.308win rifle ogive migration (non F-class/bench rifles)
- Thread starter squib
- Start date
When switching bullets, powder, primer, cases or when accuracy drops off.
The reason for including the powder, primer, cases is potential pressure increases. Obviously when you change bullet types you would want to check Ogive length for that bullet type. I have a buddy that checks ogive for every box of 100 he reloads. When he opens a new box he checks the length then loads those 100. Overkill but it works for him.
The reason for including the powder, primer, cases is potential pressure increases. Obviously when you change bullet types you would want to check Ogive length for that bullet type. I have a buddy that checks ogive for every box of 100 he reloads. When he opens a new box he checks the length then loads those 100. Overkill but it works for him.
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OK, so 1 vote for set it and forget it.
I've also seen people work up new loads when ever they change lots of powder. That includes jam measurement.
One thing to keep in mind there are some top shooters that don't use their own hand loads. They instead use high end match ammo. Because of this I think the quality of the components plays a huge factor. Also constancy is king, jam measurement makes a difference but the amount is probably negligible for most shooters.
One thing to keep in mind there are some top shooters that don't use their own hand loads. They instead use high end match ammo. Because of this I think the quality of the components plays a huge factor. Also constancy is king, jam measurement makes a difference but the amount is probably negligible for most shooters.
meketrefe
.450/400 Nitro Ex
Sorry, what is a jam measurment?
Non technical term for proper seating off of the lands and or measurement OAL bullet from the ogive or what I thought it was. Sorry I was being lazy.
Max. cartridge length where the bearing surface of the bullet touches the rifling of the barrel.
meketrefe
.450/400 Nitro Ex
Oh ok. That is what I thought I just wanted to make sure. So given that your magazine allows you to
do that or you single feed you want to find out what is the max COAL for that bullet just touching
the lands right? I don't think you want to jam anything just touching right?
If that is the case that is a good starting point but most likely your accuracy load is going to be XYZ
thousands off those lands. And most likely other bullets will show the same behaviour.
I think the most important factor regarding that jump from the case into the lands is the actual
shape of the ogive and specifically the angle of that bullet (leaded angle) and how it contacts
and engages those lands. Secant ogives like those in berger VLDs are very good for flying but
more sensitive regarding this jump and while hybrid designs in the ogive where created that
includes the top portion tangent and then secant almost straight in the remaining where
the bullet tip doesn't touch the rifling at all.
This is also why you have a number of reamers to make a 308 chamber for example and why
it is hard to decide if closer is better or worse w/o knowing the reamer and internal dimensions
of the chamber job.
On average with saami chambers many modern bullets will work well wiht a number of seating
depths and the harmonics will have more impact than the acutal position of the bullet relative
to the lands. Once one finds a formula that should stay true for a while when other considerations
for consistency are taken. you know brass, powders, primers, reloading metering, etc...
As the chamber wears off one might adjust the COAL to compensate (chasing the lands) but this
is not done so often specially with high life bores like a 308 or 7mm-08.
sorry for the long reply. I guess there is no one single formula fits all. But knowing the max coal
dictated by the chamber or magazine whichever comes first is an important piece of knowledge.
do that or you single feed you want to find out what is the max COAL for that bullet just touching
the lands right? I don't think you want to jam anything just touching right?
If that is the case that is a good starting point but most likely your accuracy load is going to be XYZ
thousands off those lands. And most likely other bullets will show the same behaviour.
I think the most important factor regarding that jump from the case into the lands is the actual
shape of the ogive and specifically the angle of that bullet (leaded angle) and how it contacts
and engages those lands. Secant ogives like those in berger VLDs are very good for flying but
more sensitive regarding this jump and while hybrid designs in the ogive where created that
includes the top portion tangent and then secant almost straight in the remaining where
the bullet tip doesn't touch the rifling at all.
This is also why you have a number of reamers to make a 308 chamber for example and why
it is hard to decide if closer is better or worse w/o knowing the reamer and internal dimensions
of the chamber job.
On average with saami chambers many modern bullets will work well wiht a number of seating
depths and the harmonics will have more impact than the acutal position of the bullet relative
to the lands. Once one finds a formula that should stay true for a while when other considerations
for consistency are taken. you know brass, powders, primers, reloading metering, etc...
As the chamber wears off one might adjust the COAL to compensate (chasing the lands) but this
is not done so often specially with high life bores like a 308 or 7mm-08.
sorry for the long reply. I guess there is no one single formula fits all. But knowing the max coal
dictated by the chamber or magazine whichever comes first is an important piece of knowledge.