Honing in on an accurate load, questions

[LawnMM]

I did another ladder test this weekend. I had posted last week about slow velocities using sierra's powder chart. Some guys put me onto alliant's own data which put the max charge about 4 grains higher.

I went as high as 44.8 grains of RE15 using winchester brass, CCI200 primers, and Sierra 175HPBT projectiles. I started getting pressure signs at 44.8 grains (50 was about max per alliant). Bolt was starting to get sticky.

Reviewing the groups I had a sub 1/2 MOA group measuring 1.385" at just under 300 yards with 43.8 grains. More impressive was a single digit SD of 5.0, an ES of 19, and average velocity of 2509 out of my 20" barrel. Should I even bother moving up and down from the 43.8 grains 2/10ths of a grain at a time or is it already about as good as its going to get?

I want to find an accurate load, start cranking out some ammo, and go shooting a bunch. I don't want to spend more time on the reloading bench than on the range chasing minute bits of accuracy all the time. What have your experiences been? Were you able to close in even further with more development after identifying an accurate load or were the gains minimal?

Thanks,

Rich

 

[MALLARD]

Re: Honing in on an accurate load, questions

if you are happy with the groups your getting i would stop load development.

does your rifle consistently shoot 1/2moa groups at 300y?

how many rounds in the group ?

what kind of chronograph are you using ?

 

[LawnMM]

Re: Honing in on an accurate load, questions

I've been able to get 1/3 out of it with different ammo at 100 if I do my part. I have some of the same load worked up that I plan to shoot next week to verify my results at 300 from this week. I shot a slower load last week at around 2200fps that was also well below 1/2 moa at 300 yards so I would say the rifle is consistently able to produce the accuracy if the driver does his part.

I was shooting 5 rounds, the group was measured with 4 of the 5, the fifth was kicked off the main group and that was my error, not the ammo or the rifle.

CED M2 Chrono with Infrared Screens.

 

[Leaddog]

Re: Honing in on an accurate load, questions

Unless you plan to shoot long range, I'd say you have a good 'slow' load. Faster is not always more accurate in a .308.

 

[LawnMM]

Re: Honing in on an accurate load, questions

I'd like to get into some F class at 800 and 1000. A quickie in JBM says the slower load is still supersonic at 1000 here at altitude but I don't know how much the slower velocity contributes to being pushed around by the wind.

That was the purpose of this weekend's workup. The load I was asking about managed the same sub half moa group size, but at an average speed of 2509fps. So it needs quite a bit less than the 15 mils of elevation to 1000 that the slower 2200fps load would need.

I'm planning on loading up another 20 rounds, 10 rounds moving up from this weekend's load in 2/10th of a grain increments, and 10 rounds moving down, and another 5 as I loaded them this weekend to compare the groups and see if I can further refine what the rifle likes.

I don't plan on doing much development past that though, I'm wondering if even that much is beneficial or if its really just more work than benefit gained.

 

[Fieldman_.308]

Re: Honing in on an accurate load, questions

It kinda sounds like you've already made up your mind. Go out and start developing your shooting. Personally I don't really feel thats a "slow" load either. I'm shooting 175smk at 2400fps and I've left them there for accuracy, but I've been shooting well to 1000 yards. Even though I hit transonic speed before it. Just a thought, have fun and good luck!

 

[Unknown]

Re: Honing in on an accurate load, questions

If I was getting 1.35 inches at 300 yards, and a velocity of 2509 out of a 20 inch barrel, I would load the ammo and enjoy shooting.

Sure, if you spent hours and hours more load development, you might improve it a bit, but it looks like your 100 yard groups would be around .45 inches...I think that is plenty food enough. Of course, you could spend those hours, and hours, and hours, and lots more money and components to get the groups to .4, or maybe .35...maybe, and maybe not...

I would just go with what you have, and start practicing so you can eliminate those flyers that you say are your fault. If you can eliminate all those flyers, your groups will improve too, and I think shooting is lots more fun than sitting in front of the loading bench.