Does this sound right? Update: second range trip

[m1ajunkie]

I got out today to try a load for 77gr smk's in my 20" sdm ar.

The hornady book max is 23.5gr of varget so that is where I stopped. All rounds have a coal of 2.25-2.254.

Any way here is what I came up with, all groups were 10 rounds except when using 23.3gr of varget.

My control ammo is SSA 5.56mm 77gr mk262 clone ammo.
After 10 rounds:
Average: 2807
Extreme spread: 60.75
Standard dev: 21.4

No pic of this group because I forgot the camera. Roughly 1.5moa about 1.5moa low of center. This load was zeroed in 75 degree weather and today was about 50 so I am thinking the zero changed due to the temp. I have heard 1moa for 10 degrees, is that correct?

Next up is 23 gr of varget with the 77gr smk

Average: 2617
ES: 52.71
Standard dev: 19.2

Group:

Next 23.3 gr, this is only a five round group because I was not planning to shoot these

Average: 2644
ES: 35.98
Standard dev: 14.62

The group on this one is hard to tell because my stickers covering the previous group fell off. Anyway, there are five rounds that seem to be within 1moa. They are the lowest shot and the other four seem to be in a line if you can tell.

Lastly is 23.5gr varget

Average: 2673
ES: 41.48
Standard dev: 13.11

Pic

My setup wasn't great due to my lack of rear bag. However I feel like next time I go back I can get these groups down to at least 1moa which is my goal. I have shot 1moa before with this rifle and the SSA ammo, but I had several factors against me today. Laying this close to the ground I had lots of mirage and wind moving left to right pretty severly that I feel like made the groups hit the right about 1 moa.

Do those velocities look correct for my setup? I have heard a chrony is the best way to tell if your loads are overpressure. My brass didn't look out of the ordinary today, but I want to be safe. The max range I have locally is 700 yds and with 23- 23.3 grs I have enough velocity to make 700yds.

Here is the setup:

I plan to go back with loads between 23gr and 23.3 gr and see how they do. I feel like that's where my rifle will shoot the best from today's results. Is that a valid conclusion?

 

[sinister]

Re: Does this sound right?

23.5 - 24.5 is generally the Varget sweet spot for 73s, 75s, and 77s for National Match Course (NRA and Army) SR-C and 300-yard targets.

23 is at the bottom end and a little slow. Give 'em a whirl at 23.5, 24.0, and 24.5 and see what happens.

Never sacrifice accuracy for velocity, but push them fast enough to cycle/operate the weapon and buck wind.

 

[m1ajunkie]

Re: Does this sound right?

I am planning to head back this week to try some loads at 23.3 and up.

I was a little nervous to go over 23.5 due to that being the max but I see a lot of people are around 24gr.

I am a little confused though. At the 23.5gr load my cases are very full and if I put anymore in I believe the powder will end up being compressed. Is that okay? I have other brass I could try and see if that changes it. I would like to get the most velocity possible for the obvious reasons though.

 

[armorpl8chikn]

Re: Does this sound right? .223 load

Use a drop tube to get the grains to settle a bit more. Compressed loads are pretty normal with Varget and heavy bullets. In my 223 custom XP100 24+ is where it starts to come alive. Same for my AR. It sounds like you have a good bit of caution and that is good. Keep it up

 

[MAGUA]

Re: Does this sound right?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: m1ajunkie</div><div class="ubbcode-body">I am planning to head back this week to try some loads at 23.3 and up.

I was a little nervous to go over 23.5 due to that being the max but I see a lot of people are around 24gr.

I am a little confused though. At the 23.5gr load my cases are very full and if I put anymore in I believe the powder will end up being compressed. Is that okay? I have other brass I could try and see if that changes it. I would like to get the most velocity possible for the obvious reasons though. </div></div>
I load 25grs of Varget with a 80gr AMAX without any problems, it is compressed for sure.

 

[sawgunner2001]

Re: Does this sound right?

Your velocities are comparable (nearly exact) to what I've gotten out of 20" AR's at those powder charges. In one rifle, I was able to push my powder charge up to 25.0gr until I saw pressure. The one I shoot now maxed out at 23.5gr. Any higher and I was getting ejector marks that I'm not comfortable with. I was a little disappointed that I couldn't wring out any more velocity in my current rifle with Varget, but it is what it is. Coincidentally, both rifles shot their best at their maximum (safe) pressure limits with Varget.

I could probably get more velocity out of a ball powder, but I chose to stick with Varget for temp stability reasons despite the lower velocities. That, and the fact that it is shooting decent groups as is.

I would suggest upping the powder charge incrementally, checking accuracy and pressure signs along the way.

Good Luck

 

[esromvre]

Re: Does this sound right?

I am pushing 75 A-Max with 24.7 out of my NM AR. shoots great. What twist does yours have?

 

[m1ajunkie]

Re: Does this sound right?

My barrel is 1/7".

I am not a fan of the 75gr amax because it cannot be loaded to mag length. I have looked at the 75gr bthp that I plan to try out after I get a load for the 77gr smk.

What are good number's for ES and standard deviation? I am thinking I read somewhere that 10 was what you should shoot for in standard dev.

Also, how can I use the chrony to tell me if I'm overpressure? I understand the brass method, but I am not sure how the chrony will tell me this. I am guessing you fire a factory bullet and then load your reloads to match without going over, is this correct?

 

[m1ajunkie]

Re: Does this sound right?

Went back to the range today to try some hotter loads. Once again, mirage was tough today.

This was the first ten shots after I cleaned my rifle this weekend. This group is Black hills 77gr .223 ammo at 2732fps with a large standard dev of 34.32. Excluding the flier which could have been the first shot it's just a hair over an inch.

Next up was a group at 23.7gr of varget which did very well.

Velocity: 2695
ES: 45.72
Standard dev: 15.62

Once again, excluding the flier(the one to the right of the caliper) this group is almost exactly an inch.

Then I moved up to 23.8gr varget which gave a nice group. I only shot five rounds as I was just checking pressure.

The next group is not impressive at all and I believe it is to hot for my rifle. 24gr varget only got me 2707fps and the worst group of the day.

Now I need help analyzing the results. Right now I am leaning toward 23.7gr of varget as it shot the best group of the day and has enough velocity to get me to 700yds. I did however have one primer that had a nipple in it, but I am not seeing any ejector marks on the brass at this powder charge.

The 24gr of powder gave me a bad group and 7 of the ten primers were nippled and most pieces of brass show ejector marks. I am curious though, did firing these hot rounds do any damage to my rifle or should it still be good to go?

Do you agree that I should stick with 23.7gr for the time being and use that as my load due to the nice grouping and lack of pressure signs, or is the one nippled primer to much?

I feel like under better conditions I could shoot a slightly better group, but not by much. The only thing against me today was mirage but thats always an issue.