Info on ARPerformance 16" LW middy

[RWH24]

I sent an email to ARP asking what size of port they drill on their 16" 5.56 Lightweight barrel, 4150 CMV, Wylde chamber.
In their FAQ section the question was asked if steel cased ammo can be used in an ARP chamber, Answer is

Can I use steel case ammo in ARP rifles?
Yes, the mid gas system allows more time for the cases to shrink back down aiding extraction. The Nitro treatment makes the chambers 70 Rockwell and very slick also aiding extraction, Our Nitro carburized barrels were made to handle steel cased ammo.

The question was asked what buffer did they recommend with their barrel. Answer to both questions are as follows:

.082”
The standard carbine buffer should work fine.
If the ammo you choose to shoot ejects forward of 3 O’clock you can change to an H2 buffer.

Apparently someone complained about accuracy from sustained firing with this barrel. Answer from them:

These are lightweight combat type barrels not target barrels. Common accuracy with decent ammo is 3/4-1.5" at 100yds, 55gr FMJ can be worse.

http://www.ar15performance.com/inc/sdetail/11562/14041

[lethal dose]

Exactly what point are you trying to make?

[RWH24]

Not a point but an FYI. Seems lots of discussion has come up on what the port size does your barrel have and what buffer weight should I use.
I asked the manufacture what size they drill their ports and what they have seen work buffer wise.
Just a matter of reference.

[C4IGrant]

Not a point but an FYI. Seems lots of discussion has come up on what the port size does your barrel have and what buffer weight should I use.
I asked the manufacture what size they drill their ports and what they have seen work buffer wise.
Just a matter of reference.

That gas ports seems on the large side to me. You could get away with an H2 buffer for sure.


C4

[RWH24]

Thank You Grant. From what I had found here, The .082" gas port seemed to be a little larger, needing a heavier buffer, spring or both to keep from battering it'self to death.

[SomeOtherGuy]

Midlength gas setup so .082" is not as huge as it would be on a carbine setup.

I've been using one of their 16" midlength uppers (slightly heavier SOCOM barrel weight, but still a 5.56 16" midlength) for a little over a year now. It's been used with several lowers, being setup with (1) H buffer and GI spring, (2) H buffer and Springco blue spring, and (3) VLTOR A5 system with standard A5 buffer. The BCG was lubed with Froglube paste prior to any use. In the first 10 rounds from new, using H buffer and GI spring, I had 3 failures to extract. Since that time I have had no failures of any kind, in temperatures from 80's to 20's, much of it competition use (fairly rapid fire for 1-3 minutes at a time). ITS/ARP mentions that their bolts fit very tight when new, and that plus ordinary break-in is what I attribute the 3 initial FTEs to. Felt recoil and speed of operation seem normal for a 16" midlength, neither harsh nor sluggish.

I think a standard H buffer will work fine. The carbine weight or H2 probably also fine.

[RWH24]

Thank You, good to know.

[Iraqgunz]

I am fairly certain that with something like M193/M855 or similar that it will run with an H2 and probably an H3.

As Grant stated, .082 is a little on the large side.

[Clint]

.082" is quite strong for a 5.56

Something seems off.

.082" is the defacto standard for 6.8x43 16" middy barrels

It might be worth a double check 5.56 vs 6.8

[dkindig]

.082" is quite strong for a 5.56

Something seems off.

.082" is the defacto standard for 6.8x43 16" middy barrels

It might be worth a double check 5.56 vs 6.8

I was going to say something about this earlier and I wish I had.

There has been an ongoing discussion on 68forums about port sizes and Clint's data matches that. I'm running an older ARP 18" 6.8 middy barrel and the port on that is .086. Harrison normally runs a .082 port on those barrels but mine was made around the time that he was trying to make them run reliably with Remington UMC SAAMI ammo so he wanted more gas for the weaker rounds.

The only flaw I can think of with that theory is that (and I'm not sure about this) with the increased dwell time of an 18" barrrel over a 16" barrel, you would think that the port would be slightly larger for a 16" barrel. I could be over-thinking the whole thing though...