Newbie Question: IMR4198 for 300 AAC Blackout Supersonic loads. Is it possible?

[SpaceMan]

I haven't been very successful in my quest for powder lately, but I have a large amount of IMR4198 stocked up for my .450 Marlin loads. I only see load data for subsonic loads using the 4198 and it seems no one has tried supersonics with it when google searching.

From the info I've gathered the problem is with the burn rate of the IMR4198 being too slow. At the same time, all the load data I've ever found for 300 BLK was tested with short barrels ranging in length from 9" - 11", causing the need for a quick burn. I assume that IMR4198 makes for good subsonic loads due to the slower moving bullet having more time in the barrel allowing the powder charge to burn. I do notice that the subsonic loads with IMR4198 only reach 25,000 psi where other powders create 40,000+ psi. Does IMR4198 not create much pressure or is that just a characteristic of subsonic loads?

I'm using a 16" barrel (14.5" with a welded muzzle device) on my build. I'll be using 120-150gr jacketed projectiles. With a longer barrel there would be more time for the powder to burn. Would this allow me to use a slower burning powder successfully? And will simply upping the subsonic charge to a more suitable supersonic charge weight give me more pressure to cycle? Is the problem with IMR4198 in supersonic 300 blk loads something totally different than what I'm thinking?

I've only been consitantly reloading for a short while so please don't be offended by my lack of knowledge. Educate me.

[SpaceMan]

Anyone?

[SKSDan]

I have a good load for 7.62x39 with imr4198. I'm not sure about the difference in case volume.

[alfred1222]

I use IMR4198 for my 223 loads

[SpaceMan]

Case volume is way less in a 300 blk cartridge. Limited to about 14-15 grains of powder and I believe that is a compressed load.

I think I found the answer, I posted my question on another forum as well.

The predominant problem seems to be limited useable case volume. It is not friendly for using a relatively low energy density powder.
IMR 4198 has a potential energy density of 3910 Kilojoules per Kilogram. IMR 4227 (a more suitable powder for this config) has a potential energy density of 4040 Kilojoules per Kilogram.

[ar15barrels]

Cartridge          : .300-221 (300 Whisper)
Bullet             : .308, 110, Hornady V-MAX 23010
Cartridge O.A.L. L6: 2.100 inch or 53.34 mm
Barrel Length      : 16.0 inch or 406.4 mm
Powder             : IMR 4198

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.22% 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

-12.2  104    18.00   1910     891   29215   3900     79.3    1.050
-11.0  105    18.25   1936     916   30336   3980     80.1    1.034
-09.8  107    18.50   1963     941   31503   4059     80.9    1.018
-08.5  108    18.75   1990     967   32721   4138     81.6    1.002
-07.3  109    19.00   2017     994   33990   4215     82.4    0.987
-06.1  111    19.25   2045    1021   35315   4292     83.2    0.971
-04.9  112    19.50   2072    1049   36696   4369     83.9    0.956
-03.7  114    19.75   2100    1077   38138   4444     84.7    0.941
-02.4  115    20.00   2127    1105   39646   4518     85.4    0.925
-01.2  117    20.25   2155    1134   41220   4591     86.1    0.909
+00.0  118    20.50   2183    1164   42868   4663     86.8    0.894
+01.2  120    20.75   2211    1194   44591   4734     87.5    0.879  ! Near Maximum !
+02.4  121    21.00   2240    1225   46392   4803     88.2    0.865  ! Near Maximum !
+03.7  122    21.25   2268    1256   48284   4871     88.8    0.850  ! Near Maximum !
+04.9  124    21.50   2296    1288   50265   4937     89.5    0.836  !DANGEROUS LOAD-DO NOT USE!
+06.1  125    21.75   2325    1320   52342   5001     90.1    0.822  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 3% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 3% relative to nominal value:
+Ba    118    20.50   2226    1211   45077   4758     89.2    0.874  ! Near Maximum !
Data for burning rate decreased by 3% relative to nominal value:
-Ba    118    20.50   2138    1116   40711   4551     84.2    0.916

Cartridge          : .300-221 (300 Whisper)
Bullet             : .308, 150, Hornady SP 3031
Cartridge O.A.L. L6: 2.200 inch or 55.88 mm
Barrel Length      : 16.0 inch or 406.4 mm
Powder             : IMR 4198

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.316% 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

-13.2   97    16.50   1690     952   30585   4011     87.7    1.189
-11.8   99    16.75   1715     979   31804   4088     88.4    1.169
-10.5  100    17.00   1739    1007   33068   4165     89.2    1.150
-09.2  102    17.25   1764    1036   34395   4240     89.8    1.131
-07.9  103    17.50   1788    1065   35773   4313     90.5    1.113
-06.6  105    17.75   1813    1095   37188   4385     91.2    1.094
-05.3  106    18.00   1837    1125   38704   4456     91.8    1.076
-03.9  108    18.25   1862    1155   40265   4525     92.4    1.057
-02.6  109    18.50   1887    1186   41893   4593     93.0    1.039
-01.3  111    18.75   1912    1217   43595   4658     93.6    1.021  ! Near Maximum !
+00.0  112    19.00   1936    1249   45371   4722     94.1    1.004  ! Near Maximum !
+01.3  114    19.25   1961    1281   47226   4783     94.6    0.987  ! Near Maximum !
+02.6  115    19.50   1986    1314   49166   4843     95.1    0.970  ! Near Maximum !
+03.9  117    19.75   2011    1347   51195   4900     95.6    0.954  !DANGEROUS LOAD-DO NOT USE!
+05.3  118    20.00   2036    1380   53317   4955     96.0    0.938  !DANGEROUS LOAD-DO NOT USE!
+06.6  120    20.25   2060    1414   55541   5008     96.5    0.922  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 3% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 3% relative to nominal value:
+Ba    112    19.00   1969    1291   47704   4759     95.8    0.982  ! Near Maximum !
Data for burning rate decreased by 3% relative to nominal value:
-Ba    112    19.00   1902    1204   43093   4664     92.1    1.027

[ar15barrels]

the flatpoint 30-30 bullets are interesting...

Cartridge          : .300-221 (300 Whisper)
Bullet             : .308, 170, Hornady FP 3060
Cartridge O.A.L. L6: 2.250 inch or 57.15 mm
Barrel Length      : 16.0 inch or 406.4 mm
Powder             : IMR 4198

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.389% 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

-13.9   91    15.50   1559     918   28669   3885     89.5    1.297
-12.5   93    15.75   1582     945   29816   3962     90.2    1.275
-11.1   94    16.00   1606     973   31018   4039     90.9    1.254
-09.7   96    16.25   1629    1002   32264   4113     91.5    1.233
-08.3   97    16.50   1652    1030   33561   4187     92.2    1.212
-06.9   99    16.75   1675    1060   34909   4259     92.8    1.192
-05.6  100    17.00   1699    1089   36312   4329     93.4    1.172
-04.2  102    17.25   1722    1119   37776   4397     93.9    1.152
-02.8  103    17.50   1745    1150   39299   4464     94.5    1.132
-01.4  105    17.75   1768    1180   40887   4529     95.0    1.112
+00.0  106    18.00   1792    1212   42542   4591     95.5    1.093
+01.4  108    18.25   1815    1243   44267   4652     96.0    1.075  ! Near Maximum !
+02.8  109    18.50   1838    1275   46068   4710     96.4    1.057  ! Near Maximum !
+04.2  111    18.75   1861    1308   47946   4767     96.8    1.039  ! Near Maximum !
+05.6  112    19.00   1884    1340   49908   4821     97.2    1.021  ! Near Maximum !
+06.9  114    19.25   1908    1374   51957   4872     97.6    1.004  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 3% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 3% relative to nominal value:
+Ba    106    18.00   1820    1250   44707   4614     97.0    1.070  ! Near Maximum !
Data for burning rate decreased by 3% relative to nominal value:
-Ba    106    18.00   1761    1171   40426   4549     93.7    1.118

[stilly]

Cool numbers! Is that from quick load?

[ar15barrels]

Cool numbers! Is that from quick load?

Yes.

[SpaceMan]

Thank you! I need to get me some of that software!