Myth Busting Pre-Resized Brass Affect On OAL Variance - Progressive Press

[LiveLife]

Discussion on a recent thread regarding the use of Pre-Resized brass reducing OAL variance triggered another myth busting thread.

For my USPSA match loads, I pre-resized brass to inspect primer pockets and cleaned as necessary. After hand priming the brass, reloading in progressive mode not only makes it silky smooth requiring little effort but with case feeder, very fast.


Test procedure:

• BLAZER 9mm brass were resized and they ranged from .750" to .752".
• Five cases measuring .751" were selected
• Rocky Mountain Reloading In-House 115 gr FMJ
• Test rounds were loaded on Pro 1000 using Lee dies
• Frankford Arsenal dial calipers verified with Vermont pin gages

Regular Reloading - Bullets were seated with all 3 stations full. OAL/COL sorted from shortest to longest:

1. 1.115"
   
2. 1.116"
   
3. 1.116"
4. 1.117"
5. 1.118"

Pre-Resized Brass Reloading - Resizing/depriming die removed from Station 1. All bullets were seated while flaring a case in Station 2. OAL/COL sorted from shortest to longest:

1. 1.115"
2. 1.115"
3. 1.116"
   
4. 1.116"
5. 1.116"

Summary - With RMR In-House 115 gr FMJ bullets and mixed range brass, I usually get around .005" OAL variance. Using same BLAZER headstamp brass produced .003" OAL variance while using pre-resized brass produced 001" OAL variance.

 

[LiveLife]

Test procedure:

• R-P 9mm brass were resized and they ranged from .749" to .753".
• Five cases measuring .751" were selected
• Rocky Mountain Reloading In-House 115 gr FMJ
• Test rounds were loaded on Pro 1000 using Lee dies
• Frankford Arsenal dial calipers verified with Vermont pin gages

Regular Reloading - Bullets were seated with all 3 stations full. OAL/COL sorted from shortest to longest:

1. 1.115"
   
2. 1.115"
   
3. 1.115"
4. 1.117"
5. 1.118"

Pre-Resized Brass Reloading - Resizing/depriming die removed from Station 1. All bullets were seated while flaring a case in Station 2. OAL/COL sorted from shortest to longest:

1. 1.115"
2. 1.115"
3. 1.116"
   
4. 1.116"
5. 1.116"

Summary - Using same R-P headstamp brass produced .003" OAL variance while using pre-resized brass produced 001" OAL variance.

 

[Hondo 60]

Results were pretty much as I suspected.
The "pull" that takes the most effort is the resizing.

Thanks for taking the time & effort in doing this.

 

[LiveLife]

Test procedure:

• WIN 9mm brass were resized and they ranged from .749" to .752".
• Five cases measuring .750" were selected
• Rocky Mountain Reloading In-House 115 gr FMJ
• Test rounds were loaded on Pro 1000 using Lee dies
• Frankford Arsenal dial calipers verified with Vermont pin gages

Regular Reloading - Bullets were seated with all 3 stations full. OAL/COL sorted from shortest to longest:

1. 1.114"
   
2. 1.114"
   
3. 1.116"
4. 1.117"
5. 1.117"

Pre-Resized Brass Reloading - Resizing/depriming die removed from Station 1. All bullets were seated while flaring a case in Station 2. OAL/COL sorted from shortest to longest:

1. 1.114"
2. 1.115"
3. 1.115"
   
4. 1.115"
5. 1.115"

Summary - Using same WIN headstamp brass produced .003" OAL variance while using pre-resized brass produced 001" OAL variance.

 

[jell-dog]

bds,
Thank you for taking the time to myth busting Pre-resized brass on variations of COL/COA.
Very interesting results!
JD

 

[WestKentucky]

Not really surprised, but curious to know how much this means on paper. I suspect that it means little to most and the most to the few who shoot for the utmost accuracy at extreme range where any difference is magnified to a visible degree by distance from shot to target. I also suspect that the difference in performance is minuscule when compared to factors such as temperature of the firearm and heart rate of the shooter.

 

[LiveLife]

As I already posted, with mixed range brass, OAL variance is about .005" while pre-resized brass OAL averaged .001".

I believe that would attribute to accuracy measurable on target.

Summary - With RMR In-House 115 gr FMJ bullets and mixed range brass, I usually get around .005" OAL variance. Using same BLAZER headstamp brass produced .003" OAL variance while using pre-resized brass produced 001" OAL variance.

 

[LiveLife]

curious to know how much this means on paper.

Repost from another thread - https://www.thehighroad.org/index.php?threads/new-auto-breech-lock-pro.832974/page-7#post-10778997

I would like to see a myth busters thread on whether .003" inch variance in OAL actually affects accuracy to any measurable degree

1KPerDay, take a step back and look at the "totality" of reloading variables.

• In the myth busting thread, it's less critical to note how much OAL varied rather they varied - https://www.thehighroad.org/index.p...-affect-on-oal-variance.833604/#post-10778746

• And the tests were conducted using same headstamp brass. With mixed range brass, I get about .005" OAL variance.

• And we recently did neck tension and bullet setback myth busting thread where we measured different amount of bullet setback depending on the headstamp when chambered from the magazine - https://www.thehighroad.org/index.p...nd-bullet-setback.830072/page-3#post-10715550

Please note, it's not the FINISHED OAL that determines holes on target rather CHAMBERED OAL (after bullet setback) and STACKING OF RELOADING VARIABLES.


So while .004"+ OAL variance may not translate to significant change on group size, add to this bullet setback variance and powder charge variance (We all know even better metering powders vary by .1 gr which is going to be my next myth busting thread), now you have STACKING of reloading variables that could be measurable on target.

I would suppose that could, or would depend upon the case volume and powder used.

And if you are using a powder measure that drifts, you have another reloading variable that could stack.

When I shot USPSA matches, we did many comparison tests. One of the tests was shooting our different match loads (different bullets, powders/charges, primers, OAL, crimp, etc.) in the same pistol to see if we could see difference on target. When my match loads got comparable/smaller groups than other match loads, they got curious.

They were shocked to find out I was loading my match loads on Pro 1000 with pre-resized brass. Back than I was using Montana Gold FMJ/JHP bullets and Winchester primers along with WST/Titegroup/W231/Universal/WSF powders and many other shooters used the same components.

So we went to different shooters' houses and examined their equipment and reloading practice with calipers and scales in hand. What we found out was some of the powder measures drifted as much as by a few thousandths during a reloading session. Let's say you start out with 4.0 gr charge but the powder measure drift ends with 4.2 gr. If you factor in the normal powder measure drop variance, you could be reaching into your ammo bag and grab two different rounds with almost 3.9 gr charge and 4.3 gr charge loaded in the same magazine. This variance WILL show on target.

What they found with me was since I was using a fixed volumetric hole Pro Auto Disk, my powder charge drops could not drift even after 1000+ round reloading session and all the rounds you grab from the ammo bag would have the normal powder charge variance of .1 gr. Of course while I used mixed range brass, I did use pre-resized brass which, as shown in recent myth busting thread, produced OAL variance of .001".

 

[Laphroaig]

So we went to different shooters' houses and examined their equipment and reloading practice with calipers and scales in hand. What we found out was some of the powder measures drifted as much as by a few thousandths during a reloading session. Let's say you start out with 4.0 gr charge but the powder measure drift ends with 4.2 gr. If you factor in the normal powder measure drop variance, you could be reaching into your ammo bag and grab two different rounds with almost 3.9 gr charge and 4.3 gr charge loaded in the same magazine. This variance WILL show on target.

bds, This paragraph got me thinking, and I went back to the "powder measure drift mythbusting thread":

https://www.thehighroad.org/index.php?threads/thr-mythbusting-powder-measure-drift.809850/page-2

The way I interpreted the posts, no one had observed any long term drift in their powder measures and the thread ended somewhat inconclusive. I did reply with an observation on my Dillon measure, but what I tried to say is that it took awhile to settle in to a consistent reading. Maybe I'm offtopic here, but can you elucidate as to which measures experienced drift?

 

[Blue68f100]

What are the measurements from the ogive vs nose? We all know bullets have a tolerance range when measured from the nose.

 

[LiveLife]

The way I interpreted the posts, no one had observed any long term drift in their powder measures and the thread ended somewhat inconclusive.

Realization I made was most members lacked the verified equipment to detect less than .1 gr or even .1 gr variance. So I did not pursue the thread further.

Bart B. did post this but attributed to normal range of reloading condition depending on many factors.

I've seen a 2/10ths grain shift in charge weight averages with the same measuring chamber setting for a given lot of powder

can you elucidate as to which measures experienced drift?

Most match shooters used Dillon equipment (I believe one or two used Hornady LNL AP) and depending on the wear of powder measure, drift was detected as early as after 100 cycles requiring adjustment. Many admitted they did QC check of powder drops every 50 to 100 rounds.

Now that I have the means to weigh powder charges to .02 gr resolution (verified by Ohaus ASTM Class 6 check weights), I may do a powder charge verification on my Dillon 650 every 50 rounds on a 500 round reloading session.

 

[Blue68f100]

I tap the side of the reservoir settling the powder. Then I do 15-20 drops and throw them back into the reservoir before I start measuring anything. One thing I do when setting up the powder dispenser is to take a 10 drop average. This will get you to the 0.01gr on std 0.1gr accuracy scales. Adj so it's as close as you want. I measure every powder drop too. I want to know if I'm getting some out of the normal. The reason I will not use Unique.

 

[LiveLife]

I think we could resume powder measure "drift" on the old thread or start a new one as this thread is about OAL variance between using pre-resized brass and not.

 

[Doublehelix]

What are the measurements from the ogive vs nose? We all know bullets have a tolerance range when measured from the nose.

I think this post by @Blue68f100 got missed in the mix. I am curious about this as well, especially with coated lead bullets.

 

[LiveLife]

I think this post by @Blue68f100 got missed in the mix.

I lack the equipment to precisely measure bullet nose tolerance. Perhaps someone who has the equipment can do the measurement.

And the measurement needs to be made where Lee bullet seating die stem contacts the bullet nose.

I am curious about this as well, especially with coated lead bullets.

I chose to use RMR In-House 115 gr FMJ bullets for testing as RMR is making them on a new machine with new dies and more consistent than other bullets/types I have used.

 

[mdi]

I can't say I've heard of "pre-resizing" Does one resize before resizing?.

 

[LiveLife]

No, just resizing in separate step.

Benefits are many:

• As illustrated, decreases OAL variance
• Allows inspection of primer pockets and cleaning if necessary
• Allows hand priming of brass
• When reloading progressively, resizing/depriming die is removed from Station 1 or can gain another station (so 3 station press can seat and crimp in separate steps)
• Makes progressive reloading silky smooth using much less effort
• Increases speed of reloading progressively as pre-resizing of brass can be done during down time

 

[Walkalong]

I can't say I've heard of "pre-resizing"

No, just resizing in separate step.

He's just pulling your chain for doubling up.

 

[LiveLife]

 

[Doublehelix]

So if your assumptions are true, you should see less variation with a turret press (and by definition with a single-stage press) than you would with a progressive when you are sizing as part of the loading process.

Would you agree with this assessment?

I do have to say that this has not been my experience, but unfortunately, it is a hard thing to compare because my LCT press is nothing like my XL650, and there are so many variations and variables to explore between systems that it would be difficult to make a blanket statement like that (different brands, designs, tolerances, etc., etc., etc.)

However, I can say that I see about the same COAL variation between my LCT and my Dillon XL650 when performing all operations on the press and using the same brand and type of dies.

This is a very "unscientific statement" without any published data to back it up (I could do some testing I suppose), but it is just based on my general observations.

But since sizing is performed as an isolated step on the LCT, there should be no additional flexing of the shell holder other than that which is exerted by seating die. ALL ELSE BEING EQUAL (which it is not), I would expect less flexing of a shell holder than a shell plate, but then again, you would probably see more flexing of the turret on an LCT than on the tool head of the XL650.

I have read discussions on the turret flexing on the LCT as adding variability to COAL, but others have countered that that flexing is the same for every case as long as the ram is fully extended so this does not add to COAL variability.

Lots to think about with this subject!

 

[LiveLife]

So if your assumptions are true, you should see less variation with a turret press (and by definition with a single-stage press) than you would with a progressive when you are sizing as part of the loading process.

Would you agree with this assessment?

Yes as resizing and bullet seating are done in two separate operations with resizing not affecting the bullet seating. As to LCT, I do not see movement of turret as an issue for OAL variance as upward travel of turret is limited by the frame and certainly no 'flex" of shell holder.

This thread was meant for progressive presses where resizing operation may affect bullet seating operation.

I asked Walkalong to add "Progressive Press" to the thread title.

 

[Blue68f100]

I lack the equipment to precisely measure bullet nose tolerance. Perhaps someone who has the equipment can do the measurement.

And the measurement needs to be made where Lee bullet seating die stem contacts the bullet nose.

I chose to use RMR In-House 115 gr FMJ bullets for testing as RMR is making them on a new machine with new dies and more consistent than other bullets/types I have used.

BDS,

Remove the seating stem from the die and use it to measure your OAL with. This will not be true OAL but it will be good reference as to change.

 

[LiveLife]

I could give that a try.

 

[Tilos]

It was suggested I re-post this as it is relevant to the discussion here:

"The bullet seater pushes/contacts the bullet somewhere along the ogive and we measure OAL at the bullet tip.
So I'm thinking any variation of the ogive would directly affect the OAL (measured at the tip).

If I were testing to find any cause of OAL variation (I'm not) I would use a totally flat point bullet of some kind and flat bullet seater to seat the bullet, to eliminate any ogive variation from skewing the results."

https://www.thehighroad.org/index.php?threads/new-auto-breech-lock-pro.832974/page-7#post-10779189

 

[LiveLife]

I do have RMR 124 gr FMJ FP bullets but my bullet seating die stem is for RN bullets.

Still, I could consider repeating the test with FP bullets.

OK. Test was done with RMR 124 gr FMJ FP bullets.

Test procedure:

• BLAZER 9mm brass were resized and they ranged from .749" to .752".
• Five cases measuring .750" were selected
• Rocky Mountain Reloading In-House 124 gr FMJ FP
• Test rounds were loaded on Pro 1000 using Lee dies
• Frankford Arsenal dial calipers verified with Vermont pin gages

Regular Reloading - Bullets were seated with all 3 stations full. OAL/COL sorted from shortest to longest:

1. 1.070"
2. 1.070"
3. 1.071"
4. 1.071"
5. 1.072"

Pre-Resized Brass Reloading - Resizing/depriming die removed from Station 1. All bullets were seated while flaring a case in Station 2. OAL/COL sorted from shortest to longest:

1. 1.069"
2. 1.069"
3. 1.070"
4. 1.070"
   
5. 1.070"

Summary - Using same BLAZER headstamp brass produced .002" OAL variance while using pre-resized brass produced 001" OAL variance