Trying to develop a safe load for my .308, need help

MichaelP776

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Minuteman
Nov 25, 2023
17
4
Fort Moore, GA
My .308 gas gun has a relatively short barrel and I’m trying to get some velocity back by mimicking MK319 mod 0. Issue is I’m looking at N133 and IMR 3031, N133 has a max load with my bullet of 39gr while IMR is at 44. Other forums people are loading it was 44gr of N133 with no signs of over pressure. Just trying to make sure I don’t blow my gun up.
 
Some questions:

Barrel length?
130gr SOST bullets?
Brass H20 capacity?

Beyond looking at the top of the primer and case head, look at the primers decapped from the brass and measure the primer pocket size. If your primer pocket is measuring over .2095" from the first firing you are too hot regardless any other non signs of over pressure.
 
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Some questions:

Barrel length?
Bullet weight?
Brass H20 capacity?

Beyond looking at the top of the primer and case head, look at the primers decapped from the brass and measure the primer pocket size. If your primer pocket is measuring over .2095" from the first firing you are too hot regardless any other non signs of over pressure.
I’ll have to check the H2O capacity, but it’ll be from a 14.5” barrel, aiming for a velocity of 2850 or so from that length with a 130gr
 
I looked up the MK319MOD0

  • 130 grain OTM (reverse draw jacket) bullet
  • Temp stable flash reduced propellant
  • Not yaw dependant
  • Reduced recoil (10%)
  • Optimized for MK 17 (16” BBL)
  • 2925 fps @ 15’
  • Accuracy, combat -NTE 2 MOA. (600 yds)
  • Intermediate barriers; auto glass/doors.
  • Terminal, Specifically CQC & behind barriers
Only thing I can offer is I used 43gr IMR3031 for 137gr Hammer Hunters with success. 20" barrel though. 3000fps.
I think you could get 2775-2800 from a 14.5" with a 130gr TSX. Brass primer pockets might not last long.
 
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Well, that seems to be asking a lot from that length barrel.

Looks to me like Win748 is your best powder alternative for "relatively" safely reaching that velocity.

My data is based on 50.392 grain H2O case, so your case volume will matter.

With N133 at 100% case fill you are only looking at 2550-ish. So, with either load it will be compressed.

Not sure you're going to "safely" get there with the powders you've listed, based on my cursory look at the data, without going dangerously close to the edge of what is safe.
 
I looked up the MK319MOD0

  • 130 grain OTM (reverse draw jacket) bullet
  • Temp stable flash reduced propellant
  • Not yaw dependant
  • Reduced recoil (10%)
  • Optimized for MK 17 (16” BBL)
  • 2925 fps @ 15’
  • Accuracy, combat -NTE 2 MOA. (600 yds)
  • Intermediate barriers; auto glass/doors.
  • Terminal, Specifically CQC & behind barriers
Only thing I can offer is I used 43gr IMR3031 for 137gr Hammer Hunters with success. 20" barrel though. 3000fps.
I think you could get 2775-2800 from a 14.5" with a 130gr TSX. Brass primer pockets might not last long.
Thank you, I’ll have to try it out. Right now I do need to chrono my factory M80 ball though because I think I’m getting way higher velocity out of the 16” than I was thinking I should. My math for my holds isn’t adding up because holding at 2.5 mile like my math is showing is sending them over it holding dead on works so my rifle might be sending stuff way higher velocity than I thought for M80’s
 
Well, that seems to be asking a lot from that length barrel.

Looks to me like Win748 is your best powder alternative for "relatively" safely reaching that velocity.

My data is based on 50.392 grain H2O case, so your case volume will matter.

With N133 at 100% case fill you are only looking at 2550-ish. So, with either load it will be compressed.

Not sure you're going to "safely" get there with the powders you've listed, based on my cursory look at the data without going dangerously close to the edge of what is safe.
Thank you, I wish I could just get the factory ammo but the supplies seemed to have dried up a while ago
 
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Well, that seems to be asking a lot from that length barrel.

Looks to me like Win748 is your best powder alternative for "relatively" safely reaching that velocity.

My data is based on 50.392 grain H2O case, so your case volume will matter.

With N133 at 100% case fill you are only looking at 2550-ish. So, with either load it will be compressed.

Not sure you're going to "safely" get there with the powders you've listed, based on my cursory look at the data, without going dangerously close to the edge of what is safe.
Try running the number with 54gr H2O. That would average out over the multiple brands I've tested over the years.
 
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Try running the number with 54gr H2O. That would average out over the multiple brands I've tested over the years
Using that case volume it looks like I can get to 2725-ish with N133, but it isn't a load I'd be comfortable shooting.

Hold on, looks like 3031 is possible, but I'm not comforatable posting the numbers here.......Something I'd also not be comfortable shooting and would have to start much lower and work up to.......But I got 2846 at just below max pressure with 3031.........AND you are burning just over 99% of your powder.

So, OP, I'd say stick with 3031 and work your way up safely, monitoring velocity and watching for signs of pressure. But you're not likely to get there with published load data.
 
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Using that case volume it looks like I can get to 2725-ish with N133, but it isn't a load I'd be comfortable shooting.

Hold on, looks like 3031 is possible, but I'm not comforatable posting the numbers here.......Something I'd also not be comfortable shooting and would have to start much lower and work up to.......But I got 2846 at just below max pressure with 3031.........AND you are burning just over 99% of your powder.

So, OP, I'd say stick with 3031 and work your way up safely, monitoring velocity and watching for signs of pressure.
Barnes has posted on their website a decent load with 3031 for this round so I might try that. Was wanting to do N133 because I’m pretty sure it has flash suppressant in it
 
Thanks, I’m just surprised by the one laid i saw online of someone using 44gr of N133. I might try to ask some guys from AMU if they have the actual load data for the production round
That load "could" be perfectly safe in your rifle, depending on your case volume and your chamber. However, its only likely to get you to 2685-ish.

FWIW my initial case volume was a statistical average of LC12 762 brass in my inventory.
 
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You shouldn't simply have a velocity in mind when developing a load, particularly with those short length barrels that you mentioned IMHO.

Find something that shoots accurately in your firearm. 1-300 fps is not going to make a substantial difference at the distances you will likely be shooting.

Just my humble Saturday morning opinion. Good Luck
 
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You shouldn't simply have a velocity in mind when developing a load, particularly with those short length barrels that you mentioned IMHO.

Find something that shoots accurately in your firearm. 1-300 fps is not going to make a substantial difference at the distances you will likely be shooting.

Just my humble Saturday morning opinion. Good Luck
I’m more worried about terminal effects than pure accuracy. The majority of my ammo is surplus M80 ball and overall I’m not planning on shooting this rifle off of bipod or tripod and rarely off of a bench except for when I’m zeroing.
 
I'm definitely not an expert at reloading but three things comes to mind.

*Use a powder that will get the velocity you need instead of trying with some that doesn't.
*Why 'pin and weld' a shorter barrel to make legal rifle lenght instead of just leaving it? Especially since you're chasing velocity and not willing to make it an SBR...
*When pushing the envelope of charges beyond published max (which are easily found in any reloading manual and online - Hodgon is great for that!) be VERY careful, slow and extremely accurate with collecting ALL possible data, and look over everything, twice!
(and, obviously, when doing anything outside safe/known load development meassure YOUR velocity.)
 
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1700946818501.png

Shooter's World Match looks like good option
 
I'm definitely not an expert at reloading but three things comes to mind.

*Use a powder that will get the velocity you need instead of trying with some that doesn't.
*Why 'pin and weld' a shorter barrel to make legal rifle lenght instead of just leaving it? Especially since you're chasing velocity and not willing to make it an SBR...
*When pushing the envelope of charges beyond published max (which are easily found in any reloading manual and online - Hodgon is great for that!) be VERY careful, slow and extremely accurate with collecting ALL possible data, and look over everything, twice!
(and, obviously, when doing anything outside safe/known load development meassure YOUR velocity.)
This kills me, but it's only my job to recommend, not question a guy's project. :)
 
This kills me, but it's only my job to recommend, not question a guy's project. :)
I agree, just looking at things from a logical standpoint. I've never understood the whole 'ad stuff to a short barrel to make it legal lenght' vs. just leave it, since it will physically be the same length so no gain in mobility, or make it the lenght you want either legally, or not...
 
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I'm definitely not an expert at reloading but three things comes to mind.

*Use a powder that will get the velocity you need instead of trying with some that doesn't.
*Why 'pin and weld' a shorter barrel to make legal rifle lenght instead of just leaving it? Especially since you're chasing velocity and not willing to make it an SBR...
*When pushing the envelope of charges beyond published max (which are easily found in any reloading manual and online - Hodgon is great for that!) be VERY careful, slow and extremely accurate with collecting ALL possible data, and look over everything, twice!
(and, obviously, when doing anything outside safe/known load development meassure YOUR velocity.)
The reason I’m doing a pin and weld is because I’ll be suppressing it. It currently has a metric threaded pencil barrel on it and the suppressor muzzle device I had on that wouldn’t sit concentric and destroyed one can already. Im rebarreling to a medium contour barrel and having it threaded to a standard pitch but with the suppressor I want to put on it it’ll benefit by having a shorter barrel so I don’t have a rifle too too long for normal use
 
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The powder you will get the highest velocity from is almost certainly going to be a dense, high energy double base powder. Single base stick powders won't get you there.

2000 MR is the best choice for maximum velocity, but it generates a ton of gas in semi autos and isn't the easiest on barrels.

Your velocity goal of 3000 fps is unrealistic, particularly in a 14.5" barrel. Somewhere around 2700-2800 is about the most you should actually hope for.

Also I wouldn't hold your breath for amazing accuracy from your FAL. Mine was a consistent 3-3.5 MOA gun even with high quality match handloads, and it chewed up brass like crazy even with the gas adjusted correctly.
 
What is the point of mimicking the load as per OP?

Sounds like a PITA and the gun doesn't even mimic the firearm intended for the load.

And why do we need flash suppressant if we’re shooting w a can?

Sometimes it’s more useful to help a guy with his goals themselves rather than their fulfillment
 
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What is the point of mimicking the load as per OP?

Sounds like a PITA and the gun doesn't even mimic the firearm intended for the load.

And why do we need flash suppressant if we’re shooting w a can?

Sometimes it’s more useful to help a guy with his goals themselves rather than their fulfillment
The gun it is designed for is a 13” scar 17. The load is designed for 2700 out of that length scar. And the suppressor is still currently in ATF jail so I’d like for it to be as low flash as I can for now
 
He's not concerned with accuracy, just terminal performance.

The projectile has to work, even if he doesn't hit the intended target...




^^^^^ let all that sink in.





Guys, just keep hitting your head with that hammer.
It'll feel really good when you stop.
I’m not looking for a sub MOA round or anything, I know that accuracy for the load isn’t really needed due to the inherent inaccuracy seen in tilting block firearms. I would be more than happy with it shooting 2.5 MOA which would allow me to hit a man sized target at a little over 700m. As long as the round is as accurate as factory ball ammunition it is fine for my needs
 
Hodgedon H335 might be worth a try for a couple of reasons. It works well with light .308 bullets (147 to 155) and because this powder is on the fast end of the spectrum, it was the only powder to reliably cycle a new FN FAL build during its initial break-in. I still use it now in the FN at 41.5gr with the 147gr bullets. Since the OP wants a short barrel gas gun, this powder might provide a burn rate to keep velocities on the higher than normal side.
 
I’ve had good luck with cfe223 and light bullets in the .308. 52.5 grains, a 125 Speer tnt, with federal brass and Cci #34 primers.
Velocity out of a 16 inch lmt are right at 2920 fps. It shoots well out of multiple firearms too.
 
So a bit of an update, I talked to one of my buddies who’s got contacts at both sniper school and the army marksmanship unit which are just down the road here. I got the official load data for this round and it’s using a way faster powder than I initially thought but this is the published load data for the round and looking at factory data and pressures it seems reasonable.
18740250-6BDC-44D0-A0E3-742988A2F1E7.jpeg
 
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