CMV
Member
Found a 100 yd outdoor range about an hour away & spent a few hours there today. I fired my first 30 reloads. Strings of 5 at each powder charge. Now that I have the Chrony data and groups I don't know what to make of it.
I started with XM193 and IMI M193 to get the Chrony set up and to sight in the cheapo carry handle scope I just got. Then I fired my strings. I stopped after each one to collect & inspect the brass.
They fed, fired, cycled the weapon, extracted, etc with no issues. I noticed slightly less recoil with my loads compared to the factory M193 but recoil is already pretty negligible with an A2 buttstock & full size buffer & spring so that might have been my imagination. I saw no signs of anything wrong like cracked/split cases, flattened primers. The only thing I noticed any different was that as the charges went up, the extracted brass flew out a little further.
AR-15, 5.56mm chamber, 20" 1:9 HBAR, 53-55°, sunny, mild to no wind. Chrony F-1 10' from muzzle per its instructions. LC brass, Hodgdon H335, CCI #41, Hornady 55gr FMJBT. Shooting from a bench with a sandbag.
Are 5 shot strings enough data points to form any conclusion? The IMI & XM193 were only 3 shots measured for velocity due to some initial Chrony errors so their std dev might be skewed because there are fewer data points?
My group sizes are all good for me. The cross hairs on the scope completely cover the target so I was actually surprised they were that tight. I think that's why the last target grouped a little better - I could see some of it. I should have used larger targets, but with the 25M zero targets I could put them all on the backstop & not have to keep waiting to go cold & walking back & forth (lazy). I never used a 4x20 scope before & didn't realize how weak it would be until I was looking at these little guys through it. I don't have the factory load targets pictured below but they were at the bigger targets too. I think they'd have spread more if I was trying to hit the zero targets.
Target #1 was 23.5 gr, #2 was 23.8, etc.
Anyway, I'm kind of lost as to what this tells me. Other than velocity, it seems any of the powder charges were just fine. The larger/smaller groups could be as much my fault as the ammo's fault. Interesting, there was no change in elevation - they all pretty much hit in the same place.
I'm also only .3 gr away from max load in my book (Lee - Modern Reloading 2nd ed) and nowhere close the the factory velocity or the published 3,203 in the book. It doesn't say what bbl length, case, or primer was used for testing, but from a 20" shouldn't I be closer? at 1.7gr over the starting load is where I'm matching the starting load velocity. Looking at how the velocity is creeping up past 24.1gr, I would estimate at max load I'd be at 3,050fps.
If anything, I thought I'd be a little higher using 5.56mm brass. The interwebs told me I'd build up more case pressure due to thicker case walls and I thought that would translate to slightly higher fps. I don't really care about velocity - I'm not making these rounds for zombies so if they fragment or not when they hit the backstop doesn't matter. What I care about is is I have a reference telling me I should be seeing X and I'm seeing (X - a lot) indicating I'm doing something wrong. Per Federal website, XM193 should be at 3290 at the muzzle and I'm only -20 from that (which may be from the 10' distance?). So that tells me the Chrony is right and I'm seeing what I should from factory loads, but not mine.
I think I'll need a better scope for one thing. My eyes aren't good enough for iron sights - nor are my shooting skills. I'll hit a B27 all day long but will be into the 9 ring in all directions with iron sights @ 100 yds. Wouldn't get tight enough groups to tell me much. But I didn't even try today. I'm so spoiled by the Aimpoint I haven't even used iron sights in a couple years. If the zombies rise & my battery dies I'm in trouble
I measured each powder charge twice on 2 different scales but I still saw a lot of variation from identical loads. the difference from highest to lowest fps for each charge weight:
23.5 - 112fps spread
23.8 - 77 fps spread
24.1 - 56 fps spread
24.4 - 77 fps spread
24.7 - 141 fps spread (2 out of this group were faster than the 25.0 average)
25.0 - 38 fps spread
So my overall conclusion is I need to play around closer to 25.0 - maybe 24.8 - 25.3 in .1 increments. I saw the tightest group, lowest SD, & most consistent velocity at 25.0. But my methods may be so flawed that I'm basing that off useless data.
Side note: it felt so weird looking for my brass! So used to just leaving it lay. Was like being back in the Army policing up brass But if I fired 5, I hunted until I found 5. And some kind soul was nice enough to leave me about 100 pieces of 1x fired LC brass around my table so if nothing else I got 100 free pieces of brass today
I started with XM193 and IMI M193 to get the Chrony set up and to sight in the cheapo carry handle scope I just got. Then I fired my strings. I stopped after each one to collect & inspect the brass.
They fed, fired, cycled the weapon, extracted, etc with no issues. I noticed slightly less recoil with my loads compared to the factory M193 but recoil is already pretty negligible with an A2 buttstock & full size buffer & spring so that might have been my imagination. I saw no signs of anything wrong like cracked/split cases, flattened primers. The only thing I noticed any different was that as the charges went up, the extracted brass flew out a little further.
AR-15, 5.56mm chamber, 20" 1:9 HBAR, 53-55°, sunny, mild to no wind. Chrony F-1 10' from muzzle per its instructions. LC brass, Hodgdon H335, CCI #41, Hornady 55gr FMJBT. Shooting from a bench with a sandbag.
Are 5 shot strings enough data points to form any conclusion? The IMI & XM193 were only 3 shots measured for velocity due to some initial Chrony errors so their std dev might be skewed because there are fewer data points?
My group sizes are all good for me. The cross hairs on the scope completely cover the target so I was actually surprised they were that tight. I think that's why the last target grouped a little better - I could see some of it. I should have used larger targets, but with the 25M zero targets I could put them all on the backstop & not have to keep waiting to go cold & walking back & forth (lazy). I never used a 4x20 scope before & didn't realize how weak it would be until I was looking at these little guys through it. I don't have the factory load targets pictured below but they were at the bigger targets too. I think they'd have spread more if I was trying to hit the zero targets.
Target #1 was 23.5 gr, #2 was 23.8, etc.
Anyway, I'm kind of lost as to what this tells me. Other than velocity, it seems any of the powder charges were just fine. The larger/smaller groups could be as much my fault as the ammo's fault. Interesting, there was no change in elevation - they all pretty much hit in the same place.
I'm also only .3 gr away from max load in my book (Lee - Modern Reloading 2nd ed) and nowhere close the the factory velocity or the published 3,203 in the book. It doesn't say what bbl length, case, or primer was used for testing, but from a 20" shouldn't I be closer? at 1.7gr over the starting load is where I'm matching the starting load velocity. Looking at how the velocity is creeping up past 24.1gr, I would estimate at max load I'd be at 3,050fps.
If anything, I thought I'd be a little higher using 5.56mm brass. The interwebs told me I'd build up more case pressure due to thicker case walls and I thought that would translate to slightly higher fps. I don't really care about velocity - I'm not making these rounds for zombies so if they fragment or not when they hit the backstop doesn't matter. What I care about is is I have a reference telling me I should be seeing X and I'm seeing (X - a lot) indicating I'm doing something wrong. Per Federal website, XM193 should be at 3290 at the muzzle and I'm only -20 from that (which may be from the 10' distance?). So that tells me the Chrony is right and I'm seeing what I should from factory loads, but not mine.
I think I'll need a better scope for one thing. My eyes aren't good enough for iron sights - nor are my shooting skills. I'll hit a B27 all day long but will be into the 9 ring in all directions with iron sights @ 100 yds. Wouldn't get tight enough groups to tell me much. But I didn't even try today. I'm so spoiled by the Aimpoint I haven't even used iron sights in a couple years. If the zombies rise & my battery dies I'm in trouble
I measured each powder charge twice on 2 different scales but I still saw a lot of variation from identical loads. the difference from highest to lowest fps for each charge weight:
23.5 - 112fps spread
23.8 - 77 fps spread
24.1 - 56 fps spread
24.4 - 77 fps spread
24.7 - 141 fps spread (2 out of this group were faster than the 25.0 average)
25.0 - 38 fps spread
So my overall conclusion is I need to play around closer to 25.0 - maybe 24.8 - 25.3 in .1 increments. I saw the tightest group, lowest SD, & most consistent velocity at 25.0. But my methods may be so flawed that I'm basing that off useless data.
Side note: it felt so weird looking for my brass! So used to just leaving it lay. Was like being back in the Army policing up brass But if I fired 5, I hunted until I found 5. And some kind soul was nice enough to leave me about 100 pieces of 1x fired LC brass around my table so if nothing else I got 100 free pieces of brass today