.308WIN 1:10 barrel; 147gr troubles

[11B3XCIB]

Was shooting my .308 for the first time and was trying some "off the shelf" ammo to get it in the ballpark and to free up some brass for reloading while I was at it. Specs: Remington 700 .308, 20" barrel with 1:10 twist. Vortex HST 4-16x. I am assuming it was the weight of the ammo, because I couldn't get groups tighter than 5" at 100 yards it was so erratic. I would like to believe the problem wasn't me, because I was pulling 1.5" groups with my AR and a red dot on the target next to my .308 target.

I have some 155gr, 168gr, and 180gr bullets to handload and try out.

Anyone else have bad results with a 20", 1:10 twist and lighter bullets?

 

[GreenBlood10]

That bullet weight is too light for .308 in that twist ratio. I'm sure someone somewhere has had success using 147gr in a 1:10 but I haven't seen it. I wouldn't go any lighter than 155. I would even go as far as saying the heavier the better. If I was you and I was looking for nice tight groups, I'd be using 168-175gr.

GB

 

[LSnSC]

Ive shot MOA groups with 110 Vmaxes at 3000 FPS out of my 20" AR-10 with a 1-10 twist. I was using them for a low recoil flat shooting load for 3 gun. The Vmaxes and H322 got tough to find so I started shooting other bullets. 135 SMKs shoot MOA or better out of the same rifle. Most 1-10 barrels will handle lighter ammo just fine.

The problem is probably your ammo. US Ball ammo is held to 2 MOA average out of a factory test barrel. The foreign stuff, who knows??? Federal M80 ball shoots well for me, the Brazilian and Privi, not at all.

 

[mark_b]

Have you checked to see if your scope base and rings are tight and have not come loose? I have had friends that had the same problem and the scope was moving on them between the shots.

 

[11B3XCIB]

Scope and rings are good; it's probably just the poor factory (Brazilian) ammo.

I've got some 155 and 168 grain bullets to load up...now I've got the empty brass to size and load some test rounds with.

Unfortunately Reloder 15 (as well as 10x)has been impossible for me to find, but Alliant has some good published loads with 2000-MR, which I've got a couple pounds of.

 

[Stan in SC]

I get excellent results using IMR-4895 and a 150 grain Sierra bullet.

Stan in SC

 

[GreenBlood10]

It definitely sounds like an ammunition issue. I would bet money that you'll see an improvement in your groups with those other loads once you get them loaded up.

Also, check your action screws and make sure they're at the proper torque specs for the rifle. Not sure what stock is on your rifle, but its probably going to be around 55 in/lbs.

GB

 

[11B3XCIB]

Had a range update using Federal 180gr .308 ammo. MUCH better. Was cutting the bullseye after a few adjustments. My first three rounds made only two holes when grouping. I shot more of it than I needed to just for familiarity with the rifle and to have some brass to reload later. Glad it wasn't a chamber issue or something not easily fixed.

 

[GreenBlood10]

That's good to hear. I figured it was a round/load issue. One last thing.....pics or it didn't happen :!:

 

[11B3XCIB]

I got a video of Tigerstripe doing a 30rd full auto 5.56mm mag dump but I can't host that.

And a pic of the target through the scope I can post later!

 

[Tigerstripe]

That's good to hear. I figured it was a round/load issue. One last thing.....pics or it didn't happen :!:

i whitnessed the whole thing.

3 rds 2 holes, well one was bigger cause it was 2 bullets. he made an adjustment and the next shot was in the x ring.

i think it does go to show there is a difference in 762x51 and 308. its a 308 rifle.

nato 556 , 762x51 barrels can use sporting cartridge but not the other way around.

i have argued in the past there was no difference. my old loading books dont differinciate between them.

 

[jfeenin]

The NATO specs are definitely different than the civilian offerings but my understanding they in a reverse fashion. 5.56 NATO chamber pressure rating is higher than the .223 Remington and the chamber throat is longer to accommodate heavier/longer bullets. I believe 7.62 NATO however is actually rated at a lower chamber pressure than .308 Winchester. I could be wrong though.

Many argue that the barrels are proof tested to the point that they will handle the higher pressure of the different loads and to some extent that is definitely true. However chamber pressure aside the throating difference can make a significant difference in accuracy.

 

[GreenBlood10]

i whitnessed the whole thing.

3 rds 2 holes, well one was bigger cause it was 2 bullets. he made an adjustment and the next shot was in the x ring.

Oh, I don't doubt it at all. I just like looking at peoples targets. I am a visual creature.

GB

 

[Underdude]

My FAL has a 1:10 twist rate with a 16 inch length. I've never had issues with 147-168gr projectiles. Isn't 1:10 the most common twist rate nowadays?

 

[11B3XCIB]

.308s are common with 1:10 and 1:12 twist barrels.

The difference is your FAL is chambered for 7.62x51mm whereas my Remington 700 is chambered for .308 Winchester. It did not like the NATO ammunition. Shooting accurately is all about finding the right combination of powder, bullets, and barrels. My barrel loves 168gr bullets, apparently. This is a slightly older picture; I was VERY green with that rifle and I've only got room for improvement with it.

.676 (group size) - .30" (bullet diameter) = .376" @ 100 yards. Was finding the powder charge that my rifle liked...it was pretty amazing when I put the 45.0gr charged rounds downrange, the groups went from fist size to touching. There's a formula for twist rate, barrel length, velocity, diameter, etc and I guess I stumbled across the velocity that made the formula balance. That's why reloaders do ladder chargers, because that's a whole lot easier than the math


I have since reloaded some fired NATO brass (fired from my rifle) and will update this thread depending on how it performs. I figure since I'm resizing the .308 WIN brass with the same dies, it may have positive results.

 

[Tigerstripe]

trim them all to the ,right, same length.

wonder if there is a 308 trim length and a nato trim length?