02-10-2020, 11:23 PM
Tell us more about your 120gr Gold Dot load.
Especially with the 18" MLGS or 16" CLGS, you have to watch what you're doing with slower-burning powders or higher charge weights.
When the port pressure is high and you have a lot of gas feeding back into the BCG to initiate rearward momentum, it can be really hard on the bolt and extractor due to rotational torsion on the lugs and the extractor lip.
One way to combat this is to regulate the gas flow with adjustable gas.
Another is to regulate the carrier and buffer mass as a rate-reducer so the bolt stays locked longer. You can also add spring weight to resist early momentum from the gas system acting within the BCG.
![[Image: AR15BCG.jpg]](https://i1085.photobucket.com/albums/j422/LRRPF52/AR15BCG.jpg)
The goal of both of these methods is to keep the bolt locked longer, allowing the chamber pressure to fully dissipate as much as possible before any rotational torsion is applied to the bolt and extractor, which are firmly in contact with the expanded case. We want as much case rebound as possible before primary extraction takes place. When you have a fully or mostly-obturated (expanded) case in the chamber and you try to pull it from the chamber with the extractor, the extractor or case rim often loses that battle and slips over or rips the rim out.
The worst case is the extractor failing entirely as you have here.
Did you measure your gas port by any chance? This dimension will also help paint the picture better.
What buffer and spring are you using?
Especially with the 18" MLGS or 16" CLGS, you have to watch what you're doing with slower-burning powders or higher charge weights.
When the port pressure is high and you have a lot of gas feeding back into the BCG to initiate rearward momentum, it can be really hard on the bolt and extractor due to rotational torsion on the lugs and the extractor lip.
One way to combat this is to regulate the gas flow with adjustable gas.
Another is to regulate the carrier and buffer mass as a rate-reducer so the bolt stays locked longer. You can also add spring weight to resist early momentum from the gas system acting within the BCG.
The goal of both of these methods is to keep the bolt locked longer, allowing the chamber pressure to fully dissipate as much as possible before any rotational torsion is applied to the bolt and extractor, which are firmly in contact with the expanded case. We want as much case rebound as possible before primary extraction takes place. When you have a fully or mostly-obturated (expanded) case in the chamber and you try to pull it from the chamber with the extractor, the extractor or case rim often loses that battle and slips over or rips the rim out.
The worst case is the extractor failing entirely as you have here.
Did you measure your gas port by any chance? This dimension will also help paint the picture better.
What buffer and spring are you using?
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com