Bat actions 17-4 SS

[jackieschmidt]

We use 416 for the steel actions at Pierce and I made myself an action for benchrest earlier last year. I’ve been able to load 31gr of 2023 lot N133 with a 68BT in a PPC without heavy bolt lift. I’ve actually prematurely loosened pockets in the Lapua 220 Russian before I got heavy bolt. We send our action body material out to be heat treated before they’re machined and then check the hardness when we get them back and they’re always within 1 point of desired on the RC scale. Our bolts are 4340 AQ and they’re also sent out as raw stock to be heat treated before any machining. I’ve never compared pressure limits of 17-4 to 416 in our actions. We did make a few actions from 17-4 but we had to change a lot of our programs to optimize it and it was more expensive and harder to work with. We went back to 416 and haven’t looked back. The lugs on my benchrest action have more surface area than a BAT DS or similar, so that could be why I’m able to run hot loads without issue. Maybe if our lugs were equal to BAT our 416 actions might pressure out sooner. I’m not entirely sure. Having said all of that, I don’t think either material matters unless you’re running MAX like many of us do in BR.

My compliments on your in house heat treating and your choice of air craft quality 4340 for your bolts.
just curious, what RC level are you using in your action bodies?

 

[Jud96]

My compliments on your in house heat treating and your choice of air craft quality 4340 for your bolts.
just curious, what RC level are you using in your action bodies?

We actually use a local business that specializes in heat treating and they do a good job for us. They do a lot of work for many shops in the area. Our actions are 36-38RC

 

[powderbrake]

I never made an action, but we made strain gage transducers from 17-4 ph Stainless. Primarily from the standpoint of it's very high fatigue strength. You can see a transducer actually bend under load. And when that load fluctuates at 1000 Hz, it tests the fatigue strength of the part.
I designed the transducers to 30,000 psi stress at nominal load with overloads to about 60,000 psi. This is still well below the yield strength of 17-4.
Actions are not designed to visually "bend" when they are functioning, but they are subjected to high stresses with each shot. Chamber pressures of 60.000 to 70,000 psi are very likely. I can see why BAT uses 17-4ph.