Load Development Advise and Comments

[browning442]

Gents,

I'm looking for your take on group interpretation. Fairly new to load development, know the basics of the different ways of doing it. So far, i've been initially doing 3-shot nodes, about 5-6 nodes total, starting at max w/quickload and backing down, that are 0.5 grains apart. I've heard of different ways using ladder and OCW tests. May try those going forward to save some cash and barrel life.

Long story short, my 280 AI is what I'm testing for. These happen to be with the 165 Sierra Game Changers. My info is on the target and my velocities are posted as well. I want to get everyone's take on:

1. This method for load workup. Have a few people that say that really velocity is only thing that matters on the initial workup, whichever method you use.

2. Brass resizing - For a while i was neck sizing only, however i've gone to full length sizing and bumping the shoulder back .002 from a fired case.

3. Interpreting these velocities and groups. I'm using a caldwell G2 which has worked better than my prochrono did, but there are a couple velocities that are "outliers" it seems to me.

4. Powder - Reloader 26 has given me good speeds but generally been more temperamental with the 280 AI.

My thought was the 62.0 to 62.5 node was where i should start and adjust seating depth. But I'd like to get some experienced thoughts, and also see if with the given groups, anyone thought seating depth wouldn't tighten them up enough to continue to use this powder.

 

[cohunt]

I see 2 things-- the vertical string height is good on the 62&62.5--also the 64

but look at the average speeds 2988,3029,3075,3073,3151,3166--- the flattening off of the velocity at 62.5-63 and the spike in velocity at 63.5 can show that you have hit your top end of the pressure curve

I would try in the 62-62.5 area as you said,just my 2 cents though

did you have any pressure signs at the 63.5-64 gr ?

 

[browning442]

Great observations cohunt, that is a great point about hitting the top end of the pressure curve.

Spot on - i had faint ejector marks at 63.5 and 64.0, at 64.0 i had one shot where the bolt was slightly stiffer lift.

Quickload numbers almost mirrored these results for velocity and the upper pressure limit. I never go by it completely, but nice to see the useful factor of it.

 

[jasonco]

I see 2 things-- the vertical string height is good on the 62&62.5--also the 64

but look at the average speeds 2988,3029,3075,3073,3151,3166--- the flattening off of the velocity at 62.5-63 and the spike in velocity at 63.5 can show that you have hit your top end of the pressure curve

I would try in the 62-62.5 area as you said,just my 2 cents though

did you have any pressure signs at the 63.5-64 gr ?

Same here, but what's with the 62.5 gr ES of 111fps?! Was that an error?

 

[browning442]

That raised my eyebrows too - could've been a chrono error, as it was getting to be dusk and i hadn't turned the lights on yet. Not real sure, i would hope it's not a product of using the RCBS chargemaster lite

 

[Lonewolf74]

The ES can easily be chrono error.

The most reliable and probably also most cost efficient way to double check your powder charge is to get a beam scale, they don't drift like the digital's do. However even if your charge master does drift a few tenths it's not gonna cause a 100+ fps velocity spread.

Some may disagree but I would always start with a seating depth test. Once you've found a sweet spot for a particular bullet it should remain constant except for maybe some fine tuning a few thous later on.

From where your at now I would do a seating depth test at your lowest charge weight and find what seating depth shoots best. Then reshoot the charge weights at the seating depth sweet spot you found, omit 64 grains if you found pressure there. If once again 62-62.5 are your best groups and have similar point of impact like they do now then that's your node.

 

[Joefrazell]

I'd play with the seating depth with 62.5 gr. And see if it tightens things up.

 

[browning442]

The ES can easily be chrono error.

I figured as much, especially seeing how the vertical impact did not change much on the second (outlier) shot. Almost certain that one was a chrono error

 

[browning442]

Say i choose 62.5 and play with seating depth... my loaded coal was 3.490" on the original group. I think i can go up to 3.510" or so... would you load a couple nodes of 3 shots at .010 increments above and below the 3.490 mark?

 

[RockyMtnMT]

Did you misprint in the original post that you started at the Mac load and worked down? Hope that is not the case.

Steve

 

[browning442]

I chose my top charge node based on max and went down in increments from there when loading.... but shooting the nodes i started at the lowest and worked up. Sorry for the confusion and causing concern LOL. I always start 2-3 grains minimum below the max, sometimes more. Always compare book loads with quickload also and come up with a comfortable tolerance.

 

[Joefrazell]

Say i choose 62.5 and play with seating depth... my loaded coal was 3.490" on the original group. I think i can go up to 3.510" or so... would you load a couple nodes of 3 shots at .010 increments above and below the 3.490 mark?

I personally would make bigger adjutant the .010". I'd do .030 shorter and I'd go touching the lands and see if either shoot better. .010" is more of a fine tune increment.

 

[browning442]

Will the seating depth changes generally show in the velocity ES & SD, or are the results going to be told by the target?

 

[L.Sherm]

I had similar groups during load development using RL26 in a 280AI using 162eldxs. I couldn't get rid of what I call the 2-1 a little bit of a flyer no matter what I did until I switched to RL23.