AR 10 Timing and overpressure

[Not_A_Llama]

Preface: Some say the plural of ?anecdote? is not ?data?.

The high pressure bolt with small firing pin hole is the answer to the otherwise disconcerting primer pressure signs you?ll see. I accept that a small degree of ejector swipe is expected.

The adjustable gas block is required on large frame ARs, in my opinion. Troubleshooting is not super straightforward, though, and overgassed can look like undergassed. Play with it a bit if you?re not getting desired operation off the bat.

Edit: AGB can help with ejector swipe. It will do nothing for primer signs.

[normandinpatriot]

Preface: Some say the plural of ?anecdote? is not ?data?.

The high pressure bolt with small firing pin hole is the answer to the otherwise disconcerting primer pressure signs you?ll see. I accept that a small degree of ejector swipe is expected.

The adjustable gas block is required on large frame ARs, in my opinion. Troubleshooting is not super straightforward, though, and overgassed can look like undergassed. Play with it a bit if you?re not getting desired operation off the bat.

Edit: AGB can help with ejector swipe. It will do nothing for primer signs.

Not_A_Llama, can you give me a little bit more info? How does overgassed look like undergassed? and vice-versa? I put an AGB(Odin Works) on it and started at about 10 clicks out from closed and the bolt didnt move. I ended up at 18clicks to get the bolt to lock back when shooting one round. I only tried 2mags with multiple rounds in them and both times the bolt didnt lock back...I did adjust the gas to the full open position(20) between the two mags. The condition/ overpressure sign on the shells seemed to be reduced to mild flattening of the primers on the Lapua ammo and mild cratering of the M118 with one popped primer. No ejector swipe to speak of.

[Not_A_Llama]

Not_A_Llama, can you give me a little bit more info? How does overgassed look like undergassed? and vice-versa? I put an AGB(Odin Works) on it and started at about 10 clicks out from closed and the bolt didnt move. I ended up at 18clicks to get the bolt to lock back when shooting one round. I only tried 2mags with multiple rounds in them and both times the bolt didnt lock back...I did adjust the gas to the full open position(20) between the two mags. The condition/ overpressure sign on the shells seemed to be reduced to mild flattening of the primers on the Lapua ammo and mild cratering of the M118 with one popped primer. No ejector swipe to speak of.

Sorry about the delay in response - the forum didn't show your post as new to me.

In my experience: Getting too much gas into the system can sometimes cause failure to lock back on a mag with a single round. Exacerbating the issue, some AGBs have steps that are too big, and you can step from undergassed to overgassed very quickly. I've found that using a continuous infinitely adjustable gas block is better than a detent-based system in large frame ARs, because they're much more gas-sensitive than small frames.

[normandinpatriot]

Sorry about the delay in response - the forum didn't show your post as new to me.

In my experience: Getting too much gas into the system can sometimes cause failure to lock back on a mag with a single round. Exacerbating the issue, some AGBs have steps that are too big, and you can step from undergassed to overgassed very quickly. I've found that using a continuous infinitely adjustable gas block is better than a detent-based system in large frame ARs, because they're much more gas-sensitive than small frames.

Thanks, that is good info... I purchased the Odin Works adg. because it was the best of what i could find to fit my barrel... I did want an infinitely adjustable ADG. I think I will run this for know and get some more of the sig or hornady ammo I started shooting and run it through the chrono i just got and compare to the Lapua and LC M118Lr that has been giving me concerns...The sig and Hornady I first shot had no overpressure signs...