bullet stability

A

afrench

Member
i noticed something odd on my targets from this weekend. this target was at 200 yards.

this is a fairly new (~400 rounds) 6 groove Shilen 14 twist barrel. i haven't chronographed this barrel but the velocity should be in the 3300-3350 range. i'm shooting Tucker's 67 gr .790 FB. after seeing this, i need to run a patch down it and check the twist.

since i'm already shooting .790s, i guess my only option is to find the next higher node with powder??

 
afrench,

I didn't elaborate more because I need more information.

1. Have you been shooting this load successfully in the past (no oblong holes) and this just cropped up?

2. What kind of powder are you using?

3. Neck Tension?

4. How did you go about finding the seating depth you have.


Thanks
Hovis
 
Hovis, thanks. i'm interested in what you've found by varying the seating depth to cause or cure bullet instability.

the lot of .790 Tucker's i have shoot exceptionally well in pretty much every other barrel i've shot them in. i went back and looked at some targets with that barrel shooting Berger columns, and they do the same thing. so, yes, my typical load with either Columns or the Tuckers shoot well in other barrels (nice round holes).

i've used both 133 and N200, and have oblong holes with both powders. 133 gets a .256 neck bushing for flat bases and the 200 seems to like .257 or .258 depending on the feel while seating a bullet. i typically use 8.3 thou neck thickness on my brass.

to find seating depth, i use the method Tony talks about in his book. seat a bullet long and let the lands push it back into the case. this is what i call full jam. from there, i come back 8-10 thou from FJ to start with button pulled barrels. so, i'm roughly 8-10 thou into the lands.

for both powders, i had to come down about 3 tenths of a grain for this 6 groove compared to my 4 grooves to get to a node. i haven't chronographed this barrel yet, but i suspect that this barrel is about 100 fps slower than my 4 grooves at this node.

maybe that answers your questions. thanks for the input.
 
Elliptical Bullet Holes

afrench said:
i noticed something odd on my targets from this weekend. this target was at 200 yards.


I had that happen once when the target was at about 75 degrees to the line of fire rather than 90 degrees to line of fire.
All of my bullet holes were of the same elliptical appearance.
It would be nice if it was something simple to fix like that was.
Probably not a simple fix tho.

Good Luck with finding the culprit.
CLP
Click to expand...
 
I'm going to make some assumptions here so correct me if I'm wrong.

1. It seems this barrel has been doing this all along and with two bullets.

2. You have used tony's method and have run the gauntlet with them so to speak. 3 - 3shot groups with a .6 or so spread between low to middle and middle to high ( I generally run 28.2, 28.8 & 29.4 grains) From .010 off jam to .035 off jam in .003 increments.

3. You have checked your crown...seen this be the problem when multiple bullets do it.

4. You have checked the land marks on the bullets to make sure they are consistant all the way around the bullet. Also, seen this do it with multiple bullets when marks are uneven.

5. The range is square....Good point Doc.

If all the above is true, then you have either a wrong twist barrel or a very poor barrel.

Hovis
 
yep, done/checked all of those things.

it'll probably have tomato vines hanging off of it in a few weeks...
 
A couple of years back Tom Libby had something similar happen at Visalia. The afternoon before he had his rail gun dialed in at a very light load. The next morning it was pretty cool. 45 to 50 degrees if I remember correctly. When he started, his sighter literally looked like a shotgun patern with bullet holes border to border on his sighter. The second match got a bit tighter. The long and the short of it was that the combination of shooting the very light load in cooler temperatures was causing the instability of the bullets.

Tom, please feel free to jump in with more detail.
 
afrench,

Bummer....I was counting barrels the other day. I have 12 barrels under the bed that were duds. I don't remember any of them not stabilizing though, just wouldn't group.

Hovis
 
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