Subsonic (suppressed) loads and accuracy issues

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OnyxATX
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Subsonic (suppressed) loads and accuracy issues

Post by OnyxATX »

Hey everyone, I don't post often but had some questions.

I'm running a 7.5" barrel (1:8) AR with a Saker 762 on the end, for the sake of this post we will only discuss results with the suppressor attached unless directly noted.

For supers, I'm running the following.
110 VMAX 18.8 w296 with 2.050 COL
125 Nosler BT 16.6 w296 with 2.060 COL
125 Hornady SST 16.5 w295 with 2.100 COL
155 AMAX 14.6 w296 at 2.220 COL

All of these are MOA, a few seem to be submoa but I won't make that claim until much more testing. Either way, the groups are one decent hole inside of 100 yards if I don't throw shots. I know folks make claims and argue about them, but at the end of the day the loads get me a dime to quarter sized group and I'm extremely pleased with that.

Now, we get to the issue I'm having with 208 AMAX and 220 SMK. I'm running both at 9.8 of A5744 with a COL of 2.225 and 2.190 respectively. The groups were not as tight unsuppressed as my supersonic loads. I feel like this is just natural with lower velocity and reaching out. However, with the can on there the accuracy difference is pretty huge. About a 1-1.5" group at 25 yards (not same hole) although no keyholes. (Moving up to like 5-6MOA and not 1MOA like the supers were)

This leads me to think the subsonic are really an indoor load, when being extremely quiet matters more than pin point accuracy and you don't have to reach out far at all. (See, guys break in with weapons, my infant daughter is 6 feet away)

SOOOOO... what I'm getting at is this. Is the whole ""My buddy can hit 450 yards subsonic all day!" type thing as much bull as I'm thinking it is? I'm wondering if the baffles on the can are creating a bit of destabilization. Not enough to keyhole or cause any major issue, but enough to help a barely stable round open up when going out past 50ish yards.

Anyone have tips for loading subs for accuracy? Or should I say "a fist 50 yards, good enough for what they are intended to do." I don't want to be chasing a load that may not really even exist. The more I use the can... the more I'm seeing that subsonic rounds seem to be really for CQB applications and range fun... where as supers are "the real" round.

Any advice, comments, or information regarding subs and accuracy are extremely appreciated!

Thank you
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TreeTopFlier
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Re: Subsonic (suppressed) loads and accuracy issues

Post by TreeTopFlier »

Interesting problem... don't know if you saw this thread but it has a wealth of information viewtopic.php?f=141&t=83844

My first thought/speculation is that you have a very short barrel 7.5" with 1:8 twist. A heavy bullet doesn't even get a complete rotation in the barrel before entering suppressor dynamics.
May be tough to get great accuracy with this combo.

Did you do a load work up/down with the suppressor. Adding the suppressor would probably change your barrel harmonics. What shoots well without may not shoot well with.

Your barrel being short makes me wonder if you wouldn't benefit from a faster burning, pistol like powder, maybe h110 or even accurate #9

Pure speculation until the more qualified chime in...
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Last edited by TreeTopFlier on Sun Nov 09, 2014 2:56 am, edited 2 times in total.
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OnyxATX
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Re: Subsonic (suppressed) loads and accuracy issues

Post by OnyxATX »

Yeah, that was my thought that it's not quite stable enough for 208/220 to really work on accuracy. It's right on the edge. The purpose is basically home defense (for subsonics) and pig dispatching (supers, the Nosler BTs and 125 SSTs have treated me well.) So really, if I can't push perfect accuracy for 208/220 it's not the end of the world. Of course, I would like to tune the loads as best I can... but I've got other suppressed things if I really need to reach out quietly.

I have done some loading up/down for the can, but only really 9.4-9.8 or so. I haven't pushed it further, although I'm sure I could. 10.2 or so didn't cause issues without the can but it hurt accuracy a bit. The other thought is changing away from the A5744... I've thought as well maybe it isn't burning quite fast enough. I'm not sure on this though, W296 and H110 work are amazing... but I don't know the exact speed they burn compared to the A5744.

I hadn't seen that thread, but will certainly look over it. If for some reason moving to H110/W296 is the solution, that's great for me. I've got enough of both of those powders sitting around to load something like 70,000 subsonic rounds.
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Re: Subsonic (suppressed) loads and accuracy issues

Post by plant.one »

i may have missed it but what primer are you using?

(edit) i'm not familiar with your powder, but i'm wondering if you're getting consistent ignition with your primer choice. also what temps were you shooting at ?
Reloading info shared is based on experiences w/ my guns. Be safe and work up your loads from published data. Web data may not be accurate/safe.
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certifiable
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Re: Subsonic (suppressed) loads and accuracy issues

Post by certifiable »

Tried responding to your pm Onyx but am experiencing technical difficulty on my end. I will get with you tomorrow.
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Re: Subsonic (suppressed) loads and accuracy issues

Post by rpk47 »

I don't think stability would be your issue, at least with the 208gr bullets, from JBM stability calculator.

Input Data
Caliber: 0.308 in Bullet Weight: 208.0 gr
Bullet Length: 1.466 in Plastic Tip Length: 0.000 in
Muzzle Velocity: 1000.0 ft/s Barrel Twist: 8.0 in
Temperature: 87.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 2.183
OnyxATX
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Re: Subsonic (suppressed) loads and accuracy issues

Post by OnyxATX »

Oh right, primers. CCI400. I've also got some Winchesters around, but haven't used them yet. It's my understanding (if I remember right) they are a tad bit hotter. I've also contemplated changing over to the hotter CCIs.

Temp was roughly 75-80 degrees.
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Re: Subsonic (suppressed) loads and accuracy issues

Post by TreeTopFlier »

OnyxATX wrote:Yeah, that was my thought that it's not quite stable enough for 208/220 to really work on accuracy. It's right on the edge. The purpose is basically home defense (for subsonics) and pig dispatching (supers, the Nosler BTs and 125 SSTs have treated me well.) So really, if I can't push perfect accuracy for 208/220 it's not the end of the world. Of course, I would like to tune the loads as best I can... but I've got other suppressed things if I really need to reach out quietly.

I have done some loading up/down for the can, but only really 9.4-9.8 or so. I haven't pushed it further, although I'm sure I could. 10.2 or so didn't cause issues without the can but it hurt accuracy a bit. The other thought is changing away from the A5744... I've thought as well maybe it isn't burning quite fast enough. I'm not sure on this though, W296 and H110 work are amazing... but I don't know the exact speed they burn compared to the A5744.

I hadn't seen that thread, but will certainly look over it. If for some reason moving to H110/W296 is the solution, that's great for me. I've got enough of both of those powders sitting around to load something like 70,000 subsonic rounds.
Here is a link to a couple powder burn rate charts so you can see where A5744 falls. H110 is faster.
http://www.accuratepowder.com/wp-conten ... _rates.pdf
https://www.hodgdon.com/burn-rate.html

I think you are going to have to try some different combinations in powder type, charge weight and OAL. Unfortunately that means putting in extra time at the range...what are ya gona do :mrgreen:
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Re: Subsonic (suppressed) loads and accuracy issues

Post by TMD »

Without a chronograph it's almost like pissin in the wind when it comes to working up subsonic loads. Too low of a velocity and grouping will be terrible at best.
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Re: Subsonic (suppressed) loads and accuracy issues

Post by bangbangping »

TreeTopFlier wrote:My first thought/speculation is that you have a very short barrel 7.5" with 1:8 twist. A heavy bullet doesn't even get a complete rotation in the barrel before entering suppressor dynamics.
May be tough to get great accuracy with this combo.
This is an often repeated theory and intuitively seems right, but barrel length doesn't matter. The bullet will be spinning exactly the same as if it came out of a 16" barrel.
TMD wrote:Without a chronograph it's almost like pissin in the wind when it comes to working up subsonic loads. Too low of a velocity and grouping will be terrible at best.
Absolutely. Also, I'd say focus on one bullet until you get it right or give up. Then move to the next.

According to Hornady, the Amax will be moving ~1025 fps with your load from a 16" barrel. I'd be surprised if you're doing 950 out of a 7.5." Absent a chrony (you really need a chrony) my suggestion would be to bump the powder to near book max and then work down.
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