Can any of yall educate me on RPM vs FPS?

Alright, please correct me if what I’m finding on the internet isn’t accurate.

I worked up a .223 plinking load today and it was around 2300 fps. Cycled just fine suppressed and unsuppressed. I figure there’s no reason to waste powder spicing up a plinking load so while I was researching I read that slower bullets are generally more accurate because of twist rate and FPS affecting RPM.

Is this true? It’s not overly important because I’m just shooting beer cans, oyster shells, and paper with this load but I’d like that make sure I’m understanding these general rules as I go.

Is this just a really confusing way to describe the importance of the proper twist rate?

LC brass
CCI SR primer
24.5 grains of reloader 15
Hornady 55gr FMJBT
2.250 COAL

10 years to retirement! Just waiting!

Posts: 6778 | Location: Georgia | Registered: August 10, 2009

sourdough44

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Just some general comments, very general.

Even though RL-15 likely is fine, it seems most manuals would suggest a faster powder with 55 grain bullets in a 223. RL-15, more often listed with heavier bullets. Yes, with high priced components, I may use what’s on the shelf, available. If you chronographed the 2300 FPS, a bit slow with most. No biggie with plinking, if they cycle, which was yes.

By faster I mean towards TAC or 4895, ballpark.

As to rifling & accuracy, with FPS added, my answer is ‘it depends’. First one needs a compatible bullet for the twist rate. A mismatch would be a 77 grain 223 bullet in a 1-12” barrel. There are plenty of examples where one gets better accuracy at higher fps, with whatever combination.

I have never heard of a trend for better accuracy at slower speeds. Of course any rifle could easily have its own preference.

Posts: 6538 | Location: WI | Registered: February 29, 2012

OttoSig

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quote:
Originally posted by sourdough44:
Just some general comments, very general.

Even though RL-15 likely is fine, it seems most manuals would suggest a faster powder with 55 grain bullets in a 223. RL-15, more often listed with heavier bullets. Yes, with high priced components, I may use what’s on the shelf, available. If you chronographed the 2300 FPS, a bit slow with most. No biggie with plinking, if they cycle, which was yes.

By faster I mean towards TAC or 4895, ballpark.

As to rifling & accuracy, with FPS added, my answer is ‘it depends’. First one needs a compatible bullet for the twist rate. A mismatch would be a 77 grain 223 bullet in a 1-12” barrel. There are plenty of examples where one gets better accuracy at higher fps, with whatever combination.

I have never heard of a trend for better accuracy at slower speeds. Of course any rifle could easily have its own preference.

Thank you, Sir. My thoughts echo yours. If slower is more accurate that’s discounting all other factors. Add in more factors like twist and bullet weight and it can’t be a universal truth in my mind.

As to the RL-15, I’ve read many accounts of it being best used for 62gr and up. However, like you said, I got several pounds of it for free so I was considering it. Might buy 8 pounds of something else and save that for heavier bullets, just hadn’t quite decided yet. I’ve got 10# of accurate 2200 that I might use a bit of instead.

10 years to retirement! Just waiting!

Posts: 6778 | Location: Georgia | Registered: August 10, 2009

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