Rock River LAR 8 - .308 Win versus 7.62 Nato

[Patriot Prepper]

I picked up my Rock River LAR 8 last night. Have not mounted a scope or shot it yet. But I was reading the booklet and noticed that nowhere does it state that it is chambered for the .308 Winchester. Neither is there a .308 stamp on the barrel. The receiver states 7.62 Nato. The caliber listed in the manual and website is as follows: .308/ 7.62 Nato. I always assumed it was chambered for the .308 Win. but a gunsmith friend said that .308 does not mean .308 Win.

Now .308 is just the outer dimension of the round and does not mean .308 Winchester. The pressure for the .308 Win and the 7.62 Nato are almost identical. One is measured in CUP and the other in PSI - but translate about the same. But the head space is different.

I called Rock River and they said is can shoot .308 Win. I asked if that was documented or printed anywhere on their literature and they said no. I notice, however, that DPMS makes a distinction between their .308 Win and 7.62 Nato chambered semi autos.

I also know of people who shoot .308 Win through the LAR 8. My question is what are the ramifications and should someone shoot .308 Win through the LAR? Is it a smart thing to do? What does the difference in head space cause? Anyone know the specifics?

 

[FCS]

Re: Rock River LAR 8 - .308 Win versus 7.62 Nato

Quick n dirty answer is:
http://www.thegunzone.com/30cal.html

Longer answer would require some go, no-go gauges.

 

[Steelhead]

Re: Rock River LAR 8 - .308 Win versus 7.62 Nato

There is a small difference in case size, but they are close enough to not have to worry about it.

I've shot both 7.62 Nato and .308 Win in my LAR-8's with no problems. The .308 Win gives me better accuracy, especially from match grade ammo and my own reloads.

I'm pretty sure that the LAR-8 is chambered for .308, not 7.62 NATO. Most of what I shoot through them are indeed .308 WIN.

 

[Patriot Prepper]

Re: Rock River LAR 8 - .308 Win versus 7.62 Nato

Thanks FCS. I read the article. There is a difference in head space. But isn't the Nato round measured in CUP at 50,000 versus PSI for the .308 Win.? Other articles have translated the difference and claim the pressures are almost equal. The Rock River is rated at I believe 62,000 psi - so it should easily handle the pressure.

What does the difference in head space mean in practical application?

 

[Patriot Prepper]

Re: Rock River LAR 8 - .308 Win versus 7.62 Nato

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Steelhead</div><div class="ubbcode-body">There is a small difference in case size, but they are close enough to not have to worry about it.

I've shot both 7.62 Nato and .308 Win in my LAR-8's with no problems. The .308 Win gives me better accuracy, especially from match grade ammo and my own reloads.

I'm pretty sure that the LAR-8 is chambered for .308, not 7.62 NATO. Most of what I shoot through them are indeed .308 WIN.</div></div>

Accuracy is one of the reasons I choose the LAR 8 - guaranteed 1 moa. I intended to shoot match grade through the gun. It was intended to be a short range 100 to 400 yard gun. I assumed it was chambered for .308 win, but the literature does not reflect that. Although, like yourself, I know people who successfully shoot .308 win through it. Just wondering what the implications would be.

 

[FCS]

Re: Rock River LAR 8 - .308 Win versus 7.62 Nato

7.62 NATO has lower max pressure than 308 Win. This is due in part to rifle the 7.62 NATO was designed for. I wouldn't be too worried about the pressure aspect.

I would be more worried about the headspace. If you really do have the longer head space chamber, will be a bit harder on your brass due to shoulder having to move further forward. Will most probably get some thinning of brass just ahead of the web and could give you a bit more wear in the neck/throat area of chamber.

Go, no-go, and field reject gauges are not all that much in the big picture. Worst case, fire a single 308 round in rifle. Use an RCBS precision mic, or similar tool, and see what it measures for HS. Always better to work from an informed position. If RR won't give you the needed information......can get there for under $100 pretty easy.
1) fired brass from your rifle and RCBS precision mic
2) go, no go, and field gauges.

 

[Patriot Prepper]

Re: Rock River LAR 8 - .308 Win versus 7.62 Nato

Thanks FCS.

I need those gauges anyway. There are a lot of things in my budget - the trouble is the things on my list are growing faster than my ability to pay for them. But like you said, the go/no go gauges and the precision mic are not that expensive. They will be priority must have items. Thanks once again.

 

[lwrkeysfisher]

Re: Rock River LAR 8 - .308 Win versus 7.62 Nato

I had this same question last year, and during a phone call to RRA I was told that it would run 7.62 fine. I had nothing but trouble with mine, but I did run 20-30 7.62 rounds through it (without any problems) before I sold it.