.300 Win Mag 200gr Maximum Velocity (with SOMCHEM S385 Powder)

So let me share this weekend's data.

Again, QuickLoad was not accurate, at all...

In the attachment, you will see different loads for my 180gr as well as the 200gr Accubonds.

I used QuickLoad to calculate the Velocity and Pmax based on my SomChem S365 being +0.8% deviation from the standard published burning rate.

There are 3 different charges for the 180's, being 67, 67.5, and 68.5, but note, I used larger internal capacity Norma Cases for an Alternate Load on 68.5gr. The 180grains are numbered 1 through 12.

For the 200grains, I loaded 2 charges, 64.5 and 65.5, also using larger Norma cases for alternate load on 65.5. The 200grains are numbered 13 through 21.

My Chrony was spot on, we cross-checked accuracy with another guys .300 as well, just to ensure the chrony is reporting correctly.

As you can also see, my measured velocities are quite consistent per charge.


So, my question to the QuickLoad Experts:

1. Why is it showing such a big difference in velocity?

2. This means that is is also reporting the Pmax incorrectly?


Another thing we can take from this, is that the larger the internal capacity of the case, the more charge is needed to reach the same velocity as with a smaller capacity case. Thus it is not madness, or "playing with fire" when you end up with a charge well beyond the Powder Manufacturers "Recommended Maximums".

From the SomChem Manual, they have claim to reach Velocity 2713 ft/s using only 63gr S365, and the reason for this is becasue they are using cases with internal volume around as low as 85 to 86gr H2O: http://www.somchemreload.com/search?c=8&f=121

I know this because I have tested PMP Cases as well, the ones we kept from firing Factory Ammo, not bought separately.

Desperatezulu points out about how far from the Published charge I am at, but that that charge only yields 2700 ft/sec on the 200grains.

I would also like Alchemist to help me understand why QuickLoad is showing such inconsistent Velocity and Pressures?

As always, I value everyone's input, positive or negative.

SlushPuppy said:

So, my question to the QuickLoad Experts:

1. Why is it showing such a big difference in velocity?

2. This means that is is also reporting the Pmax incorrectly?

Click to expand...

S365 is unfortunately not great when it comes to consistency between batches. And most recent batches have been below the standard burn rate. So although you've adjusted your burn rate according to the official deviation, you now need to adjust the burn rate again to get QL to match your actual velocities.

Yes, your Pmax will be incorrectly calculated by QL as things stand - lower burn rate means that your actual Pmax should be lower than QL predicted. Once you've adjusted the burn rate to get QL matching your velocities, QL should give you a decent Pmax output too.

Keeping the new burn rate constant and adjusting your powder load to get your desired node velocity is the next step in QL process.

SlushPuppy said:

Desperatezulu points out about how far from the Published charge I am at, but that that charge only yields 2700 ft/sec on the 200grains.

Click to expand...

Yes, I did - and you were using PMP cases at that point, so my caution was well-founded

Obviously with each and every change in the variables, you have a new load which needs testing.

Desperatezulu said:

S365 is unfortunately not great when it comes to consistency between batches. And most recent batches have been below the standard burn rate. So although you've adjusted your burn rate according to the official deviation, you now need to adjust the burn rate again to get QL to match your actual velocities.

Yes, your Pmax will be incorrectly calculated by QL as things stand - lower burn rate means that your actual Pmax should be lower than QL predicted. Once you've adjusted the burn rate to get QL matching your velocities, QL should give you a decent Pmax output too.

Keeping the new burn rate constant and adjusting your powder load to get your desired node velocity is the next step in QL process.

Click to expand...

Can you please guide me here, I would like to understand the burn rate thing so I can properly / safely apply it in the future, Attached is a screenshot of my current load, I have not configured any variables on the Charge Window, except for "Ratio of Specific Heats", which is wrong compared to the Standard Spec from the Somchem Website, the rest are all defaults.

So, QuickLoad is showing 2782fps and 56852 Pmax. Which is obviously wrong, it needs to be 2700fps as tested this weekend.

Which parameters needs tuning to get to correctly reflect 2700fps with this particular load?

I assume its not as easy as just changing the "Heat of Explosion / Potential" and "Ratio of Specific Heats" values, some sort of sclae needs to be applied?

Hi Slushpuppy. QL is not the alfa and omega but will together with the OBT tables optimise your loads for your barrel quickly. What you have done so far is 90 % correct. All you need now is to correct the with the number on Somchem website. Adjust the ratio off specific heat and heat of explosion with S365 on Somchem website. Next , correct the heat of explosion with the specific lot - label under the tin - with the lot's performance.
Once this is done, adjust the burn rate until the speed ( f/s ) reads the same that what you got on the chrony. QL is now calibrated with your barrel length, your case capasity, powder and bullet to the speed measured. Adjust the load until barrel time equals the accuracy node in OBT and you are good to go.

Alchemist said:

Hi Slushpuppy. QL is not the alfa and omega but will together with the OBT tables optimise your loads for your barrel quickly. What you have done so far is 90 % correct. All you need now is to correct the with the number on Somchem website. Adjust the ratio off specific heat and heat of explosion with S365 on Somchem website. Next , correct the heat of explosion with the specific lot - label under the tin - with the lot's performance.
Once this is done, adjust the burn rate until the speed ( f/s ) reads the same that what you got on the chrony. QL is now calibrated with your barrel length, your case capasity, powder and bullet to the speed measured. Adjust the load until barrel time equals the accuracy node in OBT and you are good to go.

Click to expand...

Okay, can you please verify the attached load then?

I increased the "Heat of Explosion" with 0.8% (from 3685 to 3714) as per lot Deviation (bottom of the tin / as also stated on the S365 WebPage for Lot 081).

Also set the "Ratio of Specific Heats" from 1.239 to 1.241 as per the Somchem website.

Then I had to reduce the Burn Rate Factor from 0.4400 to 0.4045 to reach 2700 ft/s.

Hi
Your numbers are correct BUT please verify the speed.
Please verify as your table states 65.5 gr @ 2750 f/s. You need to readjust BR untill speed equals 2750 that you measured. 64.5 gr was 2700.
I was only looking at your QL report and not tables. No 13-15

I have COL 85 mm
Powder 65.5 gr S365 lot 81 @ 2750 Have a look at the tables. 64.5 gr produced 2700 f/s
Case cap 92.5 gr H2O
Barrel 24 "
200 gr Nosler AB 300 Win Mag
My BR =0.4250 @ 65.5 gr 2750 f/s plus 8 f/s for distance between muzzle and chrony.

Please verify the numbers as you mentioned 66.5 gr@2900 f/s in an ealier post.

The accuraccy nodes for a 24" barrel is n6=1.295 ;n7= 1.419. At BT = 1.365 ms you need to go increase the the speed, by increasing the powder, to a barrel time of 1.295ms. This will give you an approx optimal speed / powder combo. Load 3 bullets and chrony again. Recalibrate if required. Next load should be spot on.

My calculation predicts ( based on the data from your tables ) 66.0 gr @ 2775 f/s to be on accuracy node 6 at 1.295 ms

I also use S365 lot 81 and found it slower than stated by Somchem.
PM me if you need more help. Will gladly assist.

Too all the gurus, based on the following load stats from this past weekend:

Bullet: 180gr Nosler Accubond
Barrel Length: 608 mm / 23.937 inches
Case: Hornady (90gr H2O)
COL: 85
Charge: 68.5gr S365 (Lot 81)
Velocity: 2939 ft/s

Bullet: 200gr Nosler Accubond
Barrel Length: 608 mm / 23.937 inches
Case: Norma (92.5gr H2O)
COL: 85
Charge: 65.5gr S365 (Lot 81)
Velocity: 2700 ft/s


Can you please verify that the following loads are SAFE and within pressure limits (don't know if my QL calculations are correct)?


Bullet: 180gr Nosler Accubond
Barrel Length: 608 mm / 23.937 inches
Case: Hornady (90gr H2O)
COL: 85
Charge: 69.5gr S365 (Lot 81)
QL Velocity: 2977 ft/s
QL Pressure: 58555

Bullet: 200gr Nosler Accubond
Barrel Length: 608 mm / 23.937 inches
Case: Norma (92.5gr H2O)
COL: 85
Charge: 67.5 S365 (Lot 81)
QL Velocity: 2774 ft/s
QL Pressure: 53122


Thank you

Hi Stephan. Based on the data supplied your QL numbers corresponds with what I am getting.
Using the calibration data is looks safe. Will email you my QL reports

Thanks for all the help Alchemist!