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View Full Version : Loading help for 240SMK, N110 subsonic

JimM44
03-29-2009, 05:11 PM
How do I set the correct bullet seating length on my dies for this barrel, I have read where some folks have powder escaping around the bullet if set too far back and then others having loading problems with it set too far foward not chambering properly.

Ok I now have my barrel, not mounted yet 16" from M1S.

I have the 240SMK bullets in hand 2K plus of them.

Brass, powder(N110) both ordered should ship next week.

I have redding dies and winchester small rifle primers, my Sierra reloading manual recommends 9.7 grains for 1050 velocity.

Is there a way to measure my chamber to get the proper length or is it known for the M1S barrels?

I am also waiting for my Gemtech HVT which I will use on this rifle, so this is not a rush as it will be a while before everything is in place.
cav_scout_tj
03-30-2009, 04:49 PM
2.2" OAL is a good place to start. You can get longer, I would start there and see how it goes with your chamber. Usually, mag length is the limiting factor, rather than chamber. YMMV

I am thinking 9.7gr will be supersonic, but give it a try and work down.

Also, dont go overboard loading a thousand rounds before the can gets here. You will probably have to drop a couple tenths of powder with the suppressor back pressure.
Fudmottin
03-31-2009, 12:17 AM
The 240 SMK has virtually the same nose profile as the 125 TNT. The bearing surface is of course much, much longer. So you can seat the 125 TNT to the same COL as the 240 SMK and only have to worry about remaining case capacity for your powder charge.

Definitely don't go loading lots of rounds before you get your can on. Although you can work up a reasonable load without the can if you keep in mind that the can will add maybe 20fps or so to the velocity and will make the action cycle a bit more positively.

I personally haven't noticed a huge difference in action cycling with or without a can in 223. Maybe 30 caliber makes more of a difference since there is considerably more cross section area and pressure changes faster as the bullet moves down the barrel.