Well,
As stated, this is not a new idea but it has been sleeping for nearly 50 years since the last serious attempt to make it a practical loading option.
The idea is to use a brass or copper flash tube of an apporpriate length for the cartridge being used. The Flash hole on the case is drilled and tapped and the flashtubing is cut to length and then also threaded so that it will thread into the threaded flashhole. This flashtube remains in the case during firing and is reused for additional loadings. A piece of sping wire is used to deprime the cases. You slide the case in your shellholder on the loading bench, run the spring wire through the flashtube and use a small hammer to tap out the spent primer. From there you use a sizing die that has the expander button and decapping stem removed. This works best with bushing dies since you can control the amount of neck sizing for proper levels of neck tension.
The idea behind forward ignition is to accomplish the following things:
1. Dramatically increase throat life
2. Dramatically reduce powder fouling
3. Increase consistancy and accuracy
4. Reduce recoil
The reason it increases throat life is because the powder in the case burns IN THE CASE. Unlike conventional ignition ammo. In conventional ammo, when the primer ignites it throws a shower of sparks through the flashhole and into the powder chamber of the case. This blast often starts the bullet moving before the powder actually ignites.
When the powder does ignite at the base of the powder colume, it forces the majority of the powder volume through the shoulder/neck area of the case which in turn pushed the barrel down the bore.
AS the powder fully ignites and burnes, a very large percentage of this occurs when the powder is actually in the throat area and first several inches of bore. This is the reason for heat cracking in the throat and initial portion of a rifled barrel.
This also causes alot of bore heat as the powder is burning at full temps directly against the bare metal of the bore.
So from a pressure stand point, not only are you driving a for example 100 gr bullet down the bore in the case of my 224 Allen Mag, you are also driving 70 gr of powder down the bore. Thats a 170 gr payload being forced down the bore.
Now with a forward ignition round, the flashtube is extended so that its mouth is positioned just under the powder level behind the base of the bullet. When the primer ignites, the powder in the flashtube ignites but instead of igniting the powder in the base of the case, the flame is carried right to the the base of the bullet and to the forward portion of the powder colume.
The powder in the front of the case ignites and converts to gas which starts the bullet moving down the bore. This is important, its gas, not unburt powder that is already pushing the bullet down the bore.
So now the bullet is started down the bore and back in the case, the powder colume is beginning to fully burn but unlike conventional ignition, the powder is burning from the front of the case to the back.
This results in no solid powder, or very little that actually passes through the shoulder/neck of the case or the throat. About 90 to 95% of the powder charge is burned INSIDE the case instead of having 40 to 60% of the powder burning in the bore with some of the large case capacity small bore conventional rounds.
So what does this do. Well, first of all, you are now driving a 100 gr payload down the bore instead of a 170 gr powder/bullet payload, this will reduce pressure dramatically.
You are also burning the powder in the case. The case protects the barrel steel from heat cracking. The gas that passes though the throat is much cooler temps then the actual burning powder which stays in the case until converted to gas volume.
Another advantage is that gun powder is abrasive, weither its stick powder or ball powder, both under 50,000 to 60,000 psi of pressure are abrasive to barrel steel, stick powders much more so then ball but both are abrasive to some degree.
Keeping that powder in the case and burning it in the case prevents this abrasive action on the throat which you get with conventional ignition.
Also, since the payload driven down the bore in this case is 100 gr compared to 170 gr with conventional ignition, recoil will be less even if the velocity potential with the same bullet is higher with the front ignition system.
The powder fouling issue is also controled better by having the powder ignite and burn in the case instead of in the bore.
I have only performed initial testing so far with this system and while there have been alot of positive results there have also been a few issues that I need to work out to make this front ignition system a viable option for the handloader.
One interesting test I did was to see what difference there would be using the same load with conventional igniton compared to forward ignition.
Using a base load of 60.0 gr of WC872 under the 100 gr ULD RBBT Wildcat Bullet, the velocity results were as follows for an average of five shots at 10 ft from the muzzle.
Conventional ignition: 2930 fps
Front ignition: 2750 fps
This tells me that the resulting effect of not having to push the 60.0 gr powder charge down the bore greatly reduced the pressure generated by the round.
It would make sense that more powder will be needed in the front ignition rounds to match FPS in the conventional ignition ammo but pressure and recoil will still be significantly less at this point. Top potential velocity should be significantly higher with the forward ignition. We are predicting a full 100 fps with top loads.
Another aspect that really caught my attention while testing this front ignition with some heavier loads was barrel temps. I shot 9 different loads from 65.0 gr up to 73.0 gr of WC872 under the 100 gr ULD RBBT. Velocities ran from 2900 fps up to 3425 fps. These were one round of each load level just to find the outer limits of the velocity potential quickly.
I shot those nine shots one after the other with roughly 15 to 20 seconds between each shot. The temperature was in the 60 degree range with bright sunlight. After the nine shots, the barrel was barely warm to the touch. I may be called a liar for this but the barrel was honestly barely warm to the touch. This is a #6 contour Lilja so its not a light barrel but also not overly heavy either.
To check this I fired six conventional rounds using only the 60.0 gr of WC872 fireforming load under the 100 gr ULD RBBT. I tried to keep the same 15 to 20 second spacing between shots. After those six shots, the barrel was to warm to comfortably hold with a bare hand.
I think that tells alot of the benefits of increased throat life with this system.
All this said, there is more tesing to do. There are a couple issues that I need to work on in upcoming tests but with the amount of positive results I have already obtained, this system shows amazing potential with rounds that would have previously proven Extremely Overbored.
I also have a theory that this system will also eliminate the powder bridging issues with huge case capacity small bore rounds when using stick powders. Only makes sense that because the powder is converted to gas in the case that there will be no powder bridging issues in the shoulder/neck area of the case.
This may prove a huge boost to rounds such as my 257 Allen Mag as it can not be used with stick powders without powder bridging occuring.
From Gibbs tests throat life is often doubled using this system. It also increases accuracy when set up correctly and reduces recoil. Velocity potential is also said to be more in most cases.
Personally, I am looking at the increased throat life for use with my Allen Magnum rounds.
Imagine an honest 2000 round throat life driving a 156 gr ULD RBBT .257" bullet to 3350 fps with 95 gr of WC872.
Basically you would have 25-06 AI throat life with ballistic performance higher then any of the huge magnums in 30 cal or 338.
It should work well in the larger calibers as well but that will come with futher testing which will take some time. Now my goal is to develope a practical, as user friendly system as possible to allow this system to be used with available loading dies at a practical cost per case level.
I will soon post pics of the system to show everyone the specifics of this system.
For now though, I have to work on customers rifles, there are many out there that have been very patient as I have been testing these new ideas, I need to get their rifles to them before to do much more testing.
This system may totally change the way we look at high performance, low expansion ratio rounds. Very exciting stuff!!
Kirby Allen(50)
