You know what I can tell from this picture?
![[Image: attachment.php?attachmentid=19141&d=1664324926]](http://www.65grendel.com/forum/attachment.php?attachmentid=19141&d=1664324926)
Extraction contributed to the failure.
What does that tell me next? Cyclic rate is too fast. The bolt is trying to rip the case out of the chamber too soon while the case is still obturated to the wall.
If I missed it already, Im sorry but was this suppressed? Brass looks too clean for suppressed, unless a flow-through can was used.
Either way, CLGS needs to be managed carefully.
The way I deal with it in the 12 Grendels I have built is with Bootleg Adjustable Gas carriers.
I choke the gas down to the suppressed setting, and they cycle wonderfully.
I also used increased weight action springs. On one, I used a Franklin Armory carbine spring + power spring.
On the other, I used the Maxim Defense PDW shot RET with tiny buffer, but it has a really short, stiff spring.
Both have been shot pretty much exclusively suppressed with high efficiency (high back pressure) TBAC cans.
I have shot a lot of 120gr Federal, 123gr American Gunner, and 123gr ELD-M through mine.
My buddy has shot a lot of factory 123gr ELD-M and 8208 XBR under 107gr SMK hand loads.
No malfunctions so far through either suppressed.
* I wonder what your gas port diameter is, what carrier weight you have, buffer weight, and action spring type/length.
The discussion about Lapua brass has really distracted us from being able to focus on the real problems here.
I dont think you have a headspace problem, but still want to see where it is.
Your other fired cases are the same lengths as mine that have come out that way for 13 years.
If your fired headspace is within spec, were looking at early extraction/too fast cyclic rate.
That is even more likely using a medium-slow-burning powder like AA2520 with CLGS under a 123gr, which is a ball powder that will hit the port with higher port pressure.
This makes perfect sense as to why your extractor didnt blow out now.
Another question: Do you have an O-ring around your extractor spring?
My guess is that you probably do.
Extraction contributed to the failure.
What does that tell me next? Cyclic rate is too fast. The bolt is trying to rip the case out of the chamber too soon while the case is still obturated to the wall.
If I missed it already, Im sorry but was this suppressed? Brass looks too clean for suppressed, unless a flow-through can was used.
Either way, CLGS needs to be managed carefully.
The way I deal with it in the 12 Grendels I have built is with Bootleg Adjustable Gas carriers.
I choke the gas down to the suppressed setting, and they cycle wonderfully.
I also used increased weight action springs. On one, I used a Franklin Armory carbine spring + power spring.
On the other, I used the Maxim Defense PDW shot RET with tiny buffer, but it has a really short, stiff spring.
Both have been shot pretty much exclusively suppressed with high efficiency (high back pressure) TBAC cans.
I have shot a lot of 120gr Federal, 123gr American Gunner, and 123gr ELD-M through mine.
My buddy has shot a lot of factory 123gr ELD-M and 8208 XBR under 107gr SMK hand loads.
No malfunctions so far through either suppressed.
* I wonder what your gas port diameter is, what carrier weight you have, buffer weight, and action spring type/length.
The discussion about Lapua brass has really distracted us from being able to focus on the real problems here.
I dont think you have a headspace problem, but still want to see where it is.
Your other fired cases are the same lengths as mine that have come out that way for 13 years.
If your fired headspace is within spec, were looking at early extraction/too fast cyclic rate.
That is even more likely using a medium-slow-burning powder like AA2520 with CLGS under a 123gr, which is a ball powder that will hit the port with higher port pressure.
This makes perfect sense as to why your extractor didnt blow out now.
Another question: Do you have an O-ring around your extractor spring?
My guess is that you probably do.
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