Magnetospeed Surprises
- Thread starter fuzzy39
- Start date
I used to build rifles and rebarrel rifles, three at a time. 3 of us were shooting.
I own my own chamber reamer (so all barrels got the same chamber) and barrels were high quality barrels. A variation of the same load between the "fast" barrel" and the "slow barrel" was in the order of 150 fps.
That is, a 150 fps difference with "identical" rifles and ammo.
So variations in the book are to be expected.
But a book max velocity probably means max pressure, so use the book velocity as a speed limit.
Most use a pressure barrel (Piezoelectric transducer) for the major calibers. This barrel is a high quality barrel mad to A SAAMI spec for the purpose.
But may calibers they develop loads for are calibers they don't test in a pressure gun. They have a library of test rifles in a variety of calibers. So their load development is much like yours.
Regardless of where the data came from, it came from THEIR rifle, not YOUR rifle, and each rifle is DIFFERENT. There is no guarantee that the Max in their rifle is safe in yours. And the longer the bullet bearing surface, the more chance that your rifle could have a problem with their loads.
Richard Balfour, who worked at HP White Labs, answered a question I had about the changes to pressure caused by the variations, but still within tolerance, in internal diameters in barrels and different types of land/groove depths.
He told me that two barrels that were identical and made on the same machine, with the same reamer etc, could easily show up to 7500 PSI difference with just .0001 variation to diameter. Velocity changes would alter accordingly.
Typical barrels used for pressure testing are 30 inches long, so they can measure pressures at different points and deduce a pressure spike, curve graph.
That's why most velocities shown in the manuals are higher than can be achieved with the average off the shelf rifle.
We live in an age where modern rifles are much stronger than their predecessors. They can usually handle higher pressures but is it worth betting an eye over???
There isn't a game animal in the world that's going to notice the difference between two identical bullets travelling within a couple of hundred fps of each other, when it impacts them in the vitals
Ghys_T3LSS
CGN Regular
- Location
- Sherbrooke, QC
Anyone ever notice if there is a limit in the speed the device can catch?
I shot some reduced loads and it failed every time.
Bullet was a 6mm. 243win reduced load. The «#full loads#» gave readings every time, but my reduced didn’t record any...?
I shot some reduced loads and it failed every time.
Bullet was a 6mm. 243win reduced load. The «#full loads#» gave readings every time, but my reduced didn’t record any...?
