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reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 11:15 am
by imyomama
Alright.. first off ..Robert .. please don't post that this thread is worthless because no OAL lenght ..
I'm posting this so people get an idea where to start and what works .. so don't take my data as gospel , merely just suggestions to your own experiments..

So , if you can't find 1680 (like me ) , I've found a load this weekend that worked for me ..

first off .. the rifle is a 9" barrel with pistol gas lenght , troy gas block , SAS arbiter 30 cal titanium can , regular buffer spring and spikes ST T2 (stainless/tungsten ) buffer ..

this weekend , I tried a load of 10 grain of IMR 4198 on 220 smk.. it cycled the action , locaked the bolt back on last round and crono was right at 1050 fps...

in the same gun , I also shot 18gr of h110 on 125 sierra spitzer , they crono 2000 fps ..

I did take a video , i'll try to post it tonight so you can hear the supersonics and subsonic back to back ...

hope this helps someone.. I know I can't find 1680 anywhere.. so this is good news for me !

different barrel lenght or gas system may give different results .. so .. use this info at your own risk!

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 11:31 am
by Kublah
Anyone's info on reloading is appreciated by me.

I have been running the H110 supers for a while like yours except I backed off a bit to 17.5gr behind 130gr. Hornady 3020's

I have had my eye out for Vihtavuori or A1680, no one carries them around here. But i do know with certainty that there is a ton of IMR4198 around! Thank you very much!

I do not have a chrono so I cannot find out for myself, so would it be possible for you to try around 950-975fps for the IMR4198? Trying to mimick the remington subs which I believe are ~965 out of a 9" aac upper.

Oh and I have a 9" AAC upper, H buffer

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 1:59 pm
by 300Blk
Wow, buying powder at a store. I never considered that. Why not just order A1680?

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 2:02 pm
by Kublah
Shipping cost and hazmat costs are what deter me..

Where do you buy your powder?

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 2:27 pm
by 82nd airborne
The 4198 load is GTG. it will cycle our carbine and pistol length guns.
I like 4198 because I have alot of it and I use it for alot of different calibers.
1680 is a good powder, but it is fairly new to Americans, so alot of us havent aquired it as much as 4198.
None of the stores here have 1680 but most have 4198 and not paying hazmat is nice, but then again I usually order enough at a time that I dont come out feeling raped by the hazmat.

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 2:56 pm
by imyomama
exactly .. I woudl have to buy lots to make up the $20 hazmat fee.. so for me .. local pickup is my preffered choice ...

Aaron , I'll make some more this week and measure OAL.. so people can duplicate and test...

I was actually surprised !! first test load , 1050 !! and cycled fine !! also seem to burn really clean !

HOW LUCKY IS THAT ?

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 3:32 pm
by 300Blk
I deal with the Hazmat fee by getting 8 or 10 lbs at a time.

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 6:27 pm
by tctlrld
Running this recipe (as well as Robs A1680 recipe) shows that it only results in ~70% burnt powder. Using something faster burning seems like it would make sense.

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 7:42 pm
by 82nd airborne
tctlrld wrote:Running this recipe (as well as Robs A1680 recipe) shows that it only results in ~70% burnt powder. Using something faster burning seems like it would make sense.
Then it wouldnt cycle in a carbine system. Im no scientist, well actually I am but biology doesnt count, but it seems pretty efficient.

Re: reloading 300 blackout for subsonic and supersonic

Posted: Mon Feb 14, 2011 8:10 pm
by tctlrld
I don't see why a faster powder wouldn't cycle a carbine action. Most faster burning powder would result in a slightly higher pressure. I suppose it could have to do with duration and dwell time. All supersonic 5.56 (and 300 BLK loads?) are high 90s burn rate in a 16".

Quickload shows that 8gr of Li'l Gun pushing a 240gr SMK through a 9" would result in 1010fps, ~78% powder fill and ~97% burnt powder, at ~27000 PSI chamber pressure. Seems like something like that would make more sense. But I don't have the upper or components to try right now.

On a somewhat different note. Does anyone have the measurements for the 220gr SMK? OAL, small diameter of taper and length of taper measurements.