Tubs wrote:Howdi all,
Trying to get my hunting rifles to replicate 30-30 dynamics.
I dont have a chrono, Blade was explaining to me how to measure bullet velocity using bullet drop stats but I dont have a PhD in physics
Anyone got any load data on 2206H loads required to get a 139gn 7mm and 130gn 30 Cal bullet down to aprox 2500 f/sec?
I figure Id be shaving aprox 15-20% off ADI's min load data but thought someone here has actually done it.
Cheers!
bladeracer wrote:Tubs wrote:Howdi all,
Trying to get my hunting rifles to replicate 30-30 dynamics.
I dont have a chrono, Blade was explaining to me how to measure bullet velocity using bullet drop stats but I dont have a PhD in physics
Anyone got any load data on 2206H loads required to get a 139gn 7mm and 130gn 30 Cal bullet down to aprox 2500 f/sec?
I figure Id be shaving aprox 15-20% off ADI's min load data but thought someone here has actually done it.
Cheers!
You can extrapolate from load data, but shooting at 100m and 200m would get you closer to the actual velocity.
Which bullet exactly? I may have them.
Do you have a .30-30 that you want these to shoot similarly to, or just using .30-30 ballistics as a basis for the load performance you're looking for?
Federal factory 150gn SP (I think they used a Speer HotCore) is rated at 2650fps and made 2649fps in my 22" Ruger the first time I chronoed it, and 2603fps the second time. Average over both tests (10rds) made 2628fps - velocities are never written in stone.
So 2500fps with a 140gn bullet is only reduced by about 300-400fps from factory levels in the .308, enough to reduce noise, recoil and throat erosion, while still hitting pretty hard. The 140gn .30-30 factory load is probably in the 2200-2300fps realm, with 130gn in the 2300-2400fps realm, although your rifles may have longer barrels than most .30-30 carbines.
7mm-08 160gn Speer BTSP makes 2435fps for me on 36gn of AR2206H, so I'd guess you're looking around the 32gn to 33gn region behind a 140gn jacketed bullet to see velocity similar to .30-30 from the 7mm-08, or 35-36gn for 2500fps. For a 130gn jacketed bullet in the .308 to make around 2500fps I would guess around the 36-38gn region with AR2206H. If it's a short bullet though you might find you need a little more powder to make the velocity, with a longer bullet you can seat it deeper into the case to reduce the volume and increase the pressure from a lighter charge. Obviously you'll need to go lower still to replicate actual .30-30 loads with those bullet weights, but if you're not using similar bullets, the trajectory past about 100m could be significantly different due to the flat .30-30 style bullet. The 7mm-08 and .308 are significantly larger cases than the .30-30, about 25% larger volume so you need more powder in them to make the same velocities as the smaller case - in the .30-30 you'd be using 30-32gn for the same velocities.
Cast bullet loads would be different.
LawrenceA wrote:There is about 400fps different between the 30-30 and the 308 for a 130gn pill.
ADI has starting loads with 2206H and lists the max load as compressed so no worries there but we also know that 2206H can be taken down to 60% case capacity so
I would suggest working out your case capacity and see if you can go below the listed minimum safely.
Please note that reducing the velocity may get to a point that the bullets will not stabilise so I would suggest starting at the minimum and working back to try and determine an accuracy node.
Extrapolating back a grain of the 2206H seems to be about 50fps. So start at minimum and work back but not below 60%.
Same sorta deal with the 7mm08
Good luck.
bladeracer wrote:LawrenceA wrote:There is about 400fps different between the 30-30 and the 308 for a 130gn pill.
ADI has starting loads with 2206H and lists the max load as compressed so no worries there but we also know that 2206H can be taken down to 60% case capacity so
I would suggest working out your case capacity and see if you can go below the listed minimum safely.
Please note that reducing the velocity may get to a point that the bullets will not stabilise so I would suggest starting at the minimum and working back to try and determine an accuracy node.
Extrapolating back a grain of the 2206H seems to be about 50fps. So start at minimum and work back but not below 60%.
Same sorta deal with the 7mm08
Good luck.
ADI says AR2206H can be reduced to 60% of "maximum loads", and maximum loads vary widely among firearms, and load data, so "maximum load" is a _very_ fluid concept. You can go way below 60% without issues, down to low-subsonic if you want. With low case fill you might see better consistency using a filler to hold the powder in place, or even better, just switch to Trailboss.
I don't believe I have ever seen any load data for AR2206H/H4895 list minimum loads, they just list a handy starting point - minimum is _way_ lower than those starting data.
Occasionally a really long bullet that is marginally stable anyway may become unstable launched at subsonic velocities, but I haven't found that as yet. If it's stable at 3000fps it's very likely to be stable at 1000fps. If it's not stable and you want to use it anyway, shorten the tip until it becomes stable, or pull out any ballistic tip it might have and use it as a hollow-point. I've read that the subsonic 190gn Sub-X is extremely effective with the BT removed.
Extrapolation is not linear with powder charges. At near-full levels, adding a half-grain of powder can see very large increases in pressure, with a lesser increase in velocity. Come down two-grains though and half a grain can make a big drop in velocity due to the increasing empty space in the case and vastly-lower pressure produced. I've never tried it myself but if you reduced the charge and kept seating the bullet deeper to maintain the same case volume I guess you might be able to extrapolate the charge-vs-velocity more closely, an experiment I probably should investigate one day.
But to get 2500fps with these bullets in 7mm-08 and .308 we're just talking a basic starting load rather than what anybody would consider a reduced load.
Oldbloke wrote:The recommendations from ADI are:
AR2206H 60% of max
All others 75% of max.
They are always conservative. But I would not go far below those recommendations. There is always a remote chance of a "detonation".
bladeracer wrote:Oldbloke wrote:The recommendations from ADI are:
AR2206H 60% of max
All others 75% of max.
They are always conservative. But I would not go far below those recommendations. There is always a remote chance of a "detonation".
Of max what though, that's the issue. Max is a wide variable, making the 60% even more variable.
I don't believe that remote chance "always" exists, at least no more than the possibility any cartridge might explode if too many tolerances added up wrong.
I wouldn't recommend all others to be 75% though, some powders in specific cartridges can be very fiddly to safely load, there are some I wouldn't experiment with at all.
Oldbloke wrote:The 60% of max is not a variable. It is 60% of the max ADI recommended in their Data. NOT what you think max is. Believe what you like, they are clear in what they recommend just read the manual.
Oldbloke wrote:If you don't understand this, it because you don't want to.
Me, I prefer to keep my face intact.