Broke 4100FPS with a .30cal today!

[gunderwood]

Finally found me some VV N550, so I loaded up a few test rounds. Got a 110gr V-max to 4113fps with 73.5-74gr in a .300WSM. Thank goodness for a slow twist barrel or else they would explode!

The gunsmith who built it has pushed them past 4200fps with 75gr, but I think I want to stay around here. 4000-4100fps makes the 110gr V-max stable in virtually any atmosphere conditions and I'm just starting to get pressure signs (flattened primers, no flow). Time to load up some accuracy test loads.

[Chasbo00]

Thats pretty impressive. What's next, a smooth bore tank cannon?

[Diomed]

How long do you expect the barrel to last?

[SgtBill]

Be carefull Garrett, you are skirting the edge.
Bill

[gunderwood]

How long do you expect the barrel to last?

Long range varmint hunting with a .300WSM is not common, so I really don't know. The number of these guns built is around 30 IIRC.

The slow twist rate helps significantly with barrel wear due to bullet velocity. That is the whole reason you choose a twist rate that is just enough to stabilize it rather than one which could also stabilize bullets heavier (technically longer) too. A secondary reason is that over-stabilized bullets tend to amplify angular dispersion components.

Most magnums get at least 2000 rounds before the barrel is toast due to throat erosion. Usually you can just re chamber the barrel and get another 2000 or so out of it. I'd consider anything more than 2000 rounds to be decent barrel life. I would prefer 3000+, but doubt I will get there because I'm guessing the barrel will wear out due to the velocity of these rounds before then.

There is still so much we don't quite understand about internal ballistics (hence all of the voodoo magic about barrel break-in, etc.). I have a 6mmBR on order which will be setup for the 75gr V-max's, but the next one I want to get is a 20BR. Technically, a 20BR should be overbore (not quite magnum), but actual rifles are not showing this. Case volume to bore area ratios are only a guide. Even pushing the 55gr Berger to 3400-3600fps, people are getting very little throat erosion compared to traditional magnums.

The short answer is I expect at least 2000, but hope for 3000. Time will tell.