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Topic: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt? (Read 821 times) previous topic - next topic

Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

New to 6.5CM. Finished up my DPMS pattern gasser over the weekend (24" Proof barrel, M5E1 builders kit and JP operating system) and am working my way through a case of Norma Match to break him in and liberate some Norma brass. Getting ready to start searching for powder and try some bullets. The Norma factory ammo shoots pretty good and I have a bunch of the 130 gr Golden Targets that I'll start working up.

But I am of course drawn to the 140 gr RDF and the .33 G7. I have had fantastic success with the 30 cal 175 RDFs in my RPR (stock 20" barrel) and regularly take them to a 12"er at 900 and a 16"er at 1k (shooting at 6600' ASL is great for the ego). Only problem is the longest I could get them in my Ruger Scout mag was 2.855 which was .1" off the lands. They're supposed to be forgiving, but they're not that forgiving! So I load them at 2.935 and load them singly.

I just ordered some C Products mags for the new 6.5CM which supposedly have a max COAL of 2.874. So the question is will this be enough to make the 140 gr RDFs work? They are longer than the 30 cal 175s, but it looks like the ogive is substantially shorter. 

Interested to hear if anyone has had success with them in a gasser as well as what sort of COAL the bolties are using. My experience will obviously differ, but it should give me an idea if I can get in the ballpark to make them work.

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #1
I've seen guys say they are up to .150" off the lands to fit in their magazines and they shoot well. Go to max feed length and start making them shorter and see if you find a sweet spot. I think I read that Nosler recommended a 2.775 OAL, what would that make you off the lands?
RPR 6.5 Creedmoor
Bergara 6 Creedmoor

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #2
That really depends on your chamber.  Make yourself a case gauge and check. I think mine is shorter than your mag length.  I don't have a comparator yet, been meaning to buy one for a while, but no bullets went out past 2.870 to hit my lands measuring COAL. 

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #3
Thanks guys. I haven't ordered any yet since I'm apprehensive about them not working and partial boxes of bullets that didn't work out are the bane of my loading bench.

I guess the best way to ask the question is if anyone knows the distance from the base of the ogive to the tip. I tried to call Nosler but couldn't get a human being. I can figure out what my OAL would be up against the lands from there.

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #4
Thanks guys. I haven't ordered any yet since I'm apprehensive about them not working and partial boxes of bullets that didn't work out are the bane of my loading bench.

I guess the best way to ask the question is if anyone knows the distance from the base of the ogive to the tip. I tried to call Nosler but couldn't get a human being. I can figure out what my OAL would be up against the lands from there.
I just tried to measure that you requested using a 6.5mm insert and best I could come up with is 0.700 from ogive to tip for 140 RDF. I have found in tests that they have a depth node at 0.012 jump and another at 0.040, did not go beyond 0.055 jump but all my powder load tests and depth tests have maximum 5 shot groups at 0.460, they are extremely forgiving projectiles to say the least.
Cheers Darryl
[Only punch holes in paper @200m, 300m, 500m & 1000yds]

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #5
Looking over the RDF's I have , I would not use them. A buddy of
mine tried working with the 142 Sierras, which are a tad shorter
but still had too much jump to suit him. Right now the favorite
load is with the standard 140 Sierra HPBT with the Hornady 140
HPBT right on it's heels. Barrel on his RRA is a 22" Kreiger HBAR,
8 twist, short throat.
Keeping my bad Kharma intact since 1952

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #6
Thanks guys. I haven't ordered any yet since I'm apprehensive about them not working and partial boxes of bullets that didn't work out are the bane of my loading bench.

I guess the best way to ask the question is if anyone knows the distance from the base of the ogive to the tip. I tried to call Nosler but couldn't get a human being. I can figure out what my OAL would be up against the lands from there.

The RDFs are 1.414" long. Base to Ogive is .7735" with a Hornady comparator.

Since you are using an autoloader and don't have any bullets yet I would go with something you know works. I'd go with the Berger 130 AR Hybrid which was designed for the AR platform and is a proven performer. Then again, a box of RDFs aren't very expensive and I bet you could easily sell what you don't use if they aren't compatible with your AR.
RPR 6.5 Creedmoor
Bergara 6 Creedmoor

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #7
I have used the Nosler RDF with huge success.  They like to jump to the lands.  I have an Aero M5 with Ballistic Advantage 22 inch barrel and Aero HP bolt.  My length to the lands is 2.248 using Hornady's comparator.  My load length is 2.188 using the comparator.  I worked up the best load at the recommended length of 2.775 OAL and then shot 5 shot groups at increments of 10 thousands.  This load length does not work in the PMag or steel ASC mag but work great with the Lancer L7 mags. Shoots 1 hole groups at 100 yards and 2 inch groups at 600 yards.  I use H4350 powder.  Most of the time I single load the rounds in a 5 round Lancer L7 magazine because I have found that the recoil changes the seating depth if I shoot too quickly.

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #8
  Most of the time I single load the rounds in a 5 round Lancer L7 magazine because I have found that the recoil changes the seating depth if I shoot too quickly.

Are you using enough neck tension? I would think three thousands may be the minimum for your application.
RPR 6.5 Creedmoor
Bergara 6 Creedmoor

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #9
Thanks everyone - just what I was looking for. I've got equipment and some supplies in shopping carts just waiting for the Labor Day sales and coupons to really start kicking in.

MLN - I've got a bunch of Norma Golden Target 130s that I plan on working up. Bought them for my Grendels but the BC / velocity trade off was a wash and I couldn't get them to do much better than MOA. I've been working through a case of Norma Match using a G7 of 0.285 (pulled it off of Prime's site) and that seems to be pretty much spot on on 1.3 to 1.6 MOA steel from 800-1000. Pretty much the same BC as the Bergers but a heck of a lot cheaper. I'm getting 2915 out of my 24" with the Norma Match and would be more than happy with a modest 1/2 MOA load in the high 2700s with a tight velocity variance.  Running #s through my ballistics program, it doesn't seem like there's a huge advantage going to most of the 140s out there - except for the RDFs. The 175s have breathed so much life into my 308 RPR that I feel like I need to give the 140s a chance provided they aren't too long (and it seems like they aren't).

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #10
Sweet - all my supplies/tools have arrived and it looks like 2.881 would put them on the lands, so plenty of room to play the whole field in the 2.874 mags. Hello Monmouth Reloading. Seems like 2.283 (0.050 off) would be the place to start looking for a node and work on length from there. Thanks again everyone!

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #11
Well this was a fine project. A COAL of 2.855 at 0.03 off the lands was the place to be. Unfortunately, the accuracy node was at 2690 with 4451 in Norma brass with single digit SDs and around 1/2 MOA, but I was getting pretty consistent ejector marks. It was very accurate throughout with H4350 in Starline Brass but the SD didn't settle down until 40.8 gr at 2730 and the primers were getting a tad flattened. SD was 4 at 1/2 MOA at 41gr for 2745, but primers were beyond a tad flattended. Next node down was 39 gr for 2625 which would do just fine as a nice mild load, but 130 gr Norma GTs at 2825 with a single digit SD and sub 1/2 MOA capability (something I'm not capable of! I need to order the clawed Atlas feet so I can consistently load my bipod better) beat that load out with a lot less drop (10%)and just a tad more wind drift (maybe 5-6%). Can't say I didn't give it the old college try!

 

Re: Do 140 gr RDFs work in a AR-10? What COAL are you using in a bolt?

Reply #12
DPMS pattern is LR308, not AR-10, just sayin'.