Which seating depth would you choose?

N

nonliberal

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This is a 30X44 that I am working up a load for with 130 grain bullets. As the target shows I used 5 different seating depths starting at jam. The top right hand group was actually a 4 shot group and I marked the shot that should have been in the 39grain range.

This was shot at 100 yards ignoring the flags other than a very strong gust and not holding for wind so I could get a feel for wind drift of each load (Just put dot on the cross and fire). Pretty similar to what Tony Boyer says to do in his book. I did the work to get the data but now I'm trying to figure out what to do with it. Nothing is really jumping out at me.

I see 2 flaws in what I wrote down
1. The second row from the bottom should say 1.9275 not 57
2 The bottom row should say 1.920 not 120

IMG_4776.jpg
 
Last edited by a moderator:
IF
the wind was left to right or right to left look for groups with small vertical...
since you did not watch the wind not much else( i think)

mike in co
 
The wind was from left to right switching but 90% left to right. I just tried to ignore it when shooting so I wouldn't hold and scew the results.
 
The "low right" holes are typical given a left to right wind. Decide which depth produces the least vertical and run with it.

Can't explain the groups with "low left" holes except to say maybe the left to right wind wouldn't support a good group. Looks like 38.5 and 39 is the way to go regardless of the seating depth.
 
Shoot more groups while paying close attention to your wind flags. You may decide to rethink what you think you know.


Glenn
 
Boyd Allen said:
Seems like I would do some more testing, paying attention to everything, around 1.9257 at 38.5 gr.
Click to expand...
That is the plan. I loaded ammo to the 1.9275 seating depth so I can shoot groups watching the flags at 38.5, 38.7, 39, 39.3, 39.5, 39.8. I'm not going to hold for wind, but I will try and be careful picking a condition.

Thanks guys.
 
Well the end result was none of them worked well enough to keep. Switching bullets and starting over.
 
My opinion only.

1.927 at 38.5 grns is where I would start. Here is my reasoning.

Look to your groups left and right of it and then at the groups above and below. What I picked is a median which gives a little play in seating depth and in charge weight, without going (in general) over a half a bullet of vertical and they seem to cut the wind. Your jumps in seating detph seem to be a little large between them and you don't have to much of train wreck. Start where I said, stay with half clicks (38, 38.5, 39) and tune seating depth at .002/.003 at a time. Looks to me the barrel will really shoot from what you got there.

Even though you shot some fairly good groups toward the top of the page, stay away....look how the black rings are at one side of the bullet holes...that's a teaser you'll never be able to stay on top of...bullets are to unstable. At the groups I referenced...see the difference in the rings around the holes.

Good luck
Hovis
 
HovisKM said:
My opinion only.

1.927 at 38.5 grns is where I would start. Here is my reasoning.

Look to your groups left and right of it and then at the groups above and below. What I picked is a median which gives a little play in seating depth and in charge weight, without going (in general) over a half a bullet of vertical and they seem to cut the wind. Your jumps in seating detph seem to be a little large between them and you don't have to much of train wreck. Start where I said, stay with half clicks (38, 38.5, 39) and tune seating depth at .002/.003 at a time. Looks to me the barrel will really shoot from what you got there.

Even though you shot some fairly good groups toward the top of the page, stay away....look how the black rings are at one side of the bullet holes...that's a teaser you'll never be able to stay on top of...bullets are to unstable. At the groups I referenced...see the difference in the rings around the holes.

Good luck
Hovis
Click to expand...

That's a great observation Hovis! I never really noticed the black rings being different until you pointed it out.
Nothing worked to my satisfaction with these 130 grain bullets. A friend gave me a handful of 118s and the first thing I tried shot better than my best results with 130s.

Isn't it typical that this barrel prefers a bullet that I don't have anymore of...

If anyone has any BIB 118 (10) ogive they want to sell, I'm looking to buy.
 
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