How critical is brass to performance of a rifle??

[Ogre6br]

HI
I am having a .20 PPC varmint repeater made.
over here in AU pricing for brass is way over what you guys pay.
Getting Lapua 220R brass is $120/100
Getting Lapua 7.62x39 is $40/100

I want to get 400 brass made up for the .20 PPC as I carry a minimum of 200 rounds with me each time I go out for a hunt,an usually another 1-200 in the truck- just in case)

I have plenty of time,3+months) before the rifle is ready so the time spent prepping brass isn't an issue here.

The cost of using 220R brass is going to make getting my required 400 almost as much as the cost of getting the rifle built.

I can get 300 7.62x39 brass for the cost of 100 220R.

What problems or issues or performance problems would I encounter if I used 7.62x39 instead of using the 220R to make my .20 PPC brass?

I understand from various article that forming 220R to .20 PPC is quite simple.

What is involved in making PPC brass from 7.62x39??

With the extra neck diameter and larger amount of necking down required what problems could I encounter in using the 7.62x39??
Will I need to anneal??
Will the necks be to thick for the .237 neck diameter I have asked for and need neck turning??
Will the LR primer in the 7.62 case create problems or pressure issues?? I have plenty of LR match primers that i can use or will I have to use L pistol primers to keep the flame propagation similar to SR match primers??

Thanks
Later
p

 

[Ackman]

Keith Candler made about 5,000 PPC cases from PMC 7.62x39 brass and even used it to shoot bencrest. Maybe he'll come on here and tell about it. Accuracy difference between that brass and the small primer of a .220 case was miniscule. But with large rifle primers velocity was the same with something like a grain less powder. I also know a guy who opened up some BR brass to use a large primer and got similar results.