358 Winchester Mold

[youngda9]

That 358Win has a max COL of 2.780". I'm shooting the Accurate 36-230D (http://www.accuratemolds.com/bullet_detail.php?bullet=36-230D-D.png)at 2200fps using 42gr H4895 with good accuracy...loading OAL to 2.600" to have full caliber portion of the bullet touch the leade. It weighs 232 grains cast from WDWW with gas check and lube. I designed this bullet to keep the check just in the neck and have the full caliber portion touching the leade.

I was thinking that I'd like to extend the bullet length by .15" for a heavier boolit. It would still be .03" shorter than max COL in the 358 Win. I've looked at a twist calculator for this length and weight of a boolit in the 358 and it is plenty stable with the 1/12" twist Ruger Hawkeyes that I have.

36-230D is currently .95" long. Extending the length by .15" would make it 1.1" long. I was thinking that .1" could be added to the bore riding section and .05" to extend the length of the nose taper for a more streamlined profile.

What do you guys think of that design idea? I'm thinking it would be about 270gr (got that by multiplying the length ratio by the current weight). I imagine that I might be able to get 2000 fps out of this boolit.

Thoughts?

[Larry Gibson]

You hunting T-Rex? Is anything really going to notice the extra 40 gr? Just a couple questions in my mind. However, it's your mould and do what you want but you are pushing top end loads and hanging a "more stream lined" longer unsupported nose out the may very well be detrimental to accuracy even at the slightly reduced velocity.

Old adage; "if it ain't broke, don't fix it"..........be better to get a new custom mould of your design than potentially ruin a good mould that is working well.

Larry Gibson

[youngda9]

I am not talking about modifying an existing mold. This would be a new design. And why the T-Rex comment? A slow heavy boolit would be perfect for larger game (elk, bear, moose, etc).

The Ruger action is chambered in much higher pressure cartridges than the 358Win...so there's no risk of anything in the "top end" of a 358 load being dangerous in a Ruger action. Not shooting high pressures with cast boolits anyways. The 42gr of H4895 that I'm using is listed as the starting charge for a 225 grain bullet according to Hogdon, with 46.5gr being the max.

Why would an otherwise identical design with a 0.1" longer supported nose section and a 0.05" longer unsupported nose section be inherently less accurate?

I was thinking a slightly smaller meplat might be better as well. At 2000 fps the boolit would mushroom just fine I think.

I thought about trying the Saeco #352 but then thought why not come up with something again on my own. The #352 has the same meplat and a slightly extended nose profile but would only be 10-15 grains more in weight...so it didn't seem different enough.

I enjoy trying different designs and molds to get the best accuracy.

[JesterGrin_1]

45_2.1 Designed this one that is 265Gr Ready to Load. I do not think there is a mold for this one as of yet though.


http://castboolits.gunloads.com/attachment.php?attachmentid=65472&stc=1&d=1364326604

[youngda9]

Jester, 0.18" meplat is the largest that will reliably cycle in one of my my rifles so I didn't want to go larger than that. That is like a similar concept to what I was going for except it looks like the entire front end is bore riding and there is no full caliber portion of that design in front of the crimp groove.

[JesterGrin_1]

I have no idea lol. Give 45_2.1 a shout and I am sure he can help out.

[Larry Gibson]

Youngda9

Please don't get the feathers ruffled. I guess I just read the post thinking you wanted to lengthen the nose of the mould you have....no mention by you of getting a new mould. The T-Rex comment simply infers that "elk, bear, moose, etc." are probably not going to notice the 40 gr difference in bullet weight especially at the 200 fps less velocity.

It is well known that long tapered unsupported noses are not conducive to best accuracy. I did not say they were inherently inaccurate; I said; "you are pushing top end loads and hanging a "more stream lined" longer unsupported nose out the may very well be detrimental to accuracy even at the slightly reduced velocity.". There is more to it than what a "twist calculator" indicates. The "top end loads" was referenced to top end loads with a 12" twist using cast bullets, not what the 358 Win is capable of in your Ruger.

Larry Gibson

[youngda9]

Larry,

I understand where you are coming from. I want to try different molds for the rifle. I decided to go up in weight instead of going down because I don't think I could get much more velocity to matter with a lighter 200grain bullet. I don't shoot at long ranges for hunting or target shooting so a flatter trajectory is not that high on my priority list. I prefer to know the trajectory and hunt to within ethical (my standards) distances for shots on game. I think the load I have is plenty good for anything I would ever shoot. The engineer in me wants to tinker, experiment, and learn.

Are you referring to the 0.05" of additional length as the "unsupported" addition...or does the 35 caliber 0.10" suggested addition of bore riding length also count as "unsupported" for a total of 0.15" ?

The current design has 0.64" of the boolit at 35 caliber or larger of the total 0.95" bullet length...for a roughly 2/3 ratio of supported/unsupported the way I was calculating it. What I was suggesting was adding the same ratio. Therefore I was under the impression that it would not inherently affect accuracy in a negative way...and actually may be a positive due to the additional .10" length of bore riding section. You seem to be under the opposite impression. I do not know of the ratios or length of other common designs but from what I've seen they tend to have a greater nose to total length ratio than I'm suggesting.

Your opinion is appreciated.

[MT Gianni]

IMO, if that bullet you have now will not exit a moose either the alloy is wrong or the shot placement. If the accuracy is good I would stick with it. If you want to play then molds are cheaper than new calibers and I understand the thoughts, though mine have leaned towards new calibers. If you are getting good groups with that velocity and cartridge it is a keeper.

[Larry Gibson]

Youngda9

Here's what may happen; the bore riding nose (not counting the nose portion where the ogive begins) is "supported" as such only as much as the surface of the lands actually solidly touch the bore riding portion of the nose. That leaves the area of the bore riding section exposed to the grooves susceptible to uneven obturation during the harsh reality of acceleration. The harder the acceleration (sharper time/pressure curve or higher velocity) the greater the inertia of the unsupported part of the bore riding nose and the greater the obturation will be. If that obturation is uneven the bullet is not balanced and inaccuracy results from that. If the bore riding portion of the nose is not solidly supported by the lands it may very well bend to one side until supported. That also imbalances the bullet with inaccuracy being the result. Additionally, if we have a longer portion of unsupported nose hanging out front it very often exacerbates the uneven obturation and bending because the inertia of it's weight and position give it additional leverage to create uneven obturation and/or bending of the bullets nose. May or may not happen with your design concepts. Just mentioning it as something to consider is all.

This is why weight for weight cast bullets with RNs are most often more accurate to a higher velocity than semi pointed or spritzer shaped cast bullets.

Larry Gibson

[youngda9]

Larry,

Thank you for the information and your time. It's something for me to think about. I don't know where this threshold lies due to the many variables (pressure curve, hardness, unsupported mass, etc.). May only be one way to find out. I'll think on it.

Dave

[Larry Gibson]

May only be one way to find out.

With many designs with bore riding noses that is usually the only way to really find out as there are so many variables. Controlling the variables and keeping them constant from casting session to casting session is alone difficult with many designs. The 311413 bullet is a prime example; many really would like to drive that cast to duplicate ball FMJ ballistics in several milsurp cartridges. They quickly find out the difficulties of such. Another example in .35 cal is Lyman's 358315 which has a long totally unsupported round nose. It generally shoots well to 1700 fps but does not do well above that. RCBS's 35-200-FN on the other hand with a good bore riding portion and a very short nose does very well in 35 cal cartridges upwards of 2400+ fps.

Larry Gibson