same powder is used in both the cases the larger case will achieve a higher peak pressure. This simply means that to maintain the same maximum pressure you must load down the larger case slightly, which has the effect of reducing the velocity improvement from the original 60-70fpr to something more like 50-60 fps.



Keep in mind that the 460 Weatherby magnum, which has a huge capacity advantage over either of these two cartridges, only achieves a muzzle velocity of 2490 fps +/- at 63000 psi chamber pressure. Of course you can handload it to 70000+ psi and get around 2600 fps.



Scott

ScottS,

Over 62,000 psi but evidently under 70,000 psi, eh?

Rich Elliott

Yes. Actually, maybe not. There are other instrumentation issues (which form the basis of liability issues) at work with most Load Manual data, which really goes beyond the scope of a public forum.

Personally, I think most shooters will have a very difficult time achieving the velocities that Hornady has publish with their powder and charge weights, but like I said the whys and wherefores are beyond the scope of this forum.

Scott

Sooooo........
I have some inquiries out to other manufacturers for load data.
While I am waiting does anyone have the load data available from a published source other than Hornady??? And....
Who has the best published load data?

If I can't get the load verified through a published work is 10% less than 84 grains of IMR 4320 a good place to start?
I have no desire to go boom?

.44,

I would recommend that you start with Nominal to MAX loads for the 458 Winchester magnum, depending upon how big your balls are.

If you are chronographing these loads, don't be surprised if you have a difficult time getting the Lott over 2200 fps without breaking the 63,000 psi barrier, because you will. If you load it up 2250 - 2290 fps you are knocking on 70,000 psi.

I would recommend Rel 7 (starting at 67 grains with 500gr Hornady) or IMR 3031 (starting with 72 grains with 500 gr Hornady). Use CCI 200 (of Fed 210) primers for both. Work you way up to ~ 2200 fps and you should be like that proverbial pig in slop.

Published load data is full of "safety factors" for liability purposes. A book could be written on how the published pressures and velocities are massaged to minimize liability.

Scott