80 or 90 grain 223 SMK? 1:7 twist spr help Ar15

[nikdanja]

 

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Just got a WOA 1:7 mid 18" and didn't know serra made these heavy bullets. I know 69 and 77 shoot great but has anyone tried these really heavy bullets in an AR15? Or are these mostly good on bolt guns?

 

 

[Flatland Shooter]

At that weight, I'd bet you cannot load them short enough to fit an AR magazine.

If you want to load them one at a time, they would be a good long range bullet.

[nikdanja]

1 minute ago, Flatland Shooter said:

At that weight, I'd bet you cannot load them short enough to fit an AR magazine.

If you want to load them one at a time, they would be a good long range bullet.

Can't you load them at normal mag length?

why would that be an issue? Pressure issues I guess?

[TonytheTiger]

If you seat them at or below 2.26" OAL the full diameter shank of the bullet will be almost entirely below the neck. The ogive will be inside the neck and you will have little or no neck tension not to mention drastically reduced powder capacity. I've gotten away with 75gr Amax/ELD's (1.18" bullet length) at 2.35" and it's as short as I would load them to maintain good neck tension without relying on a heavy crimp to keep it all together. The 90gr SMK's are a similar length, and I'm guessing also a VLD type profile with a short bearing surface so it's probably a similar story as far as minimum OAL. Then there's the fact that a 223 case doesn't have the powder capacity to push them fast enough to see any real gains over a lighter and lower BC bullet being pushed much faster.

Edited December 31, 2016 by TonytheTiger

[Flatland Shooter]

Tony pretty much nailed it.

Your barrel has a 1:7" twist and that is the max for the 90 grain bullet.  From my reading, you could load them with Varget or RL-15 and seat them 0.010"-0.020" off of the rifling and you should do well. You will have to single load them though, At that length you won't be able to load them into a magazine. 

Load them any shorter and you reduce the case volume to where you cannot get a decent velocity and it will affect accuracy.  Also loading shorter will move the bullet further back from the rifling and adversely affect accuracy.

So  you are better off loading a 69 or 75 grain bullet at a load that is optimized for accuracy and at a length that will fit into your magazines. I use IMR 8208xbr for my long distance loads.

I do not have a .223 bolt action gun so I do not know how much leade they have, if its short, you will also see problems with heavy bullets.

Edited December 31, 2016 by Flatland Shooter

[dauntedfuture]

80+g bullets are intended for single loading for the 600yd stage of NRA competition and beyond.  They are also used with some limited success at 1000yds but its tough.  If you go to sierras web site it will clearly tell you that these bullets are specialty bullets intended for single load.