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

[SlushPuppy]

Hi,

So I bought the "Reloading Powders - Ballistic Data Manual" from Rheinmetall Denel / SOMCHEM.

Checking the load data for the .300 Win Mag for 200gr Bullets using S385 Powder, the Maximum Powder load is 68.7gr.

This gets the projectile up to 2720 ft/s, I find this relatively slow compared to other hand loads I have seen around the internet as well as compared to good quality factory ammo.

Surely a 200gr Bullet should measure around 2900 ft/s at the muzzle, and not 2700?

Hopefully someone can shed some light on this, or have experience with this load I'm planning to do.

Thanks

 

[Shootist43]

Hornady lists several loads for 200 Gr. bullets at over 2900fps. Look for a Powder Burning Rate Chart and find what Somchem powder is close to the powders Hornady has listed. You need to be cautious when doing this because even though the powders may have the same burning rate they are not identical. I corresponded with an AH member about 6 months ago his AH name is Alchemist. He is a reloader that lives in Pretoria. Perhaps he can help you

 

[JimP]

If you reload a lot or even just a little you will find that this is quite common. A lot of powders reach maximum pressures quicker than others and at lower velocities and to load that powder to the velocity that you want to shoot could and can be dangerous.

So to fix the problem pick another powder that will reach your velocity that you want to shoot instead of one that doesn't

 

[PeteG]

Check with PMP, their African Elite is a 200gr AFrame at +-2800fps.
RSA powders are not great for speed according to the Somchem datasheets...

 

[gillettehunter]

With a custom 26 inch barrel and a rem action I'm getting a 215 gr Berger hybrid moving at 2980 FPS. Using H-1000. Retumbo can also work well. Don't know what powders you have access to.... Slow burning ones seem to work well in the .300 Win Mag. Bruce

 

[RolandtheHeadless]

Regardless of what the manuals say, I've never been able to get more than around 2,800 fps from my Ruger M77 .300 WM, 24" barrel, without signs of excess pressure.

 

[SlushPuppy]

Thanks for all the info peeps.

The reason I'm considering a "Higher" Velocity Load, and not just settling for a more Practical (worry free) 2500ft/s is because of the shot distances in the areas I hunt.

250 meter+ shots are not uncommon on some big game (an Eland this time), thus I'm looking for that extra advantage in Trajectory and Bullet Energy by using a "Higher" Velocity Load.

This must of course still be a safe load with proper accuracy in my new Howa .300 Win Mag (24" Barrel).

So for the load, I'm using PMP Casings (used once before), proper Magnum Primers, SOMCHEM S385 Powder, and Nosler Accubond 200gr Bullets.

I will share my results here once I start testing the loads.

 

[PHOENIX PHIL]

I have found the Accubonds like to be seated long in regards to accuracy. I would suggest determining the maximum COAL with this bullet in your rifle. This would give you just a bit more room for powder and perhaps help you reach your velocity goal.

 

[Buckdog]

i shoot 200 gr accubonds in 300 win mag behind alot of h1000 it is a compressed load and probably over pressure as it pushes them along at 3050 fps. just shot 22 animals in africa with it and i can tell you it works quite well thru and thru on zebra and eland! Literally lifted a kudu off the ground straight on at 50 yds! PM me if you want the exact grains of powder and Phil is correct accubonds like to be seated out close to the lands. zero the gun at 200yds will be about 1.5 inch high at 100 and about 6 inch low at 300. all the PH I ran into like 300 mags for plains game very much.

 

[Desperatezulu]

So for the load, I'm using PMP Casings (used once before).

I shoot the 200gr Accubonds in my 300 H&H, so pretty similar to the WM. For starters using PMP cases is an issue - they typically have the thickest case walls of virtually any manufacturer. This means smaller internal volume, which equals faster pressure spike on ignition. So you're going to reach the pressure max long before you get close to the velocities you're talking about. In fact I wouldn't be surprised if you're reach max pressure at 2500-2600 f/s with those cases. Using S385 exacerbates the problem because you approach 100% case fill with this powder in 'normal' cases - maybe S365 would work better with the PMP cases?

So step one if you're chasing velocity - buy better quality cases. Norma is a good place to start. Next step is to accept that your max velocity is going to be much lower than 2900f/s - or it should be if you're staying within acceptable pressures in a 24" barrel. I get around 2800f/s or just under in my H&H so the winmag is going to be similar. With the local SA powders you need a much longer barrel to chase those high velocities. Maybe with a 30+ inch barrel 2900f/s would be achievable safely using S385.

Alternatively, shoot a 180gr mono which will give higher speeds and similar ballistics to the 200gr AB. Something like a Peregrine VRG4 180gr might be ideal. You should get 3000f/s without too much effort and do so safely.

One final comment on the Accubonds - I have never got great groups with the 200gr's. 200gr Barnes TSX, A-Frames and Peregrine have all worked much better for me. This may be a function of my reloading technique or my gun (or my shooting!) Just throwing it out there in case you struggle with the AB groupings.

 

[Shootist43]

Given your limited powder choices many of the options and loads mentioned by AH members living elsewhere are of limited value. Your best sources of information will be from guys that live in South Africa or near by countries that are "forced" to use Somchem powders. As "Desperatezulu" suggests you may have to seek a viable alternate to your desired load.

 

[Alchemist]

The Somchem powders are generally much slower than there American equivalents. You can get info on www.somchemreload.co.za .
I use Quickload to assist me with my reloads and Somchem powder.
You can also email Manie Johannes at Somchem for assistance. He is extremely helpful. Emanuel.Johannes@rheinmetall-denelmunition.com

 

[SlushPuppy]

This means smaller internal volume, which equals faster pressure spike on ignition. So you're going to reach the pressure max long before you get close to the velocities you're talking about. In fact I wouldn't be surprised if you're reach max pressure at 2500-2600 f/s with those cases. Using S385 exacerbates the problem because you approach 100% case fill with this powder in 'normal' cases - maybe S365 would work better with the PMP cases?

The thicker walls also mean that less powder is needed to reach the same pressures as a thin wall case with slightly more powder charge.

I see the S365 Powder have very similar properties as the S385, and less grains of powder needed, so this might be a good alternative.

What would be the best method of determining excess pressure?

 

[Desperatezulu]

The thicker walls also mean that less powder is needed to reach the same pressures as a thin wall case with slightly more powder charge.

Simplistically, yes - but remember this is a dynamic situation. It's not a case of building the pressure to a particular point (like a balloon) and then the bullet pops out at the desired velocity. It's all about the pressure curve, or the rate at which pressure builds. S385 is the slowest of the Somchem powders (other than B12.7, which is not widely available) which means that it reaches it's Pmax more slowly and also requires more mass of powder to reach Pmax, all else being equal. Pistol/shotgun powders being at the other extreme - burning fast and having a sharp pressure curve.

The smaller the internal volume of your (fire-formed) case, the faster you're going to reach Pmax for the same powder charge. Using S365 because it requires less volume is going to move you in completely the wrong direction; the reduced internal volume and faster burning powder has all the makings of excessive pressure.

I see the S365 Powder have very similar properties as the S385, and less grains of powder needed, so this might be a good alternative.

As per my answer above, yes and no. S365 can certainly get you to the same, or higher Pmax, but does so fast (it's faster burning than S385) so the risk of excessive pressure is that much greater. People in SA can and do use S365 successfully in the 300 mags, but typically for the lighter bullets. All the theory points towards S385 being better suited, especially for heavier (i.e. 200gr plus) bullets. For consistency, you aspire to 100% case fill or slightly over - that's not going to happen with S365.

What would be the best method of determining excess pressure?

The absolute best way is to avoid excess pressure!!! A well-known method that gets the message across first time, every time, is losing a thumb when the chamber blows out I've heard even the sloppiest reloader doesn't fail to learn from that method..

Best practical way is to chrony your loads - start fairly low and build your way up. Use Quickload to calculate pressures and keep you within Pmax. Quickload can also be used to get you onto an accuracy node, which is ultimately what you're striving for. Max velocity is academic if the load won't group - so you need to get onto your highest accuracy node within the Pmax limit for your calibre. Forget about chasing the highest velocity possible. QL takes into account barrel length, internal case capacity etc - remember garbage in = garbage out, so you would need to measure all the variables accurately to get the most out.

The best technical solution to determine pressure is using a specialised test rig with strain gauges etc but that's not practical for the layman.

 

[Shootist43]

Once again Desperatezulu has given you some very sage advice. I have been PMing Alchemist for almost a year on the identical topic but for a different caliber i.e. 6.5 x 55. I see that he mentioned several options for you to contact knowledgeable reloaders about your questions/desires. Have you gotten in touch with any of them?

There are some signs of excess pressure that might be of service to you. Namely flattened primers and or difficulty in immediate extraction. Exceeding published/recommended loading data is a risky venture, unless there is sufficient reason for doing so. Even then it would be best to use a slightly more powerful load that has been tried and proven by someone else. There are a lot of variables that might make a given load safe for one gun that could prove very damaging and or unsafe in another firearm. I remember Alchemist telling me that Somchem Powders are not necessarily consistent lot to lot. If that is the case, loads that worked well in the past may need to be tweeked a little to yield similar results. I never just use somebody's "pet" load that exceeds published data. I back off 2 or 3 grains and load between five and ten rounds to see how they group and pay particular attention to the possibility of flattened primers and or difficult extraction. Sometimes published data is the best you are going to achieve. Good luck, keep us posted as to your findings.

 

[Alchemist]

I found some data when I assist a gentleman in SA to load Hornady 165gr SST using S385 ( can not find the lot no ) for his 300 Win Mag. Using the data in QuickLoad I tried to see if 2800 f/s would be achievable. I know the QL calibration would not be 100 % accurate as I do not have your case capacity, speed through your rifle etc.
QL predicted with the data I had that a max speed of 2820 f/s @ 62,942 Psi.

The above is basically what we see with Somchem powders. We can not get to the same speed as the US powders. Our lot differences are also huge. In my 30-06 I had to add 2 gr more to achieve the same result for my last loads.

My suggestion is to rather use the US powders if it is available or maybe look at a faster powder like S365. The data I have for S365 was 180 gr SST @ 2788 f/s and a pressure of 50,646 Psi. You might be able to get close to 2900 f/s and still have reasonable pressure.
Attached is the two QL reports I did for him

 

[Shootist43]

Slush Puppy, I may just be reading between the lines here but several accomplished reloaders have cautioned you against trying to push a 200 Gr bullet to 2900fps with Somchem powders in your 300 Win. Mag. I think you would do well to heed their advice. It looks like your best bet is going to be a 180 Gr bullet. It is much better to be safe than sorry.

 

[SlushPuppy]

So I shot my first batch of hand loads this past weekend, I used both SOMCHEM 385 and SOMCHEM 365 Powder on the 180gr and 200gr AccuBonds. My PMP Cases average at around 86gr H2O internal volume. I used QuickLoad to guide me with both powders. I loaded multiple charge batches of 4 bullets ranging from medium to maximum charges, based on SOMCHEM recommendations, as well as keeping an eye on QuickLoad Pmax.

From my groupings, it was clear that my rifle likes the S 365 Powder way better. Best grouping for the day was with the 180gr AB using 66gr S365 @ 3008ft/s (as measured with a chrony).

For the 200gr AB, I had the best grouping with 63gr S365 @ 2730ft/s (chrony). Although this grouping was not as good as what I managed with the 180gr.

So far, the 180gr AB seem to be the most accurate in my rifle.

I've tweaked the loads for the 180gr and 200gr ABs to see if I can get better groupings, if I continue struggling with properly grouping the 200gr, I'll stop shooting them and focus on getting the best possible groupings with the 180gr, which looks to be "the one" at this stage.

Also playing with seating depths now to see its effect.

Will update again soon.

 

[Clayton]

Sounds like you're on the right track.

 

[Alexandro Faria]

RSA powders are mild, to put it politely. As usual, we're behind the rest of the world. Like a cape townian driving in Joburg: Nice and slow...