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140 RDF vs 140 Hybrid COL in 260 Rem

dstoenner

Silver $$ Contributor
So I managed to snag a box of 140 RDF's and decided to build up some in order to test them for accuracy in my gun. My go to load for 140 hybrid in Lapua brass, BR-2 primers and 42.5 H4350. I set my COL for this load at .010 less than jam. Right now it is 2.950.

In order to do the load I get my Hornady COL out and put the 140 RDF and run it into the lands. Pull it out and measure it and it is 2.910. HUH??? So I get a 140 Hybrid out and remeasure at 2.960 That's weird. So now I get interested and measure each bullet from base to ogive and sure enough the RDF is .060 longer than Berger. At least that checks out and is not a fluke.

I have 50 loaded up now at 2.900 and will do some testing. However some questions come to mind that I don't have answers for and maybe somebody else has bumped into this and has answers.

1) Since the boattail is basically the same, the RDF is .007 longer, that means the RDF has a longer bearing surface. What kind of velocity difference are you seeing between these 2 bullets for the same load?

2) The other minor impact is that also the rear of the bullet is sticking into the case .040 longer and taking up powder room. 42.5 isn't a very hot load but has anybody seen signs of more pressure than the hybrid?

3) The big one in my mind is how Nosler can claim this bullet has so much more BC than the Berger Hybrid when the shank of the bullet is so long. That necessitates a shorter nose which cannot be as sleek as the Hybrid. Right now this isn't squaring in my mind so maybe somebody has some insight.

Thanks

David
 
I tried the 140 RDF with 42.5gr H4350 loaded at 2.865" and had no issues. Accuracy in my 20" Tikka CTR was the on par with my 140 Hybrid load. I have some RDF's loaded up with 42.7gr loaded at 2.900" but haven't tested them yet.
 
I tried the 140 RDF with 42.5gr H4350 loaded at 2.865" and had no issues. Accuracy in my 20" Tikka CTR was the on par with my 140 Hybrid load. I have some RDF's loaded up with 42.7gr loaded at 2.900" but haven't tested them yet.

Thanks for your report. I feel better that I am OK.

David
 
I have not shot the RDF in my .260 yet. However, yesterday I shot 50 through my 6XC. I had to seat them 10/thou deeper to meet the same depth as the Berger 105 Hybrids, my normal load. Initial shots revealed very little as they wer shot at 100. From 300 out the RDF was 2/tenths mil high at all ranges to 900, so the stated bc of .571 is a bit low. I brought them back to 500 and shot three 5 shot groups. Not very consistent. I did run them at 3080 which some say they like speed. I may test more, but doubt it.
 
Both are at .010 jump. Saturday I will see what group I can get. I will post results

What I am trying to tell you is that the 140 Hybrid shoots best 10-70 off.Dont' get hung up on what has worked with other bullets. Go way out 10 at a time, 3 shot groups with the same powder to get the absolute best distance.,
 
What I am trying to tell you is that the 140 Hybrid shoots best 10-70 off.Dont' get hung up on what has worked with other bullets. Go way out 10 at a time, 3 shot groups with the same powder to get the absolute best distance.,

I had tried this test on my previous barrel (Shilen) and found that close to the lands was best. I have a new barrel (McGowen) and its groups are about the same as the old barrel so I haven't bothered to try anything different. I will give it a go when I get a chance.

thanks

David
 
Follow up on range testing.

Good news bad news. The first group I shot at 100 was .690. That basically is what I might get from 140 Bergers. That said the bad news was that on the 5th shot, I got a pierced primer. The result of which was that the bolt got debris in it and wouldn't fall far enough to barely touch the primer. I did disassemble the bolt and tried with what tools I had at the range to clean it. I got some more groups but all were suspect as I had 2 FTF and another pierced primer.

My load was 42.5 IMR4350. My normal load for the Bergers is 42.5 H4350. My experience is that IMR4350 is not quite as energetic as H4350, ie less velocity. The primers were not flattened so I am puzzled by all of this.

Took me an hour this morning to get the bolt clean so the firing pin would fall the full distance. For now the last 47 RDF's are shelved for further investigation this fall. They look good for accuracy but if I have to reduce the load and hence the velocity, not sure how that is going to work at 1000 compared to the Bergers.

David
 
What is the freebore on your chamber, or are you using SAAMI standard? Did you shoot over a chronograph? A fatter bullet will give you more pressure and velocity. Seating deeper and holding charge constant will give you more pressure and velocity as well.
 
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What is the freebore on your chamber, or are you using SAAMI standard? Did you shoot over a chronograph? A fatter bullet will give you more pressure and velocity. Seating deeper and holding charge constant will give you more pressure and velocity as well.

I do not know the freebore of my chamber but it is a SAAMI standard reamer. I agree with both of your statements. I did not chrono the load because I wanted to shoot for accuracy and my magnetospeed shifts the POI. Plus I am not for sure how accurate things are with that wand waving in the breeze.

My next plan is to lower the load to 42.0 and see what velocity I am getting plus seeing if I pierce more primers. The Bergers would go to 43.5 before I started to see signs of pressure. The other variable I am not for sure about is how much the case influences the primers ability to hold pressure. I have had trouble all along with R-P cases and never with Lapua.

David
 
I did go out and measure each of the bullets from my current stash of 140 hybrids and my box of rdf's. they both measured the same at .263 on the bearing surface and a driving band of .2635. So that variable cannot be the reason in and of itself. The length of the bearing surface of the ref is about 10% more than the hybrid. So between that and the tail is seated deeper in the case is not good for pressure.

Thanks to all who have contributed

David
 

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