257 Roberts Ackley Improved load development

[ScreaminEagle]

Ok scotty. Ill come off the lands in .01" increments and look for a sweet spot. I think 3451fps will do! Cant wait to get a load for the 110gr AB.

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[brians356]

51.7gr IMR4350 ... 3451fps

So, referencing against the data DrMike provided, should one conclude from your figures that QuickLoad is either A) absurdly cautious, or B) greatly overestimates pressures?

 

[ScreaminEagle]

Not sure. Could also be that i didnt get the correct measurments when i found my h2o capacity. Maybe my chamber is a little oversized. Who knows. All i know is it works

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[brians356]

Not sure. Could also be that i didnt get the correct measurments when i found my h2o capacity.

I don't see the H20 measurement you provided, or is that what's in the QuickLoad header DrMike posted as "Usable" capacity?

 

[ScreaminEagle]

I averaged 60.6gr of water

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[SJB358]

This is what I get using 60.6 and the rest of the spec's you posted SE

Cartridge : .257 Ack Imp (257 Rob)
Bullet : .257, 100, Nosler BalTip 25100
Useable Case Capaci: 53.176 grain H2O = 3.453 cm³
Cartridge O.A.L. L6: 2.775 inch = 70.49 mm
Barrel Length : 26.0 inch = 660.4 mm
Powder : IMR 4350

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-20.0 82 40.00 2711 1632 33780 8105 90.6 1.459
-18.0 84 41.00 2775 1710 36066 8347 91.7 1.420
-16.0 86 42.00 2840 1791 38502 8581 92.9 1.379
-14.0 88 43.00 2904 1873 41079 8806 93.9 1.338
-12.0 90 44.00 2969 1957 43803 9021 94.9 1.299
-10.0 92 45.00 3033 2042 46705 9226 95.7 1.261
-08.0 94 46.00 3097 2130 49798 9418 96.6 1.225
-06.0 96 47.00 3161 2218 53096 9599 97.3 1.190
-04.0 98 48.00 3224 2308 56616 9765 97.9 1.156 ! Near Maximum !
-02.0 100 49.00 3288 2400 60373 9918 98.5 1.123 ! Near Maximum !
+00.0 103 50.00 3351 2493 64388 10055 99.0 1.092 !DANGEROUS LOAD-DO NOT USE!
+02.0 105 51.00 3413 2587 68681 10177 99.3 1.062 !DANGEROUS LOAD-DO NOT USE!
+04.0 107 52.00 3475 2682 73277 10283 99.6 1.033 !DANGEROUS LOAD-DO NOT USE!
+06.0 109 53.00 3537 2779 78201 10371 99.8 1.005 !DANGEROUS LOAD-DO NOT USE!
+08.0 111 54.00 3599 2876 83485 10442 100.0 0.977 !DANGEROUS LOAD-DO NOT USE!
+10.0 113 55.00 3660 2974 89161 10494 100.0 0.951 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 103 50.00 3483 2694 75659 9781 100.0 1.020 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 103 50.00 3168 2228 53315 9874 94.1 1.186

I don't think your "Dangerous" but your probably in that 65K PSI range with the load. The Ackley's seem to be tough, like the WSM's to see pressure signs on the case since they are virtually no taper to them, so they grab the chamber walls pretty well.

I'd shoot and reload your cases a few times and see what comes of it. If you get useful case life out of them and get everything you want, I'd think your okay either way.

I don't think I have seen a picture of this rifle and man, we wanna see some groups too! Jeeze! :grin:

 

[brians356]

I agree with the Ackleys being tolerant. I would pay attention to primer pockets loosening up, and sticky bolt on extraction.

ScreaminEagle, when you measured H20, how bulging was the meniscus?

For comparison, when I measured my 250 AI 40-deg., the meniscus at max bulge (just before letting go) had the H20 at 52.4 grains. (Water sat shallow overnight, temp when measured was 72f.)

 

[ScreaminEagle]

Thanks Scotty. I'll get a pic up of the rifle soon. I'm not worried about brass life. This isn't gonna be a rifle that I take prairie dog hunting. It will be used for whitetail, coyote, and the occasional chuck. Plus, I have a couple hundred cases to play with. You will have to wait till after I find the seating depth sweet spot for some group pics. Last outing I got 2-2.5" at 200yds. I'm sure the pac nor can do better than that.
Steve

 

[ScreaminEagle]

I agree with the Ackleys being tolerant. I would pay attention to primer pockets loosening up, and sticky bolt on extraction.

ScreaminEagle, when you measured H20, how bulging was the meniscus?

For comparison, when I measured my 250 AI 40-deg., the meniscus at max bulge (just before letting go) had the H20 at 52.4 grains. (Water sat shallow overnight, temp when measured was 72f.)

I just made a slight bulge.

 

[brians356]

I just made a slight bulge.

Then the usable capacity used in the QuickLoad could be a bit short. DrMike chose the max meniscus value when he ran my data. Not a huge difference, but there it is.

 

[SJB358]

I'd say if your within a .5 grain on your H20 your close enough for gov't work..

It's when you see 4-5 grains or more like I see with some 7mm Mags and 300 Win's. Those make you scratch your head till you actually weigh them out.