A new idea for 30 caliber shooters and bullet makers!

M

mturner

Member
I have been working with a few new 30 caliber bullet designs in cad, and running calculations with JBM ballistics. I have determined that with the gaining popularity of the 30BR, and the 30 caliber advancements in accuracy, there could be a need for an even shorter jacket than .925". The advantages would be as follows: bullets could weigh down to 100 grains and still lock the core in place by the ogive radius, lower recoil for the 10.5# class, and twist rates as low as 21" while maintaining a stabilization factor of 1.5. These calculations were run using a jacket length of .875". This jacket would only lend itself to ogive radiuses in the 7 - 8 range, as any larger ogive radius would result in to short of bearing length.

I would like for others to give thought to this as well. I need people like Randy Robinette to step forward with more information on the validity of this idea. With enough people, maybe we can convince Eric Stecker to add an .875" jacket to the lineup.

Michael
 
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Michael,
What would bearing length to bore ratio be, and how does that compare to current bullets?

Keith
 
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michael' What twit ratios and temps were you using also baro pressures?
I'm finding a 16 twist to be really good on a 115 on the 925 jackets. right down to 32 Deg Fh.
The finished lengths are .975 + or - .002
 
In observing some of the threads, the twit ratio appears to be about 1-4 from time to time:)

I apologize.....I just couldn't help myself :D

Rick
 
Miichael...I have been leaning towards the idea of someone making a boattail version on a .925 jacket witha 7-8 ogive...the bullets need a little help at 200-300 yds...I wonder if a short (.075") boattail weighing in at 112 grains would move the weight forward enough to improve stability at the lower speeds it will fall to at 200-300 yds...
 
As far as bearing length is concerned, with a .875" jacket, an 8 ogive would give the same bearing lenth (approx. .140) as the 9 ogive with the .925" jacket, which is the same bullet I currently shoot from Ronnie Cheek. The 7 ogive would have approx .190" of bearing length, so either bearing length is already proven to work.

As far as a boattail is concerned on the .925" jacket, Hal Drake already uses a .095" length boattail on the .925" jacket using a 7 ogive. This would also leave a bearing length of around .140". Hal has just started using this bullet that he makes from a set of Ulrich dies, and he is already winning. This is proof that a .875" jacket will work just fine, since a .925" jacket will work with a boattail that is .095" in length.

Michael
 
GerryM said:
michael' What twit ratios and temps were you using also baro pressures?
I'm finding a 16 twist to be really good on a 115 on the 925 jackets. right down to 32 Deg Fh.
The finished lengths are .975 + or - .002
Click to expand...

The 'ideal' twist rate for a 30 Cal., FB bullet (based upon the .925" long J4 jacket), at sea level and standard conditions is 1:19": at 3K FPS MV, this twist imparts a 1.5 gyroscopic stability factor. A faster twist isn't necessary - though, with BR quality bullets, it won't cause a total wreck!:eek:;)

Michael may be onto something - especially for the PPC case-head/capacity cartridges - though, unless one is locked into the PPC bolt-face, the BR capacity is a better option. I have made ten ogive bullets, based upon the .925" long jacket - they shoot GREAT . . . If your barrel will tolerate a JUMP - a 'leap-of-faith' of sorts! I shot them in a NBRSA registered group event about 6 years ago - they shot a .26 100 Yd. agg - not bad for RGR.:D RG
 
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Randy

Please do a little number cruching and see if you do find it a good thing to have a shorter jacket available. We could use it to make bullets in the 100 - 115gr range, with a possibility of a slightly wider range of weights. Berger could even offer the first production 100gr. 30 cal. match bullet. Talk about super low torque in the bags, and lower recoil in LV applications.

Michael
 
mks said:
Michael,
What would be bearing length to bore ratio be, and how does that compare to current bullets?

Keith
Click to expand...
KEITH, your totally correct in your thoughts if i recall i think its 3-1 jacket length minimum to bore ratio which would make a 925 just about right.don't you think.to eew 1350 its already been done.michael an 8 ogive won.t work as a tanget ogive it barely makes a 925 jacket work. george
 
George

geo.ulrich said:
KEITH, your totally correct in your thoughts if i recall i think its 3-1 jacket length minimum to bore ratio which would make a 925 just about right.don't you think.to eew 1350 its already been done.michael an 8 ogive won.t work as a tanget ogive it barely makes a 925 jacket work. george
Click to expand...

The 8 ogive I'm referring to would not be a true tangent ogive. It would be along the lines of the more common ogives reffered to as tangent. Kind of like the 9 ogive I currently shoot on the .925" jacket, or even the 10 ogive that Randy made on a .925" jacket that he said shoots well, but not easy to reach the lands with.

Michael
 
The 8 ogive i'm referring to is the 8S known for many years Its a clearance detsch point die.
It tapers tword the base to 307 and then 308 and a pressure ring 308.5. It seems to shoot very small groups in many rifles and twists, The 16 twist SF is well over 1.50 Its currently being used also in the 18 twist with good results,
I also have a 7.5 ogive It works very well also but the 8 seems better. The 7.5 is like a knight bullet from what i'm told. all weigh 115 grs .
 
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For some reason the 18 twist barrels don'y shoot well below 50 deg from my barrel makers information.
There is no problem in winter conditions down to 32 deg with the 16 twist,
Making a shorter jacket may help in the 110 range.
As you say maybe a 20 twist. I'm just wondering how it would shoot in the low teps with a 20 twist and a 110 bullet. It would be an interesting experiment.
 
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Gerry,
After I start swagging my own bullets, I may make a pinch trim die and test some .875" jackets in weights from 100 to 115gr. I will report on accuracy testing at that time. We could be talking 4 to 6 months before I get to that point. I just ordered bullet dies today.

Michael
 
I just started bullet making about 4 months ago, and I am making 8 ogive, 118gr bullets from Blackman dies, the pressure ring is .3086, shank is .3082. This particular bullet seems to shoot quite well from 100 out to 600 yards in my 30br., 17 twist. It took me about 2,000 bullets to get to the point where I had a bullet that looked good and shot good, even the ones that didn't look good, they had a fish mouth point shot good. I know that it sounds ridiculous, and I just wanted to see what it would do at 600, OK, I finished I think second, maybe third in the light gun group. If the regular guy that runs the Oak Ridge matches ever gets the results posted at IBS Long Range, go see.
I'm cutting cores for the next 4,000 bullets and am going to make 2 or 3 hundred at 120gr, to see what they do at short range, I'm using J-4 1" jackets.

Dan Honert
 
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Aren't we going the wrong way? I would thing the next logical step would be to go to the .45 cal. 185grs for 100yds and 200 grs for 200 yards.
In score is it not the largest bullet has the best chance of winning?
Centerfire
 
Centerfire,
In this case we are talking about the lightest bullet for 30 caliber group shooting in a 10.5 lb rifle. Current VFS matches allow 13.5 lb rifles where 30 caliber recoil is well tolerated. Maybe a LVS will be added at some point, but at this point all LV guns are mainly for group shooting.

Michael
 
I just realized that a shorter than 3 to 1 ratio jacket length has already been proven very accurate. The Sierra 110 gr bullet is made on what appears to be a .790 jacket, and I only planned for a .875" jacket. The overall length of this bullet is only.797". Anyone who has shot the 110 gr Sierra bullet knows that it is capable of shooting ones. The only problem is the meplat diameter of .125" which causes about twice the wind drift of our current bullets with a .062" meplat.

And now another one from Berger. The .600" long .224 jacket.

Michael
 
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You could change the point with one of those meplet trimers and point die system on the Sierra.
As the 600 jacket goes i have used them with great success. They make really nice 40 to 45 gr 22 bullets.
I have a friend who requested some for an experiment . He likes to shoot the 22RF mag and had a fellow that actually reloaded them. He asked me to make some 40 gr pills for the reloading prodject and it turned out really well.
I also made some 45 gr pills for another experiment that he had and they also shot really well.
The bullets were made on Detsch dies with the same shape as the Remington Br bullets,
 
Just to not open a new thread.

What jacket lenght you guys recommend for 224'' bullets with 69 and 75 grains weight ? Will they stabilize in 1/9 tw 223 rifle?

Thanks
 
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