Did a jump test with 22br. This one was kinda unique with the opening and closing after .010" jump. Would you consider the difference between each caused by the actual jump difference or natural variation and shooter error? The POI is very close to the same for each group with 17 of the 18 shots probably falling inside .5" if all shot on the same target.
Jump test result interpretation?
- Thread starter jzerfoss
- Start date
Take your best group. Repeat it with more shots. Do it again and take it out to distance.
Also don't jump .005 at a time, try .002 or .003. Your best seating depth might just be between .005 and .010, etc.
If it is, then set it closest to the lands and forget it.
Also don't jump .005 at a time, try .002 or .003. Your best seating depth might just be between .005 and .010, etc.
If it is, then set it closest to the lands and forget it.
Take your best and worst. Shoot a 10-20 shot group with each. Compare them.
That will tell you about how much noise there is in your results.
Also, no need to take it out to distance unless you’re doping or want to make sure the BC variation is low. It’s not going to shoot .2 @ 100 and then shoot .8 or 1.0 @ 1,000yds unless the velocity or BC variance is too high. You won’t obtain anymore seating depth data at distance you can’t get at 100.
If you are going to be testing your seating depth often, then you can break it down to .002 or .003 increments.
However, if you’re not planning on checking/changing often, I’d keep going past .030 and be looking for the longest range that gives you your minimal acceptable precision.
You may find that yes, .007-.010 has the smallest groups, but you have to continually test and keep your seating depth tuned.
But you find that .030-.045 still stays around .5 or less. And now you don’t need to mess with it until the throat erodes enough.
That will tell you about how much noise there is in your results.
Also, no need to take it out to distance unless you’re doping or want to make sure the BC variation is low. It’s not going to shoot .2 @ 100 and then shoot .8 or 1.0 @ 1,000yds unless the velocity or BC variance is too high. You won’t obtain anymore seating depth data at distance you can’t get at 100.
If you are going to be testing your seating depth often, then you can break it down to .002 or .003 increments.
However, if you’re not planning on checking/changing often, I’d keep going past .030 and be looking for the longest range that gives you your minimal acceptable precision.
You may find that yes, .007-.010 has the smallest groups, but you have to continually test and keep your seating depth tuned.
But you find that .030-.045 still stays around .5 or less. And now you don’t need to mess with it until the throat erodes enough.
Just an FYI . . .
Referring this to a "jump test" when it's really a seating depth test will confuse a lot of people about how important the jump is for this. It's the seating depth that's way more at play here that the effects of jump. Because various chambers can have various freebores, a .020 jump used in two very different freebore chambers will have very different seating depths with very different results. So, when you state particular jumps for your test, it really says nothing about how deep you're seating your bullets.
But . . . as for your test and there being a direct relationship with jump and seating depth over the short testing period, the results can be evaluated in terms of the increments used for changes in jump. For this particular cartridge, .005 increments in seating depth (or "jump" as you're referring), is a bit much where you might just jump over a good accuracy node; better to use .003 or even .002 which should give a better read on the paper. Going with that large of increments seems to save on components, but not really if you don't happen to land on the good node.
To me, it looks like there's probably something around that .020 off. So, I'd probably run a test from .014 to .026 (.003 increments), though it looks like something going on there around .030 too (I refer to jump distance only for your benefit, though we're really talking seating depths for your particular gun/barrel/chamber).
I would be hesitant about doing anything with the .005 off as that's close enough to effect a close to the lands spike in pressure that'll go away rather quickly as the throat erodes.
This has to be one of the dumbest things that I've read in awhile... I know what you are trying to say but you explained it very poorly. I would try to explain to you why but I can tell by the way wrote this you believe you are far more knowledgeable than you are and it fall on deaf ears.
You can reply to this comment but I have no interest in wasting my time arguing on the internet and won't be replying.
I knew what I wanted to do after this test. I posted it to really see what people's opinions were on the subject. I'm kinda surprised only one person said it was probably more related to me. This is a PRS rifle and what this test showed me is that the one flyer at .015" probably had nothing to do with the jump. It also showed me that the bullet isn't jump sensitive and I could start at the .005" jump and not have to worry about the throat erosion for awhile. Don't over complicate things guys unless you are shooting competitive BR matches which is a whole different game.
I personally would look between 25 and 35 thousandths. and stay away from the .005 area. I suspect that you'd find a more consistent load there and you won't have to chase the lands, so to speak. But your conclusion is spot on. Also, with 3 shot groups it's very hard to say that a .3" group is actually Better than a .5" group with any great confidence.
EDIT: By the way nice chronograph numbers.
What is your acceptable level of accuracy?
And what is this rifle going to be used for?
What bullet are you using and what powder?
I think those questions are most important before we jump into .002” increments etc.
I started reading a couple replies but I wouldn’t feel comfortable giving advice unless I knew what the tool was used for.
Here is my wild ass guess and answer though haha:
it’s a PRS rig because…22br. And you are probably running 90bergers pushed by 31.5-32gr of varget/H4895 with 3120fps velocity in a 28” tube. 88s might have jacket issues at that speedand twist and those are the best two powders for 22br. And if that’s the case…seat the bullets .050” off and forget about it. It will shoot in the .4s for the next 2.5k rounds even as throat erodes. And that is plenty good accuracy for PRS.
Nice lab results by the way!!
If you are doing benchrest type stuff I don’t have advice…I hate messing with seating depths to wring out another .1” of accuracy. And then having to constantly chase every hundred or two rounds as throat erodes. That technical stuff is just gross haha.
If you haven't tried it yet, I'd recommend trying some rounds loaded to a larger than usual jump... in the neighboorhood of as much as ~0.100" off or more.
The accuracy might surprise you and I can pretty much bet your barrel will last longer, all while yielding a more consistent/repeatable waterline downrange at distance the whole time and a more "durable" load that you may not ever have to touch.
I loaded my last barrel jumping 0.100" to the lands, and ran it kind of "slow" for a 6mm Creedmoor (~2900fps), and my notorious barrel-burner made it 2300rds before it died (pretty nuts for 6 creed). I didn't have to touch/change the load even once over the whole life of the barrel. I ended up feeding it the same load/round from start to finish and at the end their was hardly much throat errosion to speak of, it was just the inevitable fire-cracking that eventually/finally killed it I think.
These are shots #96-#100 through my new barrel, rounds were left over from the last barrel so they are jumping ~0.100" or so (same model Proof prefit), the barrel hasn't even had enough rounds through it to have settled in yet speed-wise, zero barrel break-in (I don't believe in that nonsense, I just screw it on, single dry patch and go), no load development at all:
I don't know what groups look like at 100 yards yet, and I'm not sure I care lol!
The accuracy might surprise you and I can pretty much bet your barrel will last longer, all while yielding a more consistent/repeatable waterline downrange at distance the whole time and a more "durable" load that you may not ever have to touch.
I loaded my last barrel jumping 0.100" to the lands, and ran it kind of "slow" for a 6mm Creedmoor (~2900fps), and my notorious barrel-burner made it 2300rds before it died (pretty nuts for 6 creed). I didn't have to touch/change the load even once over the whole life of the barrel. I ended up feeding it the same load/round from start to finish and at the end their was hardly much throat errosion to speak of, it was just the inevitable fire-cracking that eventually/finally killed it I think.
These are shots #96-#100 through my new barrel, rounds were left over from the last barrel so they are jumping ~0.100" or so (same model Proof prefit), the barrel hasn't even had enough rounds through it to have settled in yet speed-wise, zero barrel break-in (I don't believe in that nonsense, I just screw it on, single dry patch and go), no load development at all:
I don't know what groups look like at 100 yards yet, and I'm not sure I care lol!
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