Baffle stack clearance

[punkinhead]

For a .22LR k-baffle can, when you screw it together how much clearance to you want in the stack up? Right now I've got 0 clearance, so when I tighten the end caps the baffle stack is held tight. It's not under compression, but there's no clearance. I can trim the blast chamber (built into one end cap) to add clearance. I don't want the baffles rattling around, but I'm wondering if there shouldn't be a bit of clearance since the aluminum baffles will grow more than the stainless tube when heated.

[Dr.K]

I go zero clearance. No issues.

[thecat]

Could a heavy spring be used to allow heat expansion?
There are washers called "wave washers" that are wavy spring steel washers. They can be double stacked to provide very strong spring pressure.

Don't do it on my recommendation.
I just want to see what the experts think of these ideas.

thecat out...

[Dr.K]

The expansion will dissipate when the can cools, I don't imagine it would hurt a thing.

[Bendersquint]

Springs in cans have been discussed in length over the years.

Two words suggest why its a bad idea.

Pneumatic Hammer.

[whiterussian1974]

Springs HAVE been successfully used in some early designs. They fell out of favor because they aren't as strong as solid, unflexing structural members.
-1 in particular used springs as spacers b/t baffles. For a low pressure rd like .22, compression of a strong spring would be minimal. For the 9mm design I saw, each baffle would compress and release sequentially, passing the wave along the length causing added turbulance.
-I drew 1 design w a spring at each end. This avoids the Pneumo Hammer effect Bender mentions. After all, Nielsens use a piston w captive spring. The barrel recoil is several times the momentum of cooling gases.
-Just use a very strong spring under compression so that the baffles won't move. A spring at the near end shouldn't move at all. Plus, the curves will cause extra turbulance where they contact the outer tube wall. Minimal, but certainly won't worsen supression.
-Check out my 1 way valve and Finned Heatsink Threads for a well-rounded, informed discussion from several respected members.