A few years ago a friend and I decided to convert a .25 Mrod to a Cothran powered .30 cal. The Cothran valve is a beast, we had problems taming the setup, when 1st assembled it was sending 50gr JSB for 1106 fps/ 136 fpe. Way too hot for any accuracy. We tried choking the transfer port, but that just created more problems. The Powerhouse valve is really meant to push heavy lead, even 50gr was too light.
I tried some heavier .300 slugs, but the TJ .300 barrel is setup for pellets, the slugs didn't do well.
Later on I became the sole owner of the rifle and decided to see if I could work out a way to tone it down. Talon Tunes offers a nice tube extension, that along with a Lane regulator was my solution. I was able to get speeds down, maybe a little too low as the reg/gauge block setup offered too little of plenum, power was limited to 65 fpe. It shot good in this configuration, shot count was around 12 shots before it fell off reg, and the 50gr JSB printed nice groups. Over on the GTA, Bob Sterne came up with a heavier pellet designed to work with the .300 barrel. NOE makes all kinds of slug molds, a group buy for the heavy pellet mold drew my attention, I jumped onboard with high hopes of a 72gr .30 pellet. I now have the mold and have cast some primo 60 gr pellets. The mold has different pins that allow 4 different weights, from 58 upto 72 gr. Testing in MAX proved the plenum deficiency, power was still limited to 65 fpe via 60gr handcast pellets. I could've made a standoff for the reg to increase the plenum, but I had bigger ideas.
A friend of mine, Rich Dudek, made me a custom 11" Mrod tube, gauge delete, and an indexed threaded dropblock that allows use of 500cc CF tank setup with a 2600 psi regulator. On Tuesday I got the parts, Wednesday everything fell in place. 1st shot was 906 fps via handcast 60gr pellets, over 109 fpe !!! Shot count is over 30 shots before it falls off reg !!!
I ran a chrony string while testing indoors(foolish me) and drilled a hole thru my backstop of 6" of duct seal, 2 layers of 2x10, 3/8th" Lexan, and both sides of a concrete block
Today I tested outdoors for the 1st time. I need to bring the pellets speed to under 900 fps, groups were decent, but I think slower speeds will tighten them up. It was very windy too, 15-20 mph crosswinds.
I want to test at full power once i get some 72gr pellets cast up. Should be asap, I'm excited to see the outcome.
Overall this project has been fun, I hope to shoot this setup at longer diatances this summer.
Just thought Id share with y'all, I'm really starting to have fun with this .30 now.
More info can be found in my Facebook group here : https://www.facebook.com/groups/267876963412264/
I can give a rundown of all the mods once I remember all thats been done.
I also like to mention my friend Scott Keenan/OldManBlue here on the AGN, he and I started this project, without his Master machining skills it would've never come to fruition. There must be 100's of thousands of Mrods out there now, think of the possibilities !!!!!!!!!!!!!
Any questions, feel free to ask away, I am an open book. Thanks for looking, I'll have more news very soon.
I tried some heavier .300 slugs, but the TJ .300 barrel is setup for pellets, the slugs didn't do well.
Later on I became the sole owner of the rifle and decided to see if I could work out a way to tone it down. Talon Tunes offers a nice tube extension, that along with a Lane regulator was my solution. I was able to get speeds down, maybe a little too low as the reg/gauge block setup offered too little of plenum, power was limited to 65 fpe. It shot good in this configuration, shot count was around 12 shots before it fell off reg, and the 50gr JSB printed nice groups. Over on the GTA, Bob Sterne came up with a heavier pellet designed to work with the .300 barrel. NOE makes all kinds of slug molds, a group buy for the heavy pellet mold drew my attention, I jumped onboard with high hopes of a 72gr .30 pellet. I now have the mold and have cast some primo 60 gr pellets. The mold has different pins that allow 4 different weights, from 58 upto 72 gr. Testing in MAX proved the plenum deficiency, power was still limited to 65 fpe via 60gr handcast pellets. I could've made a standoff for the reg to increase the plenum, but I had bigger ideas.
A friend of mine, Rich Dudek, made me a custom 11" Mrod tube, gauge delete, and an indexed threaded dropblock that allows use of 500cc CF tank setup with a 2600 psi regulator. On Tuesday I got the parts, Wednesday everything fell in place. 1st shot was 906 fps via handcast 60gr pellets, over 109 fpe !!! Shot count is over 30 shots before it falls off reg !!!
I ran a chrony string while testing indoors(foolish me) and drilled a hole thru my backstop of 6" of duct seal, 2 layers of 2x10, 3/8th" Lexan, and both sides of a concrete block
Today I tested outdoors for the 1st time. I need to bring the pellets speed to under 900 fps, groups were decent, but I think slower speeds will tighten them up. It was very windy too, 15-20 mph crosswinds.
I want to test at full power once i get some 72gr pellets cast up. Should be asap, I'm excited to see the outcome.
Overall this project has been fun, I hope to shoot this setup at longer diatances this summer.
Just thought Id share with y'all, I'm really starting to have fun with this .30 now.
More info can be found in my Facebook group here : https://www.facebook.com/groups/267876963412264/
I can give a rundown of all the mods once I remember all thats been done.
I also like to mention my friend Scott Keenan/OldManBlue here on the AGN, he and I started this project, without his Master machining skills it would've never come to fruition. There must be 100's of thousands of Mrods out there now, think of the possibilities !!!!!!!!!!!!!
Any questions, feel free to ask away, I am an open book. Thanks for looking, I'll have more news very soon.
