More Chrony reports!! ((WARNING!)) lots of pics.

[Daveworkslocal]

I understand, no offense taken and no argument to be had - this thread is SUPER informative and I find that I get what I need off both forums.

My rig is an ARP .264 LBC 18" melonite barrel on a 7.62x39 bolt.

This could explain why I didn't see nearly the same results from Bwilds 129 gr SST load with 30.8grs of CFE. I measure the 6 shot group today, it was 3.23 inches. LOL

post #18 , see below.

http://68forums.com/forums/showthrea...ure#post247990

I think your problem might lie here. From what I understand the 7.62 bolt doesn't give you the proper head space. I could be wrong though

[LRRPF52]

The ARP bolts are correctly headspaced to their modified .264 chamber. An 18" barrel isn't likely to get what a 24" barrel does. A chamber with a traditional leade versus the compund throat of the Grendel might not get the same performance with the same loads & COALs, so you need to do development with the constraints of your particular chamber in mind. Les Baer really seems to have designed the .264 LBC chamber around 123gr VLD-type projectiles, specifically the 123gr SMK, which many people have amazing results with in that chamber.

Also, the original 7.62x39 bolt made by Colt is what the Grendel bolt is based on, with a deeper bolt face recess so you can have an ectractor with a larger groove for the larger rim of the 7.62x39 or Grendel.

The shallow bolt face depth that many after-market companies use for 7.62x39 bolts is the same as a 5.56 bolt face, which presents a challenge for how your extractor geometry will orient with the bolt and the extractor groove of the case. This is why Colt, after extensive R&D with their resources, chose the deeper bolt face and a new extractor design. Bill A. reasoned that this was a great starting point for the .50 Beowulf, and also the 6.5 Grendel, since they both use the 7.62x39 case head.

Development of the 7.62x39 AR & bolt goes like this:

Colt 7.62x39 Sporter late 1980's (.135"-.136" bolt face depth)

Armalite 7.62x39 mid-late 1990's
DPMS 7.62x39 mid-late 1990's
M1 Sales 7.62x39 late 1990's

Alexander Arms .50 Beowulf 1998
Alexander Arms 6.5 Grendel 2002

LMT Enhanced 7.62x39 Bolt
LWRC 7.62x39 bolt

Les Baer 6.5 Grendel mid-2000's
Les Baer .264 LBC 2010
AR Performance 7.62x39 Super Bolt

BHW Type I
BHW Type II

Unknown mfg's 7.62x39 bolts





ARP Super Bolts

[Bennybone]

Excellent post, a good refresher as well. Thx.

It does suck that I will have to develop my own loads based on a different chamber throat / bolt / barrel length BUT it is to be expected as well.

I will give this barrel a chance with hunting projectiles, if it doesn't like em keep your eyes posted in the classified!

OK - Back on Topic, sorry Bwild and gang.

BB

[LRRPF52]

I'm not indicating that your chamber is inferior in any way, only that you have to develop for it specifically, while possibly not being able to expect the same results posted or printed in load manuals based on another chamber. The start pressure characteristics are different for a compound throat angle, versus a conventional throat angle, and different neck diameters in the chamber can make a difference. I think it's wise to load for your specific chamber no matter what is claimed about it, which is why I like to determine my maximum COAL with each projectile I'm loading for before assuming book data COAL. This is common hand-loading protocol anyway.

In my .260 Rem, for example, I have to size new brass before loading it, otherwise it will not feed. It has a .295" neck diameter in the chamber. My fired brass comes out with a .295" neck diameter. New Lapua brass has a .297" neck diameter, and will get stuck like chuck in it, which I learned the hard way in a precision rifle match that I had traveled pretty far for. Since I had been using sized 7mm-08 brass previously, I never had a FTF, and assumed I could just load new .260 Rem brass and have no problems. I was wrong, of course.

[Bennybone]

Roger that LRR, no offense taken on your information about the chambers - I am but one of many out there in the 6.5 world, it comes with the territory.

I was going to buy a Hornady comparator tool but noticed they don't have a grendel casing to work with. Until something "easy" comes to market I will stick to the book COAL because for hunt 1 MOA is suitable. Not shooting matches here, yet.

Thx again.

BB

[ci11]

I am using Hornady cases.

First, thank you for your wonderful efforts in data logging and documenting your results with such clear pictures, Bravo!!

A quick question regarding the Hornady cases you used in these tests, what is the average of the actual case length and H20 capacity? I use the baseline of 1.515 and 35.00 for 6.5G in QL and my loads come out at 11% compressed using 34gr of CFE223 with 100gr A-Max at 2.170 COL. Also, have your cases been fired or fire-formed or are the shoulders in the exact original factory locations?

Thanks,
Steve

[Bwild97]

It is empty now.

[ci11]

OK - sent email with picture. Please check your SPAM inbox too - thanks!

[XcountryRider]

It appears that 3000 ft/sec for a 100 gr bullet is stretching things a tad unless you are using a bolt gun where higher pressures don't tax the mechanism. You might want to look at velocities about 200 ft/sec slower.

Did you mean 120 gr AMAX? The 2600 ft/sec is about right for the 120 gr weight class.

In any event, the 100 gr bullets are probably best for coyote and smaller deer, while the 120-130 grain bullets have better potential for the larger classes of medium game.

I'm getting 2930fps with a Nosler 100gr BT using 30.5gr of H-335 with my AR Stoner 24in and 2775 with my 18in.

[LRRPF52]

Lots of good data in this thread from Bwild97

[badkarmaiii]

I recently got one of the ARP 18" 5R rifle gas 750XD barrels and need to get dies to load for it.
So, it's chamber is optimized for 123gr pills and too short to get max capacity with lighter bullets?

[Popeye212]

Thank you for posting this. Very informative and well done

[Mark6.5]

Wow amazing info and testing.

I makes me want 24" Grendel barrel now lol

BFT 22 and 24 inch Green Mountain group buy barrels sir Please.

[Longtubeman]

calhoonprimers02[1].png any one need this?

[jsallen628]

That is a potful of work you have done and much appreciation and esp. highly readable. Looking at the 130 gr bullet results am I correct in seeing that cfe is approx 300ft faster than 8208? thats enormous - Im trying to figure out how to load some of the newer Lehigh controlled chaos 126 grain (yes - 126) geez these things are long, they look like a 7mm pill