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Author Topic: My dream 243 build  (Read 309 times)

Offline Dutch-Hunter

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My dream 243 build
« on: November 03, 2018, 08:07:09 PM »
Starting my dream build. This is a brief first look into my thought process.

As some of you may recall a few years ago I started a project build with the expectation of 5000 fps velocity in a .243 caliber. To my disappointment I couldnít find a bullet that could hold up at this speed. Well guess what? FOUND IT! Itís a 90 grain monolithic tactical projectile. After checking the data I really think my dream is plausible. I am hoping to at least reach this velocity and realize a .5 MOA at 2000 yards. This will enable me to at least ring steel with 12 inch POI dispersion. The steel targets are 24Ē square so a 1.0 MOA should still be successful in a gong.

This bullet maker also has a 100 grain bullet that would allow me to modify the tail to make it fly better. My biggest concern propelling a pill at this speed and rotation is spin drift. Turning the pill as rapidly as needed to achieve this velocity will increase yaw dynamics to the point of inconsistent flight path. This is why Iím thinking so much about the tail shape. First thoughts are the tail taper must be longer than normal boattails and to a finer point. I must be careful because too much drop in tail weight may have adverse effect on flight path. Both of these bullets have a nose protrusion of .8148 with the 90 grain having an overall length of 1.1824 and the 100 grain length is 1.3326. This gives me a body length of .3670 for the 90 and .5278 for the 100. Looking at these pills they appear to be mostly nose with not much for bodies. The weight differential between the nose and bogy are so close I need to be mindful of the tail trimming to not getting a weight forward scenario on the pill. Knowing that the sonic turbulence will be extremely high is why Iím so concerned about tail shape and the weight balance. Think about any supersonic aircraft. They all have sharp elongated noses to open the sonic envelopes. The rest of the craft must be able to slide through these envelopes without disrupting the dynamics.

I have gotten enough information on the supposed bullet physics to talk to barrel manufactures. Yes I have gotten a couple of interesting responses. I did however get two favorable ones. They are going to do some computer generations of their own to confirm what Iíve come up with so far. What weíre thinking about is a 2 inch to 2.25 inch chamber outside diameter to withstand the pressures that will be required. My thoughts were to hold the outside diameter the length of the barrel, bull contour. The twist rate that I computed of 1:14.5 was the same as they were suggesting. I was surprised by their 3 groove idea, I was thinking about a 5 groove. They are going to do some testing and computer modeling. When the barrel is built I asked them to lap it to 600 and then cryo treat it. When I get it Iíll finish the polish lapping to 1200 grit. I told them it didnít matter to me if it is stainless or blued.

Cartridge opening thoughts; Iíve tentatively been looking at the 300 RUM and 375 Ruger as the case choices. Iím leaning towards the Ruger because of its length, even though the capacity is 10 grains less than the 300. I have not started to work up the charge weight or powder choices. Iím guessing to go somewhere around Hodgdon Retumbo to Vihta Vouri 24N41 on the burn chart for the powder.
Well there is my plans, guessís and dreams. Iíll keep you posted as things develop.
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Offline sundowner

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Re: My dream 243 build
« Reply #1 on: November 03, 2018, 08:45:10 PM »
Good luck with the build Dutch .  ##$%#1118
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Offline MI_Bowhunter

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Re: My dream 243 build
« Reply #2 on: November 03, 2018, 09:49:18 PM »
Way over my head but I am intrigued and following this.
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Offline dave 1211

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Re: My dream 243 build
« Reply #3 on: November 04, 2018, 09:42:49 AM »
 --7-8-9   @--0--0117  what did he say after 243 I was lost


  ##$%#1118
turkey season near you sooning come on may 1




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Offline NWIAdeerhunter

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Re: My dream 243 build
« Reply #4 on: November 04, 2018, 02:16:10 PM »
All I have to say is interesting and good luck! What I'm curious about is its a 243 right? so why would you be using a cartridge size of a 300 RUM or 375 Ruger?
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Offline Dutch-Hunter

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Re: My dream 243 build
« Reply #5 on: November 05, 2018, 06:41:29 AM »
All I have to say is interesting and good luck! What I'm curious about is its a 243 right? so why would you be using a cartridge size of a 300 RUM or 375 Ruger?

I'm going to probably need 80-90 grains of powder to generate enough pressure. Don't want to use a belted case because of the inherent pressure failure of bulging/splitting at belt. Still early so just verbalizing my thoughts. As to the 243 question, it's never been done and I hate being told it's not possible. Nobody thought a 338 300gr pill could run out the barrel at 4000, but they can.
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Offline BLUETOE

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Re: My dream 243 build
« Reply #6 on: November 05, 2018, 07:31:44 AM »
Sounds good Dutch hope you reach your goal.
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Offline Madgomer

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Re: My dream 243 build
« Reply #7 on: November 05, 2018, 09:31:10 AM »
Exciting stuff Dutch, keep the updates coming.  Your initial post got me curious, so I did some web snooping & found a guy who had his .243 up into the 4700-4800 fps range.  Sounds like barrel life will be a challenge but I suspect once you prove the velocity goal can be achieved, you probably won't be shooting 300 rounds a day at a prairie dog town with it. You mentioned you weren't particular about stainless or blued steel for this project, does either one have an advantage over the other in terms of throat erosion?
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Offline gobihawk

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Re: My dream 243 build
« Reply #8 on: November 05, 2018, 07:31:53 PM »
Are you going to call it .243 DH?  ()*$%RT
Great stuff DH. Look forward to hearing  updates.
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Offline notsams

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Re: My dream 243 build
« Reply #9 on: February 11, 2019, 08:54:30 PM »
Dutch  any new info on the rifle build? Keep us informed.

 

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