Update on subsonic loads?

[204 AR]

I've scoured the internet, with the best info coming from right here (of course). It looks like with a mild charge of 8208 behind a 160 gr Hdy that it's doable to get a subsonic Grendel load that functions the rifle. With a suppressor on the way this is very interesting to me. I've been contemplating a Blackout upper but that's such a boring cartridge compared to the 6.5, and quite frankly I've got too many calibers as it is.

Is there any new info anyone would share? I run an 18" upper with mlgs. Thanks!

[kmon]

I think you will be better off with Trailboss than 8208 for subsonic loads. Know there are some loads out there that cycle 223 ARs quite well using trailboss powder. Trailboss is a bulky powder that fills up space better than many other powders. AA5744 is also used for similar reasons in some subsonic loads.

Here is a pretty good video with the guy using Trailboss for subsonic 308 loads. https://www.youtube.com/watch?v=Ix2si1M2iM8

Working up subsonic loads you have to rethink some things like working downward in velocity and pressure instead of increasing them toward max like we do most of the time. You do not want to go low enough to stick a bullet in the barrel

[Klem]

This has been discussed before and a search of the archives will reveal the frustration of others.

No offence, but that video is for .308 and his methods reveal a degree of ignorance. There is also the important issue of cycling the action of an AR to consider.

You can use Trail Boss to load subsonic with an 18" barrel but I doubt if it will cycle the action, even with a suppressor. If it is a cycling, subsonic AR you want you might have to put up getting your Blackout after all.

[kmon]

I agree Klem, if I were to want to shoot subs in an AR I would just go with a 300BO. And you are correct Sir about the video showing some things that are no where detailed enough in his practices especially powder charge weights. When working up subs start high and work your way down and a good Chronograph is necessary. Do not go too low and stick a bullet in the barrel or too high and create a pipe bomb at your face.

Have seen loads that cycle 223 AR pistol and SBR but they took hundreds of rounds to get to work with different powders than your pistol powders usually used for subs and with different primers as well along with a very heavy bullet for caliber. I know the ammo manufacture that worked those up some of the issues he had along the way but with the time and effort keeps his secrets.

Some have modified buffer springs for dedicated subsonic ARs to get them to cycle with their 223 Subsonics. Primer selection and using a fast burning rifle powder not pistol powders have helped in getting the pressures at the gas port up for them. But those slower powders leave 15 to 20% unburned powder making for a lot more cleaning necessary.

Hell we have enough problems with ARs cycling issues with full power loads discussed on here being over gassed or under gassed or other issues to go into this can of worms of getting an AR to cycle subs with the Grendel. Even if one got it to work in their AR there are enough differences between ARs that if someone tried same loads in a different AR they might or might not work.

[A5BLASTER]

Im going to show my ignorance and ask this question.

What is the use of a subsonic load in any hunting rifle?

I admit I have done no research on this but first thoughts in my mind when I hear the word subsonic is queit, slow and under powered and not accurate.

Again please excuse my ignorance on this subject, not trying to start any arguing just would like to know.

[Klem]

Im going to show my ignorance and ask this question.

What is the use of a subsonic load in any hunting rifle?

I admit I have done no research on this but first thoughts in my mind when I hear the word subsonic is queit, slow and under powered and not accurate.

Again please excuse my ignorance on this subject, not trying to start any arguing just would like to know.

Subsonic eliminates the down-range sound barrier crack that supersonic bullets make. Add a suppressor and you tame the two loudest of the four sounds made by a firearm. The 'cost' of subsonic is the shorter effective range and the loss of kinetic shock and temporary wound cavity if shooting flesh. Subsonic however can be just as accurate as supersonic, for example the .22L Bench-rest discipline.

Benefits of subsonic hunting apart from lowering the noise to yourself, others and any animals in the vicinity is that potentially more game can be taken without scaring the rest (e.g. rabbits near a warren). With subsonic and a suppressor you can also confuse the game as to where the threat is. They sometimes run towards you if you miss or if the first shot is not deadly. Or they panic less and slow quicker for follow-up shots. Admittedly the first shot may not have been deadly because it was subsonic to start with.

If you are illegally poaching or near others that do not want to be disturbed, or you are mandated not to disturb others then subsonic is a possibility.

The military potential is obvious.

A subsonic Blackout is akin to a .45 handgun round. A typical load is 220gn travelling at 1,000fps. An accurate .45 but with a narrower profile which aids feeding from the magazine but does not help expansion. A subsonic Grendel would be equivalent to a 9mm handgun (140+gns travelling at 1,000fps).

[kmon]

Well said Klem

I have loaded and used subsonic rounds for taking small game while hunting big game with bolt action rifles and pest control around the house, no hearing protection required. For bigger critters have used my 44mag carbines with subs for hogs at close range, a 300gr .429 diameter bullet at 1050fps is effective on hogs at close range.

[Von Gruff]

Well said Klem

I have loaded and used subsonic rounds for taking small game while hunting big game with bolt action rifles and pest control around the house, no hearing protection required. For bigger critters have used my 44mag carbines with subs for hogs at close range, a 300gr .429 diameter bullet at 1050fps is effective on hogs at close range.

I am selling quite a few 450gn 458 cast bullets here for the guys who are using them subsonic through suppressed rifles for deer hunting in the bush. Very accurate and good to 100 yds but most are killed inside 50yds.
For the Grendel and a 140 - 160 grain cast bullet I would be looking at 75/25 alloy (PB/ww) and maybe a tumble lube like Lee mule snot, especially if you are going to run it through an AR so you didn't get lube purge into the gas tube.

[LRRPF52]

Somebody had a 20" Grendel running with 160's. Even had video of it blowing through a lot of water jugs.
It was txgunner00:

http://www.65grendel.com/forum/showthread.php?6425-Suppressed-sub-sonic-short-video

FINALLY!!! I have a sub sonic load that cycles my action. Data is below.

20" Satern barrel, AR-15 carrier, 3.0 OZ buffer, gas port diameter .098"

Powder: IMR 8208
Case: IMI 7.62x39, necked down but NOT fire formed.
Primer: Rem 9 1/2
Bullet: 160 Hornady RN
COL: 2.220

Charges: 5 shot strings

14.5 gr, 1187 avg, 36 ES, 13 SD
14.0 gr, 1129 avg, 55 ES, 23 SD
13.5 gr, 1079 avg, 56 ES, 26 SD

All 5 shot strings were fired from a magazine, cycled properly and locked back on the last round. Temperature was 90 deg. (in March ) so the speed of sound was around 1150 fps. I still intend to do some more testing and fine tuning but these results are encouraging.

Cases were only slightly sooty and I'm hoping magnum LR primers will help with this. Most of the soot blow by could be due to the fact these are not fire formed cases so I'll load some rounds with FF cases to test this theory. I'm using non-fire formed cases specifically for the purposes of increasing load density and fire forming the cases for full power loads.

More to follow as I can get to it...

[204 AR]

Somebody had a 20" Grendel running with 160's. Even had video of it blowing through a lot of water jugs.
It was txgunner00:

http://www.65grendel.com/forum/showt...ic-short-video

That's the info I was referring to. I was hoping he would chime in, I wanted to see if he has continued using those loads or had developed others.

I have always though of it about the same as some of these replies, why would anyone want subsonic/underpowered anyway? Well, 2 main reasons for me. 1-Short range plinking with the kids and family. Can shoot mild steel targets with good power but not beat up or pierce the steel, and do it quietly. Thats a lot of fun for the kids. 2-Home defense.

Having said that I wasn't really looking to debate the why's and wherefore's. Just looking for first hand experience from the guys that have "been there, done that" with this round.
Thanks

[Klem]

Somebody had a 20" Grendel running with 160's. Even had video of it blowing through a lot of water jugs.
It was txgunner00:

http://www.65grendel.com/forum/showt...ic-short-video

Interesting.

14.5gn 8208 with a 160Hornady is a 53% case fill at 2.2" (Ref, Quickload). Below 80% case fill and we start worrying about SEE and flash-over. You could fill that space and push the powder against the base with a filler like cotton or Dacron.

Sound of the barrier break starts to build from 90fps below the speed of sound and peaks 150fps above. Those 8208 loads are not as quiet as they could be, hopefully still cycling the action at 1,050fps which looks like about 13 grains. Shorter barrels will help here. Not only for lower velocity but also more likely shorter length to the gas block...more pressure to cycle.

[Von Gruff]

It may be relevant or not but I used 6.5 gn red dot under a cast bullet to fireform a lot of 7.62x39 cases to my GM chamber. Good case fill out and a very mild report. I didn't chrono the load but it had to be on the low end. The good thing about red dot is that it is not position sensitive and even with such a small amount of powder in the case it needs no filler of any sort.

[ricsmall]

Maybe someone can get custom cutter on here to cut a 16" barrel with pistol length gas, and trail boss might cycle then. I've shot some trail boss loads with a friend in his can and they were stupid quiet. Pellet gun quiet.

Richard

[Klem]

Maybe someone can get custom cutter on here to cut a 16" barrel with pistol length gas, and trail boss might cycle then. I've shot some trail boss loads with a friend in his can and they were stupid quiet. Pellet gun quiet.

Richard

If that pistol length gas operated for supersonics as well as subs then you have an equivalent to a Blackout in Grendel. If however the pistol length gas ends up only good for subsonics then you may as well get a Blackout upper and enjoy the heavier weight subs.

[ricsmall]

It might could be tamed with an adjustable gas block. It'd b interesting to try tho.

Richard