7.62x39 123gr FP using H4895 for Subsonic Load?

[Rottentofu]

Is it possible to create a subsonic load for 7.62x39 with H4895? This will be for a bolt action, so no need to worry about cycling.

[ar15barrels]

You could try loading 12gr which would get you around 1040fps in a 20" barrel, but you are only getting 40% powder burn at the 6346psi peak chamber pressure.

Cartridge          : 7.62 x 39 (M43) Russ.
Bullet             : .310, 123, Hornady SP 3140
Cartridge O.A.L. L6: 2.190 inch or 55.63 mm
Barrel Length      : 20.0 inch or 508.0 mm
Powder             : Hodgdon H4895

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.676% 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

-06.8   40    11.19    998     272    5824    969     41.5    2.530
-06.1   40    11.27   1002     274    5859    979     41.6    2.521
-05.4   40    11.35   1006     277    5896    988     41.7    2.512
-04.7   41    11.43   1010     279    5933    998     41.8    2.504
-04.1   41    11.51   1014     281    5970   1008     42.0    2.495
-03.4   41    11.59   1018     283    6007   1018     42.1    2.487
-02.7   42    11.68   1022     285    6045   1028     42.2    2.478
-02.0   42    11.76   1026     288    6083   1038     42.3    2.470
-01.4   42    11.84   1030     290    6121   1048     42.4    2.461
-00.7   42    11.92   1034     292    6161   1058     42.5    2.453
+00.0   43    12.00   1039     295    6199   1068     42.6    2.445
+00.7   43    12.08   1043     297    6238   1079     42.7    2.437
+01.4   43    12.16   1047     299    6280   1089     42.8    2.428
+02.0   44    12.24   1051     302    6321   1099     42.9    2.420
+02.7   44    12.32   1055     304    6361   1110     43.1    2.412
+03.4   44    12.41   1059     306    6403   1121     43.2    2.404

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     43    12.00   1057     305    6351   1117     44.4    2.414
Data for burning rate decreased by 3% relative to nominal value:
-Ba     43    12.00   1020     284    6053   1021     40.8    2.477

[ar15barrels]

I would be more tempted to try blue dot as you will get a better percentage of burn, which means it's not so dirty.

Cartridge          : 7.62 x 39 (M43) Russ.
Bullet             : .310, 123, Hornady SP 3140
Cartridge O.A.L. L6: 2.190 inch or 55.63 mm
Barrel Length      : 20.0 inch or 508.0 mm
Powder             : Alliant BLUE DOT

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.676% 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

-06.8   26     6.06    988     267    6269   1315     82.9    2.767
-06.1   26     6.10    995     271    6341   1327     83.1    2.744
-05.4   26     6.15   1002     274    6412   1339     83.4    2.722
-04.7   26     6.19   1009     278    6484   1351     83.7    2.700
-04.1   26     6.24   1016     282    6556   1363     83.9    2.678
-03.4   27     6.28   1023     286    6628   1374     84.2    2.657
-02.7   27     6.32   1029     289    6701   1386     84.4    2.637
-02.0   27     6.37   1036     293    6774   1398     84.7    2.617
-01.4   27     6.41   1043     297    6847   1410     84.9    2.598
-00.7   27     6.46   1049     301    6921   1422     85.2    2.579
+00.0   28     6.50   1056     304    6995   1433     85.4    2.560
+00.7   28     6.54   1062     308    7069   1445     85.7    2.542
+01.4   28     6.59   1069     312    7144   1457     85.9    2.524
+02.0   28     6.63   1076     316    7218   1469     86.1    2.507
+02.7   28     6.68   1082     320    7294   1480     86.4    2.490
+03.4   28     6.72   1088     324    7369   1492     86.6    2.474

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     28     6.50   1077     317    7218   1460     87.5    2.516
Data for burning rate decreased by 3% relative to nominal value:
-Ba     28     6.50   1034     292    6778   1404     83.2    2.607

I don't have trail boss in my powders file, but that would do a much better job of filling the case and keeping the pressure/velocity down.

[Rottentofu]

I only have H4895 so I can only work with what I have. Thank you for the data.

[ar15barrels]

I only have H4895 so I can only work with what I have. Thank you for the data.

That's not data.
That's simulations.
Watch out for detonation due to powder location since you would only be filling the case about 40%.
Putting a little cottonball in the case to hold the powder by the primer might not be a bad idea.

More than half your powder is not going to burn so 4895 is going to be very messy.

[Rottentofu]

That's not data.
That's simulations.
Watch out for detonation due to powder location since you would only be filling the case about 40%.
Putting a little cottonball in the case to hold the powder by the primer might not be a bad idea.

More than half your powder is not going to burn so 4895 is going to be very messy.

Is detonation dangerous?

[JagerDog]

That's not data.
That's simulations.
Watch out for detonation due to powder location since you would only be filling the case about 40%.
Putting a little cottonball in the case to hold the powder by the primer might not be a bad idea.

More than half your powder is not going to burn so 4895 is going to be very messy.

I know there's .223 loads using powders like Red Dot which are made as AR15 suggests.

Get the right type of powder.

[ar15barrels]

Is detonation dangerous?

Yes.

The sure way to avoid detonation is to be sure you fill the case at least 75% or so without exceeding recommended pressures.

Detonation occurs when you have very little powder in a case, perhaps 30-50% and the powder is laying on the side of the case as the primer flash comes across the top of the powder.
Instead of starting in the middle and burning outwards, the powder starts on both ends and burns into the middle.
The resulting pressure wave instantaneously disassembles firearms in a spectacular manner.

Some examples:

[Rottentofu]

Yes.

The sure way to avoid detonation is to be sure you fill the case at least 75% or so without exceeding recommended pressures.

Detonation occurs when you have very little powder in a case, perhaps 30-50% and the powder is laying on the side of the case as the primer flash comes across the top of the powder.
Instead of starting in the middle and burning outwards, the powder starts on both ends and burns into the middle.
The resulting pressure wave instantaneously disassembles firearms in a spectacular manner.

Some examples:

Holy crap. I don't think I will risk something like that.

[McGuiver]

7.62x39 123gr FP using H4895 for Subsonic Load?

What weight projectile are you shooting? 123gr?

Why not go heavier for subsonics?

Do yourself a favor and pick up some Trail Boss powder for these light bullets.


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[J-cat]

Heavier bullets are not always an option due to the twist rate. Subsonics need a faster twist to stabilize and produce good accuracy.

Trail boss is better for this than H4895.

[JagerDog]

Heavier bullets are not always an option due to the twist rate. Subsonics need a faster twist to stabilize and produce good accuracy.

Trail boss is better for this than H4895.

I've read a bit where turning the bullet backwards can help to stabilize heavy bullets in a twist rate that's not accommodating.

[ar15barrels]

Holy crap. I don't think I will risk something like that.

That's what can happen when you use the wrong powder.
If you stick to reloading manuals, they have chosen the powders that would not do that.

[kevins750]

I have used unique in my AR

[McGuiver]

7.62x39 123gr FP using H4895 for Subsonic Load?

Is it possible to create a subsonic load for 7.62x39 with H4895? This will be for a bolt action, so no need to worry about cycling.

What twist rate is your barrel?

My Saiga AK-47 has a 1:9.44 twist rate. Most other bolt actions are 1:9, 1:9.5 or 1:10. How heavy of a bullet do you want to shoot?

Here is a good bullet stability calculator.

http://www.bergerbullets.com/twist-rate-calculator/

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