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Suppressors Subsonic loads "prohibited" in AAC cans?

C

CanadaGoose

Private
Minuteman
Aug 19, 2010
21
0
46
#1
Hey guys,

After 6 long months of waiting, I finally got my first can for my .308 last week. It's an AAC Cyclone, and it proved itself well worth the wait (and the suitcase of cash I had to hand over). I had a blast at the range today.

The reason I'm posting is because the manual that came with the thing states that shooting subsonic rounds through it is prohibited. This really put me off cause I want that eerie "click-plink." My initial thought was that AAC just didn't want the liability of damage due to people shooting the longer subsonic bullets from barrels with insufficient twist. My understanding is that at least a 1:10 twist is preferred to stabilize the longer, heavier bullets you typically see in subsonic .308 factory loads.

After some research, it seems like my assumptions were correct (and if not, please feel free to set me straight). My twist rate is 1:11 and I want to use the Lapua 200gr subsonic load. The length of that bullet is 1.34". Running those specs through the JBM stability calculator with the current weather we've been having gives me a stability factor of 1.419. If I factor in an extra 30ft/sec or so the can will add to muzzle velocity, the factor creeps up to 1.432. This is definitely not as good as the 2.154 I get with the 168gr Sierra MatchKing bullets I shoot now, but it is well within the stability threshold according to JBM. So it seems like I can go ahead and use the Lapua subsonic without fear of baffle strikes.

So here are my questions:

1. Is my logic sound? Will the 200gr Lapua be safe to use?

2. Has anyone tried this setup and how has your precision been? I typically get 0.3" or so groups at 100 yards with my current ammo. I would hate to see that open up, but it might be worth it for that wonderfully creepy sound profile.

3. I've seen other factory subsonic loads with smaller bullets, but from what I've been reading, the powder is very loose in the cartridge which is hell on precision. Is this the case? Can anyone recommend a very accurate subsonic load with a lighter bullet?

Thanks in advance for your help!
 
#3
Re: Subsonic loads "prohibited" in AAC cans?

If you asked 10 suppressor makers if they carried Product Liability Insurance the resulting answer would more than likely be "no." Very few companies are actually buying and carrying insurance that protects them against harm caused by consumer interaction with the product. Those that do, and AAC is most likely one of them, are serious about protecting their interests against mishaps. If one was to ask most manufacturers and only buy from those that have Liability Insurance....there would be about 4 manufacturers.....seriously. If everyone HAD to have it, 80% of the can makers would have to exit immediately.

Since a company cannot account for what consumers use for twist, projectile weights, seating, velocities, etc., etc. they take a strong position to use some kind of SAMMI, etc. standards. And that is why you see what you see.

As to whether or not you can shoot subs....consider the fact that some suppressor manufacturers actually produce and sell subsonic ammo...in .308....and sell truck loads of the stuff. Some of them have product liability insurance too. I shoot cases of sub .308 and, along with sub .260, it is a favorite round out to 200 yards. Perhaps if you bought a box of manufactured subs, run it through your chrony, see that it works perfectly. Then build and drop you own reloads, with similar specs, slowly to the same velocity....and your done!

You observations are generally correct, all but the loose powder comment, not all powder blends and formations are location sensitive. With a majority of subsonic accuracy found within 300 yards (in a .308) and real accuracy found to 150 yards, there is little need imo for such a heavy bullet. I recommend you build out to 165-170s. Here is a box that I have used, now granted this is certified (taking care of your concerns) and developed for take down, but the same weight without the flat nose would provide similar ballistic stability. Perhaps, buy a box, and start from there. There are of course others, but this is one heavily tested build.

http://www.awcammo.com/By-Caliber/308-WIN/308-WIN-170gr-Sub-Sonic-Flat-Point-20-Round-Box.html



 
#4
Re: Subsonic loads "prohibited" in AAC cans?

I ran the 200gr Lapua factory load thru my 762-SD with no problems whatsoever. Trying SW ammos 175gr Sub load this week, $1.00 apiece, beats the shit out of the Lapua ammo if they work
 
#5
Re: Subsonic loads "prohibited" in AAC cans?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tom Olson</div><div class="ubbcode-body">I ran the 200gr Lapua factory load thru my 762-SD with no problems whatsoever. Trying SW ammos 175gr Sub load this week, $1.00 apiece, beats the shit out of the Lapua ammo if they work </div></div>

What twist rate on your barrel? Also, how was precision with the Lapua compared to your best factory supersonic load? Thanks!
 
#6
Re: Subsonic loads "prohibited" in AAC cans?

1/10 POF barrel 16inch. I just plinked that day, first time running 308 subs. laughed my ass off it was so quiet
 
#7
Re: Subsonic loads "prohibited" in AAC cans?

Id say shoot them without the can on paper and make sure they arent keyholing first, then blast away if they arent. This isnt foolproof, but if they ARE keyholing then they most likely arent stable out of the barrel either. But they could be going through straight and unstable out of the muzzle, thats just a risk you take.
 
#8
Re: Subsonic loads "prohibited" in AAC cans?

Ok I guess this will be my stupid question on this forum...

Is it the low velocity of subsonic ammo that cause the destabilization or the weight of the ammo.

So will it be easier or better yet safer to get a heavier or lighter bullet ?

I have a 1-11.25 24in barrel with the same 762SD

sorry for the dummy question
smile.gif
 
#9
Re: Subsonic loads "prohibited" in AAC cans?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: trophyhunter</div><div class="ubbcode-body">Ok I guess this will be my stupid question on this forum...

Is it the low velocity of subsonic ammo that cause the destabilization or the weight of the ammo.

So will it be easier or better yet safer to get a heavier or lighter bullet ?

I have a 1-11.25 24in barrel with the same 762SD

sorry for the dummy question
smile.gif
</div></div>

That's not a stupid question at all. In fact, I only recently educated myself as to the answer. While velocity and weight do influence stability, the major component is the length of the bullet. The reason people often talk about just the weight is that for the most part (and this was especially true in the past), mainstream ammo is all made of the same stuff...lead...so weight tends to vary directly with length for any given caliber. There are complexities here too, like the shape of the bullet, but for the sake of simplicity, it's generally true. So, since bullet length is not typically published by manufacturers, people just go by weight when considering stability.

The reason length is the most important variable is complex, but it boils down to leverage. A bullet in flight is stabilized by 2 things: lift forces generated symmetrically around it by it's movement through the air and gyroscopic forces generated by it's spin. Obviously, weight and velocity affect both of these, which is why the JBM ballistics calculator takes these and several other factors into account. But length affects the bullet far more drastically because the longer the bullet, the more leverage random forces caused by imperfections in the bullet, the barrel, aerodybamic turbulence, etc., have in relation to the bullet's center of gravity.

A good example of this is that a squat, wide spinning top will spin in balance for some time with just a flick of your fingers. In comparison, you probably couldn't get a pencil to spin on its tip that way if your life depended on it. Even if you change the pencil to a steel rod of the same dimensions, you still could not spin it...this illustrates that weight is not as vital to stability as length.

So, to answer your question, yes, heavier bullets are less stable. But this is due to their length rather than their weight. In fact, if they were lighter but the smae length, they'd be even less stable since they would generate less gyroscopic force given the same rate of spin. BUT...you can compensate for the longer bullets with a faster twist rate, which increases their rate of spin. Here is the link to the JBM stability calculator. You are looking for a stability factor between 1.3 and 2.0. That site also has a library of common bullet lengths...very useful.

I learned all this from a REALLY informative article that goes into it in WAY more depth, but the link is on my home computer and I'm at the office right now. I will post the link later tonight if you wanna do some technical reading
sleep.gif
 
#10
Re: Subsonic loads "prohibited" in AAC cans?

I would love to read that article and thank for the info.

I'm trying to subsonic 2 rifles I own and it seems they have switched barrels.

SR-25 with 1-10 16"
REM 700 with 1-11.25 24"

I guess I'll just start sending a few down range with out the suppressor and see if I can notice any keyholes or oblong holes
 
#11
Re: Subsonic loads "prohibited" in AAC cans?

I know every round, suppressor, and rifle is different; but are you fellas able to cycle a 308 AR with any subsonic ammo? How about with swithcing out the buffer and or spring for a lighter one?
 
#13
Re: Subsonic loads "prohibited" in AAC cans?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: trophyhunter</div><div class="ubbcode-body">I would love to read that article and thank for the info.</div></div>

Here is the link to that article.

Anyone else have any suggestions for good factory subsinic loads? I wanna try several. Thanks!
 
#16
Re: Subsonic loads "prohibited" in AAC cans?

Well, YMMV, but the 200gr Lapua Subsonic rounds would NOT stabilize in my 1-11.25 twist Crusader. It wasn't keyholing at 10,25 and 50 yards, so I was able to test out some loads, but it literally was curving and tumbling the bullets by 100 yards. Looked like something out of a bad movie through the scope.

I built a project gun specifically for subsonic 308 and went with a 1-8 twist AAC barrel. night and day difference. Stabilized the 200gr Lapuas out to 300 yards (limit of the range) and was still punching round holes at 300 (with a 4" group at that range to boot).

Might want to try some 175s in that barrel.

Just my 2 cents,
madd0c
 
#17
Re: Subsonic loads "prohibited" in AAC cans?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tom Olson</div><div class="ubbcode-body">Southwest Ammo does make sub-308 ammo </div></div>

I did not find a subsonic round on their website. Am I missing something? Anyone else have any recommendations for a high precision subsonic factory 308 load? Thanks!
 
#19
Re: Subsonic loads "prohibited" in AAC cans?

madd0c - how do you like that AAC barrel? I've got one going on now. Although, I plan to use it for sub and std ammo. Have you put standard loads downrange yet? What's your overall take on it?

Thanks!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: madd0c</div><div class="ubbcode-body">I built a project gun specifically for subsonic 308 and went with a 1-8 twist AAC barrel. night and day difference. Stabilized the 200gr Lapuas out to 300 yards (limit of the range) and was still punching round holes at 300 (with a 4" group at that range to boot).

Might want to try some 175s in that barrel.

Just my 2 cents,
madd0c </div></div>
 
#20
Re: Subsonic loads "prohibited" in AAC cans?

My old FN SPR had a 1 in 12 twist. The heaviest round I could shoot sub-sonic through it was 155gr Noslers. It was accurate out to about 400yds subsonic.

Bonus part is you can find places to buy lots of 1000 for about $150 on occasion.
 
#21
Re: Subsonic loads "prohibited" in AAC cans?

I only shot some FGMM 168s through it prior to starting working up my sub load. It shot about 1.5" at 100 yard with those. It was probably over spinning those. They didn't disintegrate and left good holes, but I am sure you could get down to sub MOA with proper load workup and a heavier bullet.

madd0c

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Merlin_019</div><div class="ubbcode-body">madd0c - how do you like that AAC barrel? I've got one going on now. Although, I plan to use it for sub and std ammo. Have you put standard loads downrange yet? What's your overall take on it?

Thanks!
</div></div>
 
#22
Re: Subsonic loads "prohibited" in AAC cans?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CanadaGoose</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: trophyhunter</div><div class="ubbcode-body">I would love to read that article and thank for the info.</div></div>

Here is the link to that article.

Anyone else have any suggestions for good factory subsinic loads? I wanna try several. Thanks! </div></div>

I read that article by The AnarchAngel. Very good reading. Thanks for posting that.
 
#24
Re: Subsonic loads "prohibited" in AAC cans?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tom Olson</div><div class="ubbcode-body">1/10 POF barrel 16inch. I just plinked that day, first time running 308 subs. laughed my ass off it was so quiet </div></div>

Not quite fast enough to shoot heavy subsonic without the risk of baffle strike. But you might be using lighter bullets and trailboss.

Subsonic/Supersonic use in .30 with 200-240gr projo's is usually accomplished with a 1:8" twist See 300 whisper, Fireball and Blackout. 1:7" for dedicated subsonic.

You'll have to go to lighter bullets and trailboss powder to accomplish what you want with a .308 factory or otherwise.
 
#25
Re: Subsonic loads "prohibited" in AAC cans?

I have a 308win 20" 1x10 twist and i load my own subs:
11.0gr trail boss
180gr hornady round nose
lapua brass
210m primer

this load works perfect and shoots a single hole at 50 yds and i can even hit a 8x8 piece of steal at 200 yds, which is pretty dang far for a bullet that slow and inneficeint.

CJG
 
#26
Re: Subsonic loads "prohibited" in AAC cans?

Thanks for the data, Rotor! I will have to try that when I get all my reloading stuff bought. My twist is 1:11, so I might go with a 175gr bullet, but round nose might work even at 180 since it's shorter than a pointed bullet of the same weight.
 
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