Could use a little Quickload assistance with 458 Socom Subs

[daviscustom]

Hoping somebody can help me out with a starting load. I would like to work up a load for a 500 grn cast bullet, using Starline brass, large pistol primers (federal), and Red Dot. I would consider switching to magnum large pistol primers, as I have seen that recommended for more consistent ignition in sub loads. Wanting to shoot for about 1050 fps out of a 16.5" barrel. Ballistic coefficient is listed as 0.447 by LEE if it makes any difference.

There may be other more ideal powders, but I have a bunch of this so I would like to start here....I have seen it recommended as one of the suitable choices.

Thanks for your help.

[johndoe3]

max chamber pressure is 35,000psi for the 458 Socom.

With Red Dot, from Quickload a 10.5 gr is at 35,000 psi, and that only gives an estimated 982 fps. It shows that Red Dot is too fast a powder for your intended use. This is a very rough estimate because I don't know your COAL and exact bullet shape. Start load should be 10.0gr.

The Red Dot load at max chamber pressure and 950-980fps is going to be louder than the powders below at 1050 fps. It's because loudness is somewhat proportional to the chamber pressure used to achieve the velocity.

Much better choices for powder are (that will give at or near 100% burn in the barrel and 1050 fps, at chamber pressures below the max):
Lil Gun
H110
H4227
VV N110

Let me know if you have alternative powders to Red Dot on hand, and I can give you an approximate load for it/them.

[daviscustom]

I will have to check my powder supply to see what else I have on hand. I am getting ready for work so I will have to get back to you later. Then I can check OAL on the bullet and cartridge. This is the bullet mold I am using, I also made one into a hollow point version.....but it is a semi-pointed round nose:

http://www.midwayusa.com/product/214596 ... uctFinding


Thanks for the info. I have a couple of lighter jacketed bullets to try out for higher velocity too if you are feeling generous, but the main thing that is hard to find is sub info.

Thanks again. My barreled action is supposed to be shipping out to me this week. I have a lot of stock work to do yet, but I wanted to start getting ready.

[daviscustom]

OAL on the cartridge is 2.259", the bullet is 1.4".

Powders I have on hand:
Bullseye
Unique
2400
Red Dot
Green Dot
H322
4831
IMR 4064


If none of these will work very well, then I guess I would be curious which powders with give me the most complete burn and lowest pressure to reach the target velocity.
I recall seeing Trailboss suggested....how does it stack up?

[johndoe3]

It was fairly quick to do it all in Quickload, once everything was set up for the cartridge, barrel length and bullet. It's just a matter then of selecting the powder in the drop down menu and changing the load. Since I would have to type in the info here, I thought it would be just as time efficient to type in a table in Open Office and make that a graphic file to post here. You can save the table graphic below and have the info without copying anything, by right clicking on it and save image.

Burn rate is from the IMR website. http://www.imrpowder.com/burn-rate.html



Satisfactory powders for 458 Socom subsonic: Bullseye, Unique, 2400

Unsatisfactory powders:
1. Red Dot and Green Dot because at max chamber pressure, they yield velocities below your desired 1050 fps.

2. H322 because only 73.3% burn in barrel, and if a supressor is used it will fill up with unburnt powder. Same with 4831 with 37.4% burn in barrel, and IMR 4064 with 66.9% burn in barrel. These powders are all too slow.

3. Trailboss because with 100% fill, you can only get 832 fps; you cannot get enough in the case to work with this cartridge.

[daviscustom]

Wow, thank you for your time to put that together. You are obviously more experienced and comfortable building tables and such then I am. So would you think that 2400 might be the one to start with since it is almost half as much pressure developed?....I would suppose a 2% difference in burn is not a big deal in exchange for half the pressure, but I do have more Bullseye on hand to play with out of the three.

That you again for your help, this is great info to have. I am going to have to look into getting Quickload.

[johndoe3]

Personally, the % burn in the barrel is far more important for defensive loads in pistols, because most defensive gun uses are at night and getting 100% burn in a pistol minimizes any fireball that would ruin your night vision for follow up shots. Most people ignore % of burn in rifles, although shooting subsonic rifle at night with night vision equipment would greatly benefit from 100% burn in the barrel.

The 98.1% burn in barrel for 2400 powder is almost 100%, so of course it is a good choice, coupled with lower chamber pressure. Without a suppressor it would be just a small fireball at night, and with a suppressor probably none visual. However, it's your choice on powder usage, and using what you have a lot of on hand is a decent way to approach it.

Note on the Quickload program:
Keep in mind that these data points are a simulation in Quickload. We can fine tune the accuracy of Quickload much more by having the exact water (H2O) capacity of your brass, but I just used the default for 458 Socom. We get the H2O capacity by leaving the primer in the brass and resizing it. Then weigh the brass empty and then fill with water to even with the top and weigh it. The H2O capacity in grains is the difference in weights. I use 5 cases and average the results, and you only have to do this one time. With rifle brass there can be a significant variation of water capacity between different manufacturers of brass. However, with pistol brass there isn't generally as much difference in H2O capacity between manufacturers. The differences in internal volume of the brass affects the chamber pressure output in the program.

In this way and others a user of Quickload fine tunes the program and the results then are remarkably close to real world measurements. For example, in .308 with full power loads, my fine-tuned setup in Quickload yields results within 15-20 fps of actual chronographed full power loads.

I suppose like all modeling programs, Quickload gives more accurate results the better all the parameters are set. It's not magic, and using default settings is less accurate than fine-tuned settings for the program. For a reloader, using Quickload allows a person to quickly choose optimal powders from simulated results that aren't available any other way. I seldom look at any printed loading manuals anymore, because to me Quickload yields superior info (although once in a while I will compare a load in a printed loading manual against Quickload to check and make sure I am not screwing up the simulation).

[daviscustom]

Do you think the difference in pressure will translate into a difference in the recoil impulse? Just wondering if the 2400 might be a more gradual build up....not as sharp. I realize we are dealing with the same size bullet and the same velocity, but if it doesn't accelerate all at once it might not thump as bad.

How far below these loads would you recommend starting?.....I assume 10% under? Don't want to have to drive a bullet out of the barrel if I start too low. I have time so I could go ahead and measure my case capacity to get things dialed in a little better.

What kind of velocity can I get with this bullet with 2400 before I max out on pressure? Looks like it has the most available case capacity. I am sure there are probably better powder choices for making this one go fast though. I can also not seat the bullet as deep and feed them one at a time to gain case capacity if I max out on capacity before I get to 35K psi.

[johndoe3]

Do you think the difference in pressure will translate into a difference in the recoil impulse? Just wondering if the 2400 might be a more gradual build up....not as sharp. I realize we are dealing with the same size bullet and the same velocity, but if it doesn't accelerate all at once it might not thump as bad.

Yes. Quickload has the impulse charts and indepth recoil measurements; but I'm too lazy to make up graphics to show you. Comparing Bullseye and 2400 at 1050 fps, Bullseye has a sharper pressure curve (a peak in pressure at half the barrel travel of 2400). So your assumption is valid, although I don't know if that translates into significant real world difference in felt recoil.

How far below these loads would you recommend starting?.....I assume 10% under? Don't want to have to drive a bullet out of the barrel if I start too low. I have time so I could go ahead and measure my case capacity to get things dialed in a little better.

I assume no liability for your choices and actions. As a reloader yourself, I'm sure you can decide what are suitable actions to take.

What kind of velocity can I get with this bullet with 2400 before I max out on pressure? Looks like it has the most available case capacity. I am sure there are probably better powder choices for making this one go fast though. I can also not seat the bullet as deep and feed them one at a time to gain case capacity if I max out on capacity before I get to 35K psi.

Max velocity for a 500gr bullet with 2400 powder at max chamber pressure is 1297 fps (20.9gr).

The 3 most optimal powders for velocity with a 500gr bullet in 458 Socom are:
Lil Gun 1373 fps
H110 1361 fps
H4227 1354 fps

[Bendersquint]

The 458SOCOM was submitted but at this point it is NOT SAAMI approved.

Where are you getting these SAAMI specs for pressure?

[daviscustom]

Do you think the difference in pressure will translate into a difference in the recoil impulse? Just wondering if the 2400 might be a more gradual build up....not as sharp. I realize we are dealing with the same size bullet and the same velocity, but if it doesn't accelerate all at once it might not thump as bad.

Yes. Quickload has the impulse charts and indepth recoil measurements; but I'm too lazy to make up graphics to show you. Comparing Bullseye and 2400 at 1050 fps, Bullseye has a sharper pressure curve (a peak in pressure at half the barrel travel of 2400). So your assumption is valid, although I don't know if that translates into significant real world difference in felt recoil.

How far below these loads would you recommend starting?.....I assume 10% under? Don't want to have to drive a bullet out of the barrel if I start too low. I have time so I could go ahead and measure my case capacity to get things dialed in a little better.

I assume no liability for your choices and actions. As a reloader yourself, I'm sure you can decide what are suitable actions to take.

What kind of velocity can I get with this bullet with 2400 before I max out on pressure? Looks like it has the most available case capacity. I am sure there are probably better powder choices for making this one go fast though. I can also not seat the bullet as deep and feed them one at a time to gain case capacity if I max out on capacity before I get to 35K psi.

Max velocity for a 500gr bullet with 2400 powder at max SAMMI chamber pressure is 1297 fps (20.9gr).

The 3 most optimal powders for velocity with a 500gr bullet in 458 Socom are:
Lil Gun 1373 fps
H110 1361 fps
H4227 1354 fps

No worries, I know I am on my own. I appreciate your help.

I will have to test out the two powders and see if I can feel the difference. I was guessing you had pretty easy access to pressure curves after looking at the Quickload info page. I want to get this rifle built before I dump a $152 on it, but I am going to have to get it one of these days.

That is interesting that there is only 60-75fps difference between 2400 and the optimum powders.

[johndoe3]

The 458SOCOM was submitted but at this point it is NOT SAAMI approved.

Where are you getting these SAAMI specs for pressure?

Bender, you're right on not yet SAAMI approved, thanks. I went through and corrected my posts.

The 35,000 psi max chamber pressure for .458 Socom is the design and development max, and most likely used by Corbon and Southern Ballistic Research in their commercial ammo loads.

[daviscustom]

I didn't save the source or the load data, but I stumbled across another source using 2400 with 500 grain bullets on another forum and it was very close to a match in terms of % of case capacity, powder charge and velocity, and so on.....so I guess we must be in the right ballpark.

I knew I wasn't going to be able to push them ultra fast, but I was hoping it might beat 1400 fps......doesn't bode well for really heavy bullets making it up to 1050. I think I might like to make or buy a mold for a larger size, but I'm gonna wait and see how bad the 500's thump before I get too carried away.

[johndoe3]

I knew I wasn't going to be able to push them ultra fast, but I was hoping it might beat 1400 fps......doesn't bode well for really heavy bullets making it up to 1050. I think I might like to make or buy a mold for a larger size, but I'm gonna wait and see how bad the 500's thump before I get too carried away.

This is where Quickload can help you play "what if", in just a couple of minutes. If you had a bolt action .458 Socom and cut with a deep throat, you can get higher velocities. With the deep throat, you couldn't load the cartridges in an AR-15 magazine.

For instance, what if you increased the COAL from your 2.259" to 2.460" for the 500 grain bullet? Quickload shows that there is plenty of shank in the neck of the cartridge to seat it properly--.464". What max velocities could you get with 35,000 psi chamber pressure max (top 3 optimal powders)?

VV N120 1464 fps
IMR 4198 1455 fps
Accurate 1680 1438 fps

What if you had a deep throat so that you could load it to 2.600" COAL? It would still be seated OK in the brass with .323" of shank in the neck. Max velocities at 35,000 psi chamber pressure would be...(top 3 optimal powders)

VV N120 1505 fps
IMR 4198 1505 fps
Accurate 1680 1489 fps

So...you can get higher velocities with .458 Socom with 500gr and 600 gr bullets, just not when limited to AR-15 magazine length.

[daviscustom]

No doubt Quickload is a wonderful tool for navigating into relatively uncharted waters like this. Great for being able to make use of what you have on hand and for subsonic loads where load data tends to be scarce....and as you mentioned for exploring different case lengths too.

I just got to wondering yesterday, I assume the pressure curve shows the overall chamber/barrel pressure at the point the bullet leaves the muzzle, and I am guessing the chamber pressure you listed was peak pressure. How does the pressure compare when the bullet uncorks into the suppressor?....between 2400, Bullseye, and Unique? I presume 2400 is significantly less then the other two, but just curious how much it falls off prior to expansion into the suppressor.

[johndoe3]

I just got to wondering yesterday, I assume the pressure curve shows the overall chamber/barrel pressure at the point the bullet leaves the muzzle, and I am guessing the chamber pressure you listed was peak pressure. How does the pressure compare when the bullet uncorks into the suppressor?....between 2400, Bullseye, and Unique? I presume 2400 is significantly less then the other two, but just curious how much it falls off prior to expansion into the suppressor.

Easy enough to copy down muzzle pressure, since it is calculated by Quickload at the same time as the other data in the table above. I just didn't include muzzle pressures in the table, and I don't think Quickload can simulate an actual suppressor. Data for 16.5" barrel, 500gr bullet at ~1050fps.

Bullseye 1050 fps, chamber pressure 34,105 psi, muzzle pressure 1371 psi
Unique 1049 fps, chamber 33,677 psi, muzzle 1353 psi
2400 1049 fps, chamber 18,362 psi, muzzle 1976 psi

So...no it's the opposite of what you supposed. Unique and Bullseye burn 100% in short barrel of 5" or less, while 2400 powder burns 98.1% in the 16.5" barrel. Unique and Bullseye have much higher chamber pressures than 2400, while muzzle pressure is highest for 2400.

Keep in mind that pistol suppressors are designed to operate in the 2000 to 5500 psi muzzle pressure range; and therefore, the .458 Socom muzzle pressures for subsonic are very modest with the 16.5" barrel (if you wanted to use a .45 Octane, Tirant or other .45 pistol suppressor for subsonics in 458 Socom).

I calculated the 2000-5500 psi muzzle pressure design range by playing with Quickload using 9mm, 40 S&W, and 45 ACP handguns with different barrel lengths and light bullets and heavy bullets (and +P). They all seem to fall in that range for muzzle pressures.

[daviscustom]

Thank you again for your help....very interesting results. I look forward to trying all three to compare felt recoil and suppression.

[daviscustom]

Don't have a finished rifle yet, but I did throw one together in the stock and try out the 2400 subsonic load today just to see what we were talking about in terms of recoil. I was pleasantly surprised! I loaded three up with 14.2 grains of 2400 (10% under what johndoe3 recommended with Quickload) and just shot into a dirt berm with no scope or sights. Recoil was pretty light, we were going to put a limbsaver butt pad on my buddies 110 but now we are not so sure, probably a good idea to go ahead and do it for the full power loads though.

Anyway it looks like the heavy subs will be very pleasant to shoot. I don't own a chrono, so when I get these rifles finished I will have to find someone to borrow one from to fine tune my loads. Thanks again johndoe3.

Noise level wasn't bad either. Not sure what it compares to because I normally shoot unsuppressed firearms with earplugs, but it was not as bad as full power 308 or 243. Loud enough my ears are still ringing from two rounds shot 45 minutes ago....but still it was not bad....should be nice to suppress.

[Capt. Link.]

I'm jumping in late on this conversation.I will need to work up some data as well.Where did the 35,000 number come from.I know other large bore cartridges have a low and high pressure loading depending on host used.The cases are well made and just wonder what would be a safe top load.This was designed for the M-4 so using a softer pistol primer and keeping pressures low was not a bad call but what about bolt actions.I have a Mauser and the other gent is using a Savage both are very capable of handling much higher pressure and length.If anyone has some links to socom research that would bring me up to speed.

I don't have a finished rife either but plan on a Mauser/sleeper as a personel build.I have designed a eccentric Maxim style can for it as well.Heavy bullets at a fast speed will be very cool in my M-48 when white tail season is here again.

[daviscustom]

My understanding is the 35k is just considered the standard max pressure...as Bender said, I guess there is no SAAMI approved specs at this point.

I was wondering about using Mag Large Pistol primers for the subs to promote more consistent ignition....but I have only loaded/fired 3 rounds, so that may be a solution for a problem that doesn't exist.

I presume the primer and the rebated rim are going to be the weak link on pushing the pressure, if johndoe3 is feeling adventurous he could probably give us some data using a higher max pressure. It would be interesting to see if there are any powders that would make efficient use of the small case capacity if we were using higher max pressure......

[daviscustom]

I found a reference to the first pressure signs (the beginning of primer flattening) being around 44K. Apparently the 35K max was chosen to match the bolt thrust of 5.56 nato.

Here is a link to the pressure signs thread, the reference to 44K is toward the end, on the 458 socom forum
http://458socomforums.com/index.php?topic=658.30

[johndoe3]

If you have a bolt gun and the large pistol primer flattening takes place around 44k psi chamber pressure, then using something like 40k for max chamber pressure in a bolt gun would only gain you about 60 fps in velocity as compared to 35k psi chamber pressure (from a Quickload simulation). The upside in $$$ for using 35k psi max chamber pressure is that many users report reloading their brass 10-15 times so far, with no problems noted.

Long throat in bolt gun and bullet seated out long, 500 gr bullet, 2.600" COAL

using 35k psi max chamber pressure
VV N120 1505 fps
IMR 4198 1505 fps
Accurate 1680 1489 fps

using 40k psi max chamber pressure
IMR 4198 1570 fps
VV N120 1566 fps
Accurate 1680 1554 fps

I was wondering about using Mag Large Pistol primers for the subs to promote more consistent ignition....but I have only loaded/fired 3 rounds, so that may be a solution for a problem that doesn't exist.

I had to look this up in the Quickload program manual.

Quickload is built on the thermodynamic model and offers no capability to specify regular or magnum primers. The program assumes sufficient column burn for the powder specified. Here is a quote from page 99 of the manual.

"Ignition behavior, ignition delay and primer mix energy are not taken into consideration in QuickLOAD calculations. The mildest primer sufficient for the given task is assumed."

[daviscustom]

Hmmmmm, I guess the next option that might gain a little in Max pressure would be switching to large rifle primers, but then we will be treading into unknown territory since we don't know if the case or the primer will show pressure signs first, or at what pressure. Capt. Link may want to play around with it, but I think even at subsonic loads this bullet will have plenty of energy to deliver to the target without pushing the envelope. It doesn't look like there is a huge amount to be gained.

My little ballistics program is showing a velocity drop to around 900 fps at 400 yards assuming a 1050 fps starting point, so it will be over twice the weight as 45 acp ball ammo and probably be traveling a little faster too.....it would always be more fun to watch if it was going faster, but faster is probably not required. 1500 fps with a 500 grain bullet should be very effective though, it would still be going 1100fps at 400 yds.

[johndoe3]

Dimensionally, large pistol and large rifle primer cups are different in height although the same diameter. Meanwhile, small rifle and small pistol primer cups are dimensionally the same size.

.210" diameter for both large pistol and large rifle

primer cup height is nominally .008" less for large pistol as compared to large rifle primers

Therefore, if you wanted to use large rifle primers in the .458 Socom brass and not have the primer cup stick up above the base of cartridge in an unsafe condition, a person likely would have to cut the brass deeper with a primer pocket reamer/cutter tool to seat large rifle primers properly.

The following page has measured dimensions on large and small rifle primers from all the major brands.
http://www.jamescalhoon.com/primers_and_pressure.php

It appears from the samples measured on the page above, the Federal large rifle primer cup is slightly less in height than all other brands of primers.

[johndoe3]

I decided to do a Google search to see if anyone had used LR primers in the 458 SOCOM by reaming the primer pockets slightly. This answers the question that Capt. Link raised on low pressure for AR-15 and a higher pressure in bolt guns. In a bolt gun only, using large pistol primers, users can operate using a 40k psi chamber pressure maximum; and with large rifle primers users have done it and use 50k psi max chamber pressure with no apparent problems.

http://458socomforums.com/index.php?topic=1351.0

Big Bore:
Since you are using a bolt action, you can load the SOCOM a LOT hotter than you can for an AR. You can even ream the primer pockets for LR primers and you will not hurt anything. I initially though that might weaken the web but Marty has told me that he has several people who have done this in bolt guns with no ill affects. In my own bolt pistol I took the load up until the primers started to flatten and had intended to ream them for rifle primers to go hotter, above 44K psi, but the recoil was so severe with those 525 gr. slugs in that handgun that I really did not want to push it any further, in fact, I backed it down a half or a full grain. Too much fun for me!
Point is, in a bolt gun you can really push those pills and you are not limited to 35K psi for backthrust reasons. That bolt gun you are using is a .308 based action and is fully rated for 60,000 PSI and the associated back thrust to go with it. I doubt the .458 SOCOM case can handle that much pressure but it could easily handle 50K psi IMO, and that is the difference between night and day between a bolt gun .458 SOCOM and an AR .458 SOCOM.
People, I know someone is going to ask this so let's head it off at the pass. NO, you cannot ream brass intended for the AR to use LR primers and load hotter. The limiting factor in the AR-15 is the bolt, not the case, not the primers, and that limit is 35,000 PSI. That is why we say when you see flattened primers in the AR (pistol primers start to flatten around 44,000 PSI) that you are already WAY over pressure. Harder primers do not solve this issue.

If you used a longer throat in a bolt gun and also used LR primers and 50k psi max then you could get those 500 gr bullets going around 1650 fps.