After 6 weeks of waiting I finally received my barrel and so could complete my 300 whisper build.

What we have here:
SI Defense 300 fireball barrel. 16"  carbine gas system. 1:8 twist
Larue Eotech mount with Eotech 512
Larue Aimpoint magnifier holder thingamajig and magnifier
MBUIS that will probably never get used but I had them lying around so I put them on there
YHM Supressor mount
YHM .308 cal Phantom suppressor
Rifle length YHM free float handguard
Everything else is pretty standard





I had to drill the hell out of the handguard to get the adjustable gas tube to be able to be installed. It was an hour long wrestling match even after it was drilled out. But it is there and can't be seen unless you are right on it.  Pain in the ass. But it works and I'm happy enough.



RANGE REPORT!!
Hot damn! A mix of happy and sad. But mostly happy. I was at my local 25 yard indoor range. So don't ask about accuracy.
I made 40 rounds. A mix of things to see what I could get to work.
10 were full power. 30 were sub sonic.

The full power, once I dialed in the gas tube(only took 3 rounds), cycled and were just awesome. The feeling of throwing 150 grain bullets down range from a normal size AR was kick ass.

I switched to the subs and tried the can. No baffle strikes. So I guess it lines up fine with the bore.
Only one load would cycle. my 210 grain SMK load.  All the rest were either AA #5 with 220's which I was told would probably not cycle. Or 165 or 180 grainers.  They needed a touch more powder.  They almost cycled with the gas tube opened all the way, but not quite.

The one load that cycled, the 210 SMKs, did not like the Pmag. I loaded four and went pfft pfft and then it jammed because the round did not want to come out of the mag.  I reset and pfft pfft and lock back.
So that load probably works in a standard mag.

But......the subs through the can are....damn quiet.

Looks good man!

liking the price of that barrel. in for accuracy report.

Very Tacticool!!!  I'm waiting for my upper should be done today what loads are you shooting? do you plan on using supersonic also?

That is a nice looking gun!

looks awesome man, need range report

I will be trying the supersonic and subsonic loads posted in here.

http://www.ar15.com/forums/topic.html?b=6&f=42&t=315146

RANGE REPORT!!
Hot damn! A mix of happy and sad. But mostly happy. I was at my local 25 yard indoor range. So don't ask about accuracy.
I made 40 rounds. A mix of things to see what I could get to work.
10 were full power. 30 were sub sonic.

The full power, once I dialed in the gas tube(only took 3 rounds), cycled and were just awesome. The feeling of throwing 150 grain bullets down range from a normal size AR was kick ass.

I switched to the subs and tried the can. No baffle strikes. So I guess it lines up fine with the bore.
Only one load would cycle. my 210 grain SMK load.  All the rest were either AA #5 with 220's which I was told would probably not cycle. Or 165 or 180 grainers.  They needed a touch more powder.  They almost cycled with the gas tube opened all the way, but not quite.

The one load that cycled, the 210 SMKs, did not like the Pmag. I loaded four and went pfft pfft and then it jammed because the round did not want to come out of the mag.  I reset and pfft pfft and lock back.
So that load probably works in a standard mag.

But......the subs through the can are....damn quiet.

I absolutely  love that sound

I love shooting 220 Pro Hunters sub-sonic loads through my .300 with my 7.62 can.

Depending on what your application for the subsonics is there is now an expanding subsonic bullet on the market.  I just got 50 of them for testing but haven't played with them much yet.

Outlaw State Bullets

The owner told me they cycle best with some magazine tweaks.  I've only loaded a couple so far and did have some cycling issues due to the blunt nose but I haven't messed with the magazines yet.  I'm pretty sure I'll get it worked out soon.

They are supposed to work with 220 SMK load data.  I don't have my load data in front of me but IIRC I started with 8.5 grains of 2400 and they were subsonic.  It opens up some interesting possibilities with the 300/221 series of cartridges for hunting.

Ghetto tag for accuracy and more load information.

You might try AA1680 as your powder.  I had better luck with it cycle the action in my 300-221.  It worked great with 220gr SMKs.  It even cycles and feeds 150gr FMJs, but won't lock the bolt back on the last round.

AA1680 would be a good powder to try.  The reason the 300/221 has been gravitating toward the pistol length gas systems is that if you use the faster pistol powders the gun is much less load sensitive with the shorter system.  These fast burning powders with large subsonic projectiles works very well.  The carbine length system is better if you plan to shoot primarily supersonic with slower powders like AA1680.  With some load tuning you should be able to get the carbine system to run with subs as well, you'll just have to play with and tune the system for your specific load.  

Do you know what the gas port is drilled to?  You may have to open it up some as well for the subs and this won't be an issue since you have an adjustable gas block.

love to hear it.......glad it s working out I sure like mine.

Ruzhye, I never meant to imply there was anything wrong with your rifle and I apologize if I came across that way.  I just wanted to provide information about why you may have to use slower powder and take the time to tune the gas system to the load.  The carbine gas system is definitely viable with the 300/221 and has been working for quite some time.  Once you get some loads and gas block settings that work for you you'll be set.

I haven't personally tinkered with a carbine gas system but there is a wealth of information at quarterbore.net on every combination imaginable for the 300/221.  They could help you alot with load development if you haven't checked them out already.

Just got a can for mine!  Will be testing it this weekend and will give range report if anyone is interested.

We had to change to a slower burning powder so that our subsonic rounds would cycle properly. We are using 11.8 grains of accurate 1680 with converted LC 5.56 brass.  It is pushing 220g sierra BTHP at an average of 1060fps out of my Novesky barrel.  This barrel has a short non adjustable gas tube, so it may be different from others.  Well I hope this helps some one

Nice looking rig!

thanks!

Don't worry about it, no offense taken.  I was just agreeing that the pistol length gas seems to be ideal.  I go by Colohunter on quarterbore and some other forums, for some reason I couldn't get that name here.  

Just got back from testing a load at the range today out of my 10.5" Barreled upper, pistol length gas system, with an oversize gas port and a Gemtech HVT on it. We tested a 220 gr SIE Matchking w/8.4 gr's of Ramshot Enforcer. It croneyed at a spread of between 1001 fps and 1020 fps, with a OAL length of 2.170 on the loaded cartridge.

Later this week we will be testing the same with 8.6, 8.8, 9.0 gr's of Ramshot Enforcer and I will post the data from that after our next range trip.

We did original testing with 11 gr's of Ramshot Enforcer, which croneyed at 1350 fps and started popping primers and left bolt indentations in the fired brass.

I also have a 16" barrel w/a carbine length gas system on the way and if anyone wants ? I can post test data for that also, when we start testing on it.

Glad to see there is others starting to pick up an appreciation for this cartridge ! =-)

I need to brake out the crono.  took the rifle out and shot it for the first time with the can on it and it seamed lower than I thought.  I believe that  fps increased with the can but I do not know how much.  The reason I say this is because I had to come down on my scope with the can on about four in at 100 yd.  One good thing is that the can is repeatable.  I will get ought with the crony and see what is going on and let you all know.

You had to come down meaning the shots were lower?  That is completely normal with a can because the extra weight of the can on the front of the barrel pulls the barrel down a bit.

This is normal, especially with heavy cans and light barrels.  I use a YHM .308 can on several rifles, one of which is a 16" lightweight.  On the 16" lightweight the rounds hit low at 25 yards.  On my 10.5" and 11.5" barrels the effect is much less pronounced.

Without can loads are averaging 1060. With can that average 1140.  I nead to do some more lode development, but this lode shoots five shot raged holes at 100, I don't know if I won't to mess with it.  Well I ges I can see what happens.