Using drop tubes for mid size cases

[gene so]

Recently I read a short statement regarding use of a drop tube to pack more powder into cases. The purpose would be to attain higher velocity. The writer contended that although he was able to get more powder into his cases he could gain no more velocity.
Has anyone done any testing of this type? I am interested in mid sized cases ( 6.5 x 47 Lapua-.260 Remington etc.) If indeed using the very slowest powders with the high BC-heavy bullets along with a drop tube will gain an advantage, I would be pleased to hear of it.
Logic would dictate that when you compress powder in a case, something has to be replaced, and that must be the airspace. Thus, seemingly it would seem that more powder in a case might have an inverse effect on ignition.

Thank You, in advance,

Gene So

 

[Walkalong]

Long drop tubes do indeed work well to get powder more compacted, allowing a higher charge weigh (We'll assume it is a safe charge weight).

It doesn't seem to affect ignition or burn. The choice of powder & primer is probably more critical.

Welcome to THR.

 

[rcmodel]

it would seem that more powder in a case might have an inverse effect on ignition.

The amount of air, or oxygen in a cartridge has no effect on burn rate.

The air in the cartridge isn't used to support combustion.

The powder itself provides it's own oxidizer to support the burn.

rc

 

[Reloadron]

Welcome to the THR Forums!

Any given case has a given volume. When powder is added to the case air is displaced with powder. Below are a few examples of powder drop tubes and some associated case mouth adapters.



The drop tubes do not allow the hand loader to pack more powder into the case. The case has a volume and that is as good as it gets with the powder charge determined by credible hand loading manuals.

What the drop tubes do allow is for the hand loader to more easily fill a case when the safe published charge is around maximum capacity of the case. For example using the Remington 260. Loading a 100 grain JHP bullet my maximum charge of IMR 4064 is about 41.5 grains of powder. That charge should easily fit the case without a problem. However, if I want to use a less dense slower burning powder like IMR 4350 my maximum charge is around 47.5 grains which according to my loading manual is a compressed charge. Without a drop tube using a standard volumetric powder dispenser I can run my drop and then while holding my case to the case mouth adapter tap and shake the case trying not to spill any powder. Using a long drop tube the powder can exit my dispenser and accelerate down the tube and enter the case with a little more force and better settle in the case. Either way, the same charge is in the case but the long drop tube has made filling the case easier. The end result is the same. I have not packed more powder into the case.

Just My Take....
Ron

 

[blarby]

^^^^

Thats about as good an answer as you are likely to get.

Well done !

 

[dagger dog]

IMO using drop tubes with smokless powder is being tried in conjunction with some of the modern long bullet designs that intrude into the case, supposedly the powder is over compressed with these bullets and by using a drop tube it relieves some of the compression.

Welcome to the forum gene so !

With your first post involving the idea of more powder, just make sure you use a loading manual and stick to the guidelines in that manual to stay safe !

 

[Walkalong]

If you drop the charge all at once in a standard drop tube, it will come up higher in the case than if you use a long drop tube of smaller diameter which puts the powder in the case just a little slower. It beats the heck out of putting most of the charge in the case, and then tapping it etc to get the powder to settle so you can fit the rest in.