First timer with a few questions

[SynnTX]

Good evening all. This is my first post here and I'm excited to absorb y'alls combined knowledge! Recently I acquired my very first Form 1 stamp and built a 300blk SBR. I also purchased a SiCo Hybrid and should (hopefully) receive my stamp any day now. This mostly came about after rumors started that my agency (I work as a patrolman for a medium sized Sheriff's office in Texas) was considering adopting (adding) 300blk, SBRs, and suppressors to our rifle policy, which currently only allows for .223/5.56 on an AR platform with a 16" barrel requirement. Then the rumor turned into action, and we're expecting the new policy any day now. Personally, I think 300blk is the perfect rifle cartridge for law enforcement but I digress. I'm not a terribly inexperienced gunsmith, but have recently had the desire to form 1 a suppressor after realizing how cost efficient it can be. I want to make a dedicated can for my new work rifle. I have my reasons, but I plan on running supersonic suppressed. Plus, I like to tinker with gun stuff. I've done a bit of research and have some questions I'm hoping to get answered.

- I've heard you have to submit a design sketch or something along with the Form 1, this true? If so, is there any specific rules or can it be done on construction paper with crayon?

- I plan on going with a 7 or 8 inch 1.355 ID titanium tube, with 1.5" - 1.75" expansion chamber, using a 1.350 titanium tube as a spacer for the expansion chamber, and the first one or two blast baffles will be stainless or perhaps titanium as well. I know aluminum will erode quicker but, for cost efficiency, will aluminum Sealed Power freeze plugs for most of the baffle stack stand up to supersonic 300blk, or do i need to be looking at all stainless/titanium baffles?

-K cups or freeze plugs and why?

-Are aluminum endcaps okay to use?

Thanks in advance!

[SynnTX]

Here's a rough design i had in mind. Please excuse my rudimentary MS Paint skills. Fairly typical I think. Measurements are rough guesses but I figure around 13 baffles can be used. the first baffle being an unformed freeze plug followed by conical baffles. Does this look about right to everyone?

[fishman]

I've heard you have to submit a design sketch or something along with the Form 1, this true?

No


Your endcaps are too thin. 0.2" of threads isn't enough. The thread relief on the endcap alone will kill half of that thread engagement. 0.5 or even more is more reasonable.

Avoid aluminum in rifle cans. Go all titanium with a stainless blast baffle if you're worried about weight, or just shorten the design.

Id use something much more robust as a blast baffle.

Cones, radials, and Ks all work well for 300blk.

Make sure to clip and/or port the cones.

[ECCO Machine]

Welcome aboard.

First of all, freeze plugs suck, and you don't want aluminum in any centerfire rifle can that will see more than "sighting in" rates of fire with a relatively low total round count.

I wouldn't do less than .5" thread length on the rear and .375" at the front on a rifle can. .2 is for rimfires.

For supersonic, cone baffles are your best best with a decent sized blast chamber and progressive spacing. 300 blk supers still don't burn much powder, but you might as well make it a useful can for .308 and others with higher uncorking pressure if you're gonna optimize for super and go 8" long. I'd give it 9 or 10 baffles, first and second spaced .800 or so apart, last two .400 ish and dividing the difference between those for the remainder, and what's left over becomes your blast chamber.

Lots of opinions on clip style and size, but I like a radiused asymmetric (single side) clip, perpendicular to the cone angle and ~1/2 the radius of the bore. For a .30 cal can, I use .36" through holes with 3/16" (.188") clips.

[doubloon]

...
- I've heard you have to submit a design sketch or something along with the Form 1, this true? ...

Echoing fishman's no and adding please resist the urge to write any letters.

Take a look at fishman's 300blk form 1 build link in his signature for some good info.

There should also be some more 300blk builds in the form 1 thread maintained by wicked and linked in my signature.

[SynnTX]

Welcome aboard.

First of all, freeze plugs suck, and you don't want aluminum in any centerfire rifle can that will see more than "sighting in" rates of fire with a relatively low total round count.

I wouldn't do less than .5" thread length on the rear and .375" at the front on a rifle can. .2 is for rimfires.

For supersonic, cone baffles are your best best with a decent sized blast chamber and progressive spacing. 300 blk supers still don't burn much powder, but you might as well make it a useful can for .308 and others with higher uncorking pressure if you're gonna optimize for super and go 8" long. I'd give it 9 or 10 baffles, first and second spaced .800 or so apart, last two .400 ish and dividing the difference between those for the remainder, and what's left over becomes your blast chamber.

Lots of opinions on clip style and size, but I like a radiused asymmetric (single side) clip, perpendicular to the cone angle and ~1/2 the radius of the bore. For a .30 cal can, I use .36" through holes with 3/16" (.188") clips.

Lots of good info here! Why do freeze plugs suck? Even stainless steel ones?

[ECCO Machine]

Why do freeze plugs suck? Even stainless steel ones?

Cheap, soft material, which is further weakened by trying to form them. They universally require separate spacers, which I'm not a fan of. And it's just generally difficult to get decent geometry out of them.

I built one just for kicks once with 304 tubing and steel plugs, machined a quick forming die, made end caps, cut spacers and screwed it onto my post sample .308. Suppression was pretty eh, It didn't even survive 2 magazines, the baffles & spacers getting soft from the heat, baffles turning sideways and causing strikes. In contrast, my machined 17-4 stainless cones with integral skirts are thinner, lighter and can handle back-to-back magazines of full auto fire from that 13" barreled .308 machine gun.

[doubloon]

...
Lots of good info here! Why do freeze plugs suck? Even stainless steel ones?

A number of adventurous souls have built freeze plug designs before you, everything from 22 to 308, there are drawbacks to almost everything.

A few are below, browse wicked's thread for more or google search with the site:silencertalk.com parameter.

viewtopic.php?t=110524

viewtopic.php?t=81439

viewtopic.php?t=135243

viewtopic.php?t=132922