100 gr. 30 caliber bullet

M

mturner

Member
A little while back, I mentioned the idea of making a 100 gr. 30 caliber bullet on a J4 jacket with a length between .850" and .875". I will be using a pinch trim die to shorten the .925" jackets. I made 3 samples, and only 3 for now since these were trimmed by machining them in a collet. This wasn't quite enough to get the dies adjusted out properly, but this thing is still pretty cute. Pictured next to a .925" BIB. Both use a 7 ogive radius.

Michael
 

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Pete,
This bullet at .850" gives a stability factor of 1.4 at 3300 fps with a 22" twist. This velocity is attainable from a 30 BR at this weight. The B.C. is around .265, or the same as the current 6mm bullets used in short range BR. In the 30 PPC, I would run a 21.5" twist for the lower velocity. The 21.5" twist gives stability of > 1.4 all the way down to 2200 fps.

Michael
 
mturner said:
Pete,
This bullet at .850" gives a stability factor of 1.4 at 3300 fps with a 22" twist. This velocity is attainable from a 30 BR at this weight. The B.C. is around .265, or the same as the current 6mm bullets used in short range BR. In the 30 PPC, I would run a 21.5" twist for the lower velocity. The 21.5" twist gives stability of > 1.4 all the way down to 2200 fps.

Michael
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Sounds like a lovely thing to me. I have a small batch of 100g bullets made on a short jaket and they shoot well.
 
Looks like a slick project, Michael.

A while back, I was sent some prototype .30 jackets by a company that was interested in supplying jackets to the BR bullet makers. The jackets were .970 long and very, very light weight. It took a bit of juggling with lube in the point up stage but once that was sorted out, they made slick little 101 gr.'ers.

They shot great in the two 17 twist barrels I tested them in. But they really shot well at 200 in a 15 twist 3 groove Lilja....which backs up the Sg numbers when comparing the two against the 'baseline' 1.00"/118gr/17 twist combo. The difference in torque between the 17's and the 15 was small, but noticeable.

Kinda' dirt clod engineering to verify that when lightening up these .30 bullet weights beyond a certain point, the jacket length should be backed up and the twist rates juggled, while keeping an eye on the Sg.

How long is the bearing surface on those, Michael? -Al
 
Michael, I suppose that you have found that jacket quality, as well as any other components involved in bullet making, is paramont in producing agg winning 30 cals.

Short of going to the range and testing them, how are you checking your jackets, or anything else.

That bullet is cute. Is anybody making a 30 cal jacket shortern than .925 at this time??
 
Al,
The total bearing length that is a full .308" diameter is around .165". The bearing length based on the full engrave length to .300" bore diameter is .300" in length. These numbers, while short, compare favorably to the 9 ogive bullets that Ronnie Cheek makes on a .925" jacket which fall below .308" at just .1" from the base, and the 110 to 115 gr. Bergers with a 8 ogive on a .925" jacket that remain .308" for .200" from the base. If the jacket length was settled on at .875", we could add .025" to these numbers, and simply say that you give up .050" of bearing surface when compared to any bullet made on the .925" jacket. This should allow both 7 and 8 ogives to be used with the .875" jacket, where the .850 jacket might be a little short for the 8 ogive, only testing will tell.

The bottom line here is could we get these jackets into the hands of those interested in making lighter weight 30 caliber bullets? The only way that will ever happen is for these things to take place: I make up enough to test them myself. They shoot well. I trim enough jackets to allow you and others to test, and they shoot well. We call Eric Stecker and get him to run a batch.

The only thing is we have to find enough interest for him to run 100,000. That's the minimum # he gave me. With the popularity that 30's are gaining, we might find 10 people willing to take 10,000 each. Apparently Berger is already running considerably more .925" jackets each run, and we still run out. Eric said his pinch trim die is adjustable, so he can already run a batch just as easily as another batch of .925" jackets.

Jackie, this post may have answered your questions also. Currently these jackets are trimmed J4's, so the numbers are limited unless these things prove themselves in a big way.

Michael
 
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Mike, what kind of freebore length do you have in your reamer for these short jacket bullets to reach the rifling or are you jumping them big time? --greg

mturner said:
A little while back, I mentioned the idea of making a 100 gr. 30 caliber bullet on a J4 jacket with a length between .850" and .875". I will be using a pinch trim die to shorten the .925" jackets. I made 3 samples, and only 3 for now since these were trimmed by machining them in a collet. This wasn't quite enough to get the dies adjusted out properly, but this thing is still pretty cute. Pictured next to a .925" BIB. Both use a 7 ogive radius.

Michael
Click to expand...
 
It would be my opinion that if they work well you won't have any trouble parting with 100K. There are lots of 30 BR shooters out there who never compete in matches and who want the latest but, if they work, put me down for 1K. I prefer 7's, by the way. I have a few lod Speedy 110that are .925 long's and 8's. They shot very well.
 
Do you think felt recoil would be noticeably less with a 100gr bullet compared to a 116gr? I would love to have a LV rifle to shoot group with in 30BR, but i just dont think i can handle the recoil as it stands. Lee
 
Lee,
Get you a PAST recoil pad for your shoulder. I shoot a 7.5 x 55 Swiss in matches. It weighs about 9 lbs. And I can tell you for sure it kicks about twice as hard as a 30BR. I shoot it in military bolt action matches. 10 shots per target, 5 targets. I have arthritis and am almost 75 years old. It is no problem, just get the mag or mag plus shield. Make them hard kickers pussy cats. I am going to build a super light stock for my 30BR this winter so I can shoot it in the LV matches. I have shot it at 12 lbs and no problem so I don't think 10.5 will be too hard to handle. I might add that I am a bit recoil sensitive too. You might want to look at this sight for recoil energy. http://www.huntamerica.com/recoil_calculator/

Donald
 
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Greg,
I have about .030" freebore. It would be a little better to have zero freebore for anothe .030" of bullet in the case. Currently I am touching the lands with the 7 ogive with about .150" in the case neck, so it's not bad. I have less in the case neck with a 9 ogive on a .925" jacket.

Michael
 
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