Expected shooter variation:

10-ring sized group, with up to 1 MOA shift relative to center of target due to light, wind, and natural point of aim. Average score of 487/490-15x. Outliers due to the shooter by fundamental error or sight adjustment are noted for recent data.

Target diameters in inches. SR-1, SR-21, and MR-31 are used.

Previously... 3-Sept-16

Load Data:
- moly'd 50gr VMAX
- 4.5gr Red Dot
- CCI 400 primer
- Trimmed, chamfered, flash-hole uniformed, FC case
- OAL 2.255"

[Chrono data]
MV: 1488fps
ES: 54fps
SD: 18fps
JBM Ballistics predicts 1217fps at 100yds.











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Recently... 3-Feb-18

Load Data:
- moly'd 50gr VMAX
- 5.0gr Red Dot
- Winchester Small Rifle primer
- Trimmed, chamfered, flash-hole uniformed, FC case
- OAL 2.255"

[Chrono data from Sept. '16. 10 shots, and CCI 400 primers were used]
MV: 1571fps
ES: 60fps
SD: 23fps
JBM Ballistics predicts 1290fps at 100yds.



I zeroed the rifle from Prone in the 5 minute sight-in period at the beginning of the match. Five rounds of my usual Varget load and five rounds of the test load.

I think I gave it 1 MOA up during the Offhand string and went from a 6:00 hold to a slight Flat Tire hold. A gust caught me once.



Sitting, I let the sight be, but held 6:00. It felt fine - only one shot was very bad, but it would've been one of the 9s at 6:00 or 4:30. I saw that low one during the reload and ignored it. The sun hadn't moved much, so I blame the left bias on me.



Prone Rapid felt good. After the first two shots, I came up 1.5 MOA and right 0.5 MOA, again ignored the low one. I think the sun partly influenced the left bias this time.



For the 1st string of Prone Slow, I started with 1 MOA right, and 5 MOA up.... and shot a 6 at 12:00. Came 5 MOA back down.... and shot an X.
The 9, and 8 at 1:30 might've been me.



For the 2nd string, I think I just let the sights be, and focused on my own elevation control. Considering this was one of the windiest days at this range in a while, I was impressed with the lack of horizontal stringing.



Then I shot the PSA Challenge. Everything seemed on par here.





At home, the BCG was difficult to pull out of battery. It seems that there wasn't enough oomph from the gas to push the carrier back enough to vent properly. Residue built up at the rear of the bolt and in the cam pin track, causing friction. Normally, I just wipe the gun with a paper towel, but I had to use some Hoppe's #9 and a brush to scrub the gunk. It wasn't a lot, just in the vital locations.

Any ideas on what causes the low ones?

I don't think I've ever tried a powder-forward/powder-back test.

At 100 yards, virtually ALL of the deviation in point of impact is from YOU, the shooter.  Even the one you said was a wind gust was YOU.  The wind may have disturbed your position or blown the rifle but it did not cause that much deflection in the bullet's trajectory.  Really, this post would be better placed in the Competition Forum rather than here.

In an attempt to find a Reloading Forum issue, let me ask this.  Why are you using Red Dot?  It's a pistol powder, isn't it?

Eta: forgot red is for mods.

I might say the powder position question is enough reason to ask the reloading herd.

I'm sorry but I don't have a definitive answer. I do shoot 6gr of powder in a 7.62x54R cast bullet load without any filler but always purposely positioned the powder back before lowering the muzzle to aim. Or did the cartridge before clambering it on the bench. Maybe it's something you need to try.

Motor

I've never considered red dot particularly position sensitive but if you wanted to try it you might get some dacron fluff and use that as a filler.

Quoted:
In an attempt to find a Reloading Forum issue, let me ask this.  Why are you using Red Dot?  It's a pistol powder, isn't it? A flake, shotgun/pistol powder. Easiest way to make a manual straight-pull. And I'd hoped it would double as a <200yd wind training load w/o buying a $1000 rimfire upper, but the berms here make an effective wind tunnel.

Oh, that's a great idea.  I hadn't thought of that.  I knew there had to be a reason, I just did not understand what it was.

It's less conventional, but this is my testing ground. I take some inspiration from German Salazar, who got most of his data at Mid Range and Palma/Long Range matches.

My benchrest form isn't very good, and during day-to-day operation, I have to setup my Prone position on the concrete firing line beside the right berm and usually the lighting is shite. Add in match pressure that makes me "want" the 10 and X-ring more.

I thought so too. I'm trying to be faithful to Harris' word regarding filler, but if it's not position sensitive, what causes off-call low shots?

If you look close, a couple holes seem a little crooked, even without the effect of fingers, etc, pushing the displaced paper in slightly. With the 4.5gr load, I was thinking possibly a transonic issue, and why I tested 5.0gr.