JimGnitecki
Member
- Joined
- Mar 28, 2010
- Messages
- 1,258
You have seen (above) that in my latest efforts on COAL control, I got the COAL extreme spread variation down to about .003" and the average COAL variation down to .0017". I had also measured the COAL that would have the ogive of the bullet just barely (.002") short of the rifling, as being about 1.159".
I made 25 cartridges at that COAL, and took them and my SIG P210A to the range to see how my P210A liked them.
The P210A HATED them! It first resisted even swallowing them, refusing to fully close the slide on a percentage of them! It also literally spat them out in a shotgun pattern instead of the nice small groups I had hoped for, in effect asking me "Why did you feed me this miserable excuse for a load??"
Then, to add insult to injury, when I started to fire an assortment of rounds that each had minor defects because they were assembled during the resetup of the Dillon XL750 for the longer COAL, the pistol laughed in my face by firing one 5-shot group that had COALs with an ES of .0085", into a group that was 0.94" across!
This chart summarizes the sorry story on the 25 carefully assembled rounds:
I THINK figured out what was wrong: I was skating on too thin ice with the bullet ogive way too close to the rifling (despite what I thought was a good measurement that indicated that the COAL at which the ogive would touch the rifling did not occur until above 1.1610").
I say this because notice the amount of vertical stringing I got with this batch of cartridges. And remember, I said that the P210A would not go into proper battery on some of the cartridges until I pushed the slide closed an additional 1/32" or 1/16" or so. And notice the ES on the muzzle velocities.
I figure some of the cartridges had the bullet trying to load into the rifling, and the rest were awfully close, since the entire ES on COAL was just .003". Some rifles like that, but this pistol does NOT.
So, now I know that good COAL control via the RIGHT shape of bullet seating insert and free-floating dies, and perfect .374" taper crimp, are NOT going to do the job when the COAL places the bullet ogive (not tip) too close to the rifling (at least on THIS firearm). The long COAL here lowered the combustion chamber pressure but the immediate or "too soon" contact with the rifling probably RAISED the pressure. And worst of all, it created inconsistency, despite the close control of COAL. i.e. I undid all the good effects of reducing COAL variation by CREATING variation due to inconsistent distance from, or even into, the start of the rifling.
So, my next batch of cartridges will be in the 1.152" versus 1.159" COAL neighbourhood, and I'll see how THAT works.
For those who might say that the group sizes shown are rather ok given a 70 year old shooter shooting through progressive lens eyeglasses, from a 6" carpeted cube rest at 25 yards: They might be ok for some pistols, but not for this P210A which has shown it can do much better, even under those limitations.
Jim G
I made 25 cartridges at that COAL, and took them and my SIG P210A to the range to see how my P210A liked them.
The P210A HATED them! It first resisted even swallowing them, refusing to fully close the slide on a percentage of them! It also literally spat them out in a shotgun pattern instead of the nice small groups I had hoped for, in effect asking me "Why did you feed me this miserable excuse for a load??"
Then, to add insult to injury, when I started to fire an assortment of rounds that each had minor defects because they were assembled during the resetup of the Dillon XL750 for the longer COAL, the pistol laughed in my face by firing one 5-shot group that had COALs with an ES of .0085", into a group that was 0.94" across!
This chart summarizes the sorry story on the 25 carefully assembled rounds:
I THINK figured out what was wrong: I was skating on too thin ice with the bullet ogive way too close to the rifling (despite what I thought was a good measurement that indicated that the COAL at which the ogive would touch the rifling did not occur until above 1.1610").
I say this because notice the amount of vertical stringing I got with this batch of cartridges. And remember, I said that the P210A would not go into proper battery on some of the cartridges until I pushed the slide closed an additional 1/32" or 1/16" or so. And notice the ES on the muzzle velocities.
I figure some of the cartridges had the bullet trying to load into the rifling, and the rest were awfully close, since the entire ES on COAL was just .003". Some rifles like that, but this pistol does NOT.
So, now I know that good COAL control via the RIGHT shape of bullet seating insert and free-floating dies, and perfect .374" taper crimp, are NOT going to do the job when the COAL places the bullet ogive (not tip) too close to the rifling (at least on THIS firearm). The long COAL here lowered the combustion chamber pressure but the immediate or "too soon" contact with the rifling probably RAISED the pressure. And worst of all, it created inconsistency, despite the close control of COAL. i.e. I undid all the good effects of reducing COAL variation by CREATING variation due to inconsistent distance from, or even into, the start of the rifling.
So, my next batch of cartridges will be in the 1.152" versus 1.159" COAL neighbourhood, and I'll see how THAT works.
For those who might say that the group sizes shown are rather ok given a 70 year old shooter shooting through progressive lens eyeglasses, from a 6" carpeted cube rest at 25 yards: They might be ok for some pistols, but not for this P210A which has shown it can do much better, even under those limitations.
Jim G
