Went to range with IMR 8208 XBR with 123 AMAX and 107 Sierra.

[LRRPF52]

Loaded to 2.26 on the 107's which was about .02 short of the lands.

I had Krieger chamber the barrel in 264 LBC AR as I had purchased the reamer and go gage from Pacific Tool and sent to Krieger. After firing I noticed that the brass was .300 at the neck. I then measured the reamer which also showed .300. I do not know what I have as the 264 LBC AR was supposed to be .295 at the neck. Is the reamer a Grendel reamer that is mismarked or do I have a 264 LBC AR reamer that was cut wrong at the neck? I feel it is closer to the Grendel than the 264 LBC AR.

That's a better neck diameter to have anyway. The next thing is to look if it has a compound throat angle where the leade hands off to the rifling. If it's compound, you have a Grendel reamer, provided it is the same as one. If no compound angle, it's some hybrid.

[sneaky one]

Brick, I have to ask-- how far from muzzle to chrono- distance? thanks.

[brickcues]

I have a 28" Krieger barrel and using Oehler Model 35P chronograph. It is actually 2 chronographs in one and I place it at 12 ft. out for start of proof channel to the middle screen at 14 ft.; the primaries are measured from 14 ft. to 16". I have gotten no errors with the IMR 8208 at this distance, the proof and primary are within 4 to 8 fps. on all shots.

[brickcues]

That's a better neck diameter to have anyway. The next thing is to look if it has a compound throat angle where the leade hands off to the rifling. If it's compound, you have a Grendel reamer, provided it is the same as one. If no compound angle, it's some hybrid.

Wow, just looked at the reamer and measured throat size and angle. Yes it is a compound angle as it starts off at .265 and goes for about .125 and them it angles down to .256 at the end. The throat part of the reamer is .400 long. The 123 AMAX is touching the throat first and not the lands.

[LRRPF52]

Wow, just looked at the reamer and measured throat size and angle. Yes it is a compound angle as it starts off at .265 and goes for about .125 and them it angles down to .256 at the end. The throat part of the reamer is .400 long. The 123 AMAX is touching the throat first and not the lands.

Sounds like a Grendel reamer to me, which is exactly what it is designed to do if I understand Bill A. correctly. This is what allows it to be reliable and accurate with a wide range of bullets, rather than just have one throat angle that prefers one bullet type and COAL. It's kinda like a universal ogive throat that lets bullets touch, without much jump, if any.

[brickcues]

Call Pacific Tool and talked to Dave. There are 2 reamers for the Les Baer 264, one with .295 neck and the other with .300 neck. From what I have found out the .295 is for bolt gun and .300 for AR. The difference between it and the Grendel is the throat is alittle more open in the Grendel. My reamer is the 264 LBC AR as the throat is tighter but with the .300 neck. The 123 AMAX touches the throat with OAL of 2.245. The 107 Sierra I can load to 2.26 and still have .02 jump to throat.

[wheelguner]

Which brass and primers are you using?

[brickcues]

Lapua brass and 7 1/2 Remmington primers

[Hoot]

Which brass and primers are you using?

Remington 7 1/2s also, but Hornady brass, because I got them on sale. They're not holding me back.

Next time I need more brass, I will splurge and probably watch for AA (Lapua) Brass on sale. My primary uses are hunting and non-competitive target shooting, though I still shoot for serious results. I'm not a blammo ammo shooter.

Hoot

[BenchRider]

I've got to check the velocity of this 8208 XBR behind 123 gr Amax bullets out of my 28 inch barrel so I loaded up 5 rounds at each of 27.9, 28.1, 28.3, & 28.5 grains of powder with these 20 bullets set to start .005 off the throat/rifling. I built another identical powder series with the bullets starting .010 off. These will be shot for group size over the chrono this friday.

Posting to pull this thread up to the top so I can find it again to post results.

[Hoot]

I've got to check the velocity of this 8208 XBR behind 123 gr Amax bullets out of my 28 inch barrel so I loaded up 5 rounds at each of 27.9, 28.1, 28.3, & 28.5 grains of powder with these 20 bullets set to start .005 off the throat/rifling. I built another identical powder series with the bullets starting .010 off. These will be shot for group size over the chrono this friday.

Posting to pull this thread up to the top so I can find it again to post results.

Load them 4 at a time, fastest to slowest load, 28.5, 28.3, 28.1, 27.9, so that they shoot in the reverse order and shoot them round robin at four different bulls on the same sheet. Reload and repeat. That reduces the effect of a good run skewing the other three's result.

Like this primer experiment I did. Same everything except the primers. Different caliber, (LAR-8 Predator HP) but similar experiment. The CCI 200 group were comprised of shots #s 4, 8, 12, 16 and 20, so not just a good run of 5 in a row.




Hoot

[BenchRider]

Many thanks Hoot - I had always just gone through each load and then got the summary info off the chrony. Likely some of the "good" performances were more technique improvement than all load performance.

I actually just checked back here from another of your range reports on AR-Comp where you followed the procedure you indicated above. Makes good sense -- produces good data.

I'm planning on hand-feeding The Mistress for every shot, just to avoid any possible disturbance of the setup that a trip up the feed ramps could cause coming out of the mag. Going to be a lot of button-pushing on the Chrony Beta Master -- that dang thing better not "Err1" any of these shots this time...

[BenchRider]

8208XBR with 123 gr Amax & 28 in Barrel

Got to the range and found it breezy and about 58 deg F.

Shot the prepared loads with Hoot's suggested round-robin process off bags from the bench at 100 yards. The chronograph never burped and caught good, reasonable values for all 40 shots. This was with a dirty barrel as well.

Starting with the rounds seated to start 0.005 in off the rifling/throat:

upload005off.jpg

There was a small boo-boo with the scope that put all the groups low. I didn't check the book, thought I was zero'd for 200, and wound it down about 1.75 MOA. My bad.

The 27.9 gr of 8208XBR group is ~ 0.880 in ctc
The 28.1 gr group is ~ 0.565 in ctc
The 28.3 gr group is ~ 1.438 in ctc
the 28.5 gr group is ~ 1.153 in ctc

The chrono data is:

27.9gr 28.1gr 28.3gr 28.5gr
------- ------- -------- --------
Avg 2637 2646 2672 2672
ES 47.49 38.14 34.77 33.02
SD 20.44 14.83 13.07 15.13

1 2643 2663 2688 2688
2 2671 2652 2679 2688
3 2624 2652 2653 2662
4 2625 2625 2674 2668
5 2624 2637 2668 2655

So -- then I "fixed" the scope by dialing in 2 MOA up. And....
Shot the prepared loads in round-robin that were seated to 0.010 in off the rifling/throat:

upload010offb.jpg

The 27.9 gr of 8208XBR group is ~ 1.015 in ctc
The 28.1 gr group is ~ 0.515 in ctc (but has only 4 rounds)
The 28.3 gr group is ~ 0.655 in ctc
the 28.5 gr group is ~ 1.050 in ctc

The chrono data is:

27.9gr 28.1gr 28.3gr 28.5gr
------- ------- -------- --------
Avg 2644 2639 2671 2670
ES 26.05 39.32 27.66 54.23
SD 9.84 15.84 10.81 19.87

1 2659 2637 2668 2698
2 2647 2642 2680 2667
3 2644 2665 2655 2644
4 2633 2628 2673 2663
5 2638 2625 2682 2678


The 28.3 group has six rounds because I screwed up and lost my place. It's one of the inside holes so it doesn't affect the data significantly -- would've hit inside the 28.1 group too given same POA & POI outcome.

Out of curiosity, I shot a string of my current favorite 123gr Amax load: 30.3 gr of 2520.

AVG 2656
ES 34.50
SD 10.86

2643
2644
2653
2654
2662
2661
2677 -- round sat in the chamber a bit longer than the others...
2658

That 8 round grouping goes ~1.25 in with a poor-technique flyer. Minus the flyer, I got 0.925 with seven.

This sucks. I've gotten almost 0.25 MOA out of this gun before at 200 yards in good conditions. The interesting part is: the bullet seating depth for the 2520 load was exactly the 0.010 off the rifling/throat that I had set up for the 8208XBR test rounds. Guess that means the Amax likes about .010 jump.

The 28.3 gr 8208 XBR load interests me. It's got another 30fps over what my range chart for the 30.3 2520 load says is my average starting velocity. Every little bit counts for getting out to 1000 with enough whack to get it done...

Any observations (besides "go clean your barrel") are more than welcome...