Wanting to load for a 308 AR. What is considered to be the safe max PSI for a 308 AR rifle? Will they handle factory loads intended for a bolt action 308? Is it necessary to stay with in military spec's, 50,000 psi or less? Thanks for your help.
Safe max operating PSI , 308 AR?
- Thread starter hesp
- Start date
Never had an issue with quality factory ammo, but reloads are a different story. In addition to standard .308 Win loads, there's a sticky thread just for .308 Win AR loads in the reloading section. I'll get pressure signs on some loads in an AR-10/308 that are fine with a bolt action.
The main difference with gas guns is there is a 1. chamber pressure spec, and 2. port pressure spec to make it run reliably and also generate the velocity required by DoD and NATO.
That latter spec is what makes things very difficult for AR-10s because a lot of civilian factory ammo is not made with a gas-operated system in-mind.
7.62 NATO started out with the M14 gas system specs, as well as the FAL and its adjustable gas venting system that the user could tune to the load/conditions.
DoD has had to tweak more modern 7.62 NATO loads when dealing with the M110 and M110K.
I’ve seen some good technical discussions here with references to the gas port pressure spec for 7.62 NATO dating back to the M14, as well as modern considerations. Someone who remembers that will probably pipe-in and reference it, or you can search.
That latter spec is what makes things very difficult for AR-10s because a lot of civilian factory ammo is not made with a gas-operated system in-mind.
7.62 NATO started out with the M14 gas system specs, as well as the FAL and its adjustable gas venting system that the user could tune to the load/conditions.
DoD has had to tweak more modern 7.62 NATO loads when dealing with the M110 and M110K.
I’ve seen some good technical discussions here with references to the gas port pressure spec for 7.62 NATO dating back to the M14, as well as modern considerations. Someone who remembers that will probably pipe-in and reference it, or you can search.
Before I sold my .308 gasser I tried 7.62 NATO ammo and the gun just "acted" better. It was actually chambered for .308 Win but didn't perform well with .308 factory loads or .308 load data unless loaded on the lower end...
You might look at Hodgdon's .308 Service Rifle Load Data and use that as a guide. Nosler also has 7.62x51 load data on their site. You didn't say what brass you were going to use but Hodgdon uses Winchester brass almost exclusively for their load data... And Nosler uses their own brass. So if you're using milsurp brass like Lake City, be mindful of case capacity and pressure.
If you have a 16" barrel don't expect to set any velocity records.
Edit to add: Barnes also has 7.62x51 load data
Mike
Hornady has .308 Service Rifle load data as well, which you can compare with their regular .308 rife data.
The Varget load under a 168 is 1.3gr lower, as is RL-15 for the Service Rifle data.
Historically, Service Rifle load data meant M14 and its gas port location, piston, and op-rod considerations for plug dwell and cyclic rate.
AR-10 is a different animal, but very forgiving for high chamber pressure, but still needs to be timed. Brass will take a beating as pressure increases and cyclic rate accelerates away from the happy window.
The Varget load under a 168 is 1.3gr lower, as is RL-15 for the Service Rifle data.
Historically, Service Rifle load data meant M14 and its gas port location, piston, and op-rod considerations for plug dwell and cyclic rate.
AR-10 is a different animal, but very forgiving for high chamber pressure, but still needs to be timed. Brass will take a beating as pressure increases and cyclic rate accelerates away from the happy window.
Thank you all. Good info. I am using a 16" Bbl. Not trying to set velocity records. Just want safe, dependable loads.
