In order to participate in the GunBroker Member forums, you must be logged in with your GunBroker.com account. Click the sign-in button at the top right of the forums page to get connected.
Options
505-460 Kemp chrono test
stankemp
Member Posts: 509 ✭✭✭
Sunday I had the opportunity to finally do some chrono work on the cartridge. Results were somewhat dissapointing. While accuracy was good (just off elbows , not bags) the speed was off by about 500 FPS according to what I was looking for.
Results:
500 grain Hawk RN , 65 grains Hodgson's #4350...... 1160 FPS
400 grain Hawk RN , 70 grains Hodgson's #4350 ......1270 FPS
There was a lot of unburned powder in the barrel and ejected cases.
I used CCI Magnum rifle primers and the cases were about 75% full.
Some knowledable and helpful fellow shooters thought that inert case fill might help.
Any other insights would be greatly appreciated.
Cartridge development info at http://home.comcast.net/~stankemp/505460.html
Thanks, Stan
Results:
500 grain Hawk RN , 65 grains Hodgson's #4350...... 1160 FPS
400 grain Hawk RN , 70 grains Hodgson's #4350 ......1270 FPS
There was a lot of unburned powder in the barrel and ejected cases.
I used CCI Magnum rifle primers and the cases were about 75% full.
Some knowledable and helpful fellow shooters thought that inert case fill might help.
Any other insights would be greatly appreciated.
Cartridge development info at http://home.comcast.net/~stankemp/505460.html
Thanks, Stan
Comments
how sharp is the shoulder angle and how long is it?
4350 can be used in 06 and some belted mags, so I would think maybe running something faster in your case might get the burn and speed you are looking for. Is this close to a straight wall case now? if so, I am not all that sure 4350 burn rate will be fast enough. I could be wrong[:)]
why chase the game when the bullet can get em from here?....
Got Balistics?
Unburned powder is usually a sign of low pressure. Pressure can be adjusted in one of several ways. JustC suggests increasing the neck tension which is one but I think that you need to supply us with more information in order to let us help solve your dilemma.
What is the case length?
What is the case capacity using water?
What is the Overall Length of a loaded cartridge?
What is the operating pressure of the rifle that you're using?
How much tension is there in the neck with a prepped case?
Post these answers and we can give you hand in figuring this out.
Best.
Parameters of the cartridge are:
Empty case capacity......8.4cc
Empty case length........2.3"
Loaded case OAL..........2.86"
Bullet length............1.05"
Bullet diam.......... .505"
Viturally a straight cartridge, no shoulder ( I cut off that part from the 460 Wby brass to make the basic case).
Heavy , long crimp on the bullet(I tried to pull one out with a pliers, couldn't).
click on the site in my first post for pics.
Thanks, Stan
The rifle is a Swiss K31 , rebarreled for the 505. Boyd stock.
I don't know the operating pressure but the GP11 round approximates a 30-06 ballisticly. This rifle was checked by a very competent gunsmith for any safety issues. There were none.
Thanks again, Stan
The operating pressure of the GP11 cartridges is 55,000 PSI approximately.
The volume of the case is very important as it helps create the math that solves for the pressure. I was backtracking through your information and I wanted to know how you arrived at the volume of 8.4cc. Generally speaking, we use grains of water not cubic centimeters. I have done the conversion of cubic centimeters to grains but the volume appears to off. The 8.4cc converts to ~129.63 grains. But when I look at one of these full size cases this means that the 0.613" that you removed only has a capacity of 12 grains. My guesstimate works out to be about 30 grains of lost capacity.
Just to double check, to get the capacity of the case, you need to plug the primer pocket with a dead primer then weigh that case. Fill that same case with water to the top of the neck and weigh it again. Take that weight and subtract the empty weight and the result is the capacity in grains of water. This will help establish the basis for working up loads.
Best.
N110
4064
RL15
3031
why chase the game when the bullet can get em from here?....
Got Balistics?
I don't have a scale that can measure the grain weight required (100 grain max) . But I did go back and remeasure the water capacity . My earlier measurement was inaccurate. The actual total is 7.1 cc which works out to 109.56 grains of water. The difference is I used an unprimed case with my finger over the hole and really filled the case to a bubble at the top. You get a little extra that way.
Anyway. I did this measurement with a fired empty, and I did it 3 times to insure a good reading.
Sorry for the initial false trail. I will be more careful in the future.
I see that the dynamics of powder burn are effected by case configuration. Whoda thought?
Stan
Well, I did pretty good with my interpolation since I came up with 108.92 grains...
The best powders are going to be a bit faster than the H-4350 that you started with earlier. Straight wall cases generally need faster powders than bottleneck cases with the same or similar capacity.
I don't know what powders you have access to but here is a short list of those that will work.
AA-2520 (2nd)
IMR-3031 (3rd)
H-4895
V V N-133 (1st)
Ramshot Big Game
As an aside, these are the same powders that work well with the .458 Win. Mag. when loaded with the same bullet weights. The funny thing is that in my notes the .458 Win. Mag. will produce the same velocities and therefore similar energies when loaded with the 400 or 500 gr. bullets using the same powders but less of each when fired from a 24" barrel. The big difference is that the .458 already has a name and your wildcat gets to wear your name.
While I am a big supporter of wildcatting, some seem to be a little duplicative of existing commercial cartridges and this is where I think you are with the 505/460 Kemp. No offense.
Best.
Thanks much for the insight. Great to have people that have expansive knowledge on subjects of interest on a virtual "hotline". This is one of the best benefits of the internet. Think of what we had just 20 years ago! Write to a gun magazine and wait 3 months for (maybe) an answer.
As for the cartridge, 2 comments from friends before development:
1) " the world does not need another cartridge"
2)"what are you doing that for? just go buy a slug shotgun"
The website is , I hoped that readers see, pretty tongue-in cheek, but the development is serious fun.
Thanks again , Stan