220 vs 240 Sierra Match Kings
 

Playing around with my 300/221 1:8 twist AR upper, developing some subsonic loads while awaiting the BATFE to approve my Suppressor purchase...

Finally got the bugger cycling 100%, AA1680 was the answer. Loaded up some 200 SMK's and shot them at the range, and once I got down to 11.0 gr, heard that "whump" from the bullet hitting the berm. Wasn't able to run them through the Chronograph, as thr range was too busy to set it up.

Anyways...I'm looking to buy bullets for shooting subsonic through the suppressor. The prices below are from Midway.

240gr SMK's are pretty darned expensive, and aren't available all of the time- -I've shot them, they seem to be stable, no keyholing. (I've not seen anything but nice round holes in any of my targets while testing loads for that matter) $56.98/100 (come in a box of 50)

220's seem to be readily available, and are a lot cheaper that 240s. $38.99 (come in a box of 100)

210 SMK's - these seem to be the bullet that the long range guys are shooting, and as a result, and pretty pricy, and just as hard to get as the 240's - $54.98/100 (come on a box of 50)

200 SMK's - I can get these down to subsonic velocities, still cycle the action, and they are readily available locally. I have not accuracy tested them, so I don't know what to expect there. $34.99 per 100.


I'm leaning toward the 220s for the best weight per $. Is there any reason NOT to use them in a 300/221? Are they stable at subsonic velocities?

Use them. There's nothing wrong with them. They would not be the best hunting bullet, but as far as shooting them they're fine.

The 220 and 240 SMK's are the most popular bullets for the 300/221 as far as I can tell. I shoot the 240's if I want the most weight (highest energy). With a speed limit of 1050fps the only way to increase energy is to increase bullet weight. When I want to shoot cheaper I use 208gr A-Max bullets at $29.99 per 100 at Midway.

The only thing I dont like about the 208 Amax they are hard to find in stock.

Dustin

Admittedly I'm having that issue right now. I use them in my Whisper and intend to use them in my new 300 Win Mag but I only have a couple left and they've been out of stock for a while.

The 220 SMK is right in the middle of the "sweet spot."

Trying to incease energy by using a heavier bullet in a subsonic is a waste of time. Subsonics penetrate to such a huge degree that even lightweight bullets will overpenetrate any soft target. Adding weight just increases the amount of energy that flies out the back side of the target.

I terminal tested 150gr subsonics and found that they blew through more than 16" of wet phonebook, through the bottom of the bucket and disappeared into the dirt deep enough that I could never recover one.

If a 150gr bullet can do that, what improvement would a 220gr offer over a 200 gr bullet?

Whether it is a waste of time depends on the application. While it is true that a bullet giving full through and through penetration won't be very energy dependent a 240SMK will still leave a larger wound track than a 150gr bullet provided that it tumbles. I'm not a fan of tumbling as a wounding mechanism, but the 240 will do more damage than a shorter bullet in that regard.

More energy would also be useful if you are shooting steel targets. The added downrange energy is helpful for knocking down the targets. Of course the larger bullet also has a better BC and won't lose velocity or energy as quickly, though that is a small issue with the range the 300 Whisper is useful for.

The biggest advantage, in my opinion, is reliability. It is easier to get an AR to cycle with a heavier bullet because it allows the use of more powder, which means more gas to cycle the action.

Ummm...all things equal except bullet weight means the heavier projectile uses less powder...

If you are loading for a specific speed, like you do for subsonics, loading the lighter bullet will require a lighter powder charge. For example, I use 8.5 grains of 2400 for a 240 SMK but use 8.0 grains of 2400 for a 208 A-Max to accomplish the same velocity, 1050 fps. This is in a 10.5" Noveske barrel.