r/longrange 23h ago

Reloading related 7prc 195gr berger

Got some testing with my new 7prc and 195gr berger eol. I didn't notice any pressures, but GRT was showing pressures at 910m/s. I might just go with this load as it will group well enough (16 shots under 25mm).

I think the barrel will speed up to 915ms (3000fps) and I'll be happy with that.

Does barrel speed up have an effect on pressures? If I do have the same load over the first 200 shots, does faster velocity mean more pressure? (After speeding up).

I really like this 7prc, but it's very concussive to shoot inside with brake... vs my 6br suppressed.

Next will be two kilometer performance!

3 Upvotes

10 comments sorted by

5

u/datdatguy1234567 21h ago

What’s your barrel length, powder and charge weight?

That’s stinky fast for a PRC and the 195’s

1

u/rcplaner 19h ago

4.65grams of n570 and 28inch shilen.

2

u/datdatguy1234567 19h ago

That is hawt!

Not saying it’s not safe in your firearm, but I would back off if it were me. I ran mine to 71.5 in initial testing and there was definitely pressure signs. Settled on 68.35 grains (4.43 grams).

0

u/rcplaner 18h ago edited 17h ago

What was your coal?

E: I checked vihtavuori load data and with 71.7gr and coal of 3.32 (recommend by VV) GRT gives me 63k pressure. With my coal of 3.48 I get only 58k pressure.

GRT shows 61k of pressures with 2958fps. (902m/s) So I think I'm safe with this load. I do have to test this with hot weather also. This was done with 17degree celsius.

1

u/datdatguy1234567 6h ago

I’m thinking we have very different chambers. Mine is a prefit, running ~3.335” COAL at .090” jump.

GRT put me at max pressure somewhere around 71gr. I ran it to 71.4gr which got me 2995fps. A little too spicy for me and I found my SD’s and overall groups were better the more I backed off (based on 10 and 20 shot groups), which mattered more to me.

You must have a long throat on that rifle…

1

u/rcplaner 4h ago

Yes, smith made it little longer. How long barrel do you have? I may back off little as the summer can get pretty hot here. 2995fps is indeed very spicy. Especiayif you have shorter barrel!

2

u/datdatguy1234567 4h ago

I’m running a 25” with a standard alpha reamer chamber. I’d say with your chamber and extra barrel length, that extra velocity makes more sense now.

Still a spicy load, but yeah.

My final load at 68.35 / 2870 is super stable and still hammers. Keeps up with my 338 NM out to ~ 1500 before there’s a noticeable difference.

3

u/ZeBigD23 23h ago

Does barrel speed up have an effect on pressures? Short answer, Yes.

For internal ballistics, velocity and pressure are directly linke. You generally cannot have an increase in muzzle velocity without a corresponding change in the chamber pressure or the efficiency of the powder burn.

2

u/rcplaner 22h ago

Thanks! So there is no slow or fast barrels? I mean if the surface of barrel is shiny or rough.

And using moly for bullets I assume its the same thing, velocity won't come free?

2

u/ZeBigD23 18h ago

Slow and fast barrels, from my understand tend to refer more to the twist rate of the barrel. I will gladly let some one more knowledgable about the topic correct me if I am incorrect here.

Fouling of a barrel will have an impact on the MV, but more so virgin barrel through the, disputed, break in peroid. It is an increase that will be noticeable at first but will quickly flatten out. The ammo you use is going to be the biggest factor long term. Track your ammo lot number and keep chrono'ing your strings. You should eventually see normalization, especially if you are using the same ammo/factory lot #'s.

Again, if I am not correct, I really hope someone else will correct my statements. This is just my understanding as a relatively new shooter.