Talk me out of a 5.56 can

[drgrant]

I dont think any 9mm luger 147gr is going to be supersonic

It'd have to be really, stupid hot. Fed HST 147 +P is like 1050 FPS and I don't think that's enough, either. I don't think it's impossible to make a 147 exceeding 1100 FPS but it might be challenging to do without blowing things up. I bet I could get there with Power Pistol.

-Mike

 

[bigblue]

Yeah, but my point was 147s are gonna be dribbling out of an MP5SD unless they're loaded hot to begin with. They're not going to be leaving the gun at 1000 FPS out of an MP5SD, unless you have some really hot ammo loaded up for it. I believe HK even tells people right in the manual to NOT use subsonic with it.

-Mike

I can see that. The MP5SD's integral suppressor is HUGE. I mean, like bigger than a 7.62 suppressor huge so it wouldn't surprise me if it knocks a 115 gr bullet down to 147 gr speeds.

Trust me, I was surprised that my 147 gr loads went supersonic. They were too hot to start with coming out of my 226 at nearly 1,000 fps so they must barely be clearing 1,100 fps in the 8.5" barrel.

 

[ChevyGuy91]

I can see that. The MP5SD's integral suppressor is HUGE. I mean, like bigger than a 7.62 suppressor huge so it wouldn't surprise me if it knocks a 115 gr bullet down to 147 gr speeds.

Trust me, I was surprised that my 147 gr loads went supersonic. They were too hot to start with coming out of my 226 at nearly 1,000 fps so they must barely be clearing 1,100 fps in the 8.5" barrel.

The volume of the suppressor does not change the velocity of the bullet, the barrel length and any porting are what change the velocity.

 

[bigblue]

It'd have to be really, stupid hot. Fed HST 147 +P is like 1050 FPS and I don't think that's enough, either. I don't think it's impossible to make a 147 exceeding 1100 FPS but it might be challenging to do without blowing things up. I bet I could get there with Power Pistol.

-Mike

You are also measuring out of what, a 4.25" barrel? 9mm does gain some velocity (not much) past 6" barrel lengths.

 

[dcmdon]

Why the hell would you want to leave it mounted all the time? /boggle. Get something that uses a ratchet mount like the AAC system
or something that takes a lug.

-Mike

I have a direct attach can on my 10.5" SBR. I never take it off. I could if I wanted to. But I never do.

This pic is now a couple of years old. I've now got a magpul adjustable stock on it.

 

[dcmdon]

It'd have to be really, stupid hot. Fed HST 147 +P is like 1050 FPS and I don't think that's enough, either. I don't think it's impossible to make a 147 exceeding 1100 FPS but it might be challenging to do without blowing things up. I bet I could get there with Power Pistol.

-Mike

I run 5 gr of AA5 and although I can't remember the exact MV. It was right around 1000. The primers show slight pressure signs. Mainly an imprint of the rectangular hole i the breech for the striker of the Glock they normally are shot through.

 

[bigblue]

I run 5 gr of AA5 and although I can't remember the exact MV. It was right around 1000. The primers show slight pressure signs. Mainly an imprint of the rectangular hole i the breech for the striker of the Glock they normally are shot through.

And again you are talking out of a 4" barrel. More than double the barrel length and that HST +P gains another 50-75 fps and you get a sonic crack. Not by much but physics don't care about "much".

 

[usp45ct]

I'll deviate a bit.

do not buy a 5.56 can.

buy 2. If one is good, two is better.

 

[dcmdon]

And again you are talking out of a 4" barrel. More than double the barrel length and that HST +P gains another 50-75 fps and you get a sonic crack. Not by much but physics don't care about "much".

5" barrel. But your point is still valid. I was getting something crazy like 1600 fps out of my MP5 with some hot 115 gr bullets.

 

[mousegunguy]

Check out hickok45 newest review of a mossberg patrol in 5.56. He shoots it suppressed with and without subsonic rounds.

 

[bigblue]

5" barrel. But your point is still valid. I was getting something crazy like 1600 fps out of my MP5 with some hot 115 gr bullets.

Yeah we were getting 1500+ fps with the 125 grains so I bet those 115's are hot.

I still do not get the point of subsonic 5.56: There is not enough mass in a 55, 60, or even 75 grain bullet to do much damage at those speeds. I'm surprised that he can even get reliable cycling of the BCG at those pressures.

 

[ChevyGuy91]

I still do not get the point of subsonic 5.56: There is not enough mass in a 55, 60, or even 75 grain bullet to do much damage at those speeds. I'm surprised that he can even get reliable cycling of the BCG at those pressures.

There really isn't a point, besides saying wow that was quite. And useless.

This is why 300BLK was brought about and marketed so heavily, it is kind of useful with subsonic ammo.

 

[bigblue]

There really isn't a point, besides saying wow that was quite. And useless.

This is why 300BLK was brought about and marketed so heavily, it is kind of useful with subsonic ammo.

Yeah. A .30 cal can makes so much more sense to me: 7.62x39, .300blk, .308, etc.... $0.02 I guess.

 

[atilla]

There really isn't a point, besides saying wow that was quite. And useless.

so, so true.

i need to build the 300blk upper and get some subsonic ammo.

still chasing the unicorn that is subsonic .223 that cycles. for the lulz.

 

[dcmdon]

Yeah we were getting 1500+ fps with the 125 grains so I bet those 115's are hot.

I still do not get the point of subsonic 5.56: There is not enough mass in a 55, 60, or even 75 grain bullet to do much damage at those speeds. I'm surprised that he can even get reliable cycling of the BCG at those pressures.

No AR on the planet will cycle with subsonic 5.56 loads. A subsonic 5.56 turns an AR into a straight pull bolt gun. (Of course, in theory, if you loaded up heavy enough .224 bullets to result in a subsonic round with a full powder charge, it would cycle the gun. But any bullet that heavy (guessing in the 110 gr range) would be too long to stabilize in even a 1:7 barrel. )

I agree with you that a subsonic 5.56 AR is pointless. If you want to shoot 60 gr projectiles at subsonic speed, you are far far better off with (and don't laugh) a .22 LR with the Aguila 60 grain "Sub-Sonic Sniper"

Its easier to run, it costs a fraction of what an AR costs and you can even use .22 LR cans, which cost a fraction of what 5.56 cans cost.

In summary, a subsonic .223 is a turd, not worth anyone's time. Just buy a 10/22 or a M&P 15-22.

With respect to supersonic loads through a suppressor, it is still not hearing safe, but it is nice and quiet. Of course, if you were a sniper, a can would be mask where the shot came from. But I'm not a sniper, so this benefit makes no difference to me.

Don

- - - Updated - - -

so, so true.

i need to build the 300blk upper and get some subsonic ammo.

still chasing the unicorn that is subsonic .223 that cycles. for the lulz.

At least with a subsonic .300 blk, you can throw some mass down range. Whats the heaviest .30 cal bullet that people use in .300 blk? Its got to be close to 200 gr.

 

[ChevyGuy91]

so, so true.

i need to build the 300blk upper and get some subsonic ammo.

still chasing the unicorn that is subsonic .223 that cycles. for the lulz.

At least with a subsonic .300 blk, you can throw some mass down range. Whats the heaviest .30 cal bullet that people use in .300 blk? Its got to be close to 200 gr.

I have some 220's, but I have read of some dudes casting their own and stuffing massive lead bullets into the case and shooting them out of the H&R's.

 

[dcmdon]

I have some 220's, but I have read of some dudes casting their own and stuffing massive lead bullets into the case and shooting them out of the H&R's.

What kind of twist do those rifles have? Its got to be 1:6 or something like that.

Beware the baffle strike. Make sure you shoot it at paper first to confirm that they aren't tumbling.

Can you give me a link to the 220 grs? Are they originally intended for .300 Win Mag?

I have a 16" Rem .308 700 that I got for $335 through the Christmas time friends and family program. I also have an old Sound Technologies .30 cal can that I have on it. Its a 1:10. I'd like to work up something subsonic and as heavy as is practical. But first I need to make sure it will stabilize.

And before anyone asks why, just because. I find it fun to make stuff like this work.

Don

 

[ChevyGuy91]

What kind of twist do those rifles have? Its got to be 1:6 or something like that.

Beware the baffle strike. Make sure you shoot it at paper first to confirm that they aren't tumbling.

Can you give me a link to the 220 grs? Are they originally intended for .300 Win Mag?

I have a 16" Rem .308 700 that I got for $335 through the Christmas time friends and family program. I also have an old Sound Technologies .30 cal can that I have on it. Its a 1:10. I'd like to work up something subsonic and as heavy as is practical. But first I need to make sure it will stabilize.

And before anyone asks why, just because. I find it fun to make stuff like this work.

Don

http://www.midwayusa.com/product/16...0-grain-open-tip-match-otm-subsonic-box-of-20

I have shot a bunch of this stuff through my upper and can with no issue. My barrel is 8.5" with a 1:7 or 1:8 twist, I don't remember.

I have also shot subsonics loaded with 187 and 200 grain bullets, along with some supers loaded with 110 and 147. All of these shot just fine, how ever I have not benched the gun and shot it for groups.

 

[Kevin_NH]

I have a 16" Rem .308 700 that I got for $335 through the Christmas time friends and family program. I also have an old Sound Technologies .30 cal can that I have on it. Its a 1:10. I'd like to work up something subsonic and as heavy as is practical. But first I need to make sure it will stabilize.

The Ruger Gunsite Scout is also 1:10 and a number of people run it suppressed with commercial subsonic ammo, most popular seems to be Setpoint SS -- Setpoint's "Subsonic Scout" with 175gr Sierra Match King, this is regarded as being baffle-safe to shoot subsonic with a 1:10 twist.

You might try to get your hands on Lapua subsonic 308 for reloading; Lapua uses a 200gr bullet designed for the application and a reduced-volume case, about 10% less internal volume than .308win. Even starting from 7.62x51 brass would help a little bit.

 

[throttle-junkie]

Well I went with a 35 cal can. I was all ready to put down on a center fire rifle can but there behind the shelf were a stack of blemished YHM pistol cal cans for half off. How could I say no? So now it's time to start a 9mm SBR build. I have always wanted one. The best part now I can rationalize why I bought all that 158 grain 9mm.

 

[dcmdon]

Don't forget that if your 9mm can has changeable end caps, you can use it for a subsonic .308 load with lighter weight bullets.

Remember that a 147 gr 9mm running at 1000 fps has similar power to a 168 gr .308 running at 1000 fps. It may even be easier on the can than a 9mm pistol since the longer barrel will greatly reduce the uncorking pressures that the can will experience.