Ladder test new bullet

[RustyRick]

1st test using this bullet. 140 gr TTSX BT

7mm RM I loaded .5 grains in each subsequent load. The square hash marks are 1 MOA. And shot at 300 yrds.

My question is - I have 2 more test groups with 2 different powders.

I'm thinking I probably have what I'm looking for already, so I may as well pull the bullets on these 2 test groups.

 

[Trnelson]

1st test using this bullet. 140 gr TTSX BT

7mm RM I loaded .5 grains in each subsequent load. The square hash marks are 1 MOA. And shot at 300 yrds.

My question is - I have 2 more test groups with 2 different powders.

I'm thinking I probably have what I'm looking for already, so I may as well pull the bullets on these 2 test groups.

Why wouldn't you want to get the data from the other loads? Having a known substitute load can be very valuable if powder A is inobtainium. I have four different combinations that all shoot MOA or better in my rifle. During the powder shortage I just switched powder and kept going like nothing happened.
If you repeat your published test of 8 shots each you are only shooting 16 bullets extra so it's not like you are going to spend a hundred rounds of barrel life on a wild goose chase. Just a thought. Have fun. BTW, that is a nice group for 300.

 

[jrock]

If you have more test loads you might as well shoot them. Never can have too much data but what you have so far is very good. I've learned to be thorough when working up a new load so I leave no stone unturned and document everything.

 

[ColoYooper]

I'd highly recommend re-running the ladder test at 600 yards if you have that range available. With 8 shots, each 0.5 grains different, you should see 2 or 3 distinct nodes where the velocity deltas become significant enough that you get some separation in your groups. The problem with performing the ladder test at 300 yards is any deltas in velocity are lost in the noise.

 

[jrock]

Very true on the distance. I personally don't run ladders at anything less than 600 and really like 800 yards if the velocity is over 3000 fps. Sometimes I will shoot a round robin ladder 3 times on the same target, effectively making a group which can provide more distinguishable results than the single shot per charge method.

 

[FURMAN]

I agree with ColoYooper and jrock.

 

[RustyRick]

My guess is that the yardage you shoot the ladder test at depends on the scope power. You obviously don't want your imperfections to influence your results. So at 600 yrds you'd really need a no-wind, no-mirage, 50X scope day. ???

 

[FURMAN]

You really do not want to shoot a ladder in mirage. I would try to avoid wind but you should be fine as long as it is not having an affect on your hold. 600 yds should be no problem with a 14X or higher. I prefer 24 or 32X. The point of the ladder is to see a small extreme spread(small elevation changes in bullet impact) across a relatively large powder charge difference. You are trying to find a node that will be tolerant to changes in atmospheric conditions.

 

[ColoYooper]

You clearly have a "shooter" there in your rifle, but like a lot of us you probably want to take it to the next level. The Ladder Test finds that sweet load that for a 100 reasons you have a round that is a bit hotter than the rest (due to extra powder, increased neck tension, lighter bullet, heavy primer, warm powder...) the bullet will leave the barrel on a correctly Ladder Tested rifle as the harmonic oscillation as at the bottom of its ring, but because it is hotter, it just happens to shoot high and land with the rest of the group. Conversely, a slow bullet will leave the barrel at the top of the harmonic ring and automagically self correct to land with the rest of the group. As previously mentioned, this test can be successfully performed with a 9x scope and some wind...(note my groups always show some horizontal separation due to wind, but it's easy to find the nodes.) OK...On Occasion it was "easy" to find the nodes. A majority of the time I repeated the test multiple times increasing, then decreasing the loads and it was often like reading tea leaves to finally determine conclusive nodes. I then select the middle charge for that node, and work on my form.