Am getting close to retiring back to the family farm and am looking at getting a CVA Hunter in .45-70 Gvt to pop piggies that are proliferating now on the back 40. 
linkage to vendor that has this single shot .45-70 in stock   
Am going through the 119 page thread on how to build a $100 Form 1 suppressor and putting all the pertinent info into a Microsoft OneNote document. Used the info at about page 30 to calculate the Muzzle Pressure and Hoop Stress via an Excel spreadsheet. Due to cervical issues now days, the Hornady equivalents to light loaded .458 Win Mag(aka LEVERevolution) are definitely out and am sticking to cast 500 grain 'Cowboy Action' loads at Trapdoor pressure levels. Here is what I got when I plugged in the Trapdoor loads into the spreadsheet for this rifle once the barrel is cut & threaded at 20" .


Would the use of aluminum be OK when restricted to only the Trapdoor pressure levels? 

The .458" SOCOM is probably higher pressure, as it produces .45"-70 ballistics from a smaller case, but when I was looking @ .458" suppressors the options were titanium & stainless steel.

Given your values, you're well below the avg muzzle pressure of a 16", 22lr w/ HV ammo.

Depending on your overall design (most importantly the baffles), I wouldn't recommend a huge blast chamber length. You're listing a single-shot rifle so back pressure is almost a non-issue and you aren't showing a huge volume of gas to begin with. Use that space for baffles, you'll have a more efficient design.

Commercially purchased Solvent Trap parts?

Thanks for the info. Looking at the second Tier of .45-70 at 25,000psi with a 1.0" Blast Chamber length, the Blast Chamber Pressure is 951psi and Hoop stress at 8,843.

Is that still in the range of .22LR HV? My google fu was weak && failed to find that. 

Thanks for the info! 

Blast chamber or @Muzzle is 951psi?

Your combined bbl and case volume is 3.13in^3
Every inch of 1.5"OD x .065" tube is 1.47in^3

I'd be looking at a 1.5-2.25 blast chamber length, depending on ID and blast baffle design.

The working pressure of 7075-T6, for this size tubing, is 2500psi (safety factor of 2.5) and burst is over 6kpsi
You would need a muzzle pressure of around 5kpsi to make a 2" blast chamber unsafe for the specified dimensions. (but this would be factoring a sealed vessel, which a silencer is not)

If you really want to use Al, you can do some things to strengthen your weakest area (blast chamber):
1. Use a thicker wall tubing and turn down the OD after the blast chamber (thickening the blast chamber area)
2. Sleeve the blast area w/ another piece of tubing, preferably SS or Ti

I'd go w/ option #2, but with a twist.
Make a single-piece mount/blast chamber that threads to the back of the tube. Your blast baffle can butt into this and everything else registers off that.
In this scenario, you have a strong blast chamber, that's more corrosion resistant than Al, and mounting threads that are not Al.

I would liketo use Al, but if there are stress/safety factors that say that this isn't the smartest thing; I'm willing to listen to good advice.

As I said, It can be done. You just have to know the material's limits and be willing to design around them.
Regardless of whether or not Al could handle the pressure, sleeving the blast chamber would be standard advice.

Are you trying to do this w/ commercially available products or do you have the capability to machine your parts?

Right now, I don't have a lathe. I should have the extra tokens scratched together by June for that. Do have a milling table attachment on my drill press that I've done 80% lowers with. Want to buy commercially what I can, but will RSN^* have the capability for my end caps.

Given that Al is marginal if "Marlin 1895' level loads are used, I'll go with Ti for safety. Cheaper than a run to the ER. 





*RSN = Real Soon Now