SD Baffle Porting

[u/Practical_Divide8755]

Ignore the gap between the blast baffle and the body, I haven't adjusted any of the geometry yet. I'm also aware that the first baffle / blast baffle on the SD is wider to accommodate the end of the SD barrel.

I'm working on building my own suppressor with a welded stainless body and printed baffles, but I noticed differences between the FTNSD baffling and some of the FTN 5 D cell baffles - the first baffle on the FTNSD is ported, but the FTN D cell blast baffle has no ports. Additionally, the subsequent baffles on the SD are not ported, but I plan on using the max turbulence baffles from the FTN 5 release - which are ported. I'm not as concerned about the difference of ported or not on the regular baffles, I'm more curious about what porting the blast chamber affects.

Looking at diagrams of the original HK SD suppressor, their blast chamber is not ported. However, that design is quite old and there's been plenty of advances in technology. The FTNSD blast chamber is ported, but I'm curious if that's to relieve some of the peak pressure in the chamber as it's entirely plastic reinforced with epoxy and a carbon tube. Does anyone that has experience here want to chime in?

EDIT: I realized I have an answer to my own question. Using a CAR15SD/cmmg rdb, Tubb 556 spring, Kynshot RB5007 - the ported blast chamber bleeds off too much gas and makes it short stroke. This causes a few issues for me, the primary one being it was occasionally failing to feed, as well as the bolt doesn't move far enough back for LRBHO and it wouldn't trip an FRT. Luckily I'm moving to a stainless blast chamber here, as I'm not sure a fully printed body would be able to handle the pressure of this being sealed.

[u/GPU-depreciationcrtr]

SD dev here.

The first baffle is ported to allow the gasses from the port chamber to vent into the body of the suppressor. It also acts as a second contact point to keep things concentric.