Author Topic: AR10 in 300 win mag  (Read 12954 times)

Offline sysops666

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AR10 in 300 win mag
« on: March 24, 2011, 01:40:43 PM »
I was reading K2unit's thread on the ar10-06 and i started typing a response. the response got so big i decided to start a whole new thread.

I like the idea of a scaled up AR action for the 30.06 with one little change.....

300 win mag out of BAR mags. I mean dont get me wrong the 30.06 is great for cheap blasting but the standard should be set at the 300 win mag. Because if the want for scaling upwards to a larger bore size should ever strike your fancy then why not have magnum rated parts ready to accept that mission?

I know its not much different than whats been talked about already but its been messing with my
head the past few days and I needed some further advice thats why im starting a whole new thread.

Gas system. I dont really think its a matter of scaling up the action.... well to some extent yes but most of
the extraction, cycling, and recoil issues can be massaged and tuned with an adjustable gas block.
The only one I've assembled and worked with is Armalites SASS gasblock, which only has 2 settings, 3 if you count the "off" position between the 2 exhisting marks. the knob at the front of the block is one piece with a cylinder extending into the gasblock. The cylinder has 2 ports drilled on its side, one hole bigger than the other. the opposite end of the cylinder leads to the gastube, which is flared and has been
affixed to the cylinder with a nut.

Now by my thinking it wouldnt be too hard a job of modifying the cylinder to have more settings. Or to start with a new custom cylinder to make whatever sized ports would be necessary. drilling the gas port on the barrel to max size and working it down with cylinder settings seems like a good way to test feed and function.

bolt and barrel extention. Wether you agree with it or not a semi auto will never be as accurate as a bolt action. But I really believe this to be all related to the design of the bolt and the barrel extention itself. There are designs out there already that can mate with current AR10 carriers that can be improved upon.

Parts and pieces? well thats simple. this should run off of an ar10 parts kit. standard parts for an extraordinary build. standard buffer extention, standard handguards, i mean why scale upwards in everything? If we know where the problems lie then the max amount of standard parts can be used and the whole project can keep the regular modular nature of your everyday ar15/ar10. Your choice of stocks and handguards,all on a custom receiver that shoots a magnum sized cartridge.

i wish i had some pics to post so you guys could visualize this but maybe later. I gotta go pick up my kid from school.


Offline scooter

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Re: AR10 in 300 win mag
« Reply #1 on: March 24, 2011, 09:54:57 PM »
Not to thread crap - but I think your overthinking the gas cycling.  Chamber pressure for 300 win mag is almost the same as 308.
Maximum Pressure Recommended By SAAMI
308 Winchester - 62,000
300 Win Magnum - 64,000

"Wether you agree with it or not a semi auto will never be as accurate as a bolt action."
Technology is changing everything, and this really depends what you are comparing.
There are many, many more important factors to accuracy than the bolt and barrel extension or Bolt and locking lugs.
This is just my opinion as well and I am biased as to I only work with semi auto rifles.

I do like the idea of a Semi 300Win - I saw a 338 Lapua at shot show that was even more exiting.
I will be interested to see how your project comes along.

Offline sysops666

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Re: AR10 in 300 win mag
« Reply #2 on: March 25, 2011, 09:16:12 AM »
Your not thread crapping at all. In fact I need more people with opinions here. I was at this years shot show as well and if your talking about the onlylongrange.com semi 338 lapua then yeah I saw that. The action was scaled up with a lot of propriatary stuff. Not that I didn't like it and all but the only thing you could probably change on that thing is the stock and the grip.

Plus the idea of shooting 5 bucks a pop doesn't sit well with me. For now anyway.

Now in terms of the gas system I was only talking about cycling and recoil, while working with a standard buffer, spring, and carrier. That's pretty much where I was going with the whole bolt and extention thing.

I really think all it will really take is to stretch out an exhisting cad file for an ar10 receiver set and just go from there.


Offline wendellgj

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Re: AR10 in 300 win mag
« Reply #3 on: March 25, 2011, 11:37:43 AM »
I decided to stop at the Lapua. It is a great cartridge in the hands of a good shooter-no doubt about it. I look at the other great ballistics of affordable ammo for reloading. An AR 300 Win Mag or 338 Win Mag would be my choice. I was looking at BAR rifles with a gas system that works well in these large calibers. I know nothing about BAR gas systems. If the AR system does not work maybe some proven design could be used. This is good subject matter.

WGJ

Offline scooter

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Re: AR10 in 300 win mag
« Reply #4 on: March 31, 2011, 09:02:36 PM »
So giving a little more thought to this - 300 or 338  win mag would be the same setup just difforent barrels.

So bolt face  would be .532 vs the .308  at .4728 in mm   13.51 vs 12.01 .

Currently on the Ar15 platform we open up boltfaces on 7.62 to 11.35 from a standard 9.6  (5.56 or .223 round)

So we know on a Ar15 platform  we have opened up the bolt face by 1.75mm with some success (I say this because there has been some issues with 7.62 bolts failing).

So if we did the same thing we are looking at opening a Ar10 bolt up 1.5mm to run with a Ar10 extension (this may be doable but I have doubts).

With the assumption that the bolt needs to be bigger - the new parts that need to be designed are:
Bolt
barrel extension
Barrel
Upper receiver
Lower receiver
Magazine

Likely also need a new barrrel nut

So a fair amount on engineering for the project.

Thoughts?



Offline troysk8

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Re: AR10 in 300 win mag
« Reply #5 on: April 01, 2011, 07:18:48 PM »
seams like a lot of work for a 300 win mag

if it is ballistics your looking for in a AR you can get equivelent with a 300 rsaum or 300 wsm in a ar10

Offline wendellgj

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Re: AR10 in 300 win mag
« Reply #6 on: April 02, 2011, 08:08:14 AM »
Once you have the larger magnum components to handle and function properly you have the option to pick caliber. No matter what your agenda. I don't want to build what I cannot afford to shoot but in no- way nix a project like this. I am in the process of building an oven that will do a variety of jobs to include heat treat. I might be able to treat some parts for this project if someone has the need.

WGJ 

Offline sysops666

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Re: AR10 in 300 win mag
« Reply #7 on: April 16, 2011, 07:50:19 AM »
Once you have the larger magnum components to handle and function properly you have the option to pick caliber. No matter what your agenda. I don't want to build what I cannot afford to shoot but in no- way nix a project like this. I am in the process of building an oven that will do a variety of jobs to include heat treat. I might be able to treat some parts for this project if someone has the need.

WGJ 

i agree. its the next step in terms of scaling an AR action. you can play with all the calibers of that range and still use all the third party goodies.

While I was at the shot show i did get to play with colt's new 901 series modular rifle. As a builder I was curious as to how the lower could accept 308 and 223 mags and uppers. The colt rep let me take it apart. I found out that the receiver is a slightly extended version of the 223. the magwell block allows regular ar15 uppers to be used but the 308 is propriatary to the lower. I wrote a few notes on this picture, i know where its from so dont give me any crap ok? Its the first big picture i found.
The 308 carrier in this rifle is shorter than a regular ar10 carrier.
Oh and i also found this.
http://www.google.com/products/catalog?q=bar+magazine+300+win+mag&rls=com.microsoft:en-us:IE-SearchBox&oe=UTF-8&rlz=1I7ACAW_en&um=1&ie=UTF-8&cid=721273938366055517&sa=X&ei=3KupTZD2CI24sQOLmK35DA&ved=0CCUQ8wIwAg#

For now i'll let the ideas flow with you guys. but like i said , a majority of the parts can be AR based. thats why this project is so great, its almost done!  ;)


Offline sysops666

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Re: AR10 in 300 win mag
« Reply #8 on: June 09, 2011, 01:14:45 AM »
Ya know I feel kinda like an ass finding this but....... i completly forgot about Cobb MFG's mcr-400 and rnd rifles 300 win mag. And my dumb ass thinking it was never done before! ::)

anyone have any experience with these rifles? enough to give me some tips I can put into my plan design wise.

Offline Tango Chaser

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Re: AR10 in 300 win mag
« Reply #9 on: August 22, 2011, 11:34:23 PM »
Quote
Posted by Scooter:
"Wether you agree with it or not a semi auto will never be as accurate as a bolt action."

KAC, Noveske, LaRue and few other high end AR10 type builders say otherwise. I fired an Army issue KAC .308 with suppressor and it was as accurate if not more than any bolt gun I ever owned and the ability for fast follow up shots.

Offline sysops666

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Re: AR10 in 300 win mag
« Reply #10 on: September 04, 2011, 03:27:14 AM »
The only thing thats being drummed into my head as the reason for more accuracy off of bolt actions is lock time. I dont completly agree with it but the argument is fairly solid. My entire life has been AR's, i shot one precision rifle match with a buddy's bolt action and WOW what a difference. Big difference when your checking zero off of 2" rocks at 600yds!

And I thought I was hot stuff with my AR10.........  ::)

Offline sysops666

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Re: AR10 in 300 win mag
« Reply #11 on: April 28, 2012, 01:26:48 AM »
well i guess someone ran with the idea. I would buy it but I promised myself a long time ago I'd never buy when I could build.

http://nemoarms.com/portfolio/omen-standard-300-win-mag-ar/gallery/guns/

i wonder how much the mags will cost.....

Offline kdkerr2

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Re: AR10 in 300 win mag
« Reply #12 on: December 13, 2012, 09:33:52 PM »
This is not a bad idea for a weapons project. The smart thing to do would be to purchase a Nemo or Cobb .300 Winchester Magnum magazine first and work from that first. Draw up a blue print with a CAD program or paper in full size to make sure everything fits. It's only a matter of scaling things up. You will need a bigger bolt. I think the regular AR10 has enough surface area to handle the increased pressure but I would go with a slightly larger bolt diameter and a slightly larger bolt carrier. You'll need more mass to strip off the cartridge. The bolt will need to be slightly longer also because of the longer cartridge. If you're going to use an AR15 fire control group I'd use a hammer that was slightly heavier. I've had trouble with misfires in my DPMS LR308 because of hard military primers which had to be shot twice before they went off. During World War II the Japanese took a captured Browning .30 caliber and scaled it up to a 20mm  auto cannon to be used on aircraft I believe. This project  is just a matter of scaling everything up. Also a slightly stiffer recoil spring might be in order too.

Offline Gos

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Re: AR10 in 300 win mag
« Reply #13 on: December 17, 2012, 02:30:43 PM »
 8)
I found this thread today.
The bolt engineering has already been done and in production via the WSSM uppers from Olympic Arms. Obviously there is still length issues, but the strength issues are solved. The WSSM bolt, once fitted to a longer action, could handle any cartridge you would want to come up with.