308 100 yard ladder test

[acloco]

I know 300yds would be better and show more of a spread but only the 100 yd range was accessible and I had read Eric Cortina's article about this so I thought I would try it at 100.

Would like to receive guidance on this first attempt at a ladder test with my .308
I shot 10 rounds, one round at each charge wt. starting at 40.8 gr and ending at 44.4 gr. in .4 gr steps. The aiming point was on the horizontal line in each case. This was with 155gr Scenars in new Lapua Palma brass, Win small rifle primers and Shooter's World Precision Rifle as a Varget clone.
The vertical spread is small, but looks like 40.8 to 42.0 gr may be a node; as well as 42.8 to 43.2 for lower nodes. I didn't load any higher than 44.4, but I feel sure there may be another higher one.
Thanks for any info,
CJ
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Asking question again. 1/2 to 3/4" vertical across the entire charge weights listed?????

 

[Doom]

I would shoot 43 and 44.2.

 

[CaptJim]

Asking question again. 1/2 to 3/4" vertical across the entire charge weights listed?????

Yes sir, they ranged from 1/2 to 1.25".

 

[Full Chisel]

Yes sir, they ranged from 1/2 to 1.25".

I think @acloco has a valid point asking that again. Something ain't right with those results. Not only are they all within a narrower than normal vertical spread across a wide charge range, it looks like they are actually going lower in vertical as charge goes up. Maybe it's just the way I'm looking at the pic. My gut says there is something wonky going on with the rest causing those results, but who knows. You didn't do any holdovers at any point in the test did you?

 

[Downhill]

Something I do in a Ladder Test, I use a framing square off the side of the target marking straight lines off the bottom of each bullet hole. Noting charge weight at each line. Gives a handy improvised "graph" at edge that I can readily measure with calipers. The horizontal lines really make a node stand out.

 

[CaptJim]

I would shoot 43 and 44.2

Thanks for your input.

These are where I thought I would do 3-4 rounds each, chrono and see how they group.
CJ

 

[CaptJim]

I think @acloco has a valid point asking that again. Something ain't right with those results. Not only are they all within a narrower than normal vertical spread across a wide charge range, it looks like they are actually going lower in vertical as charge goes up. Maybe it's just the way I'm looking at the pic. My gut says there is something wonky going on with the rest causing those results, but who knows. You didn't do any holdovers at any point in the test did you?

No, the POA was the horizontal line for every shot. The rest and my inexperience with it very well may be an issue.
ETA, I too thought thought the POI should go up as the charge increases, but maybe the barrel harmonics affected those charge weights?? IDK.
CJ

 

[Ned Ludd]

I think @acloco has a valid point asking that again. Something ain't right with those results. Not only are they all within a narrower than normal vertical spread across a wide charge range, it looks like they are actually going lower in vertical as charge goes up. Maybe it's just the way I'm looking at the pic. My gut says there is something wonky going on with the rest causing those results, but who knows. You didn't do any holdovers at any point in the test did you?

A 1.25" vertical spread at 100 yd solely due to increasing charge weight is not unusual. Nor is it unusual for shots to go both above and below the POA at that distance because of muzzle launch angle. The OP's results may be hard to interpret clearly, but they are not unexpected. Increasing the test distance to at least 300 yd, or even better, 400 to 600 yd, will solve these issues. The downside to using increased distance for a ladder test is that external conditions such as wind and terrain can play a much larger role, also potentially making clear and unambiguous interpretation of the results more challenging. As has been noted by others, the use of wind flags is critical, and I would also add that choosing a testing day with minimal wind is wise when doing a ladder test at longer range.

 

[Full Chisel]

A 1.25" vertical spread at 100 yd solely due to increasing charge weight is not unusual.

The OP said they ranged from 1/2 to 1.25. That's 3/4". But yes, they may likely be very different at distance. I'm sure you're correct, but I have never seen them continually progressing downward like that over that wide a range. At least that's what it looks like in the pic. I still say something's odd.

 

[Full Chisel]

Nevermind. I'm going to assume that I read that picture wrong and it should be rotated 90 deg ccw, which would make more sense. I read his op at least three times and kept concluding he was aiming at the long horizontal line. I thought that was an odd way to shoot a ladder, lol. Proceed.

 

[acloco]

300 yards will provide a MUCH clearer view in the load ladder.

Use the SAME POA (point of aim) for every shot. Do NOT adjust scope or rest.

Do not cheat and try to see each shot before the next. Concentrate on you.

Personally, get rid of the rest. Have not experienced a rest that will provide a comfortable eye relief or ergonomic hold/squeeze of trigger on the rifle. They are too long, too short, too wide, or too wobbly. Sorry...it just is what it is.

I use a bipod and a rear sandbag. Squeeze the sand, concentrate on your breathing (gently squeeze when at/towards the bottom of the exhale)....and let that puppy fly!

Do not sit on the scope for eternity. Get in, get on, and don't turn the power up. 10-14x is plenty. You will probably see your heartbeat in the crosshairs anyways. Breathe. Exhale thru mouth, breather normal, start exhale, start the squeeze, continue applying pressure. EVERY shot should be somewhat of a surprise. Let it free!!!

 

[CaptJim]

300 yards will provide a MUCH clearer view in the load ladder.

Use the SAME POA (point of aim) for every shot. Do NOT adjust scope or rest.

Do not cheat and try to see each shot before the next. Concentrate on you.

Personally, get rid of the rest. Have not experienced a rest that will provide a comfortable eye relief or ergonomic hold/squeeze of trigger on the rifle. They are too long, too short, too wide, or too wobbly. Sorry...it just is what it is.

I use a bipod and a rear sandbag. Squeeze the sand, concentrate on your breathing (gently squeeze when at/towards the bottom of the exhale)....and let that puppy fly!

Do not sit on the scope for eternity. Get in, get on, and don't turn the power up. 10-14x is plenty. You will probably see your heartbeat in the crosshairs anyways. Breathe. Exhale thru mouth, breather normal, start exhale, start the squeeze, continue applying pressure. EVERY shot should be somewhat of a surprise. Let it free!!!

Points well taken. Thanks very much!
CJ

 

[newbieshooter]

Nevermind. I'm going to assume that I read that picture wrong and it should be rotated 90 deg ccw, which would make more sense. I read his op at least three times and kept concluding he was aiming at the long horizontal line. I thought that was an odd way to shoot a ladder, lol. Proceed.

I shoot my load development shots along a horizontal line. I don’t think that is odd.

 

[Full Chisel]

I shoot my load development shots along a horizontal line. I don’t think that is odd.

You shoot a ladder on a horizontal line?
I shoot an OCW on a horizontal line.

 

[CaptJim]

You shoot a ladder on a horizontal line?
I shoot an OCW on a horizontal line.

I shot my ladder test along the horizontal line because I figured at 100 yards there would be little variation in points of impact and I hoped the differences would be measurable. I also figured If each POA was at the same horizontal level along the line the results would be valid and easier to measure. Had I shot at a single POA I thought It would be too cluttered. In retrospect I wish I had chronographed them as well which would have provided more info. I plan to test further next week, including chrono data.
CJ

 

[Full Chisel]

I shot my ladder test along the horizontal line because I figured at 100 yards there would be little variation in points of impact and I hoped the differences would be measurable. I also figured If each POA was at the same horizontal level along the line the results would be valid and easier to measure. Had I shot at a single POA I thought It would be too cluttered. In retrospect I wish I had chronographed them as well which would have provided more info. I plan to test further next week, including chrono data.
CJ

Man, I thought I'd interpreted your graph wrong, meaning the orientation of it. If you're saying that you actually had the target oriented as in your pic, then I am back to my original stance. What I mean is I find the shots' downward vertical poi trend as you go through the charge range not normal, at least compared to any load workup I've done. Maybe somebody here can really look at it and explain it. the only explanation I'd have for that is you're at max, but I really think you're well under max.

When somebody says ladder, I interpret that strictly as shooting to ONE poa and looking at the shots essentially walk up paper (or down, or sideways). Or, if someone says OCW, then I look for groups shot horizontally along a line, or multiple lines. I knew this wasn't a ladder, but I thought it could be a one shot OCW shot with the paper oriented the way you have it shown where you're moving rifle L-R across target, OR an OCW shot with the paper rotated 90* ccw where you're moving rifle Lo-Hi as you progress through charges. If the latter, then I would need to go back and look at it again. If the former, then I say there's something odd going on with that downward POI trend as you move L-R. There are several ways to get to the same data, so whatever works. So don't trash anything yet. You really are looking for where the vertical poi is for each charge relative to a poa. As long as you know you poa and you have a shot on paper, then you can extract that.

So the question is did you shoot that with the paper oriented like it is in your pic?

 

[Ralph Littlefield]

It may be a good idea to shoot this again.

As was already mentioned, it seems odd that as powder charge is increased, all the rounds have a lower POI.

 

[CaptJim]

Man, I thought I'd interpreted your graph wrong, meaning the orientation of it. If you're saying that you actually had the target oriented as in your pic, then I am back to my original stance. What I mean is I find the shots' downward vertical poi trend as you go through the charge range not normal, at least compared to any load workup I've done. Maybe somebody here can really look at it and explain it. the only explanation I'd have for that is you're at max, but I really think you're well under max.

When somebody says ladder, I interpret that strictly as shooting to ONE poa and looking at the shots essentially walk up paper (or down, or sideways). Or, if someone says OCW, then I look for groups shot horizontally along a line, or multiple lines. I knew this wasn't a ladder, but I thought it could be a one shot OCW shot with the paper oriented the way you have it shown where you're moving rifle L-R across target, OR an OCW shot with the paper rotated 90* ccw where you're moving rifle Lo-Hi as you progress through charges. If the latter, then I would need to go back and look at it again. If the former, then I say there's something odd going on with that downward POI trend as you move L-R. There are several ways to get to the same data, so whatever works. So don't trash anything yet. You really are looking for where the vertical poi is for each charge relative to a poa. As long as you know you poa and you have a shot on paper, then you can extract that.

So the question is did you shoot that with the paper oriented like it is in your pic?

Yes, I shot from Left to right aiming at the horizontal line for each shot. Each shot increased by
.2 .4 grain. Though I didn't chrono, my assumption was that the shots next to each other and on the same horiz plane were close to the same velocity. I plan to shoot and chrono some more with 3 shots/chg wt. That should provide more concrete data.
CJ

 

[Ccrider]

Velocity tells you something- may just be that your barrel needs cleaning; could be that you somehow did not put enough powder in that one case, or that the bullet did not seat right, or was bad; or that the primer was out of spec and did not ignite the same. Who knows?

Velocity tells you something, especially if it is far away from your other shots or expected.

 

[CaptJim]

Update...
Went to range Wednesday, beautiful day, sunny, no wind.
I had selected three charge weights to try with 3 rounds each from the concrete bench at 100 yds. These were all loaded with the same Lapua brass and 155 gr Scenars at .010 off.
The loads I picked were 42.2, 43.0 and 44.2 of the same Shooter's World Precision Rifle I had used for the original test.
I forgot to bring the chrono and a rear bag (used some wadded up rags ).

The 42.2and 44.2 loads were unremarkable, but the 43.0 I think may be GTG. I loaded a fourth round for the 43.0 as I thought it would be the best shooter. Will try at 300 and chrono next time.
Thanks to all for your help
CJ