Boats I am with you, I feel you can definitely over spin a bullet not so much for stability reasons as much as for nose slump reasons. Those sharp noses on the spitzer bullets have to deny allot of forces prior to leaving the barrel and centrificul force from rate of spin is probably the hardest one to overcome. I close friend of mine made a catch box and he recorded nose slumps any where from 5 thousandths up to 12 thousandths. I refer to nose slump as the forces pushing the nose off to one side and no longer being central to the bore. A definite accuracy killer and I think this is also why I have experianced the continuing great success with the harder lead and tin alloys such as the 1-16 that I am currently using. It equates to smaller groups, less fliers and greater consistency as long as you don't experiance leading. There is also a secondary form of nose slump and that is when the bullet collapses like an accordion from the initial powder blast as the last to start moving is the nose. If the bullet does not collapse straight back and equally then the nose again will slump off to one side and no longer be central to the bore. Either way the bullet is no longer balanced and if the lube grooves are not completely full and or missing on one side the bullet cannot slump straight back and equally. I could go on with my personal findings but I think this is enough to get an idea of some of the things going on with the bullet that we tend not to think about such as your original comment / concerns with over spin.

J.Louis

John,

Here is the link, although the article is on twist rates for 30/06.

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Thing that got me thinking was the trend to fast twist 38 barrels with very long cast bullet.  And the excellent results I get with my Douglas 18 inch twist barrel and 300 gr bullets.  That barrel was set up by CPA in 1993 and is considered slow by today's standards.  Yet it shoots perfectly stabilized and effective to over 500 yards.

It's all opinion but I think cast bullets better to stick with what works. Not use ideas based on jacketed bullets in sub calibers for long range shooting.

Be interested in actual match results with fast twist long 38's

Boats

No worries I do the same thing all the time. Must be Senior moments.

Years ago when setting up my 38/55 for BPCS I went fairy pointed with one of my molds. Looking for better wind results and hit harder on Rams.  At the time was warned away from longer bullets & there were few fast twist barrels on the market then.   

It's been a very good combination but belive I was lucky with the bullet.  Several others I know of never performed well, probably due to nose slump.  Add fast twist and even longer bullet it's a roll of the dice results wise. 

Boats

I am in total agreement Dave, that bullet I shot that was always on the ragged edge and had to be pushed hard would have benefited to a slightly faster twist. Those little strange puffs of wind probably would not have pushed it over the edge. That was the best shooting bullet accuracy wise that I have ever owned in 32 cal. and Bruce now has it and it should shoot lights out in his RKS gain twist barrel ending at I believe around 11.

J.Louis

I don't know, good quality Jacketed bullet yes twist it fast is good. And I am pretty sure too slow is not a good thing.

Soft imprecise lead bullet I think you can over spin causing unintended problems. Might be gain twist is a way to get a plain base cast bullet spinning fast with less chance of trouble.   

To be clear I am not doubting fast twist for long high BC bullets.  I do doubt it's a good thing for cast bullets.  It's all theory far as I can see, unless somebody can show clear match winning results with real fast twist.

Boats

Boats,

Did you notice any trend in how the nose shapes among the 300 grain weight bullets you tried affected the accuracy with your 18" twist barrel?

Boats I think this will add some interest to our discussions on twist rates and also help us to get a better understanding on the negative effects of over-spinning. Due the calculation for your current twist rate then up it to the next fastest and one will see the RPM increase is very substantial. All though the conversation revolves around jacketed bullets it directly applies to our lead and tin bullets as well as one will soon realize while reading it.

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J.Louis