subsonic 308 loads

I developed a load for my 308 with 173gr LRN bullets with MP200. It is the only Somchem powder which can safely be used for this application, according to a Somchem technician I once spoke to. I don't know about imported powders.

An old, very experienced hunter who culled substantially with subsonic cartridges told me to keep the speed at 800fps - 1000fps. His reason was that the cartridge speeds vary too much due to atmospheric influences, and that 800-1000fps stays stable.

I loaded in 0.5gr increments from 10.5gr down to 4.5gr, and settled on 4.8gr for 900fps.

Some averages:

10.5gr - 1482fps

8.5gr - 1294fps

6.5gr - 1097 fps

4.5gr - 853fps

I stuffed ½ a block of two ply toilet paper on top of the powder.

The LRN bullet pushes into the lands.

If memory serves correct the trajectory was something like spot-on at 20m, 2" high at 40m, spot-on at 60m and 2" low at 70m.

Treeman has experience with this as well - he will probably chime in as soon as he sees that I have posted ... someone needs to check me up ;) ;)

Last things for now:
- Going close to and over the sound barrier has a negative effect on accuracy,
- Remember that subsonic ammo has very little shock effect, if any at all. It just pokes holes, hence accurate shot placement is very important.

I developed a load for my 308 with 173gr LRN bullets with MP200. It is the only Somchem powder which can safely be used for this application, according to a Somchem technician I once spoke to. I don't know about imported powders.

An old, very experienced hunter who culled substantially with subsonic cartridges told me to keep the speed at 800fps - 1000fps. His reason was that the cartridge speeds vary too much due to atmospheric influences, and that 800-1000fps stays stable.

I loaded in 0.5gr increments from 10.5gr down to 4.5gr, and settled on 4.8gr for 900fps.

Some averages:

10.5gr - 1482fps

8.5gr - 1294fps

6.5gr - 1097 fps

4.5gr - 853fps

I stuffed ½ a block of two ply toilet paper on top of the powder.

The LRN bullet pushes into the lands.

If memory serves correct the trajectory was something like spot-on at 20m, 2" high at 40m, spot-on at 60m and 2" low at 70m.

Treeman has experience with this as well - he will probably chime in as soon as he sees that I have posted ... someone needs to check me up ;) ;)

Last things for now:
- Going close to and over the sound barrier has a negative effect on accuracy,
- Remember that subsonic ammo has very little shock effect, if any at all. It just pokes holes, hence accurate shot placement is very important.

Thanks, that's very helpful, and a good starting point.

Out of curiosity, what do you think would work better? large rifle primers or small rifle primers from palma brass?

- Remember that subsonic ammo has very little shock effect, if any at all. It just pokes holes, hence accurate shot placement is very important.

Yes, very important. I was looking at either using a .204 with 32gr at 3800ft/s or developing sub sonic 308. The .204 will still give a sonic crack, but is a very quiet rifle and at that speed, has 3x the energy.

What I found fascinating is that the sonic crack is louder, the further the bullet travels, so if you shoot a pig in a pen, the neighbours are less likely to hear it than say a 200m shot at a monkey.

Thanks, that's very helpful, and a good starting point.

Out of curiosity, what do you think would work better? large rifle primers or small rifle primers from palma brass?

I really don't know - no experience with palma cases.

The LRN bullet pushes into the lands.

If memory serves correct the trajectory was something like spot-on at 20m, 2" high at 40m, spot-on at 60m and 2" low at 70m.

Treeman has experience with this as well - he will probably chime in as soon as he sees that I have posted ... someone needs to check me up ;) ;)

Last things for now:
- Going close to and over the sound barrier has a negative effect on accuracy,
- Remember that subsonic ammo has very little shock effect, if any at all. It just pokes holes, hence accurate shot placement is very important.

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If you intending to kill things with the .308 sub, use the flattest, most metplat bullet you can, then the poking holes matter becomes tissue damaging tunnels.

Has anyone done research on using monolithic bullets for subsonic purposes?

A hard metal surface would make a sharp cutting edge?

I'm out of my lane here but I doubt copper or some other metal harder than higher end lead alloy (i.e. 'hardcast') would do better for the application.

I'm out of my lane here but I doubt copper or some other metal harder than higher end lead alloy (i.e. 'hardcast') would do better for the application.

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The mono metal in Impala form will work well in regard to wounding affect, but I question the ability to stabilize the long bullet using standard twist rifle barrels?

I shot their 130gr LWHV. Accuracy was good enough for head shots at 120m.

I shot their 130gr LWHV. Accuracy was good enough for head shots at 120m.

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At sub sonic ? ?

Tree, what did you shoot with on the farm the night you showed our fellow hunters that the other people behind us would not know that you were shooting?

This is the night you shot the dead tree by moonlight, just before Jansonville.

My old .308 Mauser and 160gr Frontier bullets at sub sonic. Yes, I recall, if you shot away direction from people 20 ft away they did not know you were shooting. I remember saying, " they will probably look up at the hits on the tree"

That statement stuck in my mind.

My old .308 Mauser and 160gr Frontier bullets at sub sonic. Yes, I recall, if you shot away direction from people 20 ft away they did not know you were shooting. I remember saying, " they will probably look up at the hits on the tree"

That statement stuck in my mind.

If the old Mauser stabilised them 160gr Frontiers, one should be able to stabilise 130gr as well?

Edit: my previous post didn't go through.

How much influence does bullet speed have on stabilisation? How does it work?

Those 130 gr mono's are loong ? At lower speeds I believe speed has a lot of influence, lot more sensitive to twist rate. That is why upping speed helps stabilize marginally unstable bullets.

A good reason to try it? ;)

A bit off topic, but relevant.

Lead is significantly heavier than copper in terms of density.

Lead density: ~11.34 g/cm³

Copper density: ~8.96 g/cm³

So, for the same volume, lead will weigh roughly 1.27 times more than copper.

Roughly, a 150gr copper bullet will have the same volume as identical 190gr lead bullet.

But since most "lead" bullets have a copper cup and lead core, the ratio is less depending on the amount of gilding metal (95% copper zinc alloy) used in construction. So more like 1.2 times the volume, making a 150gr cup and core closer to a 180gr mono metal copper bullet. If you add plastic tips and cannulas and things, the ratio is potentially even less. Obviously design and bearing surface have an effect on stability in relation to twist ratio, but even if you go to a 130gr mono, the bullet volume and approximate bearing surface is that of a 150gr cup and core bullet, which stabilizes well in anything from a 1:10 to 1:13 twist barrel.

Going even lighter, a brass bullet (think Impala or Viper plains gold) will be even bigger in volume. A 132gr brass bullet is made from the same cut as a 140gr copper bullet, which is equivalent in volume to a 168gr bullet.

So going back to subsonics, a friend of mine suggested I use a 250gr bullet, so that most of the bullet will sit within the case volume, and help negate the need for fillers, as the space is filled by the bullet, and the remaining space is filled with the necessary powder to shift the heavy bullet. I just wonder how such a long bullet will stabilize at 800ft/sec from a 1:10 twist barrel, and weather it even matters on a live target?

Treeman had some very interesting quiet ammunition some years back, I recall we shot bricks with them. The results on the bricks were not impressive, some did not even break.

Less charge with a heavier bullet will assist in keeping the bullet subsonic. This should also give better penetration as momentum is higher. A 1 in 10 twist barrel should easily stabilize a 220gr bullet. The 250gr would have to be a flat pointed bullet to keep the length as short as possible. Lead bullets out of a large caliber revolver achieve incredible penetration through animal tissue.

I could not get a 220 gr bullet to subsonic stabilize, they all key-holed. I only got 165 and 170 ? gr bullets one hole accurate - I even battled with 180 gr, it all worked alright but grouping was "iffy", but 170 gr? Frontiers were brilliant, I will try again now that I have a .308 again.

I could not get a 220 gr bullet to subsonic stabilize, they all key-holed. I only got 165 and 170 ? gr bullets one hole accurate - I even battled with 180 gr, it all worked alright but grouping was "iffy", but 170 gr? Frontiers were brilliant, I will try again now that I have a .308 again.

Just check your barrel twist rate.
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Last 308 was Israeli K98 mauser, this is a Musgrave, it will also be 1-10 twist

Just for reference, a friend built a subsonic load for his 300BLK Remington with 16" 1:7" twist barrel, suppressed.

He decided on a 220gn PMP bullet, as these were available.

Performance on paper was excellent, with small groups at 1000fps.

Terminal performance on the bushpigs was dismal. The bullets zipped straight through with almost invisible exit wounds and no blood trail. Some pigs, supposedly with decent hits in the vitals, were lost in the thick bush.
Not happy with this, he switched to 110gn Barnes X type bullets at around 2400fps and the pigs all dropped in their tracks. Sound signature was louder, but that was a necessary compromise.

My personal preferred tool for this kind of job is a suppressed 44 Mag rifle, loaded with 320gn flat-nosed cast lead (and powder coated) bullets at 1000fps. These also don't expand, but cut a decent wound channel and mostly exit, except on frontal shots on big animals. Shot placement is still critical. Ideally you need to hit some bone, like skull (brain), the spine or at least front leg bones. Lung shots are not effective and heart shots only slightly better. Keep that in mind when trying smaller calibers.

I still think a bow with broad head tip on the arrow is far more deadly. Also pretty quiet.

Just for reference, a friend built a subsonic load for his 300BLK Remington with 16" 1:7" twist barrel, suppressed.

He decided on a 220gn PMP bullet, as these were available.

Performance on paper was excellent, with small groups at 1000fps.

Terminal performance on the bushpigs was dismal. The bullets zipped straight through with almost invisible exit wounds and no blood trail. Some pigs, supposedly with decent hits in the vitals, were lost in the thick bush.
Not happy with this, he switched to 110gn Barnes X type bullets at around 2400fps and the pigs all dropped in their tracks. Sound signature was louder, but that was a necessary compromise.

My personal preferred tool for this kind of job is a suppressed 44 Mag rifle, loaded with 320gn flat-nosed cast lead (and powder coated) bullets at 1000fps. These also don't expand, but cut a decent wound channel and mostly exit, except on frontal shots on big animals. Shot placement is still critical. Ideally you need to hit some bone, like skull (brain), the spine or at least front leg bones. Lung shots are not effective and heart shots only slightly better. Keep that in mind when trying smaller calibers.

I still think a bow with broad head tip on the arrow is far more deadly. Also pretty quiet.

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You have stated the absolute facts.
Subsonic =
Bigger calibre is better x 10
Flat faced lead is better than any expanding bullet, and bigger calibre is better
You MUST break bone (even head shots "duh!")
You must break bone, bigger is better and flat faced beats them all ---------------- and its still a kak idea.

One area where this comes in handy is for culling in/near built areas. My brother helped with culling on an eco estate - a subsonic .22 cartridge causes too much trouble with insufficient penetration or too little damage.