8mmRM 220 sierra 220 gr 24" barrel, Is 3200 fpsTOO much?

[8mm RUM]

HUMM think it's OK?We where out today trying some 8mm RM loads.
I have some original Rem Factory 220 gr rounds.
We ran them over our Speedometer and got 2750 FPS.
Just forward of the "Band" we mic'ed it at .505 before shot and .512 after.
A one 1 1/2 " group ( dang windy today).
I have a load we worked up with the same sierra bullet.
Speed runs right at 2990 to 3000 fps.
I shot a 1 inch at 120 yards. It Mic'ed at .512 and did not expand.
No sighs of presser.
I was looking for more, don't know what but always looking.
We got some reloader 26 ( finally), it is supposed to be great stuff. There is little to NO load info, so I'm not going to list the charges.
I had a guy do a Quickload work up on it and got some data.
At the Minimum load we got just under 3000 fps, on sign of presser
and no expansion. Groups where over an inch.
A bout 25% over min we got right at 3100 fps, about the same for groups, little more then our worked up loads.
Then we tried a charge about 2 GR under max.
We got a smidgen over 3200 fps and only slight sign of presser, primer a little flat but still very easy bolt lift, the explanation went from .512 to .5125.
Still safe in my mind at 20* but I don't know what it would be at 90* Is 200 fps increase over any published speeds out of line?
Think 5000 FP of energy will sufice ?
The group did open to just under 2 inches.
That is still better then the published groups.


Here are some published loads for a sierra 220.
220 Sierra SBt Alliant RL-25 2965 FPS 2.95 inch groups
220 Sierra SBT Ramshot Magnum 2825 Fps 2.97 Inch groups.


Should I go on?
How fast is to fast?
If I go on I would want better groups then 2" at 120 yards.
Maybe have to adgust the "Jump" to see an improvement.


:confused:

[Evlshnngns]

I wouldn't go higher, those speeds are more than plenty.

[charlie b]

Despite bolt lift and primers you have no idea how much pressure you are getting in those loads. You could be in the 70kpsi range or more and not know it. There is no reliable pressure 'sign' except measuring it with a strain gauge or similar instrument.

If I encounter velocities above book max with a powder I back off. Frequently I end up below book max powder charge to get same book velocity.

When a lot younger I tried to get the fastest loads I could to get "maximum performance". Had a couple of bad experiences that made me question my choices.

If you 'need' more velocity/energy on target then get a rifle and cartridge that easily delivers that amount with factory loads. There is a rifle/cartridge out there for every purpose.

Having said all that, if you want to keep increasing the charge until you get 'pressure signs' then it's your gun.

[8mm RUM]

There is NO info for reloders 26 yet.
It was made to get very High velocitywith less pressure.
I think I'll go up another half grain and see if there is any differance in group.