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#5963345 - 10/06/15 05:31 AM 300BLK - Need Help with 180/g Subsonic Load
dredd Offline
Tracker

Registered: 04/26/10
Posts: 868
Loc: Dallas / Fort Worth Area
I have searched and searched, but have not found what I am looking for.
I'm also not a master of the internet.

I have a few hundred 180/g Sierra Game Kings I would like to tap in to.

The closest load I have found so far is:
Bullet: Berger 190-grain VLD Hunting
Powder/Charge: Accurate 1680/12.2 grains

What would you recommend for a starting charge of A1680 using the 180/g Game King?
What increments would you Back Up while developing the round?
I have not worked a load backwards trying to achieve Subsonic before.
Once I get it "Sub", can it be tweaked from there to improve accuracy?

And of coarse, I'm open to other Powder suggestions etc .

I see that Chad offers a 180/g Sub, so I can't be totally off my rocker (I hope).

My Application:
AR Platform
16" Barrel
.125 Port
Carbine Gas System
Carbine Buffer and Spring
Silencer Co. Omega Suppressor

Thanks

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#5963618 - 10/06/15 09:25 AM Re: 300BLK - Need Help with 180/g Subsonic Load [Re: dredd]
ChadTRG42 Offline
THF Trophy Hunter

Registered: 09/16/09
Posts: 9393
Loc: Lewisville, TX
The Sierra GK 180's will work fine as a sub bullet. I actually have 2 loads with the 180's in the 300 blk out. One is for the AR platform that will cycle and the other designed for a bolt gun with a much faster burning powder for better efficiency. Since I have hundreds, if not thousands, of test rounds and R&D time behind my products, I'm very safe guarded on the load data and methods with them. But, working up a sub load is not that difficult. The main thing is you start HIGH with the powder charge, and then work down in small increments. Your best tool is a quality chronograph to help you get accurate speeds to know where you are with the sub speeds of the loads. I played with 1680, and I did not like this powder. It was a "dirty" powder for me, and hard to purchase and find, so I do not use it. But if you stay in the same burn rate, you will be fine. If you piggy back data from other similar powders with similar burn rates, you can find a good load. The 180's are a little more difficult to get the load just right for a subsonic. Generally, you want a heavy bullet to keep the bullet in the barrel as long as possible, and give more resistance to build up your pressures for cycling. The 180's make this a little more difficult. So, the load is a little more challenging to get it just right. The slower powder you use, the less complete burn you get. Most of the time a 300 blk out sub load will burn about 80-85% of the powder. So you will have 15-20% of unburned powder when the bullet exits the muzzle. This unburned powder comes back into the chamber and magazine area and in the suppressor. This is the nature of a cycling subsonic. You must have enough pressure at the gas port (which is 9" from the chamber) to cycle the action. To do this, you need a slow powder, but not too slow which will increase you % of unburned powder, and make the round more "dirty".

Your best bet is to load up a bunch of test rounds, and head to the range with a good chrono. If you have a portable loading press and a way to weigh your powder at the range, this will help reduce the time and trips to find your load. I have set up a mobile press and powder weighing station multiple times to throw powder and seat bullets and go shoot them on the spot. The main thing to watch for is going too light on your powder charge, and having a slow speed. Once you get your speeds below about 850-900 fps, you risk sticking a bullet in the barrel. I have shot a few rounds that chrono'd in the 700-800 fps, and felt lucky I didn't stick a bullet. (But, there is a 87 grain bullet stuck in my custom AR-15 in 223 as we speak!)

Nosler has some data you can piggy back some powder info from, as well as Hodgdon. If you study them, and calculate using a 180, it will get you there, I promise!!!

http://www.nosler.com/nosler-load-data/300-aac-blackout/

http://www.hodgdonreloading.com/data/rifle
_________________________

www.DallasReloads.com
Type 01 and Type 06 FFL

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#5963622 - 10/06/15 09:27 AM Re: 300BLK - Need Help with 180/g Subsonic Load [Re: dredd]
ChadTRG42 Offline
THF Trophy Hunter

Registered: 09/16/09
Posts: 9393
Loc: Lewisville, TX
Also, how you load them will make a difference on speeds. Make sure you use the same case brand, and not switch between a standard 300 blk out case and a LC or military case cut down and sized to 300 blk out. There is a difference in performance between these 2 cases.
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www.DallasReloads.com
Type 01 and Type 06 FFL

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#5963706 - 10/06/15 10:20 AM Re: 300BLK - Need Help with 180/g Subsonic Load [Re: dredd]
dredd Offline
Tracker

Registered: 04/26/10
Posts: 868
Loc: Dallas / Fort Worth Area
I appreciate your reply, Chad.

I agree that you should not give up the keys to the store.
That's your hard earned knowledge.

I am needing a nudge or two in the proper direction, which you have been kind enough to provide.

If the 180's are going to be finicky, I have no problem looking at the 208's.
I was just wanting to use stuff I had on hand, if practical.

I have a Magnetospeed Chrono that has been working well so far.

I have also formed about 8 different Head Stamps of brass.
LC proved to be one of the most consistent. S&B is so thick, it will not chamber after being formed. LOL
I think I have a around 1,000 or so LC's ready to load.

Thanks again for your advice!
Brett

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#5963752 - 10/06/15 10:47 AM Re: 300BLK - Need Help with 180/g Subsonic Load [Re: dredd]
ChadTRG42 Offline
THF Trophy Hunter

Registered: 09/16/09
Posts: 9393
Loc: Lewisville, TX
You are on the right track!!!

Also, on the sizing issue. The 300 blk out was a BIG learning curve for me, in regards to the case fit and chambering. It was a PITA with some of the issues with tight match chambers found in the Wilson and Noveske AR's, and some other rifles (why you would run a tight, match chamber to minimum SAAMI spec and a short throat in an AR built in a 300 blk out that will not be used for long range shooting, is beyond me).

If you size a 300 blk out to normal minimum specs with a cut down LC (or military brass) case, the case is right at minimum SAAMI spec (not loaded). When you load a bullet below the case shoulder (like a heavy 208 A-max or 220 SMK), the shoulder of the case flares out and pushes the shoulder outward, due to the thick military brass. This changes the shoulder head spacing by about .004" to .005". The difference between min and max head space is only .006"!! I bought all the case gauges and dies to try and fix this problem. My only solution was to have the brass sized .005" below min spec. (my brass supplier does this with very good accuracy and consistency.) I also shaved the bottom of my die by .005" on a wheel grinder to get this additional room when sizing. If you have trouble getting it to chamber, try this.
_________________________

www.DallasReloads.com
Type 01 and Type 06 FFL

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#5964213 - 10/06/15 02:52 PM Re: 300BLK - Need Help with 180/g Subsonic Load [Re: dredd]
okie44 Online   content
Tracker

Registered: 04/11/11
Posts: 612
Loc: Midland TX.
This data was developed in a 10" barrel. Just more to add to the thinking process! grin

http://up.sur-la-toile.com/iFsk

Rifle data

https://sierrabullets.files.wordpress.com/2013/07/300-aac-blackout.pdf


Edited by okie44 (10/06/15 02:54 PM)
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#5965394 - 10/07/15 05:34 AM Re: 300BLK - Need Help with 180/g Subsonic Load [Re: dredd]
dredd Offline
Tracker

Registered: 04/26/10
Posts: 868
Loc: Dallas / Fort Worth Area
I have the Sierra manual.
Thanks for putting that up.

I didn't know I could take a published load/powder and start working backwards.
I was thinking there had to be a complete powder change and lots of VooDoo.

I appreciate y'all teaching me to fish.

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