Best powder for low muzzle pressure in 12 inch 556 barrels.

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45r
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Best powder for low muzzle pressure in 12 inch 556 barrels.

Post by 45r » Fri Mar 01, 2019 9:40 am

Got a 12 inch barrel and want lower muzzle pressure for suppressed.
Wondering if it would make any difference.

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dellet
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Re: Best powder for low muzzle pressure in 12 inch 556 barrels.

Post by dellet » Fri Mar 01, 2019 10:37 am

I don’t load for the caliber, so can’t give a specific powder, only general information to help choose. Rule of thumb is the faster the powder, the less muzzle pressure and sound. The exceptions to the rules seem to need an understanding of the powder make up. Longshot is a very fast powder and reffered to as Loudshot for good reason.

A faster powder in general will have a higher peak pressure, less duration and burn out faster. It also generally takes less to create the same velocity. What you end up with is less powder, burning out sooner and pressure dropping off more rapidly. This turns into less exploding gasses out the end of the barrel and less unburned powder.

I use opening a champagne bottle for example, the more you shake it, the more pressure it builds, the bigger the pop. How much pressure being relived when the bullet exits, will make a difference in sound.

In a gas gun like an AR, ejection port pressure, is based on muzzle pressure. The lugs won’t unlock until the pressure on the back of the bolt overcomes the pressure on the face, basically when the bullet exits. So if you decrease muzzle pressure, you will also decrease the pressure blowing out the back end when the bolt opens.

Less noise on both ends.

Generally the fastest powder that will achieve the desired velocity, without exceeding max pressure will be the quietest.
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45r
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Re: Best powder for low muzzle pressure in 12 inch 556 barrels.

Post by 45r » Sun Mar 03, 2019 5:21 pm

I tried viht n-133 in my 6x45 upper with Sierra 85 grain bthp gamekings.
It has a 12.5 inch barrel.
With 23.5 grains and federal match primers it shot 1 inch at 100 yards suppressed.
If the first shot wasn't half inch high from the next 4 it would have went .550 inch.
My mystic seems to shoot the first shot high with everything.
Half inch straight above will worrk.
It's faster than xbr,tac,4895,and benchmark that shoots well in my .556.
I sometimes think the 6x45 is the better round.
It was surprisingly quiet when I tried it without earmuffs.
For as cold as it was and my hands going numb I'm happy with the results.

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Re: Best powder for low muzzle pressure in 12 inch 556 barrels.

Post by RKB731 » Sun Aug 04, 2019 2:07 pm

I use AA2230 in my 10.5” with 62 grain bullets running a SilencerCo Saker. A lot quieter than BL-C2.
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