338 Silencer

[grifter95]

Looking to do a Form 1 338 Norma Magnum Silencer. Plans are to do 12 inch long by 2 inch diameter. Question is on the tube, should it be stainless, cold roll, or hot roll. From the silencer standpoint, containing the pressure, which is best? Thanks!

[Bowen1911]

I am a fan of 316 stainless for most applications. .065 tube should be strong enough i would think.

[ranb]

I made a 4130 steel 1.75"x12" can with .095" walls for my 338 RUM. It works fine but is too heavy. I think .065" walls would be fine. My can telescopes over the barrel 4 inches and uses K baffles

Ranb

ETA; here is a drawing

[grifter95]

Will having the baffles stainless over carbon steel make that much of a difference in wear and life expectancy? Also I am planning on stepped baffles or K or cone for ease of machining and the good results another member had with his 408 silencer. Any other opinions on the baffles design? Should I really pack the baffles in tight after the blast chamber to get a higher number of baffles? Or should I space them out a little more to get more volume? Not real familiar with this type of round for suppression, as my previous form 1's have been 22lr and 510 whisper. According to Quick load my 300 gr should be doing 2800-2900 fps (depending on powder) and making 10K to 14K psi of pressure at the muzzle.
Thanks!

[Bowen1911]

Jimmy's 408 can would probably be a pretty good model to go after, as he modeled one of AAC's can's i think

I am not sure, but I think stainless will be stronger and resist erosion from the blast better, maybe a lot better, maybe a little better

[grifter95]

Thanks, stainless it will be. I have gotten pretty good on the lathe over the last few months and that had me thinking about the bore diameter of the silencer. I will be building the rifle and silencer, so I control all the variables. So what should be the minimum diameter of the bore of the suppressor for a .338 bullet? Assuming everything is perfect (which it won't be since I am human) how much over do you need for fouling? How much for bullet stability? Would .020" be too tight? Could it be tighter theoretically?
Also I was thinking about a 2"x10" can. But kinda liked the way 1.5"OD tube looks for a suppressor. Would 1.5"x12" be close to as effective? I know the volume would be reduced, but I could use more baffles? Guess it goes back to which is quieter for high volume, high pressure, more baffles stacked tighter or fewer stacked farther apart?
Thanks!

[Bowen1911]

a .338 bullet will never fit through a .02 hole

I am still waiting on my first Form 1 to come back , but I would think .02 all the way around the bullet is enough.

as long as your threads are concentric, and more importantly, coaxial.

[grifter95]

Here are two designs I'm thinking of. First is simple stepped cones. Second is Stepped K Baffles. Which should preform better in a 1.5" x 12" silencer?

[grifter95]

Decided to kinda morph both designs into a better, yet more intensive machining, design. This still uses stepped cones. However, the blast baffle is different from the main baffles. Also I reduced the diameter of my spacers, and ported them to create primary and secondary chambers. It will be much harder to machine than the first option. But heck this is going on a $3K rifle, so I might as well make it as good as I can.

Please critique it furiously as all helpful comments are wanted to get the design as good as possible!

[SRM]

I`d open that bore a little!!!

.001 out at the mount = .012 out at end of can = baffle strike

Happy building!

[grifter95]

Thanks for tip on bore diameter. It is drawn at 0.022" over now. What should the minimum be? Should it be uniform or increase towards the exit hole?

[SRM]

I bought a QSM 30, (.308) and it has a strait hole at .350 ID. Thats pretty tight but its goin on a .20 cal..

I would do a 1/32 over and not worry

[delta9mda]

grifter, check pm

[grifter95]

It was suggested to me that my tube wall thickness of 0.065" SS may not be thick enough. Can someone please calculate and let me know what minimum tube thickness should be. According to QuickLoad the pressure at the muzzle (28") would be approximately 11K-12K for most of the loads. Basically identical pressure to my 20" .308. However, the volume of gas will be much greater.
Thanks again for any and all assistance.