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Experiences with high overbore cartridges and powder bridging
- Thread starter fmuguira
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This.
Plus , light neck tension may allow the bullets to move to soon. Producing a 2nd pressure spike?
esshup
Well-Known Member
Are you dropping the powder in the case or weighing each charge and then putting the powder in the case? The only time I had problems with powder "bridging" was when using a powder drop, and it was bridging before it reached the case.
I'm loading RL-50 in a 7mm Allen Magnum (fiftydrivers design) and have no issues. Kirby said they had bridging issues, and said use RL-33 to get away from the temp sensitivity of the WC-872 that I was using, but I'm assuming that it was in the loading process. He also recommended just using a standard Federal 215 primer not a GM215M primer.
No issues at all lighting 102 grains of it and the last 3 loads that I chrono'd had a high fps of 3225 and a low fps of 3219 pushing a 195g Berger EOL bullet.
I'm loading RL-50 in a 7mm Allen Magnum (fiftydrivers design) and have no issues. Kirby said they had bridging issues, and said use RL-33 to get away from the temp sensitivity of the WC-872 that I was using, but I'm assuming that it was in the loading process. He also recommended just using a standard Federal 215 primer not a GM215M primer.
No issues at all lighting 102 grains of it and the last 3 loads that I chrono'd had a high fps of 3225 and a low fps of 3219 pushing a 195g Berger EOL bullet.
I think you didn't quite get all of FiftyDriver's point. There are 2 types of bridging with the most common being getting the powder in the case. The second type is the powder bridging in the case neck upon firing (usually in high overbore cartridges like FiftyDriver's). #1 is merely inconvenient. #2 can hurt you. I suggest you re-read this thread with that point of view. A lot of good info here.
Mike Matteson
Well-Known Member
For one I am glad I found this thread. Presently have a 6mm-280AI being built. On a 700 Rem long action, with a 30" barrel Heavy. Barrels, reamer Stock have been order. What I see the cartridge powder charge is under or about 60gr max to start with. I don't see a mag primers to light it off to start with. I totally agree that slower powders like H1000 is where I am headed for. I am extremely aware of Temperatures spread. Presently purchasing cases, bullets, and powder when, and sizing dies. Can you forward and reloading data on 6-06 loads. My email address is [email protected]. I have been reloading for almost 59yrs now. So I am no fool, but I am interested on what loading data you have if willing to share. If not I understand.
antelopedundee
Well-Known Member
I would consider taking a metal rod just small enough to fit into the case neck and insert it into a charged case and tap it lightly with a hammer in order to compress the powder and eliminate any bridging. Just a thought.
Mainmechanic
Well-Known Member
Not saying powder bridging isn't your issue but have you checked for a carbon ring yet ? Your description leads that way. Good luck.
I understand the 2 bridging types... I ve been loading for 50 years. #1 bridging is an inconvenience but that's not what I m looking for experience with. I m looking for experience with Fiftydrivers explanation regarding gas funneling through cartridge case and getting 'stuck' at small diameter neck / throat / bore area. He said stick powders were more apt to experience this vs a ball powder. That's the information/experiences I m looking for.
Sending load data via PM as requested above. PLEASE note these are max loads in our rifles. Your rifle, reamer used, etc will be different and these are only for reference. You should start lower and do your own work ups and not rely on these charges as safe in your combination. You assume all liability. ( U state you ve been loading a long time as I have too; just want to be explicitly clear that these are for reference only. Good luck )
Sending load data via PM as requested above. PLEASE note these are max loads in our rifles. Your rifle, reamer used, etc will be different and these are only for reference. You should start lower and do your own work ups and not rely on these charges as safe in your combination. You assume all liability. ( U state you ve been loading a long time as I have too; just want to be explicitly clear that these are for reference only. Good luck )
Ramshot LRT is a very slow burning ball powder, similar rates to the powder your using. This may eliminate the stick powder bridging you're referring too. Rl33 is a very dirty power and often causes carbon rings if not cleaned regularly. Idk if you've inspected the throat area for that possibility.
Haven't looked for carbon ring but round count is only at 85. I also clean thoroughly after each session but will take note of carbon ring.
We haven't shot enough US869 or Retumbo to know if this issue exists with them also. Settled on R33 due to velocity, case fill and accuracy results. Obviously more testing will be needed. Just like to get as much data/experience from others as possible as these barrels won't have long round counts!!
We haven't shot enough US869 or Retumbo to know if this issue exists with them also. Settled on R33 due to velocity, case fill and accuracy results. Obviously more testing will be needed. Just like to get as much data/experience from others as possible as these barrels won't have long round counts!!
azsugarbear
Well-Known Member
I had a 277 AM built by Kirby that I shot for many years. He warned me the the case volume of the 338 Lapua combined with the smaller 277 diameter neck could/would be prone to bridging. He recommended the ball powders to avoid that potential problem.
I did experiment with some Retumbo in the 277 AM once, It performed well until I worked up towards maximum velocities. I then started experiencing erratic pressures and velocities. I figured it was the bridging Kirby spoke of. Scared me to death. I went back to the ball powders and never had any more problems.
It is interesting to note that his larger caliber Allen Magnum cartridges based on the same 338 Lapua case did not experience the same bridging problems with stick powders as the 277. The conclusion was that the larger diameter necks were just large enough to avoid the bridging/bottleneck problem found in the 277 AM.
I did experiment with some Retumbo in the 277 AM once, It performed well until I worked up towards maximum velocities. I then started experiencing erratic pressures and velocities. I figured it was the bridging Kirby spoke of. Scared me to death. I went back to the ball powders and never had any more problems.
It is interesting to note that his larger caliber Allen Magnum cartridges based on the same 338 Lapua case did not experience the same bridging problems with stick powders as the 277. The conclusion was that the larger diameter necks were just large enough to avoid the bridging/bottleneck problem found in the 277 AM.
