Reload length variance

[Goat259]

Good Evening,

 

When I first started reloading, I had my Dillon 650 reload to a length of 1.18.” However, after double checking everything, the average of 10 rounds, came out to 1.175.” So my question today is, do dies over time just move ever so slightly, and, what is the variance on length that is acceptable if I am wanting 1.18?” 
 

Thank you. 
 

 

[Farmer]

18 hours ago, Goat259 said:

Good Evening,

 

When I first started reloading, I had my Dillon 650 reload to a length of 1.18.” However, after double checking everything, the average of 10 rounds, came out to 1.175.” So my question today is, do dies over time just move ever so slightly, and, what is the variance on length that is acceptable if I am wanting 1.18?” 
 

Thank you. 
 

 

Take your calipers, zero them and then open them .005. Now hold them up to the light and peer through the jaws and see just how small of a gap that really is. 
Machine flex, bullet flex, higher case tension, mixed brass or dirty cases, loose seater plug, shell plate flex can all attribute to that tiny amount.  Personally I’m more concerned with consistency. I had some that were all over the place +- .010.  What I found out was that the seater punch didn’t fit the nose of a particular bullet I was using and on tight brass it was mashing the nose. Once I fixed the punch everything is within .003

Edited January 25, 2023 by Farmer

[jimbullet]

flex in shell plate, combined mainly with mixed brass possibly.

[Brooke]

Mixed brass is a major contributor to the variation. Brass length, thickness, history (especially work hardening, brittleness) vary by brand.

 

Even if you sort by headstamp and only keep the brands you know to be the best from experience with them, you are very lucky to stay within a total OAL range of 0.005 . That's using the top of the line presses like Dillon 1050 and 1100 and any of the Mark 7 presses like the Apex 10. The machines  have variation as mentioned, e.g. shell plate flex, stroke length and Lord knows what else.

 

Do you realize what small variation 0.005 or even 0.010 are? I don't think you do. Just because you can measure it doesn't mean its easily controlled or even very important. The angle you get the round in your calipers causes more variation than that. Try it.

 

I would love to make every round exactly the same. That is not possible on a $1000-6000 press due to the huge number of variables involved many of those with the brass. Decide what you can deal with. With properly prepared brass and careful after production gauging for both diameter and length you can maintain +/- 0.005. Pick your center point correctly and you won't have issues with most guns. While I sometimes use that range I try hard to keep my match ammo at +/- 0.003. Im pretty successful at that with both an automated 1050 and an automated Apex 10. For match ammo I check every round for OAL and gauge all rounds in a 100 hole Shockbottle gauge. I know by experience that any round that will freely drop in any hole in my gauge will work in my gun. I also know that using my chosen bullet profile I can chamber +0.005 from the center point I use and have little problem with rounds at -0.005 from the center.  I still strive for +/- 0.003. That is easily possible with little fallout if you use a good consistent case prep and careful QA along with sorting by headstamp.  YES...I do have to change die setting for seating if I change headstamps in the middle of a long press run. If I change from Win or R-P to any other brass I have to reset the seating die. Typically between Blazer and Federal and Speer I don't have to change anything but I check carefully when I make the change.

 

A range of 0.010 can usually be used if you pick the right center point. It can be a disaster if you pick a center to close the max your gun can chamber or too close to the point where feeding short rounds is not reliable.

 

There is no substitute for knowing your guns and your presses and having a consistent process.

 

[Mknzy]

Thanks very much for the comments.  As I am new to reloading, I have been struggling with the issue of OAL and all the things you mentioned in your post.  Your point is well taken, the differences can be measured but it depends upon how you hold the calibers, the brand of brass, the variance in the press, the dies etc.  Controlling the exact actual difference is elusive.

 

The other element here is comprehending the actual length.  I cannot visually see a 0.005 or even a 0.10 difference in bullet length which leaves one only with the numbers on the digital caliber to rely upon.

 

 

Edited February 18, 2023 by Mknzy

[Davecoff13]

Also take some brand new factory ammo and measure it. Some brands will shock you!

[OptimiStick]

Yeah when I first started - also on a 650 -  I didn't like the variance either and went through about everything trying to reduce the variance. Clamping tool heat, custom seating stems, blah blah. What made by far the most difference in consistent OAL was sorting brass and loading one headstamp. But after a while convenience and lack of time overrode my OCD for trying to get that super consistent OAL. For my use case, I load mixed brass just load short enough that top end of the variation doesn't hit the lands and off I go.

Edited February 18, 2023 by OptimiStick

[anachronism]

Not all bullets of a specific catalog number from any manufacturer are identical. Each bullet forming die is a tiny bit different from the next one. This leaves us with slight ogive  profile variations, nose length variations, overall bullet length variations, and so forth. Ask any high power rifle shooter about this, even the very best bullets have some minor variations, even from the same factory box.

 

If the accuracy and reliability are there I wouldn't sweat it. The variance are enough to be measured, but the gun rarely know the difference.