Maintaining Pressure doing seating depth test

[JFrank]

Those are very consist velocity’s,
I’m looking forward to the day I can get to a range with some decent distance atm the moment I’m stuck at the 100 yard line.

I use a tuned beam scale… in your area ‘ the Tacoma sportsman club shoots out to 600 yards

 

[BJung]

Here is an observation from a test I did. I wanted to know if a 38-148WC seated to the first grease groove was less accurate than seating the bullet so the case was crimping at the second grease groove. At this length, the OAL is the same as a .357-148 WC seated to the first grease groove. I shot a series of different loads of BE for each seating depth. These are the tightest group of each. The distance is about 18 yards are more shot from a sandbag on a bench. If I was interested in your hypothesis, then I would guess that the best group of a 38-148WC seated between the two bands would be 2.85gr. I'm happy with my currently loads.

 

[Laphroaig]

In my experience seating depth in rifle cartridges doesn't have much effect on velocity unless you are jamming into the lands. Pistol cartridges are another story and are very sensitive to seating depth.

I recently chrono'd some .223 80 SMK's with a 0.030" variation in COL with virtually no change in velocity or group size between 3 10-shot groups:

0.015 from lands, 2578 fps, ES 81, SD 23
0.035 from lands, 2569 fps, ES 91, SD 25
0.045 from lands, 2588 fps, ES 62, SD 23

My thought was using QL and or GRT to simulate the pressure differential at the various seating depths to maintain the pressure values, atm I can only adjust at .01 gr so it’s a bit course +- 140 psi. I’ve ordered an autotrickler that will give me .001 of adjustment of +- 70 psi. I was just wondering if anyone else has tried to maintain the pressure values in that manner when adjusting the seating depth.

I doubt that 0.01 gr. is going to make much difference in anything let alone 0.001 gr.

Find the node with ocw or ladder then do seating depth

This is the commonly accepted practice when checking seating depth w/r to group precision.

 

[Bcwitt]

Im assuming the OP is talking about a rifle. I set depth before working up the charge. Much more time & component efficient.

 

[GTS Dean]

Powder charge stays the same. Only adj the seating depth 0.003"-0.005"/step. What your doing is changing the pressure curve. Either increasing it or decreasing it in small volume increments.

What I've settled on the last several years is to work on powder charge ladders with constant brass volume and ogive seating depth. Once I pick the most accurate/repeatable charge, I ladder from a safe setback toward the lands in increments of .003-.004". I've seen some incredible results with this approach. I can always fine-tune more later, but this method is simple and reliable.