300 PRC Build . . . What twist rate are you finding successful?

Sam Pace

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Hey guys ... I'm building a 300 PRC. I am planning to shoot heavier bullets . . . 225 ELDM and 230 A-Tip. I'm punching metal at LR . . . not planning to hunt with it . . . unless I do. Anyway, any of you have experience with a twist rate you love or hate? I'm leaning toward 1:9" btw. I'm basing it off of Bryan Litz's book and references to stability factors. 1:10" seems to be too low. I'm concerned that 1:8" will be too much. So, just looking for some experience here. Please share. Thanks!
 

L.Sherm

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This paragraph on Randy Robinetts web page is what I base my twist rates on.
I've talked with some BR guys about this and thats pretty much exactly what they told me.
 

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Ranger Rick

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⬆️ this plus in my 300 PRC build, I chose a Proof carbon fiber 26” barrel with a 1:9” twist. It shoots the 230gr A-Tips sub 0.50 MOA out to 1,000 yards at 2,600 foot elevation. Based on the manufacturers’ recommendations, reviews and posts from other 300 PRC owners, I believe that you will have increased peace of mind in your build in choosing a 1:9” twist. I may try the 250gr A-Tips, but with cautious expectations (that is in the 1:8” twist realm). Best wishes on your build, the 300 PRC is an awesome caliber!!
 

Sam Pace

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This paragraph on Randy Robinetts web page is what I base my twist rates on.
I've talked with some BR guys about this and thats pretty much exactly what they told me.
Thank you. I have Litz's work on ballistic performance. His page on the 225 ELDM indicates a 1:8" will have a nominal stability factor of 2.12 and so it seems like it would operate outside of the window according to Robinetts. 1:9" has a best case of 1.92 and worst case of 1.45 stability factors. So, my 1:9" twist rate seems optimal . . . at least in theory on paper!

Thanks Sherm!
 

Sam Pace

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⬆️ this plus in my 300 PRC build, I chose a Proof carbon fiber 26” barrel with a 1:9” twist. It shoots the 230gr A-Tips sub 0.50 MOA out to 1,000 yards at 2,600 foot elevation. Based on the manufacturers’ recommendations, reviews and posts from other 300 PRC owners, I believe that you will have increased peace of mind in your build in choosing a 1:9” twist. I may try the 250gr A-Tips, but with cautious expectations (that is in the 1:8” twist realm). Best wishes on your build, the 300 PRC is an awesome caliber!!
This is VERY help and reassuring. I'm shooting in optimal conditions here in Colorado at 5k and above. The slightly higher twist rate should help me out a bit at lower elevations. I could probably get away with the 1:10" at this elevation, but I won't always shoot here. Thanks!
 

Wachsmann

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So with the very heavy bullets not to be raining on any one's parade but can a 300PRC or a 300RUM make 3000 fps with a 245 or 250 grain bullet. I think that might be a realistic factor to consider as well. I haven't looked but what does the 250 amax or the 245 EOL and the 240 or 250 Sierra match kings run at. Almost every reloader I know seem to always tinker around to find the best option. Also may be the best option is the 225's and the 230's for the 300PRC. Don't know.
 

Sam Pace

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So with the very heavy bullets not to be raining on any one's parade but can a 300PRC or a 300RUM make 3000 fps with a 245 or 250 grain bullet. I think that might be a realistic factor to consider as well. I haven't looked but what does the 250 amax or the 245 EOL and the 240 or 250 Sierra match kings run at. Almost every reloader I know seem to always tinker around to find the best option. Also may be the best option is the 225's and the 230's for the 300PRC. Don't know.
I'm pretty conservative on my reloading. I know a lot of guys who push the limits. My experience has taught me that more conservative measures suit my shooting pretty well. Since I run rifles on metal (primarily) I don't chase increased velocities for foot pounds of pressure. Long distance accuracy is my game. That said, I think 2900 FPS is gonna be a safe top end for me on the 300 PRC. Hornady builds factory 225 ELDM's just a bit over 2800 FPS. Anyway, I'll chase bullet options and adjust my speeds for a while to get what works best.
 

Sam Pace

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So with the very heavy bullets not to be raining on any one's parade but can a 300PRC or a 300RUM make 3000 fps with a 245 or 250 grain bullet. I think that might be a realistic factor to consider as well. I haven't looked but what does the 250 amax or the 245 EOL and the 240 or 250 Sierra match kings run at. Almost every reloader I know seem to always tinker around to find the best option. Also may be the best option is the 225's and the 230's for the 300PRC. Don't know.
Oh yeah . . . on heavier bullets the data shows, for example, 250 grain A-Tips are gonna run around 2700 FPS. I don't think 3k is realistic on these heavier bullets. The advantages with these bullets rest on the BC (G7 is .442) to carry the mail at distance. While I'm sure they can be pushed a bit faster, I'm not interested in pushing them much faster really.
 

jgs8163

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I’m running a 1/10 and a 1/9.5 in my 2 PRCs and shoot bug holes with both shooting 200-225 gr projectiles. I called and spoke with Berger, Krieger and Proof when building both of mine.
 

Mram10us

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So with the very heavy bullets not to be raining on any one's parade but can a 300PRC or a 300RUM make 3000 fps with a 245 or 250 grain bullet. I think that might be a realistic factor to consider as well. I haven't looked but what does the 250 amax or the 245 EOL and the 240 or 250 Sierra match kings run at. Almost every reloader I know seem to always tinker around to find the best option. Also may be the best option is the 225's and the 230's for the 300PRC. Don't know.
Rum definitely. Prc, highly doubt it. There is a large gap between the two cartridges. Mark and sam have a cool video of shooting a 300rum with 250atips. They were getting right at 3000, but he had gone with a load around 4 grains less than max for his rifle.
 

Wachsmann

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I watch a lot of there stuff and it seem Mark is saying the longer cases do better with the heavy's then the short fat cases. So like the 300 RUM is outperforming the 300PRC on velocity for the heaviest of bullets but I guess I didn't catch how much velocity they were getting. I had some crazy number from RL26 at one point without pressure and it was hard to believe but I had used all the 1lb and never got anymore. It was something like 3100fps with the 220 ELDX shooting 1/2 MOA. I ran it out to 1000yrds with no issues. I tried the 1 mile thing and that a whole different ball game.. I was hitting about a 24 by 30 inch area but nothing closer. I thought H1000 may be more consistent. But I haven't got a load developed for it yet.
 
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