I beg to differ. Throat erosion is all about pressure and what it does to your barrel as you raise the stakes. It is more properly termed as corrosion. There is a correlation between expansion ratios and pressure. FWIW, I doubt the load listed in the original post is going to cause that much wear, but that's just a guess.

I found a load that gives me good accuracy and I would like to use that load for target practise. The load is a .270Win 90 gr. Speer MHP on top of 53grs of Norma 202, primer CCI BR in a Norma Case. I travels av. 3400 FPS.
The question is: At what speed will a load cause extensive throat erosion.

I won't use that load for targets if it wears my barrel out faster than a "normal speed" load.

The faster the bullet & smaller the bore the quicker your bore will wash out. The hot .22 & .24 are real bore burners as are the small bore mags & the .270 can be put in the small bore mag catagory. If you shoot alot, back down abit or just shoot it until it starts shooting poorly & then rebarrel.

It is not speed, per se, that washes out your bore, but flame temperature from the powder. The usual assumption is that fast bullets=high pressure=hot burning load. In any event, there is no way to quantify it that I know of.

The .270 Win was an original factory hotrod, it was 52000 c.u.p. when the venerable '06 was 48000-50000 c.u.p. Even with that, the .270 Win is not particularly hard on barrels. The 7mm Rem Mag operates sometimes around 54000 c.u.p. and is not noted for being too hard on barrels. The .264 Win is in the same area and is noted for being hard on barrels and part of that may be due to the smaller tube.

Rifle barrels are made to provide you and me with fun, not headaches, so simply find a really good load and go with it. When the time comes for a new barrel, get one put on and enjoy that one.

Is there a "speed limit"...? Meaning.. If I keep my faster .270win loads under a certain limit , then will that leave me in the safe zone/ normal barrelwear zone.

YEs, it's like a race car, if you run it @ max. all of the time then you are going to have to rebuild it sooner.
It isn't pressure per say but the powder burning in the 1st couple on inches, I think it's called powder expansion ratio or something like that. For example, a .34 bore @ 52,000cup isn't goint to burn a bbl. as fast as a .25 bore @ the same. I read an article a few years ago where they shot alot of rounds thru diff. bore dia. & reported the results as viewed w/ a bore scope. In practical application, you probably won't ever ehoot enough to notice a diff.

Hi Hot Core
Thanks for your reply. We shoot 12 shots at a running target moose or deer in competition and practise, so I will have to shoot 12 shots in about 10 min.
Is this too much with a 3400fps load in my 270 win?