Chasing Gear, the broken record of shooting lighter calibers

[RFutch]

Anyone shooting 130 RDFs?

 

[spife7980]

Anyone shooting 130 RDFs?

Not in a couple years but they were good and Im on the look out for them for when I exhaust my 140 rdf supply.

 

[JMGlasgow]

I'd like to try them.

 

[Wiillk]

Not in a couple years but they were good and Im on the look out for them for when I exhaust my 140 rdf supply.

Found three boxes of them at a sporting goods retailer in Bastrop, LA. Bought one. Spent some time talking with the manager of the Firearms department (they are a big, big outdoors store; in Bastrop no less, Only Bass Pro in Bossier City and Cabela’s in Gonzales is larger)

The manager related, “we order hunting bullets, and we get case after case of target bullets.” Unfortunately for me, not many int he caliber and weight I wanted. (They must have had ten thousand Hornady A-Tips)

 

[JAS-SH]

I am shooting 6 ARC ,I have three rifles, two of them are bolt action and they are all built with premium barrels. I have similar results as you., these rifles are tack drivers and carry the bullet down range very well. The 105 RDF is my bullet of choice loaded over Leverevolution powder. Two of the rifles shoot .5 MOA or better on a good day,
and the gas gun shoots .75 MOA. The 6 ARC is an awesome platform. It is starting to peak the interest of some of the top shooters in the sport. I have hit target at a mile with the 6 ARC using long range hybrid bullets, Not going to do that with a Valkerie

I fully concur. I'm also running 6 arc on a 26" BadRock Bolt Gun. I got into that setup after reading a lot of Brian Litz's stuff. That young mans has done an invaluable service to the shooting sports. And sure enough, the rifle is a hammer.

Recoil on this 18 pound rifle is around half that of a 5.56 16" AR! No brake needed so why put one on and get more concussion? A lot of people underestimate the importance of recoil in competition, especially at longer ranges where you have to quickly acquire the trail. I wont elaborate on that here but that is one of the reasons PRS is going 6mm.

Pic of the rig:

And best group at 100 yards - factory 108 ELDM ammo:

 

[JAS-SH]

Haven't kept up in this conversation, but are we talking wind drift, drop, or a combination of both? Here are 2 pictures of drop and wind at 15mph 90*

Drop (gravity) is a constant so it's kind of irrelevant. Time of flight is relevant though so windage is more of an issue with longer flight times. That said, one of the most important parts pf this puzzle is DISPERSION. This solely affects precision, not accuracy. If you have a very high precision rifle then the accuracy part of the equation is solely on the shoulders of the person behind the rifle.

This is a critical point. with some caveats lighter lower BC bullets are inherently more precise, again, for a number of reasons. This is why the highest precision in <300 yard benchrest is achieved with flat base lighter bullets. In the case of 6mm ~ 65-90 grains. It's more than that. lighter bullets don't require fast twist rates. The slower the twist rate the more accurate the system is.

Brian Litz's did an F-class study with real live fire and modeled that. He compared 155-160 grain rounds vs. the 190-230s. Here's the quote from one of his books:

 

[maples14]

Magazines.... What mags reliably feed, and hold 10 round of SPC sized brass, without modification, on a bolt action system ?

Mdt makes some great aics 224v mags I use them with mpa chassis and defiance action

 

[cjgemm]

"Window Lickers"

Seems appropriate...

 

[RFutch]

Mdt makes some great aics 224v mags I use them with mpa chassis and defiance action

MDT told me their metal 10 round 6ARC mag should work for the Valkyrie but you might have to tune the lips.

 

[DJL2]

I started loading 130 TMK a while back for my 6.5 CM (because that’s what I could find and I bought a bunch)… I could get 2850 or so with good accuracy versus 2650 or so for the 140s. When I replaced that barrel on that rifle, I replaced it with a 6 CM because I realized I was basically shooting the same BC with more weight, more recoil and lower MV. I still have a different 6.5 CM, running about 2825 with 130s from a 20” CF… that’s a father/son gun that I’m comfortable taking afield. Lately, I’ve spent a lot of time thinking about how I ought to have built at least one bolt gun in .223 to shoot 77-80 grain bullets before seeing this thread today. Everyone likes validation, no?

Re: wind drift. I think what gets lost in the conversation is that it’s not the ultimate difference that matters so much as the difference when we biff our wind call. If you’re a +/- 5 mph scrub (this guy), it matters more than for a better shooter. Yes, I get that “lag time” and BC are important measures of “ballistic merit,” but it’s not the whole story. Factory 108 ELD-M at 2940 fps drifts 1.22 mrad at 1000 versus 1.16 for 140 ELD-M at 2700… meaning that if I really can’t call closer than +/- 5 mph the performance difference at that range is +/- .06 mrad… maybe that 2.5” difference matters, maybe not. I shot a basic rifle course recently alongside .300 WM, .300 PRC, and a bunch of 6.5 Creed… used the same wind holds as all of the aforementioned out to 1000.