.270 Win, 140 AB & H4350?

[NYDAN]

After the holidays I hope to get back into load development for my .270 Win. I would like to work up loads for the 140 gr. AB and the 150 gr. CTBT. Both bullets have a B.C. of .496. I plan to do more testing with RL 22 and IMR 7828 powders. The H4831 powder that I have yields very poor velocities so I have given up on that.

The test targets that Remington provided me for this rifle were very impressive with .5" to .7" groups. Their load was:

135 gr. Sierra Match
53.3 gr. IMR 4350
3.340 O.A.L.
They didn't specify the brass or the primer. I would assume both were their own.

Since I have some H4350 powder left over from my 7MM-08 I thought I might try some H4350 with the 140 gr. AB. However, I can't find load data for 140 gr. AB and H4350.

Does anyone have an opinion concerning the feasibility and/or desireability of trying that combination of bullet and powder?

My target velocity for the 140 gr. AB is 2900 fps.

My components include:

Norma brass
Once fired water capacity of 71.3 gr.
WLR Primers
About a .060" bullet jump yeilding a C.O.A.L. of about 3.350"

A survey of load data for similar but different components suggest a Maximum load in the range of 52 gr. H4350.

Is it worth trying to start low and working up? Is it possible to safely get 2900 fps with these components? Does this combination have a reputation for good or bad accuracy? Should I just concentrate on the RL22 and IMR7828 powders?

Thanks for any insight you can provide.

 

[DrMike]

Here's a QL projection:

Cartridge          : .270 Win. (SAAMI)
Bullet             : .277, 140, Nosler AccuBond 54765
Useable Case Capaci: 59.393 grain H2O = 3.856 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length      : 22.0 inch = 558.8 mm
Powder             : Hodgdon H4350

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   81    43.60   2377    1756   34117   9586     90.7    1.410
-18.0   83    44.69   2434    1841   36347   9883     91.8    1.374
-16.0   85    45.78   2491    1928   38695  10172     92.9    1.335
-14.0   88    46.87   2548    2018   41187  10451     93.9    1.296
-12.0   90    47.96   2605    2109   43834  10720     94.9    1.258
-10.0   92    49.05   2662    2202   46646  10977     95.7    1.221
-08.0   94    50.14   2718    2297   49634  11222     96.5    1.186
-06.0   96    51.23   2775    2394   52809  11453     97.2    1.152
-04.0   98    52.32   2832    2493   56186  11671     97.9    1.119  ! Near Maximum !
-02.0  100    53.41   2888    2593   59780  11872     98.4    1.088  ! Near Maximum !
+00.0  102    54.50   2944    2695   63606  12058     98.9    1.057  ! Near Maximum !
+02.0  104    55.59   3000    2798   67683  12226     99.3    1.028  !DANGEROUS LOAD-DO NOT USE!
+04.0  106    56.68   3056    2903   72030  12376     99.6    1.000  !DANGEROUS LOAD-DO NOT USE!
+06.0  108    57.77   3111    3009   76671  12508     99.8    0.972  !DANGEROUS LOAD-DO NOT USE!
+08.0  110    58.86   3167    3117   81630  12619     99.9    0.946  !DANGEROUS LOAD-DO NOT USE!
+10.0  112    59.95   3221    3226   86934  12710    100.0    0.920  !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    102    54.50   3063    2916   74509  11767    100.0    0.987  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba    102    54.50   2782    2406   52873  11803     94.0    1.149

Here is the data when allowing for a case capacity of 71.3 grains of water:

Cartridge          : .270 Win. (SAAMI)
Bullet             : .277, 140, Nosler AccuBond 54765
Useable Case Capaci: 63.696 grain H2O = 4.136 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length      : 22.0 inch = 558.8 mm
Powder             : Hodgdon H4350

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   79    45.60   2405    1799   34277  10059     91.5    1.416
-18.0   81    46.74   2462    1885   36463  10366     92.6    1.381
-16.0   83    47.88   2519    1973   38780  10663     93.7    1.342
-14.0   85    49.02   2576    2063   41235  10950     94.6    1.303
-12.0   87    50.16   2633    2155   43837  11226     95.5    1.265
-10.0   89    51.30   2690    2249   46595  11490     96.3    1.228
-08.0   91    52.44   2746    2345   49518  11740     97.1    1.193
-06.0   93    53.58   2803    2442   52618  11977     97.7    1.160
-04.0   95    54.72   2859    2541   55906  12198     98.3    1.127  ! Near Maximum !
-02.0   97    55.86   2915    2641   59395  12403     98.8    1.096  ! Near Maximum !
+00.0   99    57.00   2971    2743   63100  12591     99.2    1.066  ! Near Maximum !
+02.0  101    58.14   3026    2846   67036  12761     99.5    1.037  !DANGEROUS LOAD-DO NOT USE!
+04.0  103    59.28   3081    2951   71221  12912     99.8    1.009  !DANGEROUS LOAD-DO NOT USE!
+06.0  105    60.42   3136    3057   75674  13044     99.9    0.982  !DANGEROUS LOAD-DO NOT USE!
+08.0  107    61.56   3190    3164   80416  13155    100.0    0.956  !DANGEROUS LOAD-DO NOT USE!
+10.0  109    62.70   3244    3272   85471  13249    100.0    0.930  !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     99    57.00   3086    2960   73665  12260    100.0    0.996  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba     99    57.00   2811    2456   52638  12375     94.7    1.158

Either way, 2900 fps should be readily achieved.

 

[Hegland]

I'd say it's worth trying a work-up. Admittedly, I haven't tested H4350 with a 140 bullet weight, but I have yet to see a .270 that doesn't like it with the 130 weight. Mine gives right at 3,000 ticks, and a few weeks ago I poured 5 in a row into a ragged hole. I'm inclined to believe that 2,900 with the 140 is at least within the realm of possibility.

Nevertheless, you've done your homework, and it appears to be on the warm side. Only careful load development will tell for sure. It may be that those 10 extra grains tip the balance toward the slower 4831/RL22 burn rate.

 

[NYDAN]

Oh, I forgot to indicate that the barrel length is 24".

 

[hubcap]

I would be shocked if H4350 did not deliver. I think you will end up very happy with your powder choice. The 24 inch barrel should get to 2900 easy.

 

[DrMike]

Oh, I forgot to indicate that the barrel length is 24".

Add 50-60 fps projection.

 

[NYDAN]

DrMike, thank you for your projections. They are very helpful.

 

[hubcap]

DrMike, thank you for your projections. They are very helpful.

Another thanks Dr. MIke, you are very helpfull with QL.

 

[DrMike]

You gentlemen are most welcome.

 

[bobnob]

I've used H4350 a lot with 150g SSTs. Got all the way to 54.5g of it with no pressure signs, but my 270 Win needs a little more coal on the fire than most. I reckon it has a slightly loosish bore.

I was getting good accuracy and 2970fps out of the 23.5 inch barrel.


In the average rifle I would say work up from about 51g with the 140 AB, to a max around 54 very carefully.


These days I just use H4831 in everything for the 270. 59g with the 140 AB gave me about 2940fps and superb accuracy.

 

[wildgene]

...pretty big jump in burn rates from H4350 to RL-22/ IMR-7828, I think I'd look @ the possibilities of the 4831's/ RL-19, old standards for .270 150gr. loads...

 

[Sas874runner]

I found 59 gr h4831sc and the 140 ab to be a one hole load when I do my part. Most of the time about .5"@100. Speed is 2924. Not screamin but more than enough to hunt with. I am currently working a load for the 150 ablr and magnum powder. I believe this will be my smokin fast and flat load. I have not used 4350 since this load with 4831 has been so accurate and consistent.