My 300 build is finally up and running!

[alorton]

A while back I picked up a Spike's Tactical .22LR Upper and shortly after getting it I realized it would cycle subsonic ammo, which meant I needed a suppressor. After picking up a .22 Suppressor I have had tons of fun with that rig as well as several other .22's I have threaded and used with the suppressor.

After a while I wanted something bigger. Some research on the subject of suppressed AR's led me to the 300/221. I had never messed with a wildcat before and I didn't know anyone around my area that had played with this cartridge. It was a little daunting but I decided to give it a go.

I knew I wanted a short barrel, the ability to shut off the gas for ultra quiet shooting, a side charger with the handle on the left, and a QD suppressor I could also use on 223.

Here's what I ended up with:
RRA registered SBR lower (my patrol rifle lower, it wears an 11.5" in 223 at work)
ASA sidecharge upper
Noveske 10.5" 300FB barrel
Paladan Machine 3-position gas block (open/restricted/closed)

I had to have the barrel turned down so it would take a .750 gas block in the pistol position. My research on this site led me to the conclusion that I had to have the short gas system for reliable cycling of both supersonic and subsonic rounds and only the .750 Paladan gas block would fit under a free float handguard. I went with a YHM because it gives me access to the slotted screw that is used to cycle through the 3 positions.

I also picked up a set of Redding 300/221 reloading dies, a form and trim die, and a Forster power trimmer to make brass from 223 and reload it.

This project has been over a year in the making and I finally have a working rifle! Here are some pics.

The gun:


The gas block:


The ammo:


I've worked up a few loads I'm happy with. Using Sierra's tables I started with a 110gr Sierra Varminter. I ended with using 16.0 grains of Hercules 2400 to get an average of 2050 fps. I then played around with the Sierra 240gr SMK's and had to back off to 8.5 grains of the 2400 to get an average of 1040 fps. After that I decided I wanted a better bullet in the 110gr range so I loaded up some 110gr Hornady V-Max's. I get 2100fps with the same 16 grain charge of 2400. The supersonic rounds cycle the gun with the gas port in the restricted position and the subsonics cycle with the port fully opened. I only bought the 2400 because it was all that was in stock locally that Sierra had used making its tables. I had such good luck I'm not sure if I'm gonna bother with any others. Well, I'm sure I will since that's what's so fun about it.

Accuracy has been good so far (about 50 rounds through the gun). All groups have been a ragged hole but I've only shot at 25 yards so far. I have more space but the field at my house is way to muddy at the moment (corn field).

I'm very pleased and am anxiously awaiting my YHM 7.62 suppressor. The ATF has my money and I'm just waiting on the stamp so I can go pick it up. I can't wait.

Overall I think this is a very cool little round. I'm getting more muzzle energy with the 110gr bullets out of a 10.5" barrel than I get out of my 18" barrel with 55gr .223 XM193 and I'm using less powder. I'm sure this is due to the faster burning powders used and the small shoulder used on the 300's. I also think I could get another 100 or 150 fps but I'm not sure I want to push it. After all, the whole point was the big subsonic rounds for suppressed shooting and I don't want to beat up the 1:8 barrel with alot of hot supersonic ammo.

Still, this would make a wicked CQB gun if the 110gr V-Max's perform well at these velocities. They are the bullet recommended by Hornady for Police sniping in their 308 TAP line to prevent overpenetration with head shots, but they are moving quite a bit faster. I read in a thread on AR15.com recently that the 110gr V-Max is supposed to expand down to 900 fps, but I haven't verified this.

[Rancid Coolaid]

I have a YHM Phantom in 7.62, it moves between a few bolt guns and a few ARs, it is a great can for the money.


Just got my first Whisper yesterday (built on a 700 action), might do an AR upper eventually.


Let us know what you think when the can is on.

[Rikky Lee]

Nicely step up rifle. People seem to have learned a lot about the Whisper and each new build is getting now more impressive and more versatile with the use of light weight super- and heavy weight subsonic loads.

My only advice to you is to practice your loads and groups. 25 yards can give you a false impression in subsonic load testing - the real value is at 100 yards and great groups close in can suddenly open up.

And depending on what you are wanting to hunt with the light weight bullets, think about trying a pack of 125 Nosler BTs and 130 Grain Barnes X. They are really good performers at the Whisper velocities.

Finally, I have had 180 grain SSTs open up a little at subsonic velocities but I would personally confirm any claims you read on the Internet about bullet performance at low velocity.

Well done again!

[alorton]

Rikky Lee, thank you for the kind words. I spent alot of time reading and researching because when I decided to try this I was new at both reloading and with wildcat calibers. I was very familiar with the AR platform and had built several but had never done anything with an odd caliber. This site turned out to be a wealth of info and contributed heavily to my parts selection. Thanks everybody!

I understand what you are saying about 25 yard groups. I have only shot at close range because my long range is a muddy cornfield. I'm hoping to shoot at 100 yards (with the suppressor) very soon.

I was leary of going heavier than 110gr for supersonics because I didn't want to lose velocity. Since I'm at 2100 fps now and a heavier bullet would obviously be slower I figured 110's were the way to go.

As for hunting, the only things I can legally hunt in IN with a 300 are squirrels and rabbits. Deer are shotgun or pistol caliber rifles only (minimum bullet diameter of .357 along with cartridge length restrictions) so no go there.

Since I'm a Police Officer I tend to think of critters of the 2 legged variety when it comes to terminal ballistics and if the 110 is Hornady's recommended TAP round I figured it couldn't be a bad choice provided it will expand at sub 2000 fps. I intend to check directly with Hornady about that. That said, if the Nosler and the Barnes perform well at their respective velocities there is no reason not to give them a try. I will keep them in mind.

[Rikky Lee]

I sympathize with your mud problem (but isn't that what buddies or children are for??).

If you are hunting rabbits for the meat, the 240 SMKs and head shooting does minimal meat damage and there is no chance of losing them into the brush.

Please keep the guys on the board posted on developments!

[Stan_TheGunNut]

Love the rifle. That's the same handguard that I'm planning on using, so if you don't mind, I'd like to understand what is required in mounting it. I've never attached a FF handguard before, and am unsure if I need anything other than the upper reciever, barrel, and handguard. I guess I'm asking if it is as simple as sliding the barrel into the upper reciever, and then sliding the handguard over it, and tightening everything down?

Thanks for the help.

[PFDD]

Depending on the free float tube type/manufacturer, there are a couple of nuances to proper mounting. I've mounted Surefire, KAC, JP and LaRue tubes but each have their own mounting methods. I'd highly recommend the following link from AR15.com that is picture heavy with multiple types of tube mounting instructions:

http://www.ar15.com/forums/topic.html?b=3&f=4&t=226782

It's not a difficult process, but it helps to have the receiver blocks and such. Brownells also has a guntech video that explains tube mounting among other topics: http://www.brownells.com/.aspx/lid=1...An_AR_15_Video

Good luck with your build.

[alorton]

I received a call from my class III dealer and my ATF paperwork came in today! I don't have a proper range report since I didn't have much loaded ammo. The call from the gun shop was a bit of a surprise and with it being Superbowl Sunday I didn't spend my time reloading. I did fire the rounds I had already loaded and I am satisfied with the combo. While it is definitely louder than my suppressed .22 (which I expected of course) I was shooting the rifle on my back porch I didn't need hearing protection and my family in the living room was unable to hear it at all. That is more than acceptable to me.

This might just be the coolest setup I own! I'm having alot of fun with this, in case it wasn't obvious

Pics with the suppressor:

[alorton]

Originally Posted by Stan_TheGunNut

Love the rifle. That's the same handguard that I'm planning on using, so if you don't mind, I'd like to understand what is required in mounting it. I've never attached a FF handguard before, and am unsure if I need anything other than the upper reciever, barrel, and handguard. I guess I'm asking if it is as simple as sliding the barrel into the upper reciever, and then sliding the handguard over it, and tightening everything down?

Thanks for the help.

I've done several YHM handguards and there are several tools that come in very handy. I have a YHM wrench, a vise block for the upper (though it didn't work on the ASA upper), and a Brownell's forearm alignment tool. The job can be done without any of these, but they make it easy to attach and align without much fuss.

The YHM handguard has its own barrel nut that is threaded on the inside for the upper and the outside for the free float tube. You put it on like any standard barrel nut by torquing it down and aligning a hole with the gas tube hole in the upper. Then you thread on the free float tube and align it. After it is where you want it, you tighten the locking ring against the tube. The install is fairly simple but you will have to remove your front sight/gas block. If it is a standard front sight with taper pins that is often the most difficult part of the install.

[Scalce]

Your build is very similar to what I want except my barrel is not a Noveske and originally I thought I might want a quad FF forearm.

The YHM line looks to be the most cost effective and some models have a ton of cutouts like the diamond and lightweight series.

I would like to have clearance to get a mini screwdriver head in there versus fighting with it through a slot but your build looks pretty slick and I could add a small front rail for a QD bipod or just put a standard fixed bipod stud.

What length did you get and will it accept forearm cap?