300 Norma Mag Improved reamer help.

[300SALRH]

Would appreciate some help from the cumulative experiences browsing here about input into the specification of 300 NM Imp reamer.

With regards to the neck diameter and clearance. I was able clean and uniform the necks of 10 cases if turned to 0.015”. Also read somewhere that some of the guys has found that 0.004” to 0.006” total clearance (0.002 to 0.003 on both sides) have been delivering more accuracy compared to tighter clearances. What clearance would you guys recommend?

Other than an increase of case capacity, what advantage is there in reducing the tapper on case? I’m planning to use the same tapper as standard 300 Norma Mag.

Considering the base to shoulder length, what you guys recommend? The same as a standard 300 NM or perhaps shorter or longer?

Any other consideration to take into account when doing a improved version. Planning on going with a 35* shoulder.

 

[fredo]

Usually, guys who 'wildcat' a cartridge are doing so in hopes of reaching a goal that improves upon the parent case. Given that, they already have an idea in mind about achieving it, with regard to reamer specs...

What are your aspirations for this wildcat?
What performance gains are you hoping to improve upon, over a standard .300 Norma Mag?

What is your wildcat gonna do that established wildcats don't/can't?

Considering the above, is the extra expense, time and work to design a 'one off' reamer worth the effort?

Not trying to dissuade you, just trying to provoke some thought & input from your end. That will help others tailor their responses to your post.

If ya just want a new wildcat to be different, that's cool. Just askin', is there some other goal your shooting for with this project?

 

[300SALRH]

Hi Fredo. Thanks for the input. Getting that balance right of providing just enough background and not making the post to long is not always easy.

Count yourself extremely fortunate being able to walk into a shop and select a powder with a burning rate that will optimize the volume/bullet selection. The other one is the ease of replacing a barrel, not even talking about the availability. We only recently started having access to small quantities of Hodgdon and Vihtavuori. Waited close to 1yr to source a 1:9 barrel and the permits to build and the to get a license can further take up to 2yrs. To replace the barrel can also take up to 3yrs.

Thus based on this I want to achieve and address some of the issues by improving the case. The first one is to try and divert the flash point into the case to try and extend the barrel live. I also don’t want to increase the case volume to much based on the powder that is easier obtainable. The other one is reduce brass growth and other advantages of a improved version. Then to extract as much as possible accuracy out of the case.

This rifle will be used to hunt African plains game at long ranges. Although I dint want to go to tight/benchrest specs with the reamer, I also don't have to allow for hunting specs. The type of environment will very similar to f class. The gain in velocity is not that important but if a improved case can help with a reduction in pressure to achieve the same velocity it will be considered a bonus.

I hope this helps a little.

 

[fredo]

Thanks for the response.

Your points lean toward just running a straight .300Norma Mag. Or, even a .300Win Mag.

Dunno where it is you live, but from your description of difficulty in obtaining components, it seems to make good sense to stick with a cartridge where factory available ammunition may be obtained for it? That way if your component availability dries up, you have something to fall back on?

FWIW, I went with an 'improved' Norma for a few reasons:
1. Increase performance (capacity/case life)

2. I like the 30° shoulder of the SAUM and x47L cases that I already run. Both are proven performers.

3. I like to 'wildcat', for the challenge & enjoyment of it.

4. Its fun to be different!

This wildcat's shoulder dimensions allow fireforming from straight .300 NM brass, or necked down .338NM brass. I chose the latter, to create false shoulder & achieve a nice 'crush fit' on a closed bolt.
Neck diameter allows for .004" clearance on loaded rd. without neck turning.
Freebore is a compromise to allow either a 215 or 230 Berger to be run efficiently @ ~3.600" magazine length.

P.S. I'm running the same powder that's been proven in parent case...just a bit more of it

Hope that helps?

 

[300SALRH]

Thanks for the response.

I have everything to run a straight version 300 NM and only prefer a belted case on my 375 H&H.
Live in the country where being a farmer is currently considered to be the most dangerous job in world.
I have made sure that I have enough brass, bullets and primer to potentially see out the barrel. Fortunately have some local powder called S385 to fall back onto. Unfortunately its to fast to optimize the bigger cases and heavy bullets.

Would also like to increase case life and from your decision I assume you share Dave Tooley’s view that everything more than 30* is not worth it. Also had a look at 30* shoulder and believe it is called the 300 Jazz? Do you feel that the 30* did indeed improve accuracy?What is the case volume of your wildcat?What did you increase the shoulder diameter to?

As long as different results in being better and optimized and addresses certain issue, I also agree.
I have to travel over borders so having the correct brass stamp at the back is critical. I have however had feedback suggesting that 338 NM brass is better.
Also leaning towards the 0.004 clearance but with the necks turned to .014. This will be a single shot rifle so not to much worried about COAL.

Thanks for the info.