Home Forums Hunting & Shooting Ask The Gunwriters Preliminary Load Data through Cartridge Scaling

Am lookin' to reload the 6.5x55mm cartridge/140 gr. Speer GS, for a 24" Bbl'ed Ruger Hawkeye, and am interested in using the .30-06/M2 pressure of 60K psi, instead of the SAAMI (51K psi) or CIP (55K psi).

Not much load data out there.

So thought about scale.

Looked at the .280 Remington, which is loaded to the same 60K psi., and the two cartridges' Case Volume/Bore Area ratios are w/in 1.6%.

Comparing the two cartridges:

Cartridge: .280 Rem 6.5x55mm
----------- --------- ---------
Bore Dia.: .284 .264
Bullet wt: 160 140 (-12.5%)
Bullet SD: .283 .287 +01.4%
Case Volume:
(grn. H2O) 67 57 (-14.9%)
Bore Area:
(in^2) 0.06335 0.05474 (-13.6%)
------------ --------- ---------
Volume/Area:
(grn./in^2) 1058 1041
------------ --------- ---------
% Vol./Area:
(grn./in^2) 1.0163 0.9839
% (+/-) +1.63% (-1.61%)
============ ========= =========

What the above mess represents is, that if you ignore SD, which is only useful for selection, and take the average difference in Bullet wt., Case Volume, and Bore Area:

(-12.5%)
(-14.9%)
(-13.6%)
-----------
(-41.0%)
/3
----------
(-13.67%)
=======


Speer lists the .280 REM/160 gr. max load for H4831 as 55.0 grn./2773 fps.

Scaling that:

55.0 grn.
x(0.1367)
----------
7.5 grn.

Subtract that from the listed load:

55.0 grn.
(7.5 grn.)
-----------
47.5 grn./2773 fps
============


Questions/Comments/Concerns appreciated.




GR

I highly recommend you buy Mule Deer's Gun Gack series. After you understand the content in those books get yourself a chrono to aid in your load development.

Until then, stick with published load data ..... the European CIP load data (look to Vihtavuori, Norma) was helpful for me. Also the Nosler reloading data tends to run a little hotter than many reloading manuals with SAAMI max pressures.

Good luck ..... always wear protective eye wear and remember ...... slow is smooth and smooth is fast.

Thanks.

Have a chrono - just lookin' for a way to get reasonable data for the cartridge, loaded to that pressure, to determine where to start the ladder, what to expect, and an approximate powder requirement.

Swedish Mausers were proof tested to almost 66K psi.

< 60K psi is not a concern w/ this brass, in this rifle.




GR

I realize now what is driving your questions: "Not much load data out there."

Why did you pick .280Rem?

Suggest you go through the same thought process used in your post with the .260 Remington and 6.5 Creedmoor..... leaving you with only case volume difference.

Also under the reloading section there are many loads people have used to run the 6.5x55 at its full potential.

^^^^^ This.

Both the 6.5 Creedmoor and .260 Remington have a SAAMI Maximum Average Pressure of around 60,000 PSI (the CM 61,000 and the .260 60,000, if I recall correctly.

All you have to do is measure the powder capacity of each, or look it up. Some manuals list the H2O capacity with the case filled to the neck, though a somewhat more accurate way is to measure it with the bullet you plan to use at the seating depth. When you find the H2O capacity, any difference between those cases and the 6.5x55 will be about 1/4 the potential for "extra" velocity from the 6.5x55 at the same pressure. Then load up some ammo and see what happens on the chronograph.

Thanks, will check that out.

EDIT: They actually have a pinned thread, thanks!


As stated, Case Volume/Bore Area ratios are w/in 1.6%, and SD's for the two bullets are w/in ~ 1.4%.

So, figured they would scale well.




GR

Thanks MD.

Think Nosler uses seated bullets for case volume.

Are you saying that delta grn. water is equal to delta grn. powder?




GR

Lastly, the 2nd Ed. of the Lee Reloading manual has what they call "1 GRAIN FACTOR". Some info there too for estimating pressures and velocities.... the Lee manual uses "1 GRAIN FACTOR" for reduced powder charges ...... but ...... if you manipulate the equation(s) you can estimate pressures and velocities with increasing powder charges. The key word being "estimate". Kinda the analog version of QuickLoad.

Well, for a 140 gr. bullet, QuickLOAD says 46 grn. IMR 4831/2800 fps/57.75K psi.

Figure a grain more for H4831.

Also found a QL for the same wt. bullet and H4831, unknown psi:

47.1 grn./ 2700 fps.


So the load is similar, but the velocity varies a bit.

2740 fps or so seems to be about right for the 140 gr. GS out to 350 yds.




GR

No, I'm not--though oddly enough water and powder do turn out to often weigh close to the same. But water-volume is the easiest way to compare the powder capacity of two rounds--or two different brands of brass, fired in the same chamber.

And fired brass is the easiest basis for comparing capacity in YOUR rifle, with a specific brand of brass. The fired neck allows a bullet to be slipped slowly into a case full of water, whereupon excess water eases out around the bullet's base. Dry the droplets off the outside of the case, then weigh it, and you have the water capacity with that bullet seated. (Of course, you need to weigh the case empty, before the water test.)

I might add that, as Old School_Best School suggested, you might want to buy at least one of my series of three BIG BOOK OF GUN GACKS. They're about the size of a GUN DIGEST annual, so contain a lot of info. I would suggest the first one, which appeared in 2015 and is still selling steadily seven. It describes how to do a LOT of the stuff you're asking about, so would save you considerable time.

Also, it just so happens that my wife Eileen, who runs our website and publishing business, is throwing a sale right now through Father's Day, the 19th. All the books that Eileen and I have written are 15% off the price listed on site, which always includes media-mail shipping in the U.S. The sale price of the book I suggested is $32.50, which means the sale price is $27.63, including shipping.

I have all 3 of the Gun Gack books as well as 3 of the cook books.
The Gun Gack books are a must have for any serious rifleman

Convert to percentage. If Cartridge A has 10% more volume (based on water weight delta) than Cartridge B, it will hold 10% more powder also.

Thanks JB.

Will put it on my list.

Seems like every time I'm researching a technical reloading question of late, the relevant article has invariably been one of yours.

The last but one dig was RE: the M1 rifle reloads, and the article you did a while back.


P.S. Nosler lists:
6.5x55mm/140 gr/(50.2 grn. H2O): 47.0 grn./H4831/2778 fps/23" Bbl.
.260 Rem/140 gr./(47.7 grn. H2O): 46.0 grn./H4831/2769 fps/24" Bbl.

That 6.5x55mm load right there, interpolated to ~ 2800 fps from a 24" Bbl., has to be a warm one.

And while it also may turn out to be somewhat Nosler fiction, it's still a nice piece of load data, and may still be THE load, as only ~ 2740 fps is required to suite my desire.

As this project was begun centered around IMR 4831, a lot of this was missed.


Thanks again, to all'yall.




GR

What I was thinkin'.

... and then apply JB's "1/4" velocity conversion factor to the delta powder wt..


Thanks.




GR

In fact, some of the folks who've asked to be put on the pre-publication list for my upcoming THE LITTLE BOOK IF RIFLE HANDLOADS THAT WORK have asked me to include "The Rules," the chapter in the first BIG BOOK OF GUN GACK about this sort of stuff in the little book. (It was also included in THE BIG BOOK OF GUN GACK II, for a somewhat similar reason.) Am thinking about it, but am wanting to keep the little book "little."

Following this discussion closely as I've been looking for an approach to step up the performance of the 300 Savage for the strong M722, which accommodates a much longer COAL than spec. It would seem that the Gun Gack series might be helpful.

Teebone,

While the 2.8" (or so) magazine is longer than the 2.600 overall length SAAMI limit for the .300 Savage, the SAAMI throat dimensions also limit OAL--or bullet-to-lands relationship, which is more important in terms of pressure than OAL.

Using Nosler's data the .260 has 5% less capacity than the 6,5x55.
Applying John's 'quarter rule' that would imply an expected speed reduction of 1,25% or 2,743 fps in the same 23" barrel. Nosler shows 2,769 fps with 24" which is basically the same thing. Simple and accurate and not just in this case, in others with a big difference in case size it works too.

MD, thanks. The throat is quite generous with this particular rifle, and it appears to have come from the factory that way. For now I'm working with lighter bullets, most recently the 130 TTSX. The primary constraint, if only to make me feel better, is in assuring adequate grip by seating the bullet such that the bearing surface reaches the base of the short neck. When seated this way, OAL is roughly 2.75", placing the bullet about .070 off of the lands. Likewise with the stubby Sierra 150gr PH, which has proven very accurate in this rifle, the throat dimensions haven't been limiting either. So it just seems the rifle/cartridge combo offers good potential beyond what most published data provides.