need info for IMR4320 7.62X51 NATO

Emshey

Emshey

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Hello i currently purchased a ishapore A2 rifle that is chambered in 7.62x51 (308) it is highly suggested to stay with surplus nato spec ammunition for this rifle. so my question is i currently reload 308 ammunition i currently use IMR4320 powder standard CCI primers hornady and federal brass and a hornady match 168grain BTHP bullet. i am wondering how much grain of powder i should put to try and satisfy this "NATO" spec pressure to shoot this rifle safely. i have tried to do some research can not really find much information at at least for this specific powder.

Thanks!
 
i think i got some info from the IMR website, it looks like at 41.5 grains with this type of bullet it will be producing approx 43,800 PSI, not if i go to the lower end of the table and try 34 grains it should be running a low enough PSI as i think NATO is roughly max 50,000. i do not plan to shoot very long distance just want to play around at 50-100 maybe 200-300 yards.
 
Emshey said:
I do think NATO is 50,000
Click to expand...

Yes. When the 7.62 spec was written (which was before the 308) it specified 50,000 psi measured by copper crusher. We refer to this as "CUP".

It is a different measuring system, much like mph and kph.

In transducer psi (the way pressure is measured these days) both 7.62 and 308 have very similar limits - about 62,000 psi.

Here is an ammo test done by our Explosives Branch (Federal Gov't). Note the pressure of the IVI 7.62x51. I was having it tested because it was hot in a number of rifles. Read the far right column.

Also note how much the pressure differs between a SAAMI standard barrel and a target rifle barrel.

test summary.jpg
 

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Ganderite said:
Yes. When the 7.62 spec was written (which was before the 308) it specified 50,000 psi measured by copper crusher. We refer to this as "CUP".

It is a different measuring system, much like mph and kph.

In transducer psi (the way pressure is measured these days) both 7.62 and 308 have very similar limits - about 62,000 psi.

Here is an ammo test done by our Explosives Branch (Federal Gov't). Note the pressure of the IVI 7.62x51. I was having it tested because it was hot in a number of rifles. Read the far right column.

Also note how much the pressure differs between a SAAMI standard barrel and a target rifle barrel.

View attachment 144137
Click to expand...

Oh nice thanks for the information i appreciate it!
 
Emshey said:
Oh nice thanks for the information i appreciate it!
Click to expand...

You are welcome.

Commercial and military ammo usually runs around 55,000 psi. It is not a good idea to get up to near the max because sh!t happens.

That said, I have seen a lot # of both IVI and Winchester match ammo at 62,000 psi, so there are no guarantees.
 
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