.308 vs 7.62

[MusicCityCajun]

I took my Bergara HMR out yesterday to do some shooting and picked up some NATO 7.62 to see how it shot. The rifle was previously sighted in with .308 and I shot that again first to reconfirm its zero. Then I switched to the 7.62 to compare and was shocked that it shot 7-8" low and 2-3" left at 100 yards. It was somewhat consistent in doing so but the group size was poor as well.
I expected it to shoot maybe a couple inches differently but I couldn't believe how far off it was. Needless to say I'll never buy that again for this rifle.

 

[Jcalder]

Your group size will indicate of your rifle likes it or not. Has nothing to do with where it hits on paper. Barrel harmonics is why it hit in a different spot than what you're sighted in for. Also, just note 7.62 is loaded to a lighter pressure than 308 is.

 

[EastTNHunter]

You can shoot two different loads using the same weight bullet with different profiles and/or different powders and have substantially different POIs

 

[Jcalder]

You can shoot two different loads using the same weight bullet with different profiles and/or different powders and have substantially different POIs

Not a dis at the OP, but I'm amazed at how many don't know this. And for years I thought the same way

 

[MusicCityCajun]

I know that different brands, bullets, loads will have different POIs. I just didn't expect it to be THAT drastically different at 100 yards.
The reason I was at the range was to shoot several different rounds to start getting some data on what this gun likes. I expected group sizes to be more variant than POI.

 

[Jcalder]

I know that different brands, bullets, loads will have different POIs. I just didn't expect it to be THAT drastically different at 100 yards.
The reason I was at the range was to shoot several different rounds to start getting some data on what this gun likes. I expected group sizes to be more variant than POI.

Years ago I was on a 308 kick. Shot a ton of 165s. Started playing with other bullets, like 130s. I don't remember the bullet, but it shot about 6" right. My mind was blown and I started down the road of learning barrel harmonics. I've had this discussion numerous times with the guys at work, even when changing ammo, whether it's lot number, brands, or ammo lines within the same company, always check your zero.

 

[fairchaser]

In addition to different bullets, powder, seating depths, there are some differences in .308 brass versus 7.62. You can shoot 7.62 in a .308 but not the reverse. Frankly, I wouldn't interchange them unless it said either on the box. There's a difference in headspace and pressure.

 

[tug]

I took my Bergara HMR out yesterday to do some shooting and picked up some NATO 7.62 to see how it shot. The rifle was previously sighted in with .308 and I shot that again first to reconfirm its zero. Then I switched to the 7.62 to compare and was shocked that it shot 7-8" low and 2-3" left at 100 yards. It was somewhat consistent in doing so but the group size was poor as well.
I expected it to shoot maybe a couple inches differently but I couldn't believe how far off it was. Needless to say I'll never buy that again for this rifle.

If you had zeroed with the NATO rounds, and your 308 Win group was 8 inches high and 3 inches left, would you say you are not buying 308 again?

 

[MusicCityCajun]

If you had zeroed with the NATO rounds, and your 308 Win group was 8 inches high and 3 inches left, would you say you are not buying 308 again?

For majority my intended uses I need to shoot .308 primarily. So for me no, I would switch to .308 and reset zero for them.

 

[Omega]

Most military ammo is 3 MOA, except the sniper ammo of course, so it won't always group well.

 

[DaveTN]

What are the two rounds you are comparing? Manufacturer, bullet weight brass or steel case?

 

[MusicCityCajun]

The three I shot were Remington core lok and norma whitetail in .308.
The 7.62 I believe was Winchester.
All were 150 grain and brass cased.

The Remington and Norma shot almost identical. Yesterday I picked up more boxes of those just to have something on hand that I have known patterns for.
I also got a box of 168 gr federal premium gold to compare. There was very little match grade ammo at academy yesterday but I do want to try a few of those.

 

[PillsburyDoughboy]

Just switching lot numbers on the exact load can change point of impact . Do your homework

 

[DaveB]

I started down the road of learning barrel harmonics.

I have an old and new style BOSS I use on my 300 WinMag. Right now the new one is on. If I want I can buy the cheapest factory load from china and in a few rounds downrange can adjust it to be a MOA round.

Barrel harmonics are as real as can be. Can't speak highly enough about the BOSS, which is nothing more than an adjustable weight on the barrel you can move in extremely small increments to dial that round into your desired point of impact. Once you find that sweet spot you lock it down and load up as many rounds as you have cash because any change in the load means the BOSS needs am adjustment. Just as an interesting point--get a perfect zero and change the primer. You will instantly know there is a difference when the POI changes. May be small but it definitely changes.

The original muzzle brake-adjustable weight BOSS was kind of loud. Hearing damaging loud. The newer do not have this feature. People hated it-the noise will clear the range. You absolutely must wear very good hearing protection when using it-even in the field.

 

[philsanchez76]

I got a deal on a bunch of the Winchester Lake City 7.62 and my POI doesn't change as drastically as yours but it doesn't group worth a crap. 3-4 inch groups at 100 yards no matter what. I bought it just to practice since its all full metal jacket anyway. I've been having some good experiences with the Norma ammo though. It's been very consistent.