ladder test question

[dmax1800]

I was shooting a 22-250 with 55 gr Sierra GK and Varget. I shot 2 ladders at 200 yards to test a small range of powder with a different primer. The previous primer (Rem 9 1/2) was about 200 fps slower than book and I wanted to see if a different primer (WLR) would increase velocity and not disturb the node. Their was virtually no wind.

In the 1st ladder, shots 4 and 5 were 3/16" apart (center to center) with no vertical spread and about 1" to the right of the target. In the 2nd ladder, shots 4 and 5 were 3/8" apart (center to center) with 1/8" vertical spread and about 1/2" to the left of the target.

So my question is with shots 4 and 5 so being so close in both ladders, what does it mean when in the 1st ladder they were an inch right and in the 2nd ladder they were 1/2" left of the target???

 

[texastrophy]

It doesn't take much wind to move a 55 gr bullet 3/4" at 200 yds. I would ignore the windage results.

 

[Mark611]

its the difference in the velocity, also known as spin drift IMOgun)

 

[dmax1800]

I've done some more research and have the following theories. I was using a front shooting rest, so I had the stock at exactly the same spot for each shot.

The gun was a lot warmer in the pickup going to the range than the outside temp (10F). I got everything set up before I moved the gun from the pickup to the bench.

1) As the stock (cheap Rem plastic stock) acclimated to the ambient temp, it put different pressure on the barrel, which is not free floated. Thus a shift in the POI.

2) The rifle just might need more than 5 fouler shots (or even 11 shots) for it to loosen up. I cleaned the barrel really well before going to the range. I shot 5 foulers, then the 6 shots in ladder 1 and finally 6 shots in ladder 2.

3) I waited longer (2 minutes) between shots in ladder 1. I waited about 30 seconds between shots in ladder 2. Maybe the barrel was slightly warmer in ladder 2 than in ladder 1. With it being 10 degrees outside, it never did get more than barely warm, much less hot.

Does any of this give anyone more insight into this???

 

[Mark611]

ok if your cleaning your barrel that will make a difference! I don't clean my barrels once they have proper copper fouling accept to remove powder fouling if I'm not gonna be shooting for awhile once the copper starts to affect accuracy then I'll clean it out gun)

 

[rpierce]

I think doing the ladder test at 200 might not be the best idea. 300 minimum. Do it as far out there as you can, results will be easier to see. But based on your results 4 and 5 seem to be a good area to be in. Maybe leave the gun outside for 20 minutes or so before you start shooting also since there is a big extreme from truck to outside at this time of year. I do them at 1000 yards. I will find a load for a new barrel in 15 rounds. For my 284 win I got a 2" group with .8 gr spread in powder at 1000. That was a very easy one to read. I tried the same ladder test in my other gun and it gave me the same results with the same powder charges. Both guns shot the same load equally well. Makes having a backup gun easy since both guns shoot the same ammo. Good luck and let us know how it goes.

 

[dmax1800]

I think doing the ladder test at 200 might not be the best idea. 300 minimum. Do it as far out there as you can, results will be easier to see. But based on your results 4 and 5 seem to be a good area to be in.

Yes, I've heard that the longer the distance, the better. My rifles are not ELR hunting rifles. I was concerned that they might not be accurate enough at 300 yards. Too much variation just due to inaccuracy resulting in inconclusive results. If the rifle is 1 MOA, then it could group 3" at 300 yards. One shot might be high and one low just due to inaccuracy, not rising with increasing powder charge. I agree that shots 4 and 5 seem to be in the node, but I'm still wondering (concerned) about the POI shift between ladder 1 and ladder 2.

I'll try leaving the rifle on the bench longer to acclimate and also try more fouling shots to see if it likes more fouling instead of a clean barrel.

I'm wondering now if the plastic stock and changes in temperatures are major contributors to the POI shift.

 

[rpierce]

Most factory barrels shoot better after they've been dirtied up a bit. Just been my experience with them. Some custom barrels are the same way after a really good cleaning. I remember some of the guys taking 10-15 sighters during tryouts for the national team to get their barrel fouled up and warmed up before shooting their 20 shots for record. Also pluggin in your bullet info to jbm says that a 1mph wind at 200 moves the bullet .6 inches. I would say that is the reason for the left and right.

 

[Mark611]

their are allot of variables when doing this type of shooting, assuming you have you loads perfected to your barrel with the correct OAL and bullets it shoots the best proper case prepping and a powder charge that is giving you the best results? then look at your set up! if your using a factory synthetic stock that's not bedded and has no aluminum bedding block system IMO you will not see the results your looking for! if your looking for target rifle accuracy in your set up a good stock properly bedded will greatly improve your results, the plastic stocks from out of the box rifles have to much flex! they are not rigid enough for serious long distance shooting! also take in account everything else that go's into a decent rifle set up scope, rings, scope base? the list go's on, most factory rifles have a 1 MOA out of the box accuracy claim, and the further you go out the more the MOA opens up, just my thoughtsgun)