The dissipaters where not a very good combination of barrel length, gas system length etc
The 605 was 20" barrel with a rifle length gas system and the barrel cut off and threaded back right to the FSB.
Its documented that the rifle length gas system and cutting the barrel off right after the gas block did not create an ideal dwell time to build up a reliable amount of pressure to cycle the action for the rifle to work as reliably. One of the reason they never caught on. And eventually realized that if you were going for a carbine of the AR15, you needed to cut the barrel back AND the length of the gas system to increase dwell time. Ideally 7" give or take is an optimal length of dwell time to negate any issues with the reliability of cycling as well as ammunition "pickiness" you start getting with odd ball barrel lengths.
You may be able to resolve this with fancy modern lighter weight buffers etc but your SP1 barrel will have a rifle length gas system essentially replicating this same combination as the original dissipater. There's a reason it didn't get selected as a standard once they started experimenting with shorter barrels.
There is a science to this trade off with the AR15 most don't actually research or bother to learn before they slap together whatever random combo of barrel length, gas length, buffer weight/type and how they react WRT how reliable cycling, low recoil, undue stress on the bolt/carrier, being picky on ammo etc
The best all around setup still truly is the original 20" with rifle length system. The only thing it doesn't do is work well for CQB.
The 14.5" barrel with a carbine gas system is the runner up.
This is a great article and extremely in depth on the topic. He touches on the ammo pickiness and reliability of the 18" barrels fielded by US SFG with a full length gas system as well (dissipaters were cut back even closer to the FSB increasing the problem). Give it a read!
https://www.everydaymarksman.co/equipment/ar-15-barrel-selection/
The issue you'll have is that you can't find a 16" barrel with a FSB at the very end of it (threaded right after the FSB) but also have a shorter length gas system to make the rifle not potentially a picky on ammo, jam o matic potentially you know?
Just some good often overlooked info to digest before you delve into that murky world lol Hope some of it helps brother.
