Gunsmithing Any thoughts on structured barrels?

[Ledzep]

A question - is it your experience to see SD's flatten as the barrel carbons/coppers back up? Not specific to or barrel. My intuition says "yes". With that: the question becomes how many foulers should be shot?

From a stripped clean barrel, within the first 2-10 shots, sometimes you will see goofy shots related to velocity. More rarely you'll see in the first 1-3 shots after cleaning some accuracy fliers. Suppressors can also cause 1st shots in a string to have low velocity (20-50fps slow). Not sure the physics behind that but I've seen it enough times with various combinations to keep an eye open for it.

Beyond that, I have not really noticed SD's to change unless you change bullet type, powder lot or type, or sometimes primer type (some cartridges are more or less sensitive to this). If you shoot 20-30 shot strings and get the SD on that, it stays within about 1fps pretty much every time until the fouling builds up to the point of significantly increasing peak pressure, at which point SD's and precision both suffer.

 

[JB.IC]

View attachment 8339134View attachment 8339142View attachment 8339149
6xc - Factory rounds
Tubb Gun, Vortex Gen lll, Tubb muzzle brake, Magneto Speed used for data.
60shots- group shown is 56-60- 12minute cycle.
100yds, Phoenix Bipod, rear bag, prone.
69deg ambient. Final barrel temp 110max read with a chamber value of 93deg. Wind 11:00 2-5mph. 34%RH
Stripped clean cold bore shot included.
2 Witnesses.

A question - is it your experience to see SD's flatten as the barrel carbons/coppers back up? Not specific to or barrel. My intuition says "yes". With that: the question becomes how many foulers should be shot?

Yes. I’ll send you a plot here in a few mins.

Edit:
We’ll never mind, I was changing too many reloading variables in the plot to make sense of it.

 

[John Baker]

View attachment 8339134View attachment 8339142View attachment 8339149
6xc - Factory rounds
Tubb Gun, Vortex Gen lll, Tubb muzzle brake, Magneto Speed used for data.
60shots- group shown is 56-60- 12minute cycle.
100yds, Phoenix Bipod, rear bag, prone.
69deg ambient. Final barrel temp 110max read with a chamber value of 93deg. Wind 11:00 2-5mph. 34%RH
Stripped clean cold bore shot included.
2 Witnesses.

A question - is it your experience to see SD's flatten as the barrel carbons/coppers back up? Not specific to or barrel. My intuition says "yes". With that: the question becomes how many foulers should be shot?

max	3175​
min	3164​
Ave	3166.7​
ES	11​
SD	3.743142​

Not the best at inserting charts and data....
Focusing a bit on SD drift. This represents a 30shot string with the shots 21-30 being shown. These are hand loads using Berger 215's. This barrel has north of 2000rds thru it. A Tubb Gun in 300Norma.
We recently had a demo at SHOT in which our MRAD had 30-40rds plus thru it on continuous demonstration/different shooters use. The final rounds were on a 2075yd target with a first round impact and 3 follow up. A stable SD is required to achieve that performance. An "Objective Anecdotal" moment with a couple of dozen witnesses, which was all levels of Mil and LE. The temperature was 49deg and the gun was running a suppressor. The barrel maximum heat was 81deg, chamber 61, suppressor 210degF. I would Hypothesize that a cooler barrel will hold SD's longer.

 

[John Baker]

From a stripped clean barrel, within the first 2-10 shots, sometimes you will see goofy shots related to velocity. More rarely you'll see in the first 1-3 shots after cleaning some accuracy fliers. Suppressors can also cause 1st shots in a string to have low velocity (20-50fps slow). Not sure the physics behind that but I've seen it enough times with various combinations to keep an eye open for it.

Beyond that, I have not really noticed SD's to change unless you change bullet type, powder lot or type, or sometimes primer type (some cartridges are more or less sensitive to this). If you shoot 20-30 shot strings and get the SD on that, it stays within about 1fps pretty much every time until the fouling builds up to the point of significantly increasing peak pressure, at which point SD's and precision both suffer.

It would be interesting to have a conversation with you. We have enjoyed watching the Hornady content.