Neck Tension question...

nikonNUT

The harbinger of... things not working anymore
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  • Oct 6, 2019
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    Hey guys I was loading over the Christmas weekend and noticed something. I did the usual shoulder bump and proceeded run a .336 mandrel thru the necks. The first case went really easily so I grabbed another and tried slipping it on the mandrel by hand. It slipped on with very little effort. I'm thinking I don't have enough neck tension. Is that a safe guess or have I just accidentally nailed it? My plan is to burn these rounds up, drop down one bushing size and try again. What say you?
     
    .338LM using ADG brass and I'm running a Widden FL die with bushings. As for neck thickness I'll have to grab my ball mic from work. I've been chasing a QC issue on some tubing so it's in my tool box and I am lothe to use calipers but .014" using said calipers... If that is anywhere close and my current bushing is .364 -.014 -.014 = .336" so exactly the same size as the mandrel?
     
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    Hey guys I was loading over the Christmas weekend and noticed something. I did the usual shoulder bump and proceeded run a .336 mandrel thru the necks. The first case went really easily so I grabbed another and tried slipping it on the mandrel by hand. It slipped on with very little effort. I'm thinking I don't have enough neck tension. Is that a safe guess or have I just accidentally nailed it? My plan is to burn these rounds up, drop down one bushing size and try again. What say you?
    How many times have used this brass for firing? What kind of tension have you had in the past with this brass? Couple reasons for asking the questions; depending on the number of times fired, you may have work hardened your brass enough that the normal springback isn't happening. It may be time to anneal if this is the case. With that being said, it sounds like you have been shooting with fairly light neck tension up to this point for a 338L.
     
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    IMHO, using the mandrel after FL sizing w/ bushing, if the mandrel isn't really doing much most of the time, then I'm right where I want to be as far as bushing size.

    I hear folks talking about using their mandrel to "open up" the case mouths after sizing, but I don't really want or need that, I just want the mandrel to uniform the case mouths that aren't quite there yet after seeing the bushing, and make all the case mouth ID's round (if for some reason they aren't already). I tend to think that if the mandrel is doing too much, then it's just working the brass more than is really needed. I think that's really the main advantage of using a bushing die vs a "normal" FL sizing die with a mandrel, as you can get things closer without having to overwork the necks.

    Since loading for precision is kind of all about controlling as many variables as we can, but brass spring-back is kind of random and not the same every time with every case (so much harder to control), IMO the bushing and the mandrel gives one a much better shot at having the neck tension end up more consistent.

    Most of the time my mandrel is hardly doing anything, but using it cuts my SD's in half vs not using it.
     
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    How many times have used this brass for firing? What kind of tension have you had in the past with this brass? Couple reasons for asking the questions; depending on the number of times fired, you may have work hardened your brass enough that the normal springback isn't happening. It may be time to anneal if this is the case. With that being said, it sounds like you have been shooting with fairly light neck tension up to this point for a 338L.
    This is round #2 aka will be the 3rd firing...
    Oh, and one more update. I just took a random sampling of my loaded rounds and I am getting .365" across the neck (Yes, calipers again) and I am using a .365 bushing. Good? Bad? Seems like no neck tension but I'm an idiot so...
     
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    This is round #2 aka will be the 3rd firing...
    Oh, and one more update. I just took a random sampling of my loaded rounds and I am getting .365" across the neck (Yes, calipers again) and I am using a .365 bushing. Good? Bad? Seems like no neck tension but I'm an idiot so...
    If you are getting a reading of .365 with a loaded round, I would say you need to go down to at least a .363 bushing. Have you been shooting the rounds from a mag, or single loading them? If from a mag with several rounds in it, check the OAL of one of the rounds still in the mag after firing a round. Bet it is a different length than what you initially seated the bullet to.
     
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    If you are getting a reading of .365 with a loaded round, I would say you need to go down to at least a .363 bushing. Have you been shooting the rounds from a mag, or single loading them? If from a mag with several rounds in it, check the OAL of one of the rounds still in the mag after firing a round. Bet it is a different length than what you initially seated the bullet to.

    I've been single feeding.


    Sometimes a same diameter bushing does the job. How do they feel when you’re seating them?
    Doesn't feel like they "fall" in or drag badly. Just kind of steady glide as I seat them.
     
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    If you are getting a reading of .365 with a loaded round, I would say you need to go down to at least a .363 bushing.

    I agree. You might even be able to go down to a .361 and it might still feel like the .336 mandrel isn't doing too much (which is fine).

    The amount of brass spring-back one gets is wonky and kind of impossible to nail down exactly, usually being in the ballpark is the best we can hope for, but we have to try and account for it. I usually start with (and most times end up with) a bushing that is: loaded round neck OD - .004, followed by a mandrel that is: bullet OD - .002... works every time 80% of the time 😜 ...
     
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    I agree. You might even be able to go down to a .361 and it might still feel like the .336 mandrel isn't doing too much (which is fine).

    The amount of brass spring-back one gets is wonky and kind of impossible to nail down exactly, usually being in the ballpark is the best we can hope for, but we have to try and account for it. I usually start with (and most times end up with) a bushing that is: loaded round neck OD - .004, followed by a mandrel that is: bullet OD - .002... works every time 80% of the time 😜 ...
    :ROFLMAO: (y)Everyone in this game needs to buy a set of gauge pins that they can check this info out on their cases if they are serious.
     
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    :ROFLMAO: (y)Everyone in this game needs to buy a set of gauge pins that they can check this info out on their cases if they are serious.

    I hear you on that, I've actually been meaning to order a couple Ballistic Tools Neck Tension Gages for a while but haven't gotten around to it...

    That said, I guess for me the thing is: the amount of brass spring-back one gets case to case is still random, consistently inconsistent :giggle:, and in a way it's kind of a questionable measurement since it's a moving target that's always changing...
     
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    I hear you on that, I've actually been meaning to order a couple Ballistic Tools Neck Tension Gages for a while but haven't gotten around to it...

    That said, I guess for me the thing is: the amount of brass spring-back one gets case to case is still random, consistently inconsistent :giggle:, and in a way it's kind of a questionable measurement since it's a moving target that's always changing...
    When I got serious with benchrest shooting a couple years ago, I went to non-bushing dies and use these to lap out my dies for consistent roundness and what I want for initial neck tension when I size. http://www.acrolaps.com/
    I get to play with various mandrel sizes after that to get the neck tension I want.
    Former FIL is a Tool and die guy that also shoots competitively, and he said the inconsistency in bushings is unbelievable.
     
    I agree. You might even be able to go down to a .361 and it might still feel like the .336 mandrel isn't doing too much (which is fine).

    The amount of brass spring-back one gets is wonky and kind of impossible to nail down exactly, usually being in the ballpark is the best we can hope for, but we have to try and account for it. I usually start with (and most times end up with) a bushing that is: loaded round neck OD - .004, followed by a mandrel that is: bullet OD - .002... works every time 80% of the time 😜 ...
    And forever more I shall refer to this as the Sex Panther method! 👍🏻🤣
     
    Gaugue pins??? For what?
    20201229_065935.jpg

    😂
     
    Well, I didn't spring for a set of gage pins but I had .337-, .336-, and .335- Vermont ZZ pins land today and experimented. With a .365 bushing the .335 pin will drop in slowly under it's own weight with the primer pocket pluged and the .336 is a tight slip fit with 2 fingers on the side and very little pressure. With the .364 pin the .335 pin still falls in but stops due to air pressure with the primer pocket is pluged and the .336 pin goes about 3/16" and stops hard. Full disclosure this is a sample size of 2 but it looks/feels like the .364 bushing is giving me about .003" of neck tension. Now for the $64K question (Yes I understand "It's your rifle, they are all different, etc.") how much tension does a 338 like. I'm running Ramshot LRT (Made in Belgium so P.B. Clermont?) which from reading leads me to believe it is as slow or slower than Retumbo (some info says between RL33 and US869). If I have been running .002" is .003" a good metric to start experimenting from?
     
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    IMHO, using the mandrel after FL sizing w/ bushing, if the mandrel isn't really doing much most of the time, then I'm right where I want to be as far as bushing size.

    I hear folks talking about using their mandrel to "open up" the case mouths after sizing, but I don't really want or need that, I just want the mandrel to uniform the case mouths that aren't quite there yet after seeing the bushing, and make all the case mouth ID's round (if for some reason they aren't already). I tend to think that if the mandrel is doing too much, then it's just working the brass more than is really needed. I think that's really the main advantage of using a bushing die vs a "normal" FL sizing die with a mandrel, as you can get things closer without having to overwork the necks.

    Since loading for precision is kind of all about controlling as many variables as we can, but brass spring-back is kind of random and not the same every time with every case (so much harder to control), IMO the bushing and the mandrel gives one a much better shot at having the neck tension end up more consistent.

    Most of the time my mandrel is hardly doing anything, but using it cuts my SD's in half vs not using it.
    Great observations. Quick question regarding your methodology (which I'd like to adopt) ... What's the order? FL-Size, then Neck-Mandrel ... or vice versa?
     
    If you put a mandrel in an fired case neck it will just float in space. You need to size it for the mandrel to touch anything.
    "Doh!" ... sorry for the stupid question. Should have figured that one out on my own. Hopefully this question is smarter ... Do you mandrel every case, or just the ones that indicate concentricity issues after sizing?

    1609512685279.png
     
    "Doh!" ... sorry for the stupid question. Should have figured that one out on my own. Hopefully this question is smarter ... Do you mandrel every case, or just the ones that indicate concentricity issues after sizing?

    View attachment 7516828
    I do every case. Consistency is the name of the game.

    I’m not sure that a mandrel would reverse many concentricity issues that you find already exist though, I’d say that a mandrel will just introduce less than other methods could.

    And I’d be sure of the source of whatever concentricuty issues you’re actually finding are before you hope to corrrect them through some arbitrary action: is it an unconcentric neck or is it just uneven in thickness etc based on where and how you are measuring leading to those conclusions?

    I think concentricity measuring is overrated for 99% of shooting. We have a hard enough time reading easy dimensions consistently such as case length, much less those measurements that we then have to spin around and measure in space with a little needle.

    Use good equipment and be equal and uniform in your treatment of brass and you’ll have good results.
     
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    Just wanted to close this out by saying WOW! What a difference .001" of neck tension makes! Groups have tightened up considerably and my ES/SD (while still not great) has settled down considerably. Thank you for all the help, Gentlemen. The Hide rocks!!!
     
    More tension. My original set-up let a .336- pin slide right into the neck. Went to a .363 bushing and a .336 mandrel (ADG brass) and with spring back the .336- doesn't start and the .335- pin is a snug slip fit and will just hover if the flash hole is plugged.
     
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    I'm interested in that too but I'm going to have to order on of the holders that turns gage pins in to madrels. That is in process!

    IDK if playing with the mandrel OD is really even necessary, a -.002 bullet OD mandrel should do it.

    I would go down -.001-.002 in the bushing (so .362-.361 in this case), and on annealed brass, following with the .336 mandrel it should be butter.
    (From what I've seen, most of the spring-back seems to happen during/after the bushing sizing operation, so even with a .361 bushing the neck usually springs-back to ~.363 anyway IRL...)
     
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    There is another version, from Ken Porter (search for more/later posts on that forum by that same 'Joe R') that uses a small ER collet similar to what would be used on a small milling machine. IIRC they don't have a big range of s, so you'd need one for basically every "caliber" (224, 264, 308, etc) you want to use it with.

    For the most part though I've stuck with the pre-made mandrels from K&M, Sinclair or 21st Century.
     
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    Stumbled upon something worth mentioning on this subject: brass is soft and changes... duh. So, depending on how many loadings/firings one has on their brass, or if one switches to a different bullet, one's bushing size they probably want to use can change...again, duh.

    The reason I mention this is I'm currently using some brass, that without even realizing it, I've now got 9 firings on, and things have changed. I guess I've gotten better over time at taking care of my brass, because I'm just using run-o'-the-mill Hornady brass and I don't think I've ever had this many firings on these cases before... and they're still good, I'm not running very hot loads so I'm not even really getting loose primer pockets yet or anything... I also changed bullets (which I never really took into consideration).

    For 6mm Creedmoor, my "old" loaded-round neck OD was .273" with 108ELD-M's (this was probably true for the first several firings or so I'm guessing), but I hadn't re-measured it in a while because my ammo has been great. Now, after a bunch of loadings/firings, and having switched to 115DTAC's, my "new" loaded-round neck OD is .271"... So, unknowingly, I haven't really been sticking to my formula of "loaded-round neck OD - .004 for bushing size"... I was using a .269" bushing, but I'm going to change to a .267" bushing.

    Has this been affecting my neck tension? Probably. Does it matter? IDK. Again, my ammo has been great, so this is definitely "into the weeds" kind of thing, but just something to pay attention to as one's brass neck thickness thins out over multiple firings and/or if one switches bullets...
     
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    Stumbled upon something worth mentioning on this subject: brass is soft and changes... duh. So, depending on how many loadings/firings one has on their brass, or if one switches to a different bullet, one's bushing size they probably want to use can change...again, duh.

    The reason I mention this is I'm currently using some brass, that without even realizing it, I've now got 9 firings on, and things have changed. I guess I've gotten better over time at taking care of my brass, because I'm just using run-o'-the-mill Hornady brass and I don't think I've ever had this many firings on these cases before... and they're still good, I'm not running very hot loads so I'm not even really getting loose primer pockets yet or anything... I also changed bullets (which I never really took into consideration).

    For 6mm Creedmoor, my "old" loaded-round neck OD was .273" with 108ELD-M's (this was probably true for the first several firings or so I'm guessing), but I hadn't re-measured it in a while because my ammo has been great. Now, after a bunch of loadings/firings, and having switched to 115DTAC's, my "new" loaded-round neck OD is .271"... So, unknowingly, I haven't really been sticking to my formula of "loaded-round neck OD - .004 for bushing size"... I was using a .269" bushing, but I'm going to change to a .267" bushing.

    Has this been affecting my neck tension? Probably. Does it matter? IDK. Again, my ammo has been great, so this is definitely "into the weeds" kind of thing, but just something to pay attention to as one's brass neck thickness thins out over multiple firings and/or if one switches bullets...
    Agree 100%! I never thought about a bullet change making a difference but I can see where that can come into play! Great info! Thank you!