Requesting Recommendations for a Hog Hunting Build

[michael1778]

Hello Everyone,
I have had many parts available for rebuilding an AR-15 or two but I wasn't sure what I wanted for the use case. I have decided. I want to build a 6.5 Grendel dedicated to hog hunting. I have not hunted before but I want to try it and build my proficiency.

Long term, I would like to have a suppressor and likely two different optic configurations, one for day and one for night.

Today, I have an 18" Satern barrel (mid-length gas) that was gifted to me. I have a S&W M&P15 receiver set from their original production run years back. MagPul ACS stock.

Given that I want to run suppressed in the near-ish future, I am keen to get your recommendations on the buffer, spring, bolt carrier, and gas block to use. Seems like piston systems are not in favor here? That's fine by me.

Thanks for your help,
Mike

[VASCAR2]

[michael1778]

I appreciate your informative and thought provoking reply! This barrel was a strange blessing over 5 years ago. A guy on another forum pulled it off a buddy's rifle because he wanted to go another direction from 6.5 Grendel. Being a poorly paid school teacher at the time, he selected me as the gift recipient of a few that expressed interest on a forum post offering it up. It has about 150 rounds through it, so I have been told. I will need to carefully check the bolt face depth. I have no idea on cut vs button rifling but, I was wondering the same myself.

I am glad I am not the only one that thinks the gas port is large. Just looking at it I have always thought it looked huge. I like your suggestion to measure the port size will do that when I get a chance. I put it all over at a friend's place while I was in California for a few months. I am back in NC now so I can have nice things again! Time to return all my stuff home.

[LRRPF52]

[michael1778]

I will have the port measurement by Tuesday night.

[michael1778]

As promised, I have some measurements. I also have a correction. The barrel is a Shilen, not a Satern.

Gas port was measured two ways.
Method One: inserted a hex key into the port. The largest one that fits (and fits nicely, snug but I didn't have to force anything) is marked as 3/32 inch. That's 0.09375 inch, right?
Method Two: My friend got out his digital calipers and measured the inside of the gas port. He is using a small but flat pair of surfaces inside the circular gas port. He measured a few timers and got numbers from 0.074 to 0.078 inches.

My understanding of geometry tells me the inserted hex key (Allen wrench) is the better measurement method but am I missing something?

[Edited to add that I checked the headspace with my JP Rifles Enhanced Bolt using a round of factory Hornady 123 grain A-max (yes, I have some old ammo) and it fits well for that method]

Thanks for your help.

[VASCAR2]

http://www.shilen.com/ar15Barrels.html

[LRRPF52]

[michael1778]

Thank you.
The barrel had engraving on it that was the same font and style for all the wording. Shilen 6.5 Grendel. Seeing the table in that link you shared reminded me how I had looked it up a few years ago. 1 in 9 twist worries me for longer, heavier hunting bullets like the Nosler 129gr ABLR or the 130 Swift Scirocco.

[michael1778]

Yes it is definitely mid-length gas and 18 inches total length.

[grayfox]

As promised, I have some measurements. I also have a correction. The barrel is a Shilen, not a Satern.

Gas port was measured two ways.
Method One: inserted a hex key into the port. The largest one that fits (and fits nicely, snug but I didn't have to force anything) is marked as 3/32 inch. That's 0.09375 inch, right?
Method Two: My friend got out his digital calipers and measured the inside of the gas port. He is using a small but flat pair of surfaces inside the circular gas port. He measured a few timers and got numbers from 0.074 to 0.078 inches.
[...]
Thanks for your help.

3/32, 0.9375 is flat to flat, your diameter is vertex to vertex, which will be slightly bigger than the 3/32 measured. I need to break out my geometry brain but it is calculatable.

edit to add: using cos 30* (corrected to 30) for the internal angle, and 1/2 of flat-flat as the adjacent side, the diameter is 2*0.0541, or 0.108" diameter.
Of course some 3/32 hex keys are not exactly 3/32, could be a tweak smaller, so I would say best est of the diameter is 0.100".

[michael1778]

OK. That tracks with what I measured myself on that Allen wrench with my own iGaging calipers. I measured vertex to vertex across the hexagon and got slightly more than 0.10". I'm wondering if I might be happier with a 20" rifle-length gas, 1-8 twist barrel. I appreciate all the help and comments so far. I have time to do this all "right"

I have a 12 inch barrel out of a forum group buy on this forum from 2 or more years back. That is set to become a pistol build like what LRRPF52 has done.

I have an old Loki Weapon Systems non-standard receiver set AR-15 that will get a new, long 6mm ARC barrel and become a long range practice and competition gun. If I enjoy doing that I could move up to a dedicated bolt gun. This was apparently one of the last rifles that guy shipped before he closed up shop suddenly and stiffed some customers.

[Morvandium]

Thank you.
[...] 1 in 9 twist worries me for longer, heavier hunting bullets like the Nosler 129gr ABLR or the 130 Swift Scirocco.

While I'm sure someone else can offer some advice on the specific bullet weights you mentioned combined with 1:9 twist rate, the thing that made me go with 1:9 for my 24" barrel is because it's what Bill Alexander went with for Alexander Arms 20"-24" barrels. Alexander, I believe, acknowledged that his choice varied from standard wisdom on the topic, but it was based on his testing as he developed the cartridge.

From my limited understanding, the additional muzzle velocity from the longer barrel lengths translates increased RPMs over the same cartridge from the same twist but shorter barrel, and closer RPMs to the same cartridge from the shorter barrel with a faster twist rate. My understanding is admittedly cursory. Google will produce articles on the topic with the right keywords and some sifting through results. (Slightly off topic, any articles about Q's development of the 8.6 Blackout (8.6 Creedmoor) have a good chance to mention some progressive approaches to using twist rate to affect ballistics wound cavity size. Interesting stuff, if you nerd out on ballistics.)

[LRRPF52]