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Old AR guy/ new to the big ones checking in.

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11 years 10 months ago #14688 by gdcpony
Old AR guy/ new to the big ones checking in. was created by gdcpony
Hello all. My craving for a large frame AR has finally been met! My wife gave me the go ahead to pick up a base model LR-308. I have shot AR-15's since the 90's. As a Marine, I get to shoot the military version quite often as well.

I have had a dream of building this one into a .257Roberts AI for deer and predator shooting. I will need allot of advice to do this. Port sizing, feeding issues, and gas tube length are all foreign to me as I have always used pre designed pieces proven to work.

I look forward to all the help I gain here.

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11 years 10 months ago #14689 by 13fcolt
Replied by 13fcolt on topic Old AR guy/ new to the big ones checking in.
Welcome to the forums!

I love custom projects like this. A .257 Roberts AI will be an interesting build indeed. I must ask, why that particular cartridge?

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11 years 10 months ago #14693 by Sharkey
Replied by Sharkey on topic Old AR guy/ new to the big ones checking in.
Welcome Sir. You have come to the right place indeed and I see you are already in good hands with 13fColt's wheels already turning.

We've got some incredibly knowledgeable people on here and what little they can't answer off the tops of their heads, they will usually be happy to dig for until they find it.

Always happy to see new members and new projects so welcome aboard Sir. :welcome:

Sharkey

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11 years 10 months ago #14702 by LebbenB
Replied by LebbenB on topic Old AR guy/ new to the big ones checking in.
First, welcome to the forums and thank you for your service.

From what I've read of .257 Roberts AI (Ackley Improved), wouldn't your COL be too long to fit in a .308 AR mag?

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11 years 10 months ago #14717 by 13fcolt
Replied by 13fcolt on topic Old AR guy/ new to the big ones checking in.
I know nothing about the .257, but what I googled up it looks like max on a 120gr is in the 2850ish. Not really blowing my skirt up, but it appears folks rave about it for anything up to elk sized game out to 300yds. I never thought about mag length, I figured the OP already had that part worked out.

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11 years 10 months ago #14718 by Sharkey
Replied by Sharkey on topic Old AR guy/ new to the big ones checking in.
you're wearing a skirt? :rotfl:

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11 years 10 months ago #14721 by gdcpony
Replied by gdcpony on topic Old AR guy/ new to the big ones checking in.

13fcolt wrote: Welcome to the forums!

I love custom projects like this. A .257 Roberts AI will be an interesting build indeed. I must ask, why that particular cartridge?


The .257Roberts was the first center fire I ever used in an old Mauser action sporterized by "Johnson Automatics." I have that gun today as my friend's dad finally sold it to me after a couple of decades of my begging.

I fired a ton of cartridges through many types of rifles between that first shot and today. I came to love Mausers and AR's. I developed a set of cartridges I love too: 22lr, .223, 7x57 Mauser, and the .257 Roberts. I know their are better choices, but being different is also a favorite of mine.

The hunting and shooting I do today is at small and medium game. I am also very recoil shy (53 broken bone including both collar bones and shoulder blades) so the least amount of kick for the greatest amount of downrange punch suits me best. I get 3200fps out of my current .257 with 100gr bullets and no more recoil than a .243. It is the perfect middle ground.

I want the AI for the additional powder and ease of reloading (less case stretch even FL sizing). I figure that 3300fps with 100gr SPBT's will suit about anything I need and with this build it should kick like a 22 center fire. Great for someone who used to put 500rds a weekend out of his weapons.

The OAL is the similar enough to work. The .308 runs 2.8ish depending on bullet and the .257 runs 2.9ish in some older books 2.8 in newer ones. Older guns had longer throats in them and seated the bullets out further. In fact you can get the upper in .257 Roberts through a couple companies. The AI only changes some case angles and capacity. It will work just fine length wise.

Feeding might be an issue as the shoulder will be steeper and closer to the ramp. I am wondering on that but the standard .257 goes through the ramp fine on mine, but obviously doesn't chamber in a .308 barrel.

I am also worried about the gas system. I would figure everything would work fine with the standard rifle length system and an adjustable block, but have no idea. Things to work out.

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11 years 10 months ago #14724 by Sharkey
Replied by Sharkey on topic Old AR guy/ new to the big ones checking in.
I see are a Marine and just hoping you don't mind me asking, how the heck did you get so busted up?

If it's none of my business, I totally understand and take no offense.

Tell me you aren't just clumsy though ok?? :)

Sharkey

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11 years 10 months ago #14728 by gdcpony
Replied by gdcpony on topic Old AR guy/ new to the big ones checking in.

Sharkey wrote: I see are a Marine and just hoping you don't mind me asking, how the heck did you get so busted up?

If it's none of my business, I totally understand and take no offense.

Tell me you aren't just clumsy though ok?? :)

Sharkey


It goes with thinking you are invincible, having bad luck, believing you would rather regret doing something than regret not doing it.

The worst was a 25mph car accident in which my seat belt was on but didn't lock when I somehow (don't remember) hit a tree. That cost me 12 breaks, 750 stitches, and my only hospital stay ever. That was in 1993.

I have fallen off cliffs while climbing them, been kicked by horses, broke in football, even managed to lay down my motorcycle dodging a deer. No combat injuries, but a few training ones. I now have few funny stories and sore joints, but I still lick my young Marines in football and out shoot all of them on the range.

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11 years 10 months ago #14729 by Sharkey
Replied by Sharkey on topic Old AR guy/ new to the big ones checking in.
I've got a couple of old training booboos myself Marine. I was Army in the early 80s and then went REALLY stupid after that - graduating to higher levels of mindlessness as I went along... :laugh:

Glad you're hear to laugh about the tales with us today GDC.

Happy to have you aboard.

You sound like you know you're stuff pretty good and it's always good to see guys smarter than me joining the board..

Not that that is all that tough but ya know... :)

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