Cast bullet weight

[rodmkr]

Is there a program that will tell you the optimum cast bullet for a particular barrel twist?

Reason for asking.
Have a Mauser that I installed a Kreiger bull barrel on
Barrel was on a varmit shooters rifle and he did not like it.
Have not slugged it to see what twist but was told it was a 1:9 twist.
Shooting Lee C309 150 F bullets it groups 2.5 inches at 100 yards but always has a number of fliers.
Thought a heaver bullet might be the answer but would like to ( run the numbers) so to speak and see What cast bullet would be the best.

Jim

 

[Ian]

Yes, there are multiple programs. I use the JMB ballistics program, available free online, just plug and chug with no download necessary.

Is that your problem? Likely not. What kind of throat does the rifle have?

 

[Bass Ackward]

I can tell you that you could have multiple .... issues causing your concerns. You can choose to take steps to address them one at a time until you find the problem. Or .... you can spend a bunch of money only to find out that you STILL have to address these “issues”. Gear picked you up to begin the education process. I’d listen & do what he asks. The process he walks you through is what you will need to perform for each & every rifle that you wanna shoot cast from.

 

[RBHarter]

A 1-9 30 cal will run the NOE or Lee 230 probably the 250s .
Likely without very special attention you'll peak about 1900 fps .

 

[waco]

My guess is Ian and Bass wanna see a pound cast.........

 

[Brad]

I’m trying to figure out who this “Gear” dude is that Bass speaks of.....

 

[Ian]

Just another "deplorable"......

 

[fiver]

some dude with a Big hat on the rack in the front hall.

one more [Colombo type] question.
how fast was you getting these groups at?
were there flyers making the group that size or just random holes that far apart?
was the 'groups' round?
were the holes clean and round or smudgy looking or oval shaped?

 

[CZ93X62]

I was just thinkin' (always hazardous, that)........1-9" twist in a 30 bore is kinda fast.

 

[Brad]

Not sure why a guy would want a bull barrel 30 cal with a 9 twist. Not unless you wanted to shoot a very long bullet at very long range.

I would look at bullet quality and fit as your starting points. That pound cast will tell you a lot about fit.

Damn, I am starting to sound like that big hat dude.....

 

[fiver]

aird there are 2 lee 150's also.
one with lube grooves and a horrible COG and the other one with horrible lube groove but better balance and shoots better.

 

[Bass Ackward]

And the first & easiest thing to do is measure your twist rate. Use your cleaning rod, a tight patch, & a marker pen. Mark the rod at the muzzle & back by the handle. Push it in till the handle mark comes round again & mark the rod at the muzzle. Pull it out & measure between the 2 muzzle marks.

 

[rodmkr]

The twist is 1:9.(measured) as Bass recommended
The chamber is a 308 match chamber (new) when the barrel was cut back and rethreaded for the Mauser action.
Got the barrel for free so that is why I have it.
It shoots jacketed just fine with 175 grain sierra match kings and 39 grains of varget.
Will hold a 1/2 inch group at 100 meters.
Just wanted to shoot cast in it and have the Lee 150's available to try!
Will look up the JBM balistics program and give it a whirl.
Thought someone might of had a recommendation.

Jim

 

[Ian]

There are as many .308 "match" throats and necks as there are .308 "match" barrels, so that means nothing. Proper fitting of the bullet in three dimensions to the throat size and shape that you have is critical for fine accuracy. In order to find a bullet that will truly fit your rifle, you must measure the chamber neck and throat. Best way to measure that is to make some sort of durable cast or impression of that area of the rifle and measure it very, very carefully to create a drawing representative of the shape. Then you can select a bullet mould. You cannot fit a bullet very well blindly. After that, it's mostly about using the correct alloy and powder to achieve your desired results, with some further fine-tuning along the way. It's a long road with a lot of "shoot'n'see" unless you want to hang out around 14-1500 fps and only fit bore/groove.

Instructions on how to do all this is in the read-only "tips/tricks" section.

 

[fiver]

some insights on why one would want a 1-9 twist 308 barrel.
they would want to shoot slow and need the faster twist for more stability.
or they wanted to shoot heavy bullets and wanted the stability.

there is a third possibility and it does involve light weight bullets.
Jim mentioned the original owner was using it for a vermin rig of some sort.
overspinning a light weight fragile bullet does help the bullet become more frangible on contact with stuff.
I can [vividly] imagine the effects of some 90gr 311 diameter bullets smoking out the barrel at 3+K fps and hitting a 2lb P-Dog 100 yards away.
I know what the 125 TNT Speer bullet does to a rock chuck [about 3 times the size of a P-dog] at about 300 yds from my XCB rig.
got a good view of that through my scope a couple of times,, it's a 10 twist.
I have also seen what a 40gr '22 hornet' bullet does to one at 200 yards through an 8 twist barrel at about 3-K fps and the results are pretty similar.

 

[rodmkr]

My twist measure has had a breakdown.
Actual twist (Remeasured by me) is 1-10
The lee C312-150-2R shoots to point of aim at 100 yards using 13 grains of Red Dot.
The chamber was cut to exact match specs( whatever that is) and there is little or no throat or leade.
The Lee bullet is sized .309 and fits the fired case with little or no neck sizing.
All other bullets I tried have to be seated well into the case to be able to close the bolt.
Tried some 173 grain cast and it was 1/4 inch past the neck.
only fired 3 as I was pushing my luck I thought.

Here are a couple of pics of the rifle mostly to show Ben the stock.
It is hardware store Walnut Hand cut and formed by me.
It is the last stock I will ever make as the stroke sorta messed with the left hand and it dont work so good anymore as I found out when I was making the stock.

 

[fiver]

nice job,,
I really like those roll over shadow line combs, especially on hunting rigs.

 

[Bass Ackward]

Actual twist (Remeasured by me) is 1-10
The chamber was cut to exact match specs( whatever that is) and there is little or no throat or leade.
The Lee bullet is sized .309 and fits the fired case with little or no neck sizing. It is the last stock I will ever make as the stroke sorta messed with the left hand and it dont work so good anymore as I found out when I was making the stock.

Glad you are makin progress there Rod. Ain’t nothin like knowin your rifle. Fun’s bout to start now.

But I’m confused, & I know you folks on the left coast see things differently from the rest of the country, why would you make another stock? Don’t like that one or what?

Get a dog. That’ll help that left hand get in shape petting the pouch. Time to load some shells up.

 

[rodmkr]

Don;t be confused Bass.
The Mauser action was one I had in a drawer.
Added the barrel and muzzle brake and made the stock so it is the only one the poor little rifle ever had.
Didn't want it to be shivering out in the cold
It now has a Timminy trigger and 2-6 VX2 Leupold scope

No dogs allowed. Wife is allergic to them plus scared to death after being bit by one!!
Jim