So...Just what good is RPM theory

[45 2.1]

What has it done good for you? Anything? Cost you some money for a slow twist barrel that doesn't shoot well wxcept in a narrow range or for very light jacketed. A couple of people here found that out the hard way. And there are those "told you so" statements.

[Char-Gar]

It is pretty good for starting an argument on this and other boards.

[scrapcan]

Chargar you are right on. It starts controversy just like talking about high velocity in a 6.5 swede. Oh wait that is all one topic at the roots!

It does make for some good reading and lots of material to digest and make up your own mind. I like data and I like to make up my mind as to what the data tells me.

[Char-Gar]

I have yet to see this subject come up where it did not cause far more heat than light.

[HollowPoint]

I've read and re-read alot of the RPM posts and I still find it hard to come to a conclusion.

In the end I just take it with a grain-of-salt because, to me, it comes across as just logical-
sounding theory.

Even the few graphs and charts that come up do little to convince me otherwise.

I think the reason I read these debates or arguments revolving around RPM and Velocity is
to be convinced that it's true. That is yet to happen.

HollowPoint

[btroj]

It gives me another topic to stay the heck away from.

Why can't we have easy topics like blondes vs brunettes? Ford vs Chevy? We seem to always have topics that don't have a logical conclusion- just supposition and theory.

I figure that whatever a person does, if it makes them happy and they get the results they want- so be it and good for them. M? I just want to cast, load, and shoot. Too much math makes my head hurt.

[felix]

. Me? I just want to cast, load, and shoot. Too much math makes my head hurt.

Yeah, a bunch of us are artists first, and scientists way down the list, perhaps last. It's in the genes of most shooters. A group with all holes slightly touching is a wall picture indeed, but a pattern of one hole groups is satisfactory only to a weatherman who would gladly trade it for cash to purchase newer equipment for a repeat in a different class. ... felix

[waksupi]

It DOES tend to bring all the trolls into one convenient place to watch!

[swheeler]

It DOES tend to bring all the trolls into one convenient place to watch!

And I don't like feeding them, so stay away RPM threads!:drinks:

[white eagle]

What has it done good for you? Anything? Cost you some money for a slow twist barrel that doesn't shoot well wxcept in a narrow range or for very light jacketed. A couple of people here found that out the hard way. And there are those "told you so" statements.

has the same effect as how many lube grooves make a accurate boolit [smilie=p:

[tonyjones]

I have been a member here for about a year and a half and I am new to bullet casting. The RPM threads/discussions are a source of considerable information for me. I follow them with interest. It is stunning how much one can learn here. Thanks to all who participate.

Best regards,

Tony

[crabo]

So has anyone actually changed their position due to this discussion?

[dromia]

It DOES tend to bring all the trolls into one convenient place to watch!


:lol::lol::lol:

Too true! ;-)

[303Guy]

The trouble is, somewhere in there are the true facts! I'm don't understand why they have to be obscured by mud slinging and dogged regidity.:violin:


So has anyone actually changed their position due to this discussion? Well, I have given it a lot of consideration as to the applicability of what I am trying to do with my rifles. But like I say, the facts get obscured. The truth is out there!

[Wayne Smith]

If we remember the context of the original discussions Larry himself has said several times that it probably doesn't matter inside 300yds. That severly limits the applicability of the theory to a very small percentage of cast shooters.

When you deal with those who are pushing the envelope in any discipline they tend to: a) be on the extreme of thinkers b) be vastly experienced in their discipline c) create their own language and d) argue voscifereously (sp) with one another without agreement until the data is finally in.

How is this subset of our group different?

[Larry Gibson]

Wayne is correct; to the vast majority of cast bullet shooters who shoot cast at short ranges and are very satisfied with rilfe loads in the 1500 -- 1900 fps range the RPM threshold doesn't really matter. They are just looking for a cast bullet load that will put holes in paper, for close range hunting or perhaps to plink with. Many, if not most, also are looking at the economy part to get more shooting out of the $s they have to spend on shooting and light charges of faster burning powders that give 1500 fps or so are fine with them as economy is a primary concern so the RPm threshold really doesn't matter to them either.

However, to those very few who pursue the avocation of cast bullets at high velocity for target shooting at longer range, for hunting or just for the fun of it will very quickly come up against the RPM threshold. So what good is the RPM threshold? Well, in and of itself it's not very good because it is a PITA to deal with if one wants to push naked cast bullet velocities. However, it can be delt with. Understanding the RPM threshold, when it happens and why it happens helps us push it upwards. It will always be there but understanding the RPM threshold does make it easier to push upwards to a point.

It's not a "theory" BTW as it can easily be proven and replicated on demand. That takes it out of the "theoretical" field and makes it a reality. 45 2.1 deals with the RPM threshold a lot. That's why he developed his super secret method to get accuracy at high velocity. He may not think the RPM threshold is real but he does deal with it all the time. He also proffers advise on how to push the RPM threshold up. However, the RPM threshold still bites him and others using his techniques. He doesn't admit it but take the 6.5 Swede for example; with a 130 gr j bullet the Swede is quite capable of 2900+ fps. Yet 45 2.1s and others (myself included) max out accuracy wise at 2100 - 2385 fps) (that's in long whippy 29" barrels which should have lots of harmonics according to felix). None of us claims the same accuracy, or even close to the same accuracy at 2900+ fps with 129 gr cast bullets. The reason is with all the technique used we can only push the RPM threshold so high with cast bullets in the 6.5 Swede's 7.8" twist before inaccuracy befalls us. 45 2.1 knows this, starmetal knows this and so does everyone else who's tried to go there.

45 2.1 and other want to call their level of accuracy in the 6.5 Swede the "sweet spot". But in reality it is just below the RPM threshold with their load and componants. When they try to load to higher velocity accuracy goes south. If it didn't they would load to higher velocity. The sweet spot may be where the accuracy is but the RPM threshold is lurking just above it. They all know that. The also know the RPM threshold is real and how to push it higher whether they admit to it or not.

An example of the "good" part is when someone new to cast bullet shooting asks how to shoot naked RCBS or Lyyman cast bullets at 1 moa out of his AR with a 7" twist at 2900 fps we can send him down the right path instead of a lot of frustration trying to do what isn't going to be done. Same with the guy with the 10" twist '06 that wants to shoot a 311291/311284, etc. at 2600 - 2700 fps with moa accuracy. Or the cast bullet shooters with any twist that wants to push to the highest possible velocity with cast bullets. Knowing what the RPM threshold is and how it happens will help them better understand and deal with it, if they want to.

To the majority of cast bullet shooters who don't push above "the load" at 1500 fps or so the RPM threshold is a moot point because they simply don't get there and have to deal with it. I guess for them "ignorance is bliss".

Larry Gibson

[wiljen]

Pretty sure I know where this road leads based on previous iterations of this thread. I am going to suggest that rather than rehash this topic that users re-read the old threads. I see nothing new here on either side of the argument so no reason to keep this going ad nauseam.

[HollowPoint]

So has anyone actually changed their position due to this discussion?


That's a negative Ghost-Rider.

HollowPoint