.300/221 - .300 Whisper AR questions

[smores]

I'm doing some research and think I know the answer but wanted to see if anyone here knows anything about these setups.

I was originally going to roll with the mid-length gas system with a JP Enterprises adjustable gas block, but after reading several forums it seems like I should go with a carbine, or better yet pistol length gas system for the .300 Whisper cartridge.

Some say that an adjustable gas block is a must, while others say it's not necessary - but they seem to be dialing in for a specific load. The Noveske "switchblock" is popular, but you have to buy an upper from them to get it (not going to do that). There's this guy "tp555" on the quarterbore forums makes switchable gas blocks that seem pretty decent, and those that have them say they work well. From what I understand JP Enterprises makes good stuff, and although the set-screw type of adjustment isn't as quickly repeatable as a switch design, it does allow finer tuning.

What do you guys think? I'm leaning to a low-profile adjustable JP Enterprises block under my 9" DD rail with a pistol-length gas system.

 

[Biggfoot44]

When in doubt, go with the inventor. SSK Ind ( J.D. Jones) .

 

[smores]

When in doubt, go with the inventor. SSK Ind ( J.D. Jones) .

If I weren't getting a grade in school for building this I would.

I'm gonna just set this up and see how it works. I'm pretty confident I'm setting this up correctly. I have a 1:12" twist .308 barrel too... this should be awesome.

 

[Biggfoot44]

1:12 should work for supersonic loads. For subsonic heavy bullets, a really fast twist is used .
If your goal is to duplicate 7.62x39 w/ .223 case head, you're good. For subsonic 200gr + .....

 

[smores]

1:12 should work for supersonic loads. For subsonic heavy bullets, a really fast twist is used .
If your goal is to duplicate 7.62x39 w/ .223 case head, you're good. For subsonic 200gr + .....

Yeah I did a shit-ton of reading. Apparently 1:12 is no bueno. I'm going to build a .308 on my Krieger 1:12 I got, and get a Shilen Match Grade barrel in 1:8 for the AR build.

I just need to figure out what length of gas system is ideal....

 

[JSW]

pm CKOD he just finished one

 

[smores]

I've decided to turn this into my build thread. Here are some of the components I've assembled so far. List of parts shown in pics (off the top of my head):

- DPMS lower & LRPK
- Cardinal Forge A4 flat-top upper, High-Standard parts (fwd. assist, dust cover)
- D.S. Arms Mil-Spec receiver extension
- Brownells action spring
- Colt receiver end plate & castle nut (staked)
- Midwest Industries ambi QD sling swivel end plate adaptor (heavy duty swivels)
- BCM H-marked buffer
- BCM M16 BCG
- D.S. Arms charging handle
- Magpul CTR Buttstock
- Magpul MOE grip
- Brownells barrel extension
- Colt barrel nut
- KAC free-float quad rail

Sorry for the messy bench, it's not usually that bad lol. And hope you liked the rail lol... here are the rest of the parts going in this build:

- Shilen 1:8 twist .300-221 barrel (16.25")
- YHM Phantom 5C2 flash suppressor
- JP Enterprises SS low-profile adjustable gas block
- Pistol-length gas tube
- Colt Delta Ring ass'y
- Daniel Defense 9.0 Omega rail
- Magpul XTM rail panels
- Magpul AFG
- Magpul MBUS
- Aimpoint CompM2 & QRP mount with spacer

Accessories:
- Wilderness Giles sling
- Brownells "SOCOM Tan" mags w/ Magpul Gen III followers
- Magpul PMAGs (2, non-window, think I'm gonna start rocking the window versions)

What do you think? I'll have the barrel chambered and headspaced by tomorrow, waiting on a reamer to cut the gas port... so for now it'll be "bolt action"

 

[BenL]

I've decided to turn this into my build thread. Here are some of the components I've assembled so far. List of parts shown in pics (off the top of my head):

- DPMS lower & LRPK
- Cardinal Forge A4 flat-top upper, High-Standard parts (fwd. assist, dust cover)
- D.S. Arms Mil-Spec receiver extension
- Brownells action spring
- Colt receiver end plate & castle nut (staked)
- Midwest Industries ambi QD sling swivel end plate adaptor (heavy duty swivels)
- BCM H-marked buffer
- BCM M16 BCG
- D.S. Arms charging handle
- Magpul CTR Buttstock
- Magpul MOE grip
- Brownells barrel extension
- Colt barrel nut
- KAC free-float quad rail

Sorry for the messy bench, it's not usually that bad lol. And hope you liked the rail lol... here are the rest of the parts going in this build:

- Shilen 1:8 twist .300-221 barrel (16.25")
- YHM Phantom 5C2 flash suppressor
- JP Enterprises SS low-profile adjustable gas block
- Pistol-length gas tube
- Colt Delta Ring ass'y
- Daniel Defense 9.0 Omega rail
- Magpul XTM rail panels
- Magpul AFG
- Magpul MBUS
- Aimpoint CompM2 & QRP mount with spacer

Accessories:
- Wilderness Giles sling
- Brownells "SOCOM Tan" mags w/ Magpul Gen III followers
- Magpul PMAGs (2, non-window, think I'm gonna start rocking the window versions)

What do you think? I'll have the barrel chambered and headspaced by tomorrow, waiting on a reamer to cut the gas port... so for now it'll be "bolt action"

I'm not sure, but I think your rail is a knock-off.



Seriously, can't wait to see this done.

 

[smores]

Chamber end of barrel turned down to 1.000", shank turned down ready for cutting threads:

Threads done. Extension threads on barely by hand, no play:

Extension on, headspace gauge time:

There's a Go gauge under that bolt, and you're looking at barrel steel through the lugs:

Tomorrow if I finish the Luger I've been chipping away at, I'll get the barrel chopped and turned down to the correct profile so I can test fire it this weekend or early next week. Still trying to source a reamer to cut my gas port... so it'll be "straight-pull bolt action" for a while lol.

 

[midcountyg]

Very nice! I will be building a couple of these before long. I'm just waiting on my Shilen blanks and Pacific reamer. Going to build a couple Rem 700s first, then a couple ARs. Maybe we can compare some notes when it comes time to develope some loads.

 

[smores]

Very nice! I will be building a couple of these before long. I'm just waiting on my Shilen blanks and Pacific reamer. Going to build a couple Rem 700s first, then a couple ARs. Maybe we can compare some notes when it comes time to develope some loads.

The reamer I used was a PTG. Luckily another guy at school had bought it and the gauges so I didn't have to buy them myself. Once I get set up in a shop and if there's demand, I will probably acquire them.

Today I ordered my reloading setup (RCBS Master kit), Redding .300-221 dies, some .221 Fireball brass and a bunch of 180gr bullets. I've got a box of CorBon .300 Whisper stamped rounds I'm going to try. I'll reload the CorBon stuff, neck the .221 up, and chop/resize some .223 and figure out what works best. I've also found a guy on SnipersHide who forms his own .300-221 brass, 100 rounds for $25, so I'm picking some of that up too. I've read a lot of stuff, but of course I'm going to have to work with it myself to find out what works best. I hear .221 sized up works well for subsonic loads, where chopped 5.56x45mm NATO cases work best for the hotter loads.

Barrel should be done tomorrow except for the gas port, and test fired for function if all goes well.

 

[CKOD]

I prefer going from .223 rather then .221, lot less of a chance of a non-concentric neck, or neck splitting. But trimming all that length is a pain. I'm considering a dillon electric trimmer, so it'll be just running .223 cases up in the die and .300 whisper coming out with no splits. Plus 5.56 cases are rated to more pressure then .221, which should make for a longer brass life at lower pressures.

 

[BenL]

This is a great project. I'm planning a Phantom suppressor purchase for my BA rifle, and the can could double on a whisper rifle. It won't be until next year, but may be a future project.

 

[longshot1911]

Are you on this site yet?

http://www.homegunsmith.com/cgi-bin/ib3/ikonboard.cgi?;act=SF;f=3

If not, you need to be.

I went through the 300 whisper craze several years ago. Without a doubt, go with the pistol length gas system. If you are only shooting subsonic, do not worry about an adjustable gas system. You will likely drill the port as large as possible anyway. For hot supersonic, you may want to slow down the BCG a bit.

 

[smores]

I prefer going from .223 rather then .221, lot less of a chance of a non-concentric neck, or neck splitting. But trimming all that length is a pain. I'm considering a dillon electric trimmer, so it'll be just running .223 cases up in the die and .300 whisper coming out with no splits. Plus 5.56 cases are rated to more pressure then .221, which should make for a longer brass life at lower pressures.

I agree. Makes more sense, I figured I'd just try it out. Never hurts to try, and I believe sometimes it's better to learn from failure lol.

I got this thing done except for the parkerizing/bluing and gas port today, but ran into a small issue I'll explain below.

60* crown with 90* face, should be nicely accurate:

Here's the barrel chucked in my vise, to clean chips/debris from the bore. Bead blasted the barrel except for the threads and area under the gas block:

Put some of the pieces together, hand tight just for demonstrative purposes. After it's parked/blued I'll test fire it tomorrow to ensure my chamber is sound:

That barrel does look pretty long eh? Good thing I still have 10" of good barrel blank left over for a pistol/SBR build down the road...

Now with the JP adjustable gas block on there, I was just checking the fit of my Daniel Defense 9.0" Omega Rail (which is wayyy too damn short for this barrel lol) and the gas block won't allow it to seat all the way down. I'm going to call Brownells and find out if the Troy rail will fit over it as they say on their site.

I cut the threads to fit the AAC Cyclone suppressor, as I was looking on AAC's site and I like what I see. I'll do more research of course but I've got 5/8-24 threads so I'll need a suppressor that fits that.

So glad to have this thing almost done. Just waiting on the gas tube and a proper reamer for the gas port and it's complete! Oh yeah and my delta ring assembly and Magpul MBUS... still on backorder from Brownells.

 

[CKOD]

The cyclone is the quietest Ive seen independantly reviewed on a .308 rifle, unsure how it fairs with lower pressures (something designed for low pressure could be better, not sure but with that much volume, its hard to go wrong )

Can you turn your gas block down in a 4-jaw chuck? I know Ive seen somewhere, someone that turned down a JP gas block to fit under a rail. My gas block is pretty low profile, but still rubs on my YHM handgaurd putting it on.

 

[Eudaimonia]

You guys are giving me an itch for something in .300/221...

 

[midcountyg]

Have my Rem 700 action all apart on the bench waiting for the barrel blanks, gauges, and reamers to arrive. Also have most of my AR parts and a can from YHM that should ship out this week. I can't wait to get someof these together. If you ever want to hear yours through a YHM Phantom, bring it by
I have made a bunch of casings from 5.56 brass, and will start with them. I trim them close to the needed length before sizing by using a lathe. Then size and on to the hand trimmer to finish up. It's a process, but once you get the hang of it... I have a couple hundred SMK 220gr to start off with, seeing as I am most interested in subsonic and suppressed.

 

[smores]

The cyclone is the quietest Ive seen independantly reviewed on a .308 rifle, unsure how it fairs with lower pressures (something designed for low pressure could be better, not sure but with that much volume, its hard to go wrong )

Can you turn your gas block down in a 4-jaw chuck? I know Ive seen somewhere, someone that turned down a JP gas block to fit under a rail. My gas block is pretty low profile, but still rubs on my YHM handgaurd putting it on.

I called Brownells' Tech dept and had them check the Troy Industries MRF-RX (13.8") against the JP adjustable low-profile block. They say it'll fit, and it looks wider in pictures too.

Got out to the range and ran 6 rounds through it, cleaning the bore thoroughly and lubing with Tetra Gun Lube after every shot to start the break in process. I don't plan on shooting it again until I get the gas port cut, but the brass is coming out nice, no obvious signs of problems. I'll mic it and check with the case dimensions I have tomorrow.

All I can think of now that I have this almost built is a can. Must get a can. I'll have to take up offers to try some out so I can make a sound and informed decision. I should be able to start working on loads once I get some more powder and primers. Brass, bullets and dies arrive tomorrow.

 

[smores]

Got it parked/blued the other day, took it to the range and test fired. Fired brass mics at 0.375" at the base. Absolutely no stretching, looks like I pulled the bullets and struck the primers. Chamber is nice and tight.

Got my 0.0756" reamer (could NOT find a .0750" reamer in stock to save my life, and I doubt .0006" will make a difference for the gas port) in, but don't have a bushing for the sight mounting jig (will ensure the hole is drilled TDC and perfectly straight) to drill the port before I ream it. Sooo I started making the bushing yesterday, got it drilled and knurled, just need to turn it down to proper dimensions and harden/temper it on Monday to get that finished.

I've got a guy who's going to engrave markings on the barrel as well. It should be looking nice pretty soon. Feels great to be on the cusp of finishing a project!