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big honkin jeep
12-18-2018, 03:05 PM
I'm assembling some reduced loads for the grandson using H4895.
I've talked to the techs at Hodgdon and know I'm within the safe parameters as far as pressure, but was hoping someone could help me with an approximate velocity.
The load is for .308 Winchester using a 125gr Hornady SST over 38.5gr of H4895 with a Winchester LR primer.
We'll be shooting both 16" and 22" barreled rifles with the stocks cut down for the kids.
My rough guess is 2400 but if someone could confirm for me that would be awesome.
The kids have been shooting this load with various 125 and 130Gr bullets but I would like to try and confirm my velocity guesstimate and don't have access to a crony.
Any help appreciated BHJ

CFJunkie
12-18-2018, 04:58 PM
At SAAMI recommended seating depth of 2.800 and case trim length of 2.005:

For a 22 inch barrel:
At 60 deg. F. = 2442 fps and 28537 psi
at 50 deg. F. = 2424 fps and 27963 psi
At 40 deg. F. = 2405 fps and 27408 psi

For a 16 in barrel:

At 60 deg. F. = 2221 fps and 28537 psi
at 50 deg. F. = 2204 fps and 27963 psi
At 40 deg. F. = 2186 fps and 27408 psi

The effects of temperature are essentially linear.
Changing seating depth will change the velocity and pressure but changing the seating depth by 0.01 will only cause a 4 fps change in velocity.
Changing the trim length by 0.01 will change will only cause a 4 fps change in velocity.
Increasing seating depth decreases velocity and pressure and increasing trim length increases velocity and pressure.

bigedp51
12-18-2018, 08:22 PM
The first thing you do with Quickload is enter the correct case capacity of a fired case from your rifle. Quickload defaults to the lowest case capacity and as a example with .223/5.56 cases it can cause a 5,000 psi difference in chamber pressure.

The second thing you do "IF" you have a chronograph is change the burn rate in Quickload until the velocity matches the chronograph.

After doing the above the Quickload chamber pressure "estimates" will be closer to actual chamber pressure.

There are simply too many variables in reloading components and firearms for accurate Quickload readings unless it is tweaked and adjusted.

big honkin jeep
12-18-2018, 11:58 PM
Thanks a ton for the responses.
I had some loose data from several sources that I had used to guesstimate velocity. Looks like I guessed pretty close and I thank you for the rough confirmation.
The load of 38.5gr H4895 in .308 Winchester even though reduced is well above the absolute minimum of 29.4 Gr of H4895 for a 125Gr SP , as calculated using the Hodgdon (H4895 only) 60% of max reduced load formula. All the kids in the extended family love to shoot them. Very very mild recoil and muzzle blast as compared to full hunting loads and factory stuff. Still have plenty enough giddy up to take deer cleanly at reasonable hunting distances. We've used the 130 TTSX and 125 NBTs with good success and I'm hoping the 125gr SSTs will provide equivalent performance since they're much more economical.
I've gotten where I love to shoot them myself and may try to tune up a reduced recoil accuracy load soon.
Thanks again BHJ