Velocity Effect of Bullet Tension

7stw

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I do not recall the name of the person that conducted this experiment. And maybe my partner in crime cam assist on this, but he did a incremental test using a crimp die, and with different torques applied to the crimp, he got different , but consistent , velocities, and es readings. I've ran into the same thing when my adjustment slipped, or if I didnt use it, because I forgot it was part of my set up. I'll argue that neck tension definitely affects the overall performance of any round. Said again, consistency is is the key word here.
 

7mmTikkaShooter

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I am working on a load for a 243AI and I want to play with neck tension a bit. I have an accurate load with an 80 gr Hammer Hunter running about 3550fps. I'm hoping to shrink SD but was wondering if changing neck tension will affect velocity, increasing or decreasing it? Or will average velocity remain relatively constant and simply shrink ES/SD?
In my experience varying neck tension has marginal effects on velocity but can be just the ticket with regards to a great SD/ES. Where is your tension now? What I’ve found is a touch more tension with the slower powders and a touch lighter with the faster powders has benefited those ES/SD numbers. No experience with Staball but I’m interested in what I’ve heard. Thinking about a PRS gun build with a case design around the 22-250 AI and 95 gr Sierra’s, and that powder looks like a great option. Would be curious to find out what you learn.
 

nicholasjohn

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I talked with the guy at Hammer Bullets a while back and he recommended a little more neck tension with his bullets, due to the reduced bearing surface. As I recall, he said to go with 3 or 4 thousandth's under bullet diameter, rather than the two thousandth's most guys seem to prefer. This is to let some pressure build up before the bullet gets moving, and it does something that is favor-able when the bullets initially get engraved by the rifling. I don't know if this will improve the parameters you mentioned, but the fact that he mentioned it suggests that it must improve something in the equation.
 

Methow Packer

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I have had different results, with increased neck tension, as I've seen more velocity, and lower es. My theory, is that you are holding back a little on the bullet, to get a more consistent ignition, and burn. Neck tension has always been one of my pet peeves, and I've junked a lot of brass that wouldn't give it to me. Theres a fine line on the tension issue. And threads about the use of Lee factory crimp dies have helped with that somewhat. It's a touchy subject, and has kindled a few fires here, but I can tell you in all honesty, that whether its tight, or not so tight, isn't as important, as long as its all the same
I found that most of the slow burning powders, perform better, when held back. The overall quality of your brass is key, which in turn, usually provides better, and more CONSISTENT neck tension!
My opinion you’ve got it right on. Consistent neck tension is the key to small groups and low ES. I think a good annealing regiment also helps with consistent neck tension. I shoot a 243AI using Bergers 108 Elite Hunter. Amazing out come of accuracy in my 8 Twisp Brux barrel
 

epoletna

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I am not doubting that other people on this forum understand this issue better than I do, but I do doubt that resistance in seating a bullet equates in a linear fashion with neck tension when the cartridge is fired and the bullet begins to move into and through the barrel. There are variables associated with resistance in seating, variables that we have all experienced: whether or not the neck is chamfered, whether or not the brass is annealed, whether or not the bullet is aligned with the case as it begins to slide into the neck, whether or not the insides of the case necks are all similarly cleaned, and certainly other variables.

All of those will affect the resistance we feel as we are seating a bullet. But do they all have the same effect on resistance the bullet experiences as it begins to move forward? I doubt that.

Which means we cannot measure the resistance of the bullet being seated and assume that equates directly to the bullet starting down the barrel. Which makes me skeptical of gauges that measure the resistance of the bullet when seating.

Not to be a doubting Thomas, but that's my gut feeling. . .
 

cajun

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Well I can tell you the really good f class shooters are doing it and sorting rounds by seating pressure. They want them all the same or pretty close. They also point and sort bullets etc. every little bit makes a difference at 1000 yds.
 

Pro2A

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I have had different results, with increased neck tension, as I've seen more velocity, and lower es. My theory, is that you are holding back a little on the bullet, to get a more consistent ignition, and burn. Neck tension has always been one of my pet peeves, and I've junked a lot of brass that wouldn't give it to me. Theres a fine line on the tension issue. And threads about the use of Lee factory crimp dies have helped with that somewhat. It's a touchy subject, and has kindled a few fires here, but I can tell you in all honesty, that whether its tight, or not so tight, isn't as important, as long as its all the same
I found that most of the slow burning powders, perform better, when held back. The overall quality of your brass is key, which in turn, usually provides better, and more CONSISTENT neck tension!
One can adjust, compensate for anything except variations......inconsistency. CONSISTENCY IS KING!!!!!
 

snox801

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You might have a good grouping load, but pressure with Staball might be very high at 3550fps. Reloader would be a much better call for speed and lower pressure.

I’m not sure on that. I’ve done a few load works with stabil 6.5 in standard.243 with the 70gr hammer in savage axis. Can touch 3600 in most before any pressure and that’s a 22” tube.
Which reloaded would you recommend? I may give that a try next.
 

7stw

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One can adjust, compensate for anything except variations......inconsistency. CONSISTENCY IS KING!!!!!
Absolutely. It's one of things I strive for , and when I get to the seating stage, and you've done your homework, and when you get that one or two that just seem to slip right in, you know they aren't going to stay in the group. Been there, done that. I do seem to get it much less with premium brass. I'm struggling with it now in my 25.06AI. Time for some Lapua brass I guess. Take care, and thanks!
 

L.Sherm

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I'm struggling with it now in my 25.06AI. Time for some Lapua brass I guess.
Get you some, even though it will be a little short it will be fine.
Take care of the carbon ring just like you should on any cartridge and all will be fine.
Lapua brass is one of the reasons I believe my nephew's 6.5x06AI is a hammer.
 

ButterBean

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Powder charge will take care of neck tension.....pick something between 1-3 tho and run with it...testing with neck tension after you have a finished load may or may not show any improvement.
I will have to disagree with that, neck tension Variable with any Bullet will make a big difference in everything
 

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