Chopping 20" SFAR down to 16"

[MarksmanJelly]

Just got my new 20" SFAR. My question is, would any issues come from taking the barrel length down to 16", considering it came with a rifle-length gas system? My reasoning for doing this is because I plan on throwing a suppressor on it and a 20" barrel + suppressor length is just too long for my liking.

 

[hittman]

Considering the problems some have had with the gas adjustment I’d wonder if shortening it would create a problem in reliability.
Why not just sell it and buy their 16 inch model?

Welcome to the forum.

 

[MarksmanJelly]

I've seen a lot of these issues with the gas adjustment and 99% of what I find are with the mid-length gas system that comes with the 16". I was wondering if these problems could be easier to fix or even solved if I had the rifle-length gas system on a 16" barrel. Just as long as it wouldn't be too undergassed with only 4" between the gas block and the end of the barrel when cut down to 16".

 

[Mobuck]

I don't own a SFAR(never even handled one) but I do have a fair amount of experience with the common AR platform.
Here's what happens when you try to run a rifle gas on a 16" barrel: the 'dwell time' is often insufficient to achieve proper cycling. Dwell time is a function of bore diameter, gas port size, gas volume(of the cartridge used), and the distance the bullet moves beyond the gas port which what maintains gas pressure in the gas tube long enough to provide the force to cycle the bolt.
I've had excellent results using rifle length gas and a .223 18" barrel but this might not work with a different cartridge. Using a rifle gas with a 16" barrel cuts the dwell time to nearly nothing and function would be questionable IMHO. At the very least, the gas port would have to be larger to get more gas quicker--very tricky process.

 

[s4s4u]

Just got my new 20" SFAR. My question is, would any issues come from taking the barrel length down to 16", considering it came with a rifle-length gas system? My reasoning for doing this is because I plan on throwing a suppressor on it and a 20" barrel + suppressor length is just too long for my liking.

Been done by several folks with success. If using a suppressor you are adding effective dwell time to make up for the barrel length loss.

 

[Tim the Tool Man]

Hey, I see that this post is old but I have the 16 inch version and if you’re interested in trading barrels and associated gas items, I would like to make a musket out of mine. A 20 inch barrel with a 7 inch suppressor would be pretty sweet. I am planning on hunting not room clearing so don’t care about length.

 

[MarksmanJelly]

Sorry I haven’t been active, I’d actually be willing to make this trade if the offer still stands. I see you’re in Tennessee, how close to Chattanooga are you? Feel free to dm me.

 

[Tim the Tool Man]

Nice. I'm an hour west of Nashville so maybe 3 hours. Call my office and ask for Tim at nine three one 325-0000

 

[instructor]

The shortening of a 7.62/308 cartridge barrel is probably not a good idea for the best performance of that round, but to each his own. If your plan is to shoot targets at relatively short ranges likely not a problem. As for handling a shortened barrel system certainly is a plus factor but as mentioned may create operational issues with the firearm. Have been giving some thought to buying the SFAR but do see a lot of complaints for the rifle & many are for the shortened barrel configuration.

 

[6GUNSONLY]

I realize you guys are talking suppressed rifles here, but for what it's worth i find a 16.5" barrel .308 to be distinctly unpleasant to shoot.