Home Forums Reloading Big Game Rifles Ladder test with a “magnetospeed” chronograph attached to barrel?

Looking to work up loads just to see where max loads (velocity/ pressure signs) top out before loading for groups. Just wondering if a ladder test would be valid if I have the magnetospeed attached to the barrel? I know it throws my impact off slightly, just wondering if that also invalidates any kind of ladder results as well. I am shooting at a range where it’s a pain in the butt to set up a chrono in front of the firing line. Consequently, it’s much more convenient to use the Magnetospeed. What say you?

I use mine for ladder test. Then it is on there for all my group work up to the verification loads. Where I pull it off to see if there is any change in grouping. There is a bit of poi change but not in grouping so far as I can tell. I cant see how using it invalidates anything. Maybe I'm missing something, but I have been doing it like this since I got my magneto for the same reasons you are wanting to use one. M8x57

The magnetospeed is basically a weight attached to the end of your barrel. Adding a weight to the end of a bar changes how it vibrates. The point of a ladder test is to find a node in the vibration of your barrel that allows consistency. Do you see the problem?

I would certainly not be using a Magnetospeed (or any other device attached to the barrel) for a ladder test. Of course there will always be some guys who'll say "it works fine", ymmv.

Pretty sure Scott Satterlee uses a magnetospeed for his ladder test....if it works for him..................

I sold my Magneto in favor of the Labradar, best thing I ever did.

This^^^

It would be pretty pointless to do a ladder test with something attached to the barrel.

I’ve used the magnetospeed on very heavy barrels and very light. Zero chance you can evaluate anything related to POI with a light barrel, and I wouldn’t trust results on the heavy barrel even though it has much less impact. Though I have not done enough with it to say either way whether group size is different with or without.
I have a Labradar for that. I only use my magnetospeed for shooting into a bullet trap solely for measuring velocity.

I have used a magnetospeed when doing ladders and it saves me time and rounds. Does it change barrel harmonics, yes. But it changes it the same for all rounds fired. I always try to do multiple trips to the range to "proof" a specific recipe and do final sight-in without it of course. I have yet to see a change in grouping, only POI.

I 100% believe the magnetospeed will have ZERO effect on the accuracy of a ladder test.

David

I have a Magnetospeed. I love how it reads velocity. You’ll never catch me running any sort of accuracy test with it attached to my rifle. It throws my accuracy and POI way off. To the point I can’t believe there are actually people advising you’ll be okay to run the test with it attached...

Todd

I use mine solely to satisfy my curiosity about a load's velocity.

Ladder testing seems to mean different things to different people. Some only think of it as an POI grouping/accuracy search, others include the term for pressure and velocity testing, as well. I wonder if that's part of the reason for the broad variety of responses here. Reasonably speaking, any test using incremental changes in charge weight is a "ladder test", whether you're looking for accuracy or pressure & velocity. Which was the original usage of the coined term is probably material for a typical Campfire pissing contest, which I'm not interested in, because frankly, there are far more important things to be concerned with. Somewhere there's a guy who swears he was using the term for one or the other before it was ever used in some article or book and he still turns purple when he hears it because he didn't get the credit he deserves. Maybe he'd even be right. It's not that creative of a term.

I first read the term used as an accuracy measure, but I've since seen it used for chronograph and max load search, as well. If you're "ladder testing" for pressure signs and a velocity window, the Magnetospeed will work just fine. The bayonet on the barrel is not changing anything in the chamber. If you're "ladder testing" looking for an "accuracy node" like the previously mentioned Satterlee method, that would work, too. You'd find that "node" or sweet spot in velocity with or without the bayonet on there.

If you're final testing for accuracy, remove the bayonet. Even if you found your sweet spot with it, when you switch to loading multiple rounds for each of a few promising loads in that velocity window, you'll need more precision in the testing. The bayonet changes barrel harmonics, as noted by several above, and it usually alters POI or grouping, sometimes both. I have a few loads where the difference is so slight that it doesn't matter, and those are all in heavier barreled rifles. My light contour barrels see a bigger change. When I first began using mine, I encountered several of those loads with minimal change. For a time, I thought it didn't matter a much as I expected. I understand, now, it was a function of the first few rifles I tried it with. As a general rule, the bayonet will shift POI and or alter group size enough that I will not do an accuracy test or a pre-hunt final sight-in with the bayonet on. Whether it's multiple inches difference, or .5" difference, I don't want to worry about it.

To date, I only use mine when I get to the point of wanting to determine velocity averages for chosen loads, or for checking the velocity difference in incremental powder increases.

Anecdotally, based on observation and recollection, but not on recorded data in my book, I would say that the best loads shoot the best with or without the bayonet on the barrel, but I'm not willing to absolutely depend on that, therefore, I accuracy test without it. In theory, it's logical to assume that the bayonet would have the same effect on each load, but in practice this will not be the case, because the bayonet tends to move on the barrel, even with light recoil, no matter how tight you draw it down. Moving the bayonet strap and hub on the barrel even a little forward or back will alter the harmonics some, especially in a light contour barrel. There's no way to guarantee that the bayonet strap and hub are in the exact same spot for every round if it's attached to the barrel, unless you paint or tape a line on the barrel and reset it precisely for every round. Even then, is the strap the exact same tightness or did it loosen a bit? Maybe splitting hairs, maybe not. I had a rifle with a BOSS on it years ago, and I satisfied my curiosity for how much slight changes can affect the harmonics.

If you want to test for accuracy and velocity/pressure at the same time, the Magnetospeed is not the ideal tool, unless you dismount it and set it up on its own rest at the muzzle, then shoot over it. A few of the guys here on the forum have done that. I haven't yet, but I intend to. It's a good solution to the only drawback I've found to the tool.

Pretty sure Scott's focus is on velocity nodes... not POI nodes.

i am lookingfor velocity nodes. Not accuracy testing. Just trying to be efficient with my time at the range when working up charge volume data in a new rifle.

I posted earlier in this tread that I do all my testing with the magneto attached, and was wondering how much I might be missing by doing this. I decided to run a ladder test with a new powder I had yet to try in my 8x57. I made two strings, one to run with the magneto on and one with out. In doing so to try and kill 2 birds with a single stone. One string to see what sort of velocity I was getting, and the other to compare the ladders to each other.

this first pic is of the the ladder test using the magneto speed attached.
(images are turned on there side for some reason not sure why. They stringed more verticlly than horizonal)


you will see there is grouping within the shots
(No change in zero for next ladder)

This is the string without the magneto


again there is distinct grouping but with out the added weight of the magnetospeed it is much more apparent. While it is a must to know the velocity of your loads I have to agree that trying ladder test and accuracy test should be done with out a magneto. I also had some loads out to verify accuracy with another load I was working on and it preformed will but not as well as with the magneto attached. The ladder test loads ranged in velocity from 2370 to 2680. M8x57