Subsonic 308 loads?

[Wapiti]

Have any of you avid experimenters ever knocked up any 308 Win truly subsonic loads? Just wondering what your recipes were, chrony'd velocity (if you know) and in what barrel length you tried it in?

I'm open to projectile weight and powder type, but it'd be great if it was something in the 125-150gn bullet weight, and with a powder that is available fairly readily here. Heavier bullets might be easier to get going slower though, so keen on that too if it's the only way.

It's only for plinking, not game, and just for fun. Just to try something fun.

[Oldbloke]

Just go to the Hodgen site. They have data using AR2206H.

Hodgdon-Powder-and-ADI-The-Australian-Connection-10-ADI.jpg (174.35 KiB) Viewed 1208 times

[bigpete]

Have any of you avid experimenters ever knocked up any 308 Win truly subsonic loads? Just wondering what your recipes were, chrony'd velocity (if you know) and in what barrel length you tried it in?

I'm open to projectile weight and powder type, but it'd be great if it was something in the 125-150gn bullet weight, and with a powder that is available fairly readily here. Heavier bullets might be easier to get going slower though, so keen on that too if it's the only way.

It's only for plinking, not game, and just for fun. Just to try something fun.

Yes.
Remington 7 .308,1 in 10 twist, 20 inch barrel, sierra 170 flat point 30 30 projectiles, 9.3gn of trailboss, 1070fps.

[bladeracer]

Have any of you avid experimenters ever knocked up any 308 Win truly subsonic loads? Just wondering what your recipes were, chrony'd velocity (if you know) and in what barrel length you tried it in?

I'm open to projectile weight and powder type, but it'd be great if it was something in the 125-150gn bullet weight, and with a powder that is available fairly readily here. Heavier bullets might be easier to get going slower though, so keen on that too if it's the only way.

It's only for plinking, not game, and just for fun. Just to try something fun.

The ideal is Trailboss but AR2206H will also get you subsonic. AR2207 would likely work as well, but get Trailboss if you can. Yes, it is easier with heavier bullets because it requires a larger charge of powder while also reducing case volume, but you shouldn't have any trouble making subsonic 100gn rounds. The lightest jacketed bullet I've found is Hornady's 86gn designed for the .30 Luger pistol cartridge. The 60gn XTP may be an option as well if your throat is large enough to accept the cartridge with the fat bullet seated in it. If it's just for plinking fun though try the .311" 123gn Berry's Copper-Plated bullet or cast bullets. Berry's do .308" CP bullets but I've found them undersize in my rifles as they're basically just hardcast. Start high using the chronograph and work down until you get to where you want to be. Aim to average around the 1070fps so the odd anomaly doesn't give a sonic crack.

[Wapiti]

Thanks fellas. A real help.
I did see that The Barn advertised that Trailboss was back again but I'm going to have some trouble getting to Oakey, bugger. I will try and swing a trip but there was quite a heap of customers hanging out waiting for some so I might be out of luck.
But I bought up on 2206H ages ago because it is so flexible here, both 223 and 308. I will have to research a load, but I'm dubious about any info from the USA.
If anyone has used a powder charge with 06H at around that 1070fps, that'd be great too.
I have 900 of those Sierra 125gn Matchkings that were very cheap.

[fussy]

150gn projectile.
Trail boss, 14.2 grains.
16" Barrell
Groups ok, but not long range load.

[Oldbloke]

Thanks fellas. A real help.
I did see that The Barn advertised that Trailboss was back again but I'm going to have some trouble getting to Oakey, bugger. I will try and swing a trip but there was quite a heap of customers hanging out waiting for some so I might be out of luck.
But I bought up on 2206H ages ago because it is so flexible here, both 223 and 308. I will have to research a load, but I'm dubious about any info from the USA.
If anyone has used a powder charge with 06H at around that 1070fps, that'd be great too.
I have 900 of those Sierra 125gn Matchkings that were very cheap.

Why would you be dubious regarding data from Hodgen?

[Wapiti]

Sorry dude but "just go to the hodgedon site" isn't advice and wasn't what I was after. No offence, but I was interested in loads that someone had personally experimented with.
Who knows where you'll find some experience and pearls of wisdom.

[Oldbloke]

Sorry dude but "just go to the hodgedon site" isn't advice and wasn't what I was after. No offence, but I was interested in loads that someone had personally experimented with.
Who knows where you'll find some experience and pearls of wisdom.

Fair enough. But they do list data for 308 subsonic using 2206H (H4895)

[bladeracer]

Thanks fellas. A real help.
I did see that The Barn advertised that Trailboss was back again but I'm going to have some trouble getting to Oakey, bugger. I will try and swing a trip but there was quite a heap of customers hanging out waiting for some so I might be out of luck.
But I bought up on 2206H ages ago because it is so flexible here, both 223 and 308. I will have to research a load, but I'm dubious about any info from the USA.
If anyone has used a powder charge with 06H at around that 1070fps, that'd be great too.
I have 900 of those Sierra 125gn Matchkings that were very cheap.

Why would you be dubious regarding data from Hodgen?

I think the vast majority of ADI/Hodgdon data is merely calculated, I think very little of it is derived from actual testing. But it is only load data, its only purpose is to give you some idea of the region of charge weights you want to start playing within while developing your own data. I did most of my own subsonic AR2206H development with 8x57mm, .303, .223 and 7mm-08, which gave me enough real-world experience to work up subsonic loads in any chambering I'm playing with. I make an educated guess at where I'm likely to wind up subsonic with whichever bullet I'm using in whichever rifle I'm using, add a fair bit to make life easier (take a good rod with you, not a cleaning rod - I'm using 300mm lengths of 5mm brass rod for clearing squibs). I make a round up and shoot it into the ground over the chrono, reload the same piece of brass with another charge, shoot it over the chrono, and so on until I wind up around 1070fps. It can be worth firing a test round first so your piece of brass is fireformed or you may see quite a discrepancy in velocity with the second load (a virgin piece will have less case volume than one that is fireformed, thus will make higher pressure). When I reach that point I'll load ten or twenty rounds and shoot them for groups and to ensure I don't get any anomalous sonic cracks. Usually I don't have any difficulty getting adequate accuracy for the close ranges I want to use subs for, but it is possible you might want to try to improve the load. Try crimping for a start as it's quick and easy and can add a little more time to build pressure, or add some filler material to keep the powder around the primer rather than laying in the bottom of the case.

Regarding load data with AR2206H and 125gn, with the bullets seated as deep as possible, I would start with around 20gn over a chronograph first and work down until you find where you want to be. Then I would load ten at that and shoot them for groups as well as over the chronograph to see if they're accurate and consistent. Barrel length will play a very significant role if you want all your shots to remain subsonic so chrono the load in any other rifle before assuming it will be subsonic. If you expect to ever need to use the load with a suppressor I would drop the the velocity further, to around 1050fps, to ensure the suppressor doesn't punch it up to sonic velocities.

I just had a Google, this guy tested subsonic H4895 behind 190gn jacketed bullets - https://ultimatereloader.com/2023/08/18/amazing-308-subsonic-loads-and-fun-too/ He went too low though and got poor results, but doesn't seem to have tried to improve the load at all. He used Hodgdon's data, with an expected velocity of 1044fps, but it only gave him 802fps and he left it at that. I think he let himself down by not doing any further testing with it. He went with Trailboss instead, which is my first recommendation, if you can get it.

Hodgdon claims 24" barrel length for this data but I don't believe that. Start high (especially if you have a long barrel) and work down, or take a rod with you to punch the bullets out of the barrel. I doubt shooting subsonic loads has any detrimental effect on the brass (quite the opposite I reckon) but I like to keep my subsonic brass separated from my high-velocity brass just for consistency. I figure if I work up a load that is just subsonic, then fire a full-noise charge in that case the case will probably expand more, increasing its volume so when I then load subsonic I might see a discrepancy - I like consistency.

[Wapiti]

So thanks heaps for all that info BR, appreciate the work there.
So really great tips. I think I'll try bolt-action-only trials, although there's a couple of 16" barrel 308s here which would definitely shoot slower... but then again maybe not with such a low 06H load.
I know I'm making it strange using light bullets, its just that I've got so many of them because of their usual uses around here.
I hope to get to one of the shops that sell Trailboss too, in a week or so.
The brass rod suggestion is a good one, better make sure there's a clear view through the tube eh.

[bladeracer]

So thanks heaps for all that info BR, appreciate the work there.
So really great tips. I think I'll try bolt-action-only trials, although there's a couple of 16" barrel 308s here which would definitely shoot slower... but then again maybe not with such a low 06H load.
I know I'm making it strange using light bullets, its just that I've got so many of them because of their usual uses around here.
I hope to get to one of the shops that sell Trailboss too, in a week or so.
The brass rod suggestion is a good one, better make sure there's a clear view through the tube eh.

If you work up a load which is high subsonic in a 24" barrel I would think it would go sonic in a 16" barrel due to the reduced friction. I tested a .38 Special low-subsonic load six months ago in 20" and 24" barrels, it made around 500fps in the 20" but the bullets stopped in the 24" barrel.

I do subsonics with light and heavy bullets for different purposes. It can be easier with heavier bullets to get a consistent load, but you should be able to find decent consistency with light bullets as well.

Since getting into Cowboy I've had lots of squibbed bullets in the rifles, and seen heaps more at the club. Cowboy rules are minimum 400fps and Power Factor of 60 - basically a 150gn bullet doing 400fps. When you build a load that makes the bare minimum in a short rifle you definitely don't want to feed it into a longer rifle I bought short lengths of clearing rod as they can fit in my ammo boxes so no excuse not to have them with me.

[Wapiti]

Great tips, thanks.

[Wapiti]

Sorry dude but "just go to the hodgedon site" isn't advice and wasn't what I was after. No offence, but I was interested in loads that someone had personally experimented with.
Who knows where you'll find some experience and pearls of wisdom.

Fair enough. But they do list data for 308 subsonic using 2206H (H4895)

And appreciate your input also, OB. I will surely put the info from hodgdons into the pot when starting knocking up something to try.