Surprising neck tension test ... (at least it surprised me)

MarkyMark007

Gunny Sergeant
Full Member
Minuteman
Jan 31, 2018
537
206
Europe
not-on-google.shit
I had knowledgeable response for you but after reading your response to the OCW thread your not worth the time and just a fucking retard or a troll.

look. the thing is that bryan litz is testing those thing and he didnt find any strong corelation between seating force and velocity spread, and for ladder test he say that it is statistical anomaly because people are doing it only with 2 or 3 shots, which is pure bullshit.

so, if you have some stronger and bigger statistical data to share wit us, you are very wellcome, but if you are doing it with your lousy equipement and cheap rifle with 3 shots, than it's better to keep those anomalies to yourself!
 

bax

Sergeant
Full Member
Minuteman
Oct 25, 2009
516
198
Southwest Michigan
Been screwing around lately with different things that impact neck tension, specifically "Bushing" and "Mandrel" combinations. Took a test out to the range today, and was surprised by the results. This was with a MPA 300-WMBA rifle with maybe 1500 rounds down the barrel. Common elements between the test groups were Lapua 2x brass (annealed), Federal 215 Magnum primers, Berger 200.2x bullets, Retumbo 74.7gn of powder, and seating depth the same (obviously). The ONLY difference between test groups was the Bushing and the Mandrel.

The top-left, center, and top-right of this target is with .335 bushing and .3055 mandrel. Average velocity was 2989 with SD of 8.83 ... and crappy groups.

The bottom-left and bottom-right are 5-shots each with .333 bushing and .3050 mandrel. Average velocity was 2944 (a full 45 ft/sec less) with SD of 7.46 ... and nice tight groups.

The "pull" on the ram for the larger bushing/mandrel combination was consistent, but very light resistance. The "pull" on the ram for the smaller bushing/mandrel combination was still smooth, but with slightly more pressure to seat the bullet.

The small surprise here was that a small change to increase neck tension provided much smaller group sizes at 100 yards.
The big surprise here was that slightly more neck tension actually reduced my velocity by a significant number, all other things being equal.

Any other surprises or observations from you "Neck Tension Mavens" out there.

I use a .332 bushing and a .306 mandrel. The goal is a .304 neck ID when using a .308 bullet. Based on your results, I think I will try a .305 mandrel.

I think that the ride from the magazine to the chamber might increase runout so I use more "squeeze". Watch a cartridge as it is stripped off the magazine - see where the bullet hits the ramp? Seems to me that could that account for flyers on the top of your target. Looking at your bottom two targets, I love horizontal. It tells me that I am on the barrel node and the velocities are the same - and - I need to watch the wind better :) Watching the wind is my job, I let the gun do the rest of the work.

I seat with an arbor press and Wilson seaters. I don't have one of those nifty force-measurement devices. I am curious but the force number doesn't matter to me and I can't afford it. I think I can find a good load by experimentation and I get to work on my wind-reading skills at the same time.
 

Yondering

Sergeant
Full Member
Minuteman
Mar 16, 2017
1,910
1,361
Skagit Valley, WA

What gave you the impression that I need help with torque? That was not the point of anything I said in this thread that you pulled back from the dead.

The point was that someone was quoting "force" numbers in units that did not describe force. So there were questions about what he was actually measuring and how.
 

BuildingConceptsllc

Don't Start None, won't be none.
Supporter
Full Member
Minuteman
Supporter+
  • Nov 13, 2020
    4,515
    3,635
    Alabama
    I had some interesting results today with the same basic situation and the same thing happened.

    I was switching a load from Fed brass to Starline brass. Starline needed .1 gr more powder to accout for volume difference as measured via H20 method. Seating depth, bullet, powder, primer, all exactly the same.

    The velocity of the starlines rounds was exactly the same as the Fed rounds, YET, the Starline rounds produced a group about twice the size of the Fed rounds. After talking to @Elite_KG , I realized that I had used a bushing die on the fed brass, as is typical for all my loads, and the starline being virgin brass, I just ran a mandrel through them. This resulted in a slightly tighter fit in the Fed brass vs the Starline brass.

    So.... did the difference in in fit (about .002", maybe even .0015"), had the same velocity , but cause a significant difference in group size?

    I welcome other opinions and any other questions and observations. There are two different brass involved here but the velocity was literally tracking identically so, the fit or "neck tension" as we like to call it, is the most likely culprit imo. I will run some statline through the bushing die and try again and see if that fixes it. I sure hope so. As much as I don't want to run all 1000 cases through a bushing die, I do want to be able to load this round exactly as I had it, but in the much better starline brass.
     

    nick338

    Commander- of what I have no idea
    Supporter
    Full Member
    Minuteman
    Supporter+
    Feb 21, 2013
    1,304
    918
    What was the ES and SD of the 2 loads, how many groups of each did you shoot and when you say "twice the size", what did they measure? Was the difference in size measured more in vertical or horizontal?
     
    • Like
    Reactions: waveslayer

    BuildingConceptsllc

    Don't Start None, won't be none.
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Nov 13, 2020
    4,515
    3,635
    Alabama
    What was the ES and SD of the 2 loads, how many groups of each did you shoot and when you say "twice the size", what did they measure? Was the difference in size measured more in vertical or horizontal?

    I'd have to look at my book to be sure but both were around 12 SD and 40 ES. (20 shot groups for each - 10 per target).

    The vertical was fairly close between the two I guess but hard to say really exactly. When I shot the fed groups I shot em kind if quick because I was really just getting chrono numbers to check the starline against and not shooting to get the smallest groups since I'd shot that load several times already and knew it would shoot very well in that rifle.
     

    nick338

    Commander- of what I have no idea
    Supporter
    Full Member
    Minuteman
    Supporter+
    Feb 21, 2013
    1,304
    918
    I'd have to look at my book to be sure but both were around 12 SD and 40 ES. (20 shot groups for each - 10 per target).

    The vertical was fairly close between the two I guess but hard to say really exactly. When I shot the fed groups I shot em kind if quick because I was really just getting chrono numbers to check the starline against and not shooting to get the smallest groups since I'd shot that load several times already and knew it would shoot very well in that rifle.

    So you shot 4, 10 shot groups total and I'm assuming at 100 yards? Both Starline groups were shot after the Federal groups? Also, how dirty was the barrel when you started? Not trying to interrogate you but there's so much going on that we don't even think about that can affect group size that sometimes we are looking for the answer in the wrong place.

    Also, as much as 10 rd groups may give you a great idea of the potential accuracy and precision of the rifle and load, it also introduces other variables that may sku the results for testing loads.

    I think I would clean the barrel, load up 8-10 foulers and 10 rds each of the Federal and Starline loads exactly as they were before and shoot them at 300 yards in alternating 5 rd groups ( 1 Fed, 1 Starline, 1 Fed, 1 Starline) and wait the same amount of time between shots and also groups.
     

    BuildingConceptsllc

    Don't Start None, won't be none.
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Nov 13, 2020
    4,515
    3,635
    Alabama
    So you shot 4, 10 shot groups total and I'm assuming at 100 yards? Both Starline groups were shot after the Federal groups? Also, how dirty was the barrel when you started? Not trying to interrogate you but there's so much going on that we don't even think about that can affect group size that sometimes we are looking for the answer in the wrong place.

    Also, as much as 10 rd groups may give you a great idea of the potential accuracy and precision of the rifle and load, it also introduces other variables that may sku the results for testing loads.

    I think I would clean the barrel, load up 8-10 foulers and 10 rds each of the Federal and Starline loads exactly as they were before and shoot them at 300 yards in alternating 5 rd groups ( 1 Fed, 1 Starline, 1 Fed, 1 Starline) and wait the same amount of time between shots and also groups.

    Oh it's all good. This is what I expected. I may be way off in my thinking. Yes it was at 100 yds. I shot the 20 rounds if fed then the 20 rounds of starline. The barrel wasn't pristine but I did look at it with my bore scope the day before and it wasn't too bad. That's a good idea to shoot at 300 and see what happens. I wish I'd used my normal procedure for testing but I just didn't expect this and was really only focused on getting the velocity right with the starline. (It's actually a little too hot of a load anyway I think so I will back off of it also after testing.) I did let the barrel cool roughly the same amount of time between each 10 shot group and then a longer time between the 2 different brass.

    I thought if I got the velocity the same it would shoot the same even with a minor difference in bullet fitment. I wonder if the bullet was moving on the starline or something too?

    I will shoot them both in my normal procedure at 300 and see how that goes before I run the starline through the bushing that's for sure.
     
    • Like
    Reactions: nick338

    nick338

    Commander- of what I have no idea
    Supporter
    Full Member
    Minuteman
    Supporter+
    Feb 21, 2013
    1,304
    918
    I've been left frustrated and scratching my head many times going from 100 to 300 or beyond so now I'm just checking for pressure and zeroing at 100. All my fine tuning will be at 300 or greater.
     

    BuildingConceptsllc

    Don't Start None, won't be none.
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Nov 13, 2020
    4,515
    3,635
    Alabama
    I've been left frustrated and scratching my head many times going from 100 to 300 or beyond so now I'm just checking for pressure and zeroing at 100. All my fine tuning will be at 300 or greater.

    Yeah, I've heard frank say that same thing and I always just forget really. I need to do that but I've never tried to take one load with one brass to another type of brass before either, so I've never had any issues tuning at 100yds and then rolling with it.

    I'm kicking myself for not doing my usual routine for any testing. I also didn't offset my poa and my zero enough so after you hit 4 or 5 times it's gets super hard to aim at the same spot for 10 rounds, which I'm sure induced some error as well.


    So in theory , IF the velocity is the same, same bullet, same gun, ect and the only difference is the brass (though same velocity so).... then what would the expected results be? I might should start a new thread and ask this question to get more replies.
     

    nick338

    Commander- of what I have no idea
    Supporter
    Full Member
    Minuteman
    Supporter+
    Feb 21, 2013
    1,304
    918
    The Federal brass may just fit your chamber better. One of the reasons why I like to stick with the same brass for the life of the barrel, preferably Lapua or Peterson.
     

    BuildingConceptsllc

    Don't Start None, won't be none.
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Nov 13, 2020
    4,515
    3,635
    Alabama
    The Federal brass may just fit your chamber better. One of the reasons why I like to stick with the same brass for the life of the barrel, preferably Lapua or Peterson.

    Yeah could be. That's why I'm doing this so all my ar's can use the starline brass. I shoot starline in 6.5cm and lapua in all else but the starline is excellent brass. Probably should size the fired brass and repeat the test and do it at 300yds also
     
    • Like
    Reactions: nick338

    MarkyMark007

    Gunny Sergeant
    Full Member
    Minuteman
    Jan 31, 2018
    537
    206
    Europe
    not-on-google.shit
    ultimate device, which will tell you if there is some corelation between seating force and pull-out force:
    https://www.mecmesin.com/publications/bullet-extraction-and-seating-force-testing

    bullet-extraction-test-system.jpg


    but this does NOT mean that this is corelated to velocity spread 🤡
     

    bax

    Sergeant
    Full Member
    Minuteman
    Oct 25, 2009
    516
    198
    Southwest Michigan
    ultimate device, which will tell you if there is some corelation between seating force and pull-out force:
    https://www.mecmesin.com/publications/bullet-extraction-and-seating-force-testing

    but this does NOT mean that this is corelated to velocity spread

    Nifty device. It could be used to compare the force to insert versus the force to remove. Is that interesting?

    Seems to me that when you fire a round, the bullet is not pulled out of the neck, it is pushed out by pressure against the base of the bullet. So the device is measuring something but not a thing that is happening when the round fires. When the powder flashes the case expands to fill the chamber. By the time we can get our hands on it, the brass neck has expanded to chamber size and probably won't hold a bullet - the neck exerts no grip on the bullet. Did the bullet start to move before the brass loses its grip or after? There is a lot of pressure here, does the base of the bullet move before the nose?

    FWIW, Gordon's says that my 308 with LC LR brass, 175 SMK, and 41.52 grains of IMR 4064, COL=2.820 achieves maximum pressure at about 411 microseconds after the powder starts to ignite.

    As we change how much the neck grips the bullet, will we discover that grip matters to velocity and/or accuracy or not? If it does matter then what is happening that makes it matter? I guess that some people will perform experiments and make observations then go from there. For my part I think I will purchase two more expander mandrels then shoot some groups. I will try neck id 306, 305, 304, and 303 all with identical powder charge and COL.
     

    iceng

    Non-Privates
    Full Member
    Minuteman
    Sep 2, 2017
    1,486
    1,383
    South Aus
    www.iceng.com.au
    Seen a balloon pop in ultra slo mo ? The rubber contracts around the compressed air (or gas, whatever) and doesn't fling outwards. The rubber appears to contract faster than the air can expand. That's not exactly what's happening, but that's a "explain it for Poor's".

    Do you thing the propellant gas in a cartridge expands the brass neck BEFORE the bullet moves forward into the rifling ?
     

    straightshooter1

    Private
    Full Member
    Minuteman
    Dec 5, 2017
    1,880
    1,168
    AZ
    Nifty device. It could be used to compare the force to insert versus the force to remove. Is that interesting?

    Seems to me that when you fire a round, the bullet is not pulled out of the neck, it is pushed out by pressure against the base of the bullet. So the device is measuring something but not a thing that is happening when the round fires. When the powder flashes the case expands to fill the chamber. By the time we can get our hands on it, the brass neck has expanded to chamber size and probably won't hold a bullet - the neck exerts no grip on the bullet. Did the bullet start to move before the brass loses its grip or after? There is a lot of pressure here, does the base of the bullet move before the nose?

    FWIW, Gordon's says that my 308 with LC LR brass, 175 SMK, and 41.52 grains of IMR 4064, COL=2.820 achieves maximum pressure at about 411 microseconds after the powder starts to ignite.

    As we change how much the neck grips the bullet, will we discover that grip matters to velocity and/or accuracy or not? If it does matter then what is happening that makes it matter? I guess that some people will perform experiments and make observations then go from there. For my part I think I will purchase two more expander mandrels then shoot some groups. I will try neck id 306, 305, 304, and 303 all with identical powder charge and COL.
    You've asked some questions I've pondered over the last few years after I started to precision reloading to understand the details. It's difficult to quantify answers, particularly when you don't have the means to take the measurements. But here's what I've come up with in my thinking:

    Does the bullet start to move before the brass loses its grip or after?
    What I'm about to describe is events for a bullet that's being jumped, as a bullet jammed is going to be quite different. When the powder begins to ignite, pressure begins to build starting at -0-. At some point there's enough pressure to begin the forward movement of the bullet. We're talking about very small movement in milliseconds. That pressure to start the bullet's forward movement is somewhere close to what it took to seat the bullet and not enough to expand the case. The bullet's bearing surface has not cleared the neck by the time the case has expanded and sealed the chamber. But as the case is expanding and as the bullet is accelerating there's blowby around the bullet and before the chamber is sealed, some gas from the powder burn gets deposited on the outside of the neck just before the chamber is completely sealed. The slower the sealing process the further down the neck and shoulder the deposit is placed. OK, now at some point the bullet is fully released and then chamber is sealed, but maximum pressure isn't achieved until the bullet engages the lands. When bullet first engages the lands and begins to engrave to the contours of the rifling, pressure is relatively low (like 3600 psi for cartridge like a .308, varying depending on the nature of the bullet's material). From this Shot Start Pressure, the pressure builds quickly until that pressure can rapidly overcome the resistance between the bullet and the bore. Before that contact with the lands, the bullet has some velocity (with increase in mass) where it takes less maximum pressure to move the bullet past the lands than if it was at rest jammed into the lands.

    Bottom line to the answer is, the bullet MUST start moving when the interior pressure had enough force to overcome the resistance that's holding the bullet, where that force isn't much different than what it take to seat it (unless you've got cold welding going on ;)).

    As we change how much the neck grips the bullet, will we discover that grip matters to velocity and/or accuracy or not?
    How much the neck grips the bullet effect the timing, but not much for the MV's, if at all. That timing, along with barrel time, has to do with the timing to the barrel's harmonics where the bullet is clearing the muzzle at the right time. I'd say this effects "precision" more than "accuracy".

    If it does matter then what is happening that makes it matter?
    The time it takes for the neck to release the bullet is part of the time it take for the bullet to clear the muzzle. It's kinda like what "lock time" does to you're shooting, only it's about the barrel harmonics.
     

    iceng

    Non-Privates
    Full Member
    Minuteman
    Sep 2, 2017
    1,486
    1,383
    South Aus
    www.iceng.com.au
    I got a good one for you.

    No powder, primer only. Bullet will jam into lands. From primer explosion only.

    Consumer grade gun powder requires pressure to work. If you remove pressure, it burns not explodes.

    Let theorize something. Normal cartridge, with powder charge, bullet jump is 50thou, just for reasons.. pull the trigger. Primer goes off, and with the pressure from that alone, the bullet may potentially start on its way to the lands. The powder is igniting, however internal volume is increasing, this lowering (or reducing the propellants burn rate, so it's expanding, just slower than if it was under pressure).

    The friction of the bullet jammed in the lands, is it more or less than the pressure (at that moment) of the propellant expanding potential ?

    Would this result in the bullet momentarily stopping, before starting to move again ? What happens when the bullet is fully engraved ?? What happens with jumping vs jamming ?

    GRENADE !! (Leaves room).
     

    MarkyMark007

    Gunny Sergeant
    Full Member
    Minuteman
    Jan 31, 2018
    537
    206
    Europe
    not-on-google.shit
    As we change how much the neck grips the bullet, will we discover that grip matters to velocity and/or accuracy or not?
    How much the neck grips the bullet effect the timing, but not much for the MV's, if at all. That timing, along with barrel time, has to do with the timing to the barrel's harmonics where the bullet is clearing the muzzle at the right time. I'd say this effects "precision" more than "accuracy".

    how much neck grips the bullet is good question. like I said and post links to bisonballistics, when we seat bullet the neck is streching permanently. at some point it is irrelevant if we have 0.005' 'neck tension' or 0.009', because our bullet is becoming mandrell which permanently streches a neck and there in not bigger pull-out force in 0.005' neck tension or in 0.009' neck tension, just bullet will deform.

    and this maximum 'neck tension' could be 0.002'. any bigger than that it wont hold bullet more, it will just deform it.
     
    • Like
    Reactions: iceng

    Pete B

    Private
    Full Member
    Minuteman
    Nov 1, 2017
    160
    161
    Australia
    in my 223REM a few times I hadnt powder in the cartridge, and bullet NEVER moved. not for a single thou!
    No offence mate, but seems unlikely..... Ever set a primer off in a case, in your barrel (minus projectile) and held a rag over the end of the barrel with your hand?
    It is SIGNIFICANT pressure.....
     
    • Like
    Reactions: LR1845 and iceng

    MarkyMark007

    Gunny Sergeant
    Full Member
    Minuteman
    Jan 31, 2018
    537
    206
    Europe
    not-on-google.shit
    No offence mate, but seems unlikely..... Ever set a primer off in a case, in your barrel (minus projectile) and held a rag over the end of the barrel with your hand?
    It is SIGNIFICANT pressure.....
    I know that all internet is talking about this, but mine didnt move out of the brass.
     

    Yondering

    Sergeant
    Full Member
    Minuteman
    Mar 16, 2017
    1,910
    1,361
    Skagit Valley, WA
    I got a good one for you.

    No powder, primer only. Bullet will jam into lands. From primer explosion only.

    Consumer grade gun powder requires pressure to work. If you remove pressure, it burns not explodes.

    Let theorize something. Normal cartridge, with powder charge, bullet jump is 50thou, just for reasons.. pull the trigger. Primer goes off, and with the pressure from that alone, the bullet may potentially start on its way to the lands. The powder is igniting, however internal volume is increasing, this lowering (or reducing the propellants burn rate, so it's expanding, just slower than if it was under pressure).

    The friction of the bullet jammed in the lands, is it more or less than the pressure (at that moment) of the propellant expanding potential ?

    Would this result in the bullet momentarily stopping, before starting to move again ? What happens when the bullet is fully engraved ?? What happens with jumping vs jamming ?

    GRENADE !! (Leaves room).

    Your questions are not a grenade, unless someone claims the answer is always one way.

    There are way too many variables involved to claim to know the answer to any of those questions is something that always happens a certain way.

    Like MarkyMarks 223 primer comment. Many of us have seen bullets move with only a primer, but sometimes they don’t. Anyone claiming he’s lying is just showing that they haven’t seen enough to know. Same for anyone claiming bullets never move in that situation.
     
    • Like
    Reactions: iceng

    Yondering

    Sergeant
    Full Member
    Minuteman
    Mar 16, 2017
    1,910
    1,361
    Skagit Valley, WA
    No offence mate, but seems unlikely..... Ever set a primer off in a case, in your barrel (minus projectile) and held a rag over the end of the barrel with your hand?
    It is SIGNIFICANT pressure.....

    You should experiment more with actual bullets. Get enough neck tension in work hardened brass, or milder primers, etc, and results can be different than what you’ve assumed.
     

    Pete B

    Private
    Full Member
    Minuteman
    Nov 1, 2017
    160
    161
    Australia
    You should experiment more with actual bullets. Get enough neck tension in work hardened brass, or milder primers, etc, and results can be different than what you’ve assumed.
    If I am EVER that bored, I need to assess what the fuck I am doing in life!!!🤣
    All good man, it is an assumption so no further arguments from me, all the best.
    Pete
     
    • Like
    Reactions: iceng

    moaorbust

    You make the lord very nervous...
    Full Member
    Minuteman
    Nov 12, 2019
    248
    122
    Sacramento, CA
    I know that all internet is talking about this, but mine didnt move out of the brass.
    I agree. When I was first learning to reload I missed powder filling a few cases. I went to the range and pop but no boom. I took them apart at home to determine the issue. I had three conclusions. A. I forgot the powder, B. primers alone may not move the bullet and C. I am a dumbass.
     

    MarkyMark007

    Gunny Sergeant
    Full Member
    Minuteman
    Jan 31, 2018
    537
    206
    Europe
    not-on-google.shit
    same here.
    i was also woried if the primer realy goes off or it was a defective primer. but the bullet was dirty at the base, but I know that I seated shiny new bullet...
    so primer had to be good, but bullet still didnt move...😳
     

    BuildingConceptsllc

    Don't Start None, won't be none.
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Nov 13, 2020
    4,515
    3,635
    Alabama
    same here.
    i was also woried if the primer realy goes off or it was a defective primer. but the bullet was dirty at the base, but I know that I seated shiny new bullet...
    so primer had to be good, but bullet still didnt move...😳

    I've had it happen due to somehow my powder getting super wet , and the primer did go off but no powder and neither moved the bullet.
     

    Tempest 455

    Sergeant
    Full Member
    Minuteman
    Mar 4, 2012
    1,021
    760
    55
    Middle TN
    I've had it happen due to somehow my powder getting super wet , and the primer did go off but no powder and neither moved the bullet.
    I've had that from loading in a rush thinking the cases were dry. :(

    You know what's also fun. Middle of string in 1,000 yard F class match where you want to shoot fast in condition if you are in 10/X ring. Click and no bang and you wait 30 sec pull round and primer is seated backwards. :)
     

    straightshooter1

    Private
    Full Member
    Minuteman
    Dec 5, 2017
    1,880
    1,168
    AZ
    I got a good one for you.

    No powder, primer only. Bullet will jam into lands. From primer explosion only.

    Consumer grade gun powder requires pressure to work. If you remove pressure, it burns not explodes.

    Let theorize something. Normal cartridge, with powder charge, bullet jump is 50thou, just for reasons.. pull the trigger. Primer goes off, and with the pressure from that alone, the bullet may potentially start on its way to the lands. The powder is igniting, however internal volume is increasing, this lowering (or reducing the propellants burn rate, so it's expanding, just slower than if it was under pressure).

    The friction of the bullet jammed in the lands, is it more or less than the pressure (at that moment) of the propellant expanding potential ?

    Would this result in the bullet momentarily stopping, before starting to move again ? What happens when the bullet is fully engraved ?? What happens with jumping vs jamming ?

    GRENADE !! (Leaves room).

    I got a good one for you.

    No powder, primer only. Bullet will jam into lands. From primer explosion only.

    Consumer grade gun powder requires pressure to work. If you remove pressure, it burns not explodes.

    Let theorize something. Normal cartridge, with powder charge, bullet jump is 50thou, just for reasons.. pull the trigger. Primer goes off, and with the pressure from that alone, the bullet may potentially start on its way to the lands. The powder is igniting, however internal volume is increasing, this lowering (or reducing the propellants burn rate, so it's expanding, just slower than if it was under pressure).
    Whether an ignited primer alone has enough force to move the bullet forward will depend on a few things, like:
    - case volume
    - mass of the bullet
    - interference between the bullet and case neck
    - amount of bearing surface in the neck (related to the interference)

    The friction of the bullet jammed in the lands, is it more or less than the pressure (at that moment) of the propellant expanding potential ?
    There a reason why one sees a pressure spikes then drops like this:
    Pressure graph.jpg


    Would this result in the bullet momentarily stopping, before starting to move again ?
    It doesn't have to actually stop for that result, just slow down until pressure is enough to get the forward acceleration going over a very short period of time.

    What happens when the bullet is fully engraved ??
    . . . less resistance and the resistance being constant (assuming uniformnity through the bore)

    What happens with jumping vs jamming ?

    Jumping: the bullet has increased mass (a function of speed) as it moves forward and volume behind the bullet is increasing. That mass and movement into the lands requires less pressure for the bullet to overcome the resistance of engraving.

    Jamming: the bullet is at rest and requires more pressure than jumping to overcome the resistance of the engraving process. And while the pressure is building the volume is constant until the bullet moves.

    Anyway . . . this is my limited understanding of interior ballistics. :cool: 🤷‍♂️
     
    • Like
    Reactions: iceng

    iceng

    Non-Privates
    Full Member
    Minuteman
    Sep 2, 2017
    1,486
    1,383
    South Aus
    www.iceng.com.au
    Jumping: the bullet has increased mass (a function of speed) as it moves forward and volume behind the bullet is increasing. That mass and movement into the lands requires less pressure for the bullet to overcome the resistance of engraving.
    You were doing so well until this part.

    Mass of the bullet never changes. It's weight changes, which is a function, but physical mass is a constant. It's MOI (moment of inertia) is most likely what you are referring to.

    Also not less pressure, constant pressure, or amplitude of.. (can be reduced pressure, inverse to the expansion rate of the propellant, which is expanding, which increases pressure, etc..) less pressure behind the projectile and friction (in this example) would overcome it's inertia factor, and slow down, or stop.

    I'd like to argue another point you made, but won't, as you did a great job of trying to establish your position.

    👍 For you.
     

    Yondering

    Sergeant
    Full Member
    Minuteman
    Mar 16, 2017
    1,910
    1,361
    Skagit Valley, WA
    If I am EVER that bored, I need to assess what the fuck I am doing in life!!!🤣
    All good man, it is an assumption so no further arguments from me, all the best.
    Pete

    So - you're the kind of guy ready and willing to voice an opinion, but would have to re-evaluate your life before ever finding out if that opinion is correct?
    Honestly, that's kinda sad.
     

    bax

    Sergeant
    Full Member
    Minuteman
    Oct 25, 2009
    516
    198
    Southwest Michigan
    in my 223REM a few times I hadnt powder in the cartridge, and bullet NEVER moved. not for a single thou!
    I have seen that too. I have had VERY few mis-fires - maybe 5 or so over a very long time. I recall one case where I had to go home and tap the bullet out of the rifling and that was a pistol and a lead bullet. In the other cases, the bullet did not move. In every case, it was my mistake - I screwed up and didn't charge the case so only the primer fired. I shoot most primer sizes so maybe (probably) at least one of those mis-files was a magnum primer.
     

    straightshooter1

    Private
    Full Member
    Minuteman
    Dec 5, 2017
    1,880
    1,168
    AZ
    You were doing so well until this part.

    Mass of the bullet never changes. It's weight changes, which is a function, but physical mass is a constant. It's MOI (moment of inertia) is most likely what you are referring to.

    Also not less pressure, constant pressure, or amplitude of.. (can be reduced pressure, inverse to the expansion rate of the propellant, which is expanding, which increases pressure, etc..) less pressure behind the projectile and friction (in this example) would overcome it's inertia factor, and slow down, or stop.

    I'd like to argue another point you made, but won't, as you did a great job of trying to establish your position.

    👍 For you.
    Thanks for you comment, it makes me rethink what I was thinking. That's always a good thing in my mind. :)

    Rather than thinking of the moment of inertia, I was simply thinking of the equation Force=Mass x Acceleration. 🤷‍♂️ I'll have to think about that more. ;)
     
    • Like
    Reactions: iceng

    memilanuk

    F'ing nuke
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Mar 23, 2002
    2,318
    573
    East Wenatchee WA
    Circling back to the neck tension testing... Based on my own experience, I'd say the consistency of the surface finish on the neck ID is definitely worth paying attention to, particularly if you are trying to compare/contrast seating forces. You don't necessarily need to go nuts with cleaning to bare metal, polishing or special lubes - though you can if you like. Simply brushing the neck after dry tumbling works pretty darn well.

    And a handful of gauge pins off Amazon will answer a *lot* of questions regarding the effects of various things that you may be doing to your case necks - sizing with bushings, expanding with mandrels, annealing, etc. You can calculate *this* bushing combined with *that* mandrel, allow X amount for brass spring back, etc. etc... or just measure with a pin gauge for a slip fit.
     

    iceng

    Non-Privates
    Full Member
    Minuteman
    Sep 2, 2017
    1,486
    1,383
    South Aus
    www.iceng.com.au
    I still have questions about corn dry tumbling after anneal / size / case prep, as it leaves a tiny ass powder residue in and around the case. A few people swear by it.. rice also.

    I wet tumble, and never tried dry after, but I know people who do and swear by it.

    aint no one for time for that !
     

    memilanuk

    F'ing nuke
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Mar 23, 2002
    2,318
    573
    East Wenatchee WA
    I still have questions about corn dry tumbling after anneal / size / case prep, as it leaves a tiny ass powder residue in and around the case. A few people swear by it.. rice also.

    If you are getting dust, throw some dryer sheets in the tumbler with the brass. It should pick up most of the finer dust easy peasy.

    I wet tumble, and never tried dry after, but I know people who do and swear by it.
    Dry... what? Lube?
     
    • Like
    Reactions: iceng

    iceng

    Non-Privates
    Full Member
    Minuteman
    Sep 2, 2017
    1,486
    1,383
    South Aus
    www.iceng.com.au
    Some people around my parts WANT the corn / rice "dust". Acts as a lub inside the neck. Sorry if I didn't explain it properly the first time.
     

    Rider47

    Private
    Minuteman
    Jan 4, 2022
    30
    31
    Maryland
    Has anyone tried using moly on the inside of the case necks?
    My regular procedure results in a very uniform surface. Cases are first immersed in hot (heated on stovetop) ultrasonic cleaner and run for at least 3-six minute cycles over about two hours, then wet tumbled with SS pins in hot/warm ultrasonic cleaner for about a half hour. After rinsing and oven drying the cases the inside of the necks are lightly cleaned with a properly sized rotating bronze brush. (Periodically a fresh deburr is needed from repeated SS tumbling.)

    I am now experimenting with a light coating of moly on the inside of the case necks. The moly powder is suspended in GunScrubber and applied with a Q-Tip after resizing. 6BR cases shown below. Optimum precision for this rifle seems to be with minimal neck tension and bullets seated slightly into the lands. (Hybrid 105 / 30.4 Varget)

    eVstHf6.jpg

    V3XX6wy.jpg
     
    • Haha
    Reactions: Huskydriver

    memilanuk

    F'ing nuke
    Supporter
    Full Member
    Minuteman
    Supporter+
  • Mar 23, 2002
    2,318
    573
    East Wenatchee WA
    Some people around my parts WANT the corn / rice "dust". Acts as a lub inside the neck. Sorry if I didn't explain it properly the first time.
    Correct. A little bit helps (in my opinion). Too much, and you start tracking dust into your sizing dies, etc. That's where the dryer sheets help.
     
    • Like
    Reactions: iceng

    Yondering

    Sergeant
    Full Member
    Minuteman
    Mar 16, 2017
    1,910
    1,361
    Skagit Valley, WA
    Some people around my parts WANT the corn / rice "dust". Acts as a lub inside the neck. Sorry if I didn't explain it properly the first time.

    Huh. You must be using the corn cob completely dry then, no polishing compound or wax?

    I've never seen the corn cob I use leave any dust at all, but I always use polishing compound (I mean, it stays in the media, not like it gets added every tumbling or something). In the past 3-4 years or so I've been adding some car wax to it as well; that seems to do just enough for the inside of the necks to smooth things out a bit and avoid cold weld, etc. No dust on my cases though, ever, with corn cob, unlike with walnut which leaves a ton of dust.

    However - not all corn cob is equal, and most of what I've found in the past few years has a lot of chaff in it. Not something I'd call dust, but larger lightweight pieces of corn husk or something. I usually have to blow that stuff off the brass with compressed air; probably should just scrap this latest batch and find media without the chaff, like we used to be able to get.
     
    • Like
    Reactions: iceng

    Haney

    Gunny Sergeant
    Full Member
    Minuteman
    Apr 2, 2020
    826
    438
    Huh. You must be using the corn cob completely dry then, no polishing compound or wax?

    I've never seen the corn cob I use leave any dust at all, but I always use polishing compound (I mean, it stays in the media, not like it gets added every tumbling or something). In the past 3-4 years or so I've been adding some car wax to it as well; that seems to do just enough for the inside of the necks to smooth things out a bit and avoid cold weld, etc. No dust on my cases though, ever, with corn cob, unlike with walnut which leaves a ton of dust.

    However - not all corn cob is equal, and most of what I've found in the past few years has a lot of chaff in it. Not something I'd call dust, but larger lightweight pieces of corn husk or something. I usually have to blow that stuff off the brass with compressed air; probably should just scrap this latest batch and find media without the chaff, like we used to be able to get.
    Untreated corn cob has plenty of "dust" .
     
    • Like
    Reactions: iceng

    Cascade Hemi

    Major Hide Member
    Full Member
    Minuteman
    Feb 9, 2019
    1,783
    1,588
    PNW
    Huh. You must be using the corn cob completely dry then, no polishing compound or wax?

    I've never seen the corn cob I use leave any dust at all, but I always use polishing compound (I mean, it stays in the media, not like it gets added every tumbling or something). In the past 3-4 years or so I've been adding some car wax to it as well; that seems to do just enough for the inside of the necks to smooth things out a bit and avoid cold weld, etc. No dust on my cases though, ever, with corn cob, unlike with walnut which leaves a ton of dust.

    However - not all corn cob is equal, and most of what I've found in the past few years has a lot of chaff in it. Not something I'd call dust, but larger lightweight pieces of corn husk or something. I usually have to blow that stuff off the brass with compressed air; probably should just scrap this latest batch and find media without the chaff, like we used to be able to get.

    Berry's sells corncob media in a 5 gallon bucket. It is the best form of corncob media I've used.
     
    • Like
    Reactions: Yondering

    Huskydriver

    Not here for a long time but here for a good time
    Supporter
    Full Member
    Minuteman
    Apr 17, 2018
    7,043
    13,493
    SLC, Utah
    Has anyone tried using moly on the inside of the case necks?
    My regular procedure results in a very uniform surface. Cases are first immersed in hot (heated on stovetop) ultrasonic cleaner and run for at least 3-six minute cycles over about two hours, then wet tumbled with SS pins in hot/warm ultrasonic cleaner for about a half hour. After rinsing and oven drying the cases the inside of the necks are lightly cleaned with a properly sized rotating bronze brush. (Periodically a fresh deburr is needed from repeated SS tumbling.)

    I am now experimenting with a light coating of moly on the inside of the case necks. The moly powder is suspended in GunScrubber and applied with a Q-Tip after resizing. 6BR cases shown below. Optimum precision for this rifle seems to be with minimal neck tension and bullets seated slightly into the lands. (Hybrid 105 / 30.4 Varget)

    eVstHf6.jpg

    V3XX6wy.jpg

    Wtf has time for that lol
     
    • Like
    Reactions: Supersubes

    Yondering

    Sergeant
    Full Member
    Minuteman
    Mar 16, 2017
    1,910
    1,361
    Skagit Valley, WA
    Untreated corn cob has plenty of "dust" .
    Uh, no kidding genius. Did you read what I wrote?

    It’s pretty pathetic how you keep following me around to make petty snide remarks about all my posts. Like a teenage drama queen after someone offended her.
     

    Cascade Hemi

    Major Hide Member
    Full Member
    Minuteman
    Feb 9, 2019
    1,783
    1,588
    PNW
    Sometimes I don't even clean my brass. If it isn't covered in dirt I just anneal it, neck size it (yeah I said it), and load it up. Some people are their own worst enemies; load the cartridges to moon, clean the brass spotless, and try to size back their blown out case webs. It just isn't that hard.
     

    nick338

    Commander- of what I have no idea
    Supporter
    Full Member
    Minuteman
    Supporter+
    Feb 21, 2013
    1,304
    918
    I'm just wet tumbling without the pins. Cleans the outside of the cases enough but leaves the carbon on the inside of the neck. Quick clean of the primer pocket after and I'm done.
     
    • Like
    Reactions: Hetzer

    Haney

    Gunny Sergeant
    Full Member
    Minuteman
    Apr 2, 2020
    826
    438
    Uh, no kidding genius. Did you read what I wrote?

    It’s pretty pathetic how you keep following me around to make petty snide remarks about all my posts. Like a teenage drama queen after someone offended her.
    Wow, you sound very insecure . I was only stating a fact you obviously did not know . Did you read what you wrote ? Maybe your concob is coated with shit ?