Should I be "Padding out" cases

[angrybear]

Pretty much the above question, should I be padding out half empty cases & if so with what? or do I leave them half empty.

I've got some Sierra 1210 45gn Hornet bullets to try and while Hodgson data say's 12-13.5gn of lil-gun which is a full case, for any & every bullet weight, Sierra's own loads start at under 8gn so the case is only little over half full.

In fact to be precise Sierra don't list lil-gun for my K Hornet, but in the std Hornet case they give it 1gn less than N110 across the board for the same MV so I'm going with 1gn less in the K as well.

Any advice ?

[223AI]

Obviously you need to work up a safe load but in my rifle I have found the best accuracy with 35gr, 40 gr & 45 gr bullets is 12.9gr of lil gun and I've had no pressure signs, and I've always worked up from 11.8 - 12gr. the 35 gr are loaded at 1.719" the 40/45s at 1.745" which is the longest my mag will take. 52 gr SMK on the other hand gave pressure signs at 11 grains (and keyholed).

I would compare the seating depth for the 2 sets of data as perhaps the Sierra data is for a much shorter OAL.

I have heard of people using Dacron as filler and also ground coffee to give an even burn and prevent secondary detonation. Personally I'd go with hodgdon's data, particularly as you're loading a roomier K case so your going get less pressure, but it's your call of course!

(my loads are all close to max and won't necessarily be safe in someone else's rifle so work up as always peeps)

[sackot]

I've done it but would definitely not recommend it across the board. When a case comes up where you need it, you'll know exactly what you're doing and why. That's important, because it can be dangerous and or deleterious to your rifle.

I used BPI plastic shot buffer to fill a case when using a reduced load. I didn't want to drive the (cast) bullet any faster, but without it the pressure was not getting high enough to give a consistent burn. I used Quickload to approximate the effect of buffer, by adding the buffer weight to the moving mass of the bullet, and subtracting it's solid volume (found from density of the material) from the case volume, and choosing a combination of powder and buffer weight which took the predicted pressure above 10k, but not by very much. I convinced myself that it was shrinking my groups a bit, but looking back I'm not entirely sure, plus it was a pain.

If you just cheerfully top up a case without doing the calculations, you risk overpressure. There is also an enigmatic phenomenon called chamber ringing, where the explosive pressure of the charge acting against the buffer is said to bulge the case in a very localized ring, over time distorting your chamber and making extraction difficult.

In effect, the requirement for buffer says that you are using an inappropriate powder for the calibre. There can be times where that is unavoidable, I'm limited in the range of powders I can obtain (can't get Accurate/Lovex, Vectan, for example) and with reduced loads for cast you are always off piste to some extent.

[kmahow2]

Most necked cartridges, produce their best accuracy with 90%+ case fill. If you end up using light powder loads, its not recommended to use normal powders.
As the powder volume goes down, you should use a faster powder to avoid detonation, which can cause extreme pressure spikes.

The Hornet tends to use medium/slow powders for a full case, or similar powders to 357/44 magnum loads. So moving to faster powders as the case fill falls below 75% would be simple.

YMMV

[pjinoz]

Maybe, but I would only ever do it with a straight sided case to obviate the possibility of an incompressible plug being formed from the padding because of poor initial ignition and then the powder "firing up" and sending pressure through the roof. Whilst the following example is not quite the same it surely left me wondering what MIGHT have happened. I had worked up a moderate load for the .264 Win Mag (60 + grains 4831 and a Magnum primer - which turned out to be not so magnum and a 139 grain projectile) and when I pulled the trigger I heard something a bit louder than the firing pin falling, but no discharge. So I pointed the gun at the ground for a minute or so and opened the bolt and ejected an "empty" case. However on closer inspection I could see the case neck and body was jammed full of compressed powder which I could not dislodge with a screwdriver; the projectile was jammed in the throat. When I got home and cut the case open with a hacksaw I found that the powder charge had completely moulded itself into the front of the case and neck and was near impossible to break up with a screwdriver. Now, the scary part; the rear of this plug of powder was "singed" and if the powder had a delayed burn there would not be much gun left. Yes I have padded out cases but only straight sided ones where there cannot be a plug formed but it is far safer and better to choose a powder that the manufacturer suggests you use for reduced loadings. Of course it would be far better to revert to a lower power cartridge!
Happy New Year to all!

[223AI]

Maybe Angrybear can confirm but from what I've read in his post he's not after a reduced load, just concerned with the difference in load data from 2 sources and wondering where would be a safe place to start.

As for a smaller cartridge unless you go for something really obscure or go to rimfire you'll not get much smaller than the hornet, though there are powders around that allow it to be downloaded to WMR velocities with a decent case fill such as trail boss or unique.