Overpressure differences. Where to next?

rick357 said:
and 0.020 is 20 thousandths or 2 hundredths = 2/100ths = 0.02.

But the statement "Headspace is 0.02" from the lands." still doesn't make any sense at all. Thinking he might mean it is 0.02" jump to the lands but one cannot measure this by using OAL. Should be using the 'ogive'.
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It's a .02" jump to the lands. I loaded some dummy rounds and marked the bullet before inserting it in the chamber. Once it was short enough not to have a mark from the lands, I shortened it another 0.02". I've also marked some of the live rounds while at the range and checked to make sure nothing was touching the lands.
 
groundrush said:
It's a .02" jump to the lands. I loaded some dummy rounds and marked the bullet before inserting it in the chamber. Once it was short enough not to have a mark from the lands, I shortened it another 0.02". I've also marked some of the live rounds while at the range and checked to make sure nothing was touching the lands.
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It was pretty clear what you meant, for some power of deduction is severely lacking apparently.
 
groundrush said:
It's a .02" jump to the lands. I loaded some dummy rounds and marked the bullet before inserting it in the chamber. Once it was short enough not to have a mark from the lands, I shortened it another 0.02". I've also marked some of the live rounds while at the range and checked to make sure nothing was touching the lands.
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And 0.02" should be enough to keep the bullet from the lands assuming that the bullets are all identical. If you are using all one make and type of bullet then this should be the case as 20 thou is a fairly reasonable distance and should be enough to accommodate the differences in bullet to bullet ogive to tip length. This is definitely not the case if you are using other bullet makes, even though they might both be called BTHP or whatever.
 
rick357 said:
And 0.02" should be enough to keep the bullet from the lands assuming that the bullets are all identical. If you are using all one make and type of bullet then this should be the case as 20 thou is a fairly reasonable distance and should be enough to accommodate the differences in bullet to bullet ogive to tip length. This is definitely not the case if you are using other bullet makes, even though they might both be called BTHP or whatever.
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Yes, so far all I have been using are Hornady Match 68gr BTHP. If I change manufacturers or bullet weight or style, I will need to start all over again to determine a new OAL for that load. I still check once in awhile to make sure there isn't a difference in bullet profile that causes jamming into the rifling.
 
Primer condition is not a very reliable method of watch pressure. That said, the same load with the same primer in the same rifle should look similar, one day to the next.

Velocity is a good surrogate for pressure. Was the velocity the same on each day?

One variable that can crop up is bullets in the box came from more than one machine. Should not happen with match bullets.
 
Ganderite said:
Primer condition is not a very reliable method of watch pressure. That said, the same load with the same primer in the same rifle should look similar, one day to the next.

Velocity is a good surrogate for pressure. Was the velocity the same on each day?

Unfortunately I didn't have the chrony out the first day. It was my first batch of reloads and I was interested in finding the safe pressure range and likely charge weights for best accuracy. I didn't want to load a bunch of rounds at the higher end of the published data just to take them apart due to excessive pressure.
Velocity is a good surrogate for pressure, if you gradually work up the loads and watch for rapid increases. I couldn't find (and don't expect) anything saying this velocity is good for X rifle or X barrel. Without a chrony, brass and primer condition seems to be the best pressure indicators. Thats why it really surprised me when good brass and primer indicators on one day were not so good on the second day.

I'll be loading up more rounds this weekend at and below the lower end of published data. It seems this rifle likes these bullets going less than 2800 fps for consistent grouping. I'll double check settings and measurements to ensure consistency. I'm only using an inexpensive Gem 20 electronic scale and a hand trickle for each powder drop which can only give me an accuracy of +/-0.02 grains. Slower process, but that's life on a budget :)
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