Help with 8208xbr & Amax

[outlaw45]

I have a chronograph. Do I look for inconsistent velocities?

[LR1955]

I have a chronograph. Do I look for inconsistent velocities?

Look for a huge increase in velocity for a shot or two out of a sample of twenty. I mean a 30 fps plus increase over your mean velocity.

This means you will be shooting a sample of two or three each, 10 shot groups.

While you are at it, load ten with 27 1/2 grains and ten with 28 grains and run them over your chronograph. What you are looking for is to see (A) consistent SD's of 10 or less and (B) how much velocity you are gaining from that extra half grain. You may find that between 27 1/2 and 28, you see a reasonable increase in velocity but between 28 and 28 1/2 a much less increase in velocity. The law of diminishing returns indicates your load is about as maxed out as your powder, case, primer, and bullet allow. Once you hit that point of diminishing returns, more powder means only one thing -- more pressure.

Given you now have three loads you chronographed and shot for group, you can probably make a very sound decision on the load you want to keep.

LR55

[outlaw45]

Switched to magnum primers, CCI450, still running 8208xbr. Started out with 27.0, 27.3, 27.5, 27.8, 28.0 grains. 27.3 gr with 2380 fps and 27.5 gr 2406 fps seemed to both group nicely.

I also loaded 28.5 grains to see what it would do. It did the best so far. Velocity was averaging 2495 fps. I think this is the best load, I'm just wondering if its too hot. Velocity spread wasn't any different than other loads I tried. C.O.A.L. is 2.260 and I'm compressing the powder when I seat the bullet, is this normal?

I'm going to load up 27.5 and 28.5 again and hopefully one will be my final load. Wish I would have switched to magnum primers awhile ago, I feel like I've been wasting my 123 Amaxes.

[dmsims21]

I don't think 28.5 is too hot. It is at or near max though.
That is a compressed load.

[Adam Lilja]

I'd stick with 27.5!

[LR1955]

Switched to magnum primers, CCI450, still running 8208xbr. Started out with 27.0, 27.3, 27.5, 27.8, 28.0 grains. 27.3 gr with 2380 fps and 27.5 gr 2406 fps seemed to both group nicely.

I also loaded 28.5 grains to see what it would do. It did the best so far. Velocity was averaging 2495 fps. I think this is the best load, I'm just wondering if its too hot. Velocity spread wasn't any different than other loads I tried. C.O.A.L. is 2.260 and I'm compressing the powder when I seat the bullet, is this normal?

I'm going to load up 27.5 and 28.5 again and hopefully one will be my final load. Wish I would have switched to magnum primers awhile ago, I feel like I've been wasting my 123 Amaxes.

Compressing charges isn't something you want to do unless you have to.

Load up some with 28 grains of 8208 and see what their velocities, SD's, and ES's are compared to 27 1/2 and 28 1/2.

See if the change in velocity between 28 and 28 1/2 is over 30 fps. If it is near 30 fps and your SD's are under 10 fps, with no extremely high velocities from your sample, then your load is probably as efficient as you can get. When increases in velocity with 1/2 grain increases in powder (for the Grendel) are under about 30 fps, most likely you are pushing pressures without getting any practical benefit in terms of external and terminal ballistics.



LR55

[outlaw45]

I don't have the numbers in front of me now but I think 28.0 gave me about ~2440 fps. If so, it would be more than 30fps. The SD's were between 9 and 11 for loads 27.5, 28.0 and 28.5. So again, its right where you are saying.

So if those numbers are right, you're saying I should back it off to 27.5 or 28.0?

[LR1955]

I don't have the numbers in front of me now but I think 28.0 gave me about ~2440 fps. If so, it would be more than 30fps. The SD's were between 9 and 11 for loads 27.5, 28.0 and 28.5. So again, its right where you are saying.

So if those numbers are right, you're saying I should back it off to 27.5 or 28.0?

Not necessarily.

You got 2485 with 28 1/2 and for me, that would mean around a 40 fps increase with 1/2 grain more powder. Your SDs are good and although you didn't say you had any outliers in terms of one shot or so being very high, I will assume you didn't

You don't want to go to 29 grains of 8208 so you are working with a max (for you) of 28 1/2. I have shot 29 grains of 8208 with 120 and 123 Sierras and they were way too hot.

So, your max is probably 28 1/2 and there is no need to go under 28 since lower charges would be inefficient.

Now it is up to you to decide which one you want to use, 28 or 28 1/2. The factors going into your decision will probably be based on your intent for the cartridge and how much wear you think 28 1/2 is putting on your brass and rifle. You can probably get away with 28 1/2 for a thousand rounds without shearing a bolt lug. May be 200 rounds, too. One thing I would take to the bank is that specific load is about as hot as I would go after using 29 grains. And I wouldn't shoot it as a rule.

Now you know how to test loads using a chrono.

LR55

[waveslayer]

I don't have the numbers in front of me now but I think 28.0 gave me about ~2440 fps. If so, it would be more than 30fps. The SD's were between 9 and 11 for loads 27.5, 28.0 and 28.5. So again, its right where you are saying.

So if those numbers are right, you're saying I should back it off to 27.5 or 28.0?

To add what everyone else has added, I think you don't need to back off unless you don't care about higher velocities to reach out there. I have one load that is very low, but it is a tack driving Son of a B! I use 26.6 grains of XBR with the 123 AMAX. I don't use it a lot for long distance but it is a go to if I need to save tape and paper. "single holes"

[Adam Lilja]

To add what everyone else has added, I think you don't need to back off unless you don't care about higher velocities to reach out there. I have one load that is very low, but it is a tack driving Son of a B! I use 26.6 grains of XBR with the 123 AMAX. I don't use it a lot for long distance but it is a go to if I need to save tape and paper. "single holes"

26.4 is the exact same for me behind a 123 AMAX

[outlaw45]

Thanks for all the input. I'm not looking to squeeze every bit out the this cartridge, I just want an accurate 1/2 minute load.

[montana]

26.4 is the exact same for me behind a 123 AMAX

Interesting, I'll have to try this load, thanks.

[jjjefferson]

Hello Montana.....

I'm new here and I just built my first Grendel. I thought I'd share my load results from the Hornady 8th Edition. I found the difference between quarter sized groups and dime size groups in "my" Grendel barrel was finding the right OAL to the Ogive on the bullet. I seated my quarter sized groups a safe .020 off the lands. But my groups were terrible compared to the Hornady factory loads. I was getting great results with factory and found they seat about .015 off the lands. Setting my seating die to hit that distance made my groups tighten up to match the factory performance at 100 yards. I was very pleased at the range today :-) Hope you find something here helpful. I have been loading for a few years now and have worked up loads in .223, .32 Win Spl., .357 Maximum, .300 WBY Magnum, .50 Beowulf (yeah...not much to workin the Wulf..LOL)

I don't have pics of todays groups but they matched my factory groups from my first outing posted here: http://www.65grendel.com/forum/showt...-Grendel-Build

Load:
OAL: 2.26
Length to Ogive: ~1.675
Mild Taper Crimp
Primer: CCI #41
Case Length: 1.510
Powerder: Benchmark 26.6gr
Bullet: HDY 123gr A-MAX
Barrel: 20 in Shillen 1:9 with target crown and matched bolt .136 depth
Chamber: OAL to lands ~1.690 (measured many times with Hornady depth tool and averaged with high and low excluded)
Trigger: Geiselle SSA-E
Temp: upper 70's
Alt: about 5 feet above sea level.
Wind: Calm.
Velcoity: 2210 ave variance +/- 15fps
Distance: 100 yards.

[montana]

Hello Montana.....

I'm new here and I just built my first Grendel. I thought I'd share my load results from the Hornady 8th Edition. I found the difference between quarter sized groups and dime size groups in "my" Grendel barrel was finding the right OAL to the Ogive on the bullet. I seated my quarter sized groups a safe .020 off the lands. But my groups were terrible compared to the Hornady factory loads. I was getting great results with factory and found they seat about .015 off the lands. Setting my seating die to hit that distance made my groups tighten up to match the factory performance at 100 yards. I was very pleased at the range today :-) Hope you find something here helpful. I have been loading for a few years now and have worked up loads in .223, .32 Win Spl., .357 Maximum, .300 WBY Magnum, .50 Beowulf (yeah...not much to workin the Wulf..LOL)

I don't have pics of todays groups but they matched my factory groups from my first outing posted here: http://www.65grendel.com/forum/showt...-Grendel-Build

Load:
OAL: 2.26
Length to Ogive: ~1.675
Mild Taper Crimp
Primer: CCI #41
Case Length: 1.510
Powerder: Benchmark 26.6gr
Bullet: HDY 123gr A-MAX
Barrel: 20 in Shillen 1:9 with target crown and matched bolt .136 depth
Chamber: OAL to lands ~1.690 (measured many times with Hornady depth tool and averaged with high and low excluded)
Trigger: Geiselle SSA-E
Temp: upper 70's
Alt: about 5 feet above sea level.
Wind: Calm.
Velcoity: 2210 ave variance +/- 15fps
Distance: 100 yards.

Sounds like you found a sweet load for your Grendel. I have never tried Bench mark powder before with my Grendel but will give it a try. I'm always open to others loads and appreciate everyone's input . Great bunch of people on this forum even though it can get hard on ones wallet LOL Thanks for your load results, it is going into my future loads to try log.

[GatewayShepherd]

I have a Lilja AR740 20” as well and have been struggling with the load development also. i had very high expectations after spending “good money” on a premium barrel…but to this point have been disappointed. Haven’t had the chance to use any Factory 123 ammo..but have run several strings of hand loads using 123 Amax, 129 SST and 107 SMK…along with several boxes of PPU 120 HPBT. I’ve seen pics of groups all over this forum of 1 to 1.5 MOA groups with members stating that is acceptable. In my mind…it’s not. i have several other outfits including other Lilja barrels that will easily and without a bunch of load development drama shoot .5 moa or better. This barrel is troublesome. i’m pretty good about keeping records and such…at this point i’m going to regroup and sit down and look at all the information i’ve gathered and decide where to go from here.