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Question on VV N320 and 124g minor loads


muncie21

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I've been shooting USPSA for several years, however only decided to start reloading recently.

I'm working to develop a minor load using Bayou 124g TCN and RN bullets, using VV N320 powder.  

In my most recent tests:

  • I've got the RN loaded with 3.8g and seated at 1.15 OAL, they are chrono'ing at an average of 982 FPS.
  • The TCNs chrno a bit faster than the RNs using the same load.  So the TCNs are averaging 985 with 3.7g, when seated at 1.08 (I'm shooting a CZ, so need shorter than typical OAL)

With the 124 bullet, both loads (RN & TCN) are below minor PF.  VV's website shows max velocity for FP & RN to be 1096 and 1070 respectively.  

So here's my question, I'd rather not load to max, to get to a 130 PF (I like a little bit of cushion), any suggestions?

BTW, I plunk test every round, so I'm confident the bullets are not engaging the rifling.  I've also pulled the bullets on some loaded rounds to check for crimp marks on the bullets, very light to no marks on the samples I've pulled.

Edited by muncie21
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You can do what most others will say and load some at 3.9, 4.0, 4.1 etc and chrono looking for pressure signs etc. 3.8 isn't even close to what you need.

130 PF is not enough cushion for me. I generally aim for 7 over minimum. You won't be able to tell the difference between 130 and 133 anyway.

if you want a good 132-133 load without making repeated changes to the press, load them to 4.1 and chrono. Will be mighty close to perfect.

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^^^  Everything Sarge said ^^^

Viht doesn't have exact data for the bullets you're using, but it has data for two bullets that are relevant.  When you're looking for data, match bullet weight first -- 124/125 -- then surface type second -- lead.  They list data for two bullets for that: the 124gr Intercast LSWC, with a load window of 3.8gr - 4.1gr -- AND the Ranier 124gr RN, which is supposed to use lead data, so it works both ways, and that is 3.8gr - 4.1gr.  It looks like you have some agreement there between your two relevant bullets.  I'd say your load window is 3.8 - 4.1gr. ;)   

I know you're trying to be safe, but at 3.8gr, YOU are loading at the bottom of the load window.  You might not even be getting a good pressure seal.  It's safe for you to move up, and N320 is very well-behaved. 

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Thanks (both) for your feedback.

ID you're correct in that I'm trying to be safe/conservative with the load.  My worry is with the TCN bullet.  It needs to be seated ~1.08 in order to pass the plunk test.  The load chart on VV's web site list the OAL as 1.142 (except Megashock) and max powder at 4.1.

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9 minutes ago, muncie21 said:

Thanks (both) for your feedback.

ID you're correct in that I'm trying to be safe/conservative with the load.  My worry is with the TCN bullet.  It needs to be seated ~1.08 in order to pass the plunk test.  The load chart on VV's web site list the OAL as 1.142 (except Megashock) and max powder at 4.1.

I'm not saying one doesn't need to play it safe when reloading, but when loading 9 minor ammo, unless you just ignore the charts and add a bunch of extra powder you will be fine. Powder companies are VERY conservative with recipes due to liability. A modern 9mm pistol will run +P+ defense ammo with no problem to an extent. When loading 132 PF loads that's more like running weak REM UMC stuff. Then throw in what IDescribe said about differing bullets etc we are are almost always experimenting with these loads and sometimes just safely guessing about oal differences etc. My point being, unless you are just wreckless you are not going to go from 130 PF to +P+ by upping powder .2 or so over the charts or shortening a load by .001.

Someday if you ever load 9 MAJOR, THEN you need to be a little OCD since the book loads stop 3.5 grains from where you need to be! :)

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First, I'm assuming you're talking about the Bayou 124gr TCG.  I'm not familiar with a TCN.  

In developing loads, the OAL difference is good to pay attention to, but you need to recognize that when you are looking at different profiles, it's no longer an apples to apples comparison.  There is a point on the ogive that is going to make contact with the rifling with both bullets.  Your max OAL is dependent on how far past that point the bullet extends.  An RN is more likely to extend further ahead of that point that a truncated cone, in part because the truncated cone is... well... truncated. ;)   And the space between the nose and that point on the ogive that will contact the rifling has NO BALLISTIC EFFECT in terms of how the powder burns.  What will have an effect on how the powder burns is how deeply the bullet's base is seated into the case.  The deeper the base is seated, the smaller the initial size of the combustion chamber is, and the faster and higher pressures will climb.  That seating depth is really what you're trying to account for when you adjust for OAL differences, but when the bullets are different profiles, it's not apples to apples.  

For a specific example, that Bayou 124gr TCG plunks and spins freely at 1.079 in my 75 Shadow Line.  I seat it at an OAL of 1.070.  The old model BBI 125gr RN, I used to seat at an OAL of 1.1.  That's an OAL difference of .04, which might concern someone trying to account for OAL difference, but in reality, the Bayou TCG at 1.07 has a seating depth of .240, and that old BBI 125gr RN at OAL 1.1 had a seating depth of .246, so the bullet with the longer OAL was actually seated deeper, and that's where you're going to affect powder burn and pressure.  The truth is that the seating depths are so close together -- .006 -- that the difference isn't even worth worrying about, but the point is that a difference in OAL between two different profiles may not mean much difference at all in terms of seating depth, which is where the real difference in how pressures build comes from.  And to make the same point in a different way, I also have used the MBC 125gr SWC, which I have to seat at 1.066, and THAT is a seating depth of .310.  So if compared to the 124gr TCG, we have two lead bullets where the OAL difference is only .004, almost the same, but we have a seating depth difference of .070, and THAT is significant and should be accounted for.  

So it's not just OAL.  As I've said many times, the powder doesn't care how much distance there is from the headstamp to the nose; the powder cares how far you jammed the bullet down into its space. ;) 

And as to not wanting to load near max... why?  Max is max standard pressure. Above that is +P.  Above that is +P+ and proof loads.  I will be the first person to say that people are better off not running up in +P as standard practice while looking for ever softer and softer recoil, but you certainly don't need to be shy of max standard for fear you might drift a hair over.  Don't sweat it.  

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Vihtavuori is playing it safe in their data too.

Work up in small steps and pay attention to any flattened primers or other unusual things.

VV's max loads of 4.1 gr for 124gr lead bullets seem to be in Minor with a bit of margin - and that is with a 4" test barrel.

Your low velocities could mean that you don't have enough pressure. I wonder if your bullets are a fraction too small for your barrel...

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Looks like I'm headed (slowly) in the right direction.  Created a test set at 3.8 and 3.9g and chrono'd them today. It looks like a 4.0g load will put me solidly in the 130PF range 

 

Set: 13
Created: 01/19/17 11:54
Description: 124 TCG
Notes 1: 3.8gr
Notes 2: 1.08 COL
Distance to Chrono(FT): 8.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 124.00
Temp: 40 °F
BP: 30.08 inHg
Altitude: 0.00
#          FPS  FT-LBS      PF
10    1028    291.02  127.47
9    1049    303.03  130.08
8    1028    291.02  127.47
7    1018    285.39  126.23
6    1032    293.29  127.97
5    1044    300.15  129.46
4    1017    284.83  126.11
3    1016    284.27  125.98
2    1029    291.59  127.60
1    1000    275.38  124.00
Average: 1026.1 FPS
SD: 14.2 FPS
Min: 1000 FPS
Max: 1049 FPS
Spread: 49 FPS
 

Set: 15
Created: 01/19/17 11:59
Description: 124 TCG
Notes 1: 3.9g
Notes 2: 1.08 COL
Distance to Chrono(FT): 8.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 124.00
Temp: 40 °F
BP: 30.10 inHg
Altitude: 0.00
#          FPS  FT-LBS      PF
10    1037    296.14  128.59
9    993      271.54  123.13
8    1019    285.95  126.36
7    1053    305.35  130.57
6    1040    297.85  128.96
5    993      271.54  123.13
4    1050    303.61  130.20
3    1035    295.00  128.34
2    1048    302.45  129.95
1    1017    284.83  126.11
Average: 1028.5 FPS
SD: 22.2 FPS
Min: 993 FPS
Max: 1053 FPS
Spread: 60 FPS

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I agree with Sarge, Muncie.  I'd up your velocity a bit more, as well.  If you're worried about recoil, think of it this way: your extreme spreads of 50 and 60 with a 124gr bullet equals a PF spread of 6 and 7 respectively.  Did you notice the different recoil from one round to the next when shooting those?  No?  So don't sweat moving up a couple more PF from a recoil standpoint.  You'll never notice. ;) 


 

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Yep, as always you're both on point (Sarge/ID) I'm going to target a 132/133 PF.  Loaded up another set and can't wait to try'em out! 

I'm also a bit curious to see if there is a noticeable difference in velocity between the TCG and RN bullets at this load.  I'm really digging the intricacies and complexity that comes with reloading, but then again, I've always enjoyed a good puzzle.

Edited by muncie21
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On 2017-01-18 at 7:28 AM, Sarge said:

You can do what most others will say and load some at 3.9, 4.0, 4.1 etc and chrono looking for pressure signs etc. 3.8 isn't even close to what you need.

130 PF is not enough cushion for me. I generally aim for 7 over minimum. You won't be able to tell the difference between 130 and 133 anyway.

if you want a good 132-133 load without making repeated changes to the press, load them to 4.1 and chrono. Will be mighty close to perfect.

I've shot a lot of the above load. Makes pf without fail, is accurate, and runs the gun well (P320, G34, and XDM 5.25) in my experience. A good recommendation.

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Yep, as always you're both on point (Sarge/ID) I'm going to target a 132/133 PF.  Loaded up another set and can't wait to try'em out! 

I'm also a bit curious to see if there is a noticeable difference in velocity between the TCG and RN bullets at this load.  I'm really digging the intricacies and complexity that comes with reloading, but then again, I've always enjoyed a good puzzle.


I too enjoy the complexity and intricacies of reloading. Just when I think I've finally got a firm grasp on it I find something that makes me realize just how much I don't know.
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Here's the data from the latest test set using 4.0g of N320 and a target OAL of 1.08.  I'm pretty happy with these, now to crank out some and start practicing. 

Created: 01/20/17 11:48
Description: 124 TCG
Notes 1: 4.0g
Notes 2: 1.08 OAL
Distance to Chrono(FT): 6.00
Bullet Weight(gr): 124.00
Temp: 49 °F
BP: 29.76 inHg
#          FPS  FT-LBS      PF
10    1048    302.45  129.95
9    1075    318.24  133.30
8    1076    318.83  133.42
7    1086    324.79  134.66
6    1086    324.79  134.66
5    1080    321.21  133.92
4    1103    335.03  136.77
3    1057    307.67  131.07
2    1085    324.19  134.54
1    1089    326.58  135.04
Average: 1078.5 FPS
SD: 15.9 FPS
Min: 1048 FPS
Max: 1103 FPS
Spread: 55 FPS
Shot/sec: 0.6
True MV: 1079 FPS

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