Lighter bullet for AR-10 in .260 Rem?

[rg1911]

Right now, my Armalite AR-10 seems to like Lapua 139-gr Scenars (a bit better than 1/2 MOA at 200 yards with TBAC 30P-1 attached). However, I've seen a number of recommendations to use a lighter bullet, such as 123-gr.

The rifle will be used for matches out to 600 yards, although I'm hoping to get it to a 1,000-yard range.

Is this something that deserves a try (assuming bullets are available)? The barrel is a Krieger 1-in-8 twist.

Thank you,
Richard

 

[Kiba]

If your rifle currently functions well with the 139s and there aren't any pressure signs on the brass I might not make the change.

If you are thinking about testing other bullets, both my GAP10 and JP LRP-07 in 6.5CM really like the 123 Scenar. G7 BC is 0.265 and both rifles have no issues getting them to 2920ish and are right about 8 mils to 1K down here at sea level depending on the DA that day.

The Berger 130 VLD (.282 G7) shoots great too but your rifle may or may not shoot them well when loaded to mag length depending on the jump. They are certainly worth a try because if your rifle likes them they shoot very well. The VLDs grouped a little better than the Scenars out of both of my rifles but I couldn't find any in stock at the time whereas I found 2 1k boxes of the Scenars at a good price.

 

[Newtrick]

My AR in .260 really likes 140 SMK's. Short and long.

 

[flatland1]

I built myself an AR10 on DPMS receivers several years ago, going with the 6.5x47 Lapua in a 28" Krieger 1-8tw bbl. It shot lights-out with S123MKs, using RS Hunter, right up until I ran out of that first jug of Hunter. The 2nd jug is from a much later lot, and I've found that the same charge weights that shot so well using powder out of the 1st jug don't shoot anywhere near as well with the newer lot. Simply got to devote the time to start load development over again, and work up with this newer lot, in hopes I can find a charge that'll duplicate the results I got out of the older lot of Hunter. Point is, the 123s out-shot every other bullet I've tried in this bbl, including Berger 130VLDs, 140 BTHP, VLD, & Hybrid, S142MKs, and Lapua 139 Scenars. IIRC, the Sierra 123s even out-shot the Lapua 123s, which was the first & only time that's happened in any of my 6.5s.

 

[lte82]

My dpms 260 rem likes the 123 smk and 139 scenar equally. I can get slightly better down range performance with the 139 but the 123 is so close it probably doesnt matter. The 123 definitely shoots flatter out to 1000 but gets pushed by wind a tiny bit easier. I say use the one that groups the best.

 

[slm9s]

my LR260 shoots the 123 amax accurately and they're cheap so I use those.

 

[Pat M]

I run the Sierra 142s in my DPMS, i looked at the 123s - but at long rang i would have to up the speed quit a bit to gain the wind busting / and i don't want to burn my throat/barrel out too fast.


But with the lack of 6.5 bullets - i'll run what i can get in quantity

 

[260shooter]

I've had very good luck with 123 Scenars and 130 Norma BTHP's. The 130's have a .585 G1 BC.

 

[rg1911]

Thank you for all the information. I think it's worth giving the 123-gr SMK and Lapua bullets a try (assuming I can find them). The rifle did not like the 142-gr SMK or the Hornady 140-gr A-Max. Even the Berger 140-gr Hybrid bullets were 3/4-MOA at best. Usually closer to 1 MOA.

I also have a large number of Hornady 95-gr V-Max I'll try.

Richard

 

[FALex]

My AR in .260 really likes 140 SMK's. Short and long.

Any reason you're not running the 142 SMK over the 140? Printed BC of .572 (142) vs .526 (140). Quite the difference if you're shooting out past 300 or so...if not, it makes not much of a difference then.

 

[LRRPF52]

You have more OAL to work with if using Armalite steel mags for the AR10/M14 mod mag. Try loading the 130gr VLD or Norma out as long as your magazine/chamber will allow, use H4350 or RL17SC, and see what happens.

I had GAP cut my chamber for mag-fed VLD's, so the 130gr VLD shoots insane accurate for me, as do every other bullet mentioned here except the 140gr A-MAX for some odd reason. I'm not sure I'll ever mess with anything in the 139-142gr class after the performance I get from 130gr, speed, drop, and wind-wise.

 

[CORNHOLIO1]

rg1911. Did you find another bullet your rifle likes? I have the same upper and it loves the 139 Scenars, but I am looking for a hunting bullet. The Bergers look good but I heard they have problems feeding in an autoloader.

 

[DavidAR10]

Any reason you're not running the 142 SMK over the 140? Printed BC of .572 (142) vs .526 (140). Quite the difference if you're shooting out past 300 or so...if not, it makes not much of a difference then.

The old rule of thumb was/is 300yds = flat base and 600yds = boat tail.

There's no "quite the difference" till after 600yds. There're F class shooters that won't waste time
rolling their own for 600yds and below.

And it doesn't take the integral f(x) by separation of parts to figure this stuff out.

 

[CORNHOLIO1]

Since rg1911's and I have the same type of upper and they both like 139gr Scenars, I think they like the same bullets. I'd like to post recent range findings to eliminate duplication of effort, and money. I am trying to find a hunting load.

Load #1- 120gr TTSX; 43.6gr H4350. 2.265 ogive; Range: 50yds
2 rounds touching; the third round was approx 1" away; mild primers

Load #1- 120gr TTSX; 35.4gr H4895. 2.265 ogive; Range: 50yds
avg accuracy; mild primers

It doesn't seem like the barrel likes 120gr TTSX.