Subsonic load accuracy at 50-75 yards

The Rossi Model R92, a lightweight carbine for Cowboy Action, hunting, or plinking! Includes Rossi manufactured Interarms, Navy Arms, and Puma trade names.
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Subsonic load accuracy at 50-75 yards

Post by trekker »

Hi folks, nice forum you got here. I was wondering if any experienced members could weigh in on accuracy for subsonic loads. I am looking to equal 38+P power in my 357 with 24" barrel. Figuring on trying 3-4 grains loads of powders like like clays, trailboss or 700X etc for 900-950fps, whatever is just fast enough to avoid bullets stuck in the long barrel. Bullets would be 158 grain poly/hi-tek coated RNFP. I am collecting some samples from different manufacturers to test. One thing that concerned me is the 1:30 twist in the Rossi and such light loads. Any guesses on whether I might get lucky and find plinking load that gets 2" at 50 yards? Or will I likely need to slug bore and cast my own ? I', sort of hoping not to have to cast, as I'm not really set up for it accomodation wise. Long 2nd post, thanks for any replies :)
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Re: Subsonic load accuracy at 50-75 yards

Post by GasGuzzler »

I am confused on 38+P power with a standard weight bullet at subsonic velocity.
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Re: Subsonic load accuracy at 50-75 yards

Post by trekker »

not sure what is confusing? 900-950fps with 158 grain bullet is a 38+ P power level, and is subsonic..
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Re: Subsonic load accuracy at 50-75 yards

Post by HarryAlonzo »

Plus P muzzle velocity from a 4 inch barrel is 900 - 950 fps, yes? And this is the velocity that you want from your 24 inch barrel, yes? I think it's the mention of +P that left me confused.
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Re: Subsonic load accuracy at 50-75 yards

Post by trekker »

so we are all on the one page then, any stories of accuracy from these levels? The coated bullets I have on hand are 16BHN which is pretty hard and I assume wont obturate much at the low pressures. I might load some up and see how they do. Only one way to find out.
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Re: Subsonic load accuracy at 50-75 yards

Post by HarryAlonzo »

I run a 44, so I don't think I can help, but I'm curious about your goal. Are you lookin' to supress? Or do you want to optimize accuracy by avoiding transonic buffeting?
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Re: Subsonic load accuracy at 50-75 yards

Post by trekker »

harry, yes supress but without a supressor. That is we can't hunt with them here but I want to reduce the sound signature as much as possible with a reduced load. A particular task I have coming up is nailing some small forest hogs coming into a banana plantation to feed at night and its preferable to keep noise as low as possible due to neighbouring properties. The farmer says '22LR stinger' noise levels are okay, and while I have head shot small hogs with 22LR, I figured a subsonic load in 357 with a 24" barrel( maybe 2.8 grains clays) might be as quiet. I don't need extreme accuracy as ranges will be under 50 yards, but if a bigger one wanders in I may take the ear shot, in which case I'd like it to be able to group decently. This would be an ongoing small game and plinking load as well if I like it.

Accuracy from the bullet not dropping through the sound barrier would be an indirect bonus but it wasn't the purpose of the project.
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Re: Subsonic load accuracy at 50-75 yards

Post by Coote »

Trekker! Your question is the main reason I joined this forum. I think you are on the right track.

I have a 16" Rossi 92 .357. I have used many rifles over the last fifty years, but right now I'd say this is the rifle that I have enjoyed the most. I was raised with simple rifles and open sights. We can use suppressors here, and I appreciate them.... but they stop rifles looking and handling like the rifles I grew up with. And when a scope is added, it subtracts even more fun from my outdoor activities. A year or two back I sold my two suppressed .308s (one was devoted to cast subsonics)... and I bought the Rossi. The Rossi feels and looks right.

I still like to have the choice of using a 'scoped and suppressed rifle. If I am wanting to maximise my chance of bringing home meat from an open country hunt, or in low-light conditions, I will take my scoped and suppressed .223 and use full-powered loads. I also have a scoped and suppressed .22 rimfire. But if I am hunting in a scrubby area, or just simply exploring, I far prefer to carry a sleek, rugged rifle with open sights.

I often hunt near homesteads... or where other people may be wandering around. So I like to keep things as safe as I can, and I don't want to make any more noise than is necessary. I have loaded reduced-power cartridges for the .357 using lead projectiles and Trail Boss powder. They travel at around 900 fps. Are they effective?.... yes, at sensible ranges they most certainly are. Considering that I've successfully used subsonic .22 rimfire ammo to kill goats and pigs, the larger and heavier .357 projectiles have to be better. The projectiles go straight through a goat's chest and make a decent hole. Very effective.

But are my reduced .357 loads accurate? Hmmm. I'm still trying to improve things.

When I first got the Rossi, I got a Lee mould to make 158 grain solid flat-nosed bullets. I also bought a pack of 158 grain swaged lead round-nosed projectiles (I think they might be 'Speer' brand). I sighted the rifle in and I was happy enough with the groups, although I didn't formally measure and record them. I was pleased to be able to shoot a standard sized business card at about fifty yards. Back then I didn't put much of a crimp on my cases, and I seated the bullets to just under the recommended maximum 'LOA' length.

More recently, I started to think about taking longer shots and maybe shooting something like a hare out to 80 or 100 yards. This was a fairly ambitious thought, because the trajectory of the subsonic Rossi loads would never be better than the trajectory of standard velocity .22 LR ammo... and probably a bit worse because of the chunky bullet and my lower speed. Having the mindset that you can seldom have too much ammo, I purchased a big box of swaged 158 grain hollow semi-wadcutter bullets. I loaded up some of these and some of my others and did some serious testing.

According to a reputable website, the maximum recommended load of Trail Boss for .357 Magnum is 4.2 grains. So I carefully measured 4 grains for each cartridge. I also trimmed all the brass to the same length and, this time, I applied a seating-die crimp to my loads. I also started using CCI 400 primers instead of the Federal primers I'd used previously. The results I got were disappointing. Sometimes my groups were as big as maybe 2.5 inches at 25 yards. That would theoretically give me groups of 7.5 inches at my maximum point-blank range of near 75 yards which is terrible. I shot my Anschutz .22 with open sights just to see if I was the major part of the problem, but was relieved to get much tighter groups.

I have to add the warning here that everybody should do their own careful research about powder quantities and which components to use when reloading. I may be mistaken.

So... I don't know for sure what all the factors were with that poor accuracy. But I have since tried some different things and have got some encouraging results...

I loaded some more ammo with Federal primers. Still poor grouping.

I loaded more ammo using the usual plain Starline brass, seated the bullets a bit deeper, and did not apply a crimp. Shooting cartridges with my home-cast bullets or the round-nosed Speer bullets, I tightened the groups to well under two inches at 25 yards. The bullets seem to be held well without the crimp, but I will continue to monitor them. While I'm fairly confident about getting better groups than this eventually, I am satisfied that the rifle with these loads is accurate enough for shooting pigs up to fifty yards. The groups I shot using the swaged hollow semi-wadcutter bullets were not nearly as tight as the other two projectiles (but oddly, when I 'shot off' some of these projectiles I'd loaded and crimped into some nickel plated cases at a much earlier date, they grouped very well indeed!! Dunno why. The nickel cases certainly seem to be harder).

I loaded some subsonic loads using some old 148 grain Lapua wadcutter lead projectiles I was given. They didn't protrude from the case much at all. I was pleased that these cartridges fed easily into the rifle chamber from the ramp, although if more than one is placed in the magazine, there is insufficient bullet curve to allow the spring-loaded stop to work. So the rifle becomes a 'two-shooter'... which is fine with me. These grouped very well... certainly good enough for close range hunting.

It has been suggested... and it is beginning to dawn on me... that 125 grain (shorter) projectiles might work better at low speed considering the relatively slow twist of rifling in the Rossi. So I expect my new Lee 125 grain round-flat mould to arrive here on Monday. I might have some good news to report after that.

So, Trekker, yes... I believe that .357 subsonic loads will do the job you want up to fifty yards. I am fairly confident that I will eventually prove that they should be good up to 70 yards and perhaps a bit more. I have not yet experimented with jacketed .357 projectiles, but I believe that plain lead bullets will probably fly a bit faster with an identical load of powder. I personally believe that accuracy, and then penetration, are more important than expansion. If you find a projectile that expands in the best way at these speeds, then that is a bonus. A hole of .357 inches in diameter is comparatively big anyway. However, while I've done a lot of shooting I am a relatively inexperienced reloader... so I hope I don't lead you astray.

Dunno how much subsonic reloading you may have done, but I understand that jacketed projectiles are more likely to get stuck in your barrel compared to plain lead projectiles. Having said that though, I loaded quite a few jacketed .308 subsonics and didn't have a problem with bullets getting stuck. But if you ever get an odd-sounding shot without the 'plop' of the bullet hitting, it would be best to check the bore. I recommend lead projectiles for slow bullets.

I think that if your rifle has a longer barrel than mine, you might be pleasantly surprised at how relatively quiet your subsonic loads may be.

Here is the 25 yard wadcutter group I mentioned. The cartridges at the bottom show the home-cast flat point projectile and the store-bought round-nosed swaged projectile.

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Here is my beloved Rossi. In case you are wondering about the tape around the barrel, I generally put tape over the muzzle to stop twigs and rain getting in. I keep spare tape wrapped around the barrel.

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Re: Subsonic load accuracy at 50-75 yards

Post by HarryAlonzo »

Very pretty rifle!

Have you slugged the bore? Sometimes the mystery is in the bullet diameter. Or sometimes it’s still a mystery after you stumble across the right combination.

Part of the mystery can be barrel harmonics. Make sure the barrel band isn’t over-constraining the barrel.

A lotta guys would use 38 Spl for low velocities. Higher case fill can produce lower variation.
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Re: Subsonic load accuracy at 50-75 yards

Post by Coote »

Thanks Harry. No... I haven't slugged this bore yet, but I've been thinking about it. If the new 125 grain projectiles don't help me, then I might slug it... but if I find it is oversize, then I have to decide whether it is worth the trouble to get a suitable bullet mould. I've also hoping to try my loads in a single shot Henry with a 16 inch twist. I agree about filling the case. The wadcutters I loaded almost touched the top of the powder... and they shot the best of all my loads. I'm not saying case fill is the only factor here, but my experience certainly supports what you are saying.

I'll take a look at my barrel band, but I don't really know what I should be looking for. Thanks again.
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