What is the consequence of uneven bumping on precision/accuracy?

[jlow]

Thanks Boyd!

There are a few challenges when it comes to hand annealing. The first is a consistent heat source. That means the same size flame at the same distance from the case. The first is a little easier as you can put an index mark on the torch and just make sure that it is not close to empty. The second is tougher when hand annealing since two things held by two hands tends to drift. Another problem is where you are pointing the flame at, if you are not pointing at the same spot, then you have another variable. Finally, the time factor is yet another challenge. I think the metronome is an excellent idea and I thank you for that.

However, I am still wondering how well I do with the second and third variables. I thinking about a metal jig that fits on the end of the torch that one can slot the drill drive socket holding the case into that correctly and reproducibly place the socket/case and then at the same time allows it to rotate freely. Seems like this would be a relatively easy thing to make if you know how to work metal.

Anyone interested in making one? It’s my idea but I have no problem some else making use of it to make some cash. Seems like something that most handloaders that do not require a high capacity annealer could use. Just make sure I get first dibs on one - LOL

 

[BoydAllen]

I would build a mounting bracket for what ever is turning the case, and leave that in a fixed position. You can figure out a way to pull the hot cases without getting burned. Then I would make a holder for the torch and bottle that had a hinge, that allowed the torch to be swung into and out of case heating position, with a positive stop. I would have a common base for both of these. I have seen case holders that were designed to be use in the vertical position that were just a flat surface with a nub in the center that fit the primer pocket with a little clearance. You could build one of these, and simply brush the case off of it with a gloved hand. or do the same thing with a shallow well for the head.

 

[jlow]

I think there are many ways to skin this cat. I think the method you are describing is slightly more complicated since it is dependent somewhat on the configuration of the device used to turn the case. That would be the way to go if you can make your own jig and customize it to your exact needs.

The method I was thinking of is simpler and would have more general application and appeal. It would only require that you have a drill driver, a way for it to drive a socket and to have a specific socket which the jig would fit. It would fit a regular torch head and the distance and spot where the flame would be aim would be fixed, so a pretty simple device and of course low cost. To change the case, all you would have to do is to slide the socket with the case out and drop it somewhere it can cool. A slightly more complicated version will allow you to use different size sockets and so adapt it for different types of cases.

 

[6BRinNZ]

To continue, do you guys think my problem with the variable bump has to do with annealing or something elese?

Are they all the same before you size? If not relative to their post fired measurement are they bumping the same amount?

How much are you trying to bump? Have you setup the bump mount relative to the shortest or longest case?

Do you over cam the press...maybe describe how you set this up?

Did this behaviour occur before you started hand annealing?

 

[jlow]

6BRinNZ – The fired cases (20 samples) had an average headspace of 1.6231” with a range of 0.0030” thousands and a SDEV of 0.0007”, so not all the same even though all fired 5 times out of the same chamber. I am shooting a gas gun and so the targeted final headspace was 1.6201”. I used a Redding Type S FL resize without the bushing and their competition shell holder.

I setup the bump relative to the average fired case length. I use a Lee Classic Cast Breech Lock single stage press which has is suppose to have a travel stop to prevent “cam-over” but in all honesty, I worked on this last night and am finding that the amount of down force at the bottom of the stroke does have an effect on final headspace i.e. the hard the stroke, the shorter the headspace. So this appears to be yet another factor (apart from annealing) that affects headspace consistency.

Cannot say if this occurred before I started annealing as I am pretty new at this and when I started, I had lots of other problems which muddy the picture.

For interest sake, here is a picture that shows the distribution of headspace in the brass I have processed thus far. As can be seen, most do gravitate around 1.6205” and 1.6210” which is close to my target length of 1.6201” but there are outliers which are shorter.

 

[BillPa]

I would build a mounting bracket for what ever is turning the case, and leave that in a fixed position.

One option, the ANNEAL-RITE II http://www.cartridgeanneal.com/

A friend uses one and is quite pleased with the results.

I would imagine one with a little creativity could ........ ;D

Bill

 

[jlow]

Nice! Simple but yet effective. Price point is not set correctly but as you say with a little creativity.....

 

[6BRinNZ]

Jlow - if I understand you correctly - out of the gun they have .003" variance? After sizing you still have .003 spread but the SD has changed for the better?

Where you mention "the harder the stroke the shorter the head space", is this change in feel driven by the force needed to size the case or your technique with the press? Is this extra force associated with cases that are longer than the averge?

 

[jlow]

6BRinNZ – yes, you are correct, out of the gun they have 0.003” variance and after sizing I still have 0.003” variance. My thought was that the variance out of the gun was due to charge/pressure difference and was hoping that I could do better…. SDEV got very slightly worse.

No most of the force needed to size the case come in the first 10-60% of the down stroke, its much lower force at the end. I think this is because the area in the case that swells the most is the area immediately above the head which is what you are forcing back in that first 10-60% down stroke.

The force I was describing that affected headspace is what is applied after the handle comes all the way down to the stop. I am guess here but the cases that are longer are longer by such small values that you will never feel the difference. Just that last extra effort, seems like the more you crank after the press comes to the end, the shorter the headspace. Have not done an exhaustive study by this is what I got after working with the batch.

 

[BoydAllen]

Annealing makes the differences get very much smaller. I think that the reason that you are seeing the differences in fired case "headspace" is the differences in the hardness of the cases, not pressure differences. Dwell time with the ram at the top of its travel in sizing, will affect bump, as will the amount of lube applied. Start with two fired cases that measure the same, size the first one as dry as you dare, with no pause at full insertion in the die, and then do the other sloppy wet with lube and let is sit at the very top of the ram stroke for a slow count of five. Wipe the lube off and measure their shoulder bumps.

 

[6BRinNZ]

OK - I'm not convinced that annealing is creating the issue, possibly factor just not sure to what degree.

Here re my thoughts

Brass - IMO annealed or otherwise has a tendency to "overreact" in the direction of the movement if largish changes are made. This is more typically shown up when neck sizing ~.005"...the necks will end up ~.0005 undersized.

You might be seeing this in your SD numbers when sizing the longest pieces. I'm not pure accuracy related so others may disagree with this. I size to the longest fired length...shorter pieces will grow into this length. Typically I am having to only bump .001 -.0015". annealed brass reacts well to this IMO.

Force - that extra push can make a big difference...I have found this to be the case when seating bullets...if its .001" out, push a little harder on that supposed dead stop and it will bring it right in line....it sounds like you can achieve something similar with your sizing press....others have mentioned dwell time as having an impact as well.

If it was me I would

1./ Bump against longest piece (maybe this isn't good with a gas gun...I don't have experience there)
2./ focus on my technique with the press and dwell time
3./ look to cull cases that consistently don't align (sometimes the horse is just dead)
4./ annealing - I went with a machine as annealing to me is purely about consistency

 

[BoydAllen]

I have compared the bump consistency of fired brass from the same batch and rifle, using loads that were weighed to the nearest tenth of a grain, and a consistent press stroke. With the unannealed brass the bump would vary as much as .003 and annealed, the total variance was cut to .001. Did you ever think that the time that you took to push harder on the handle was extending dwell time? My press does not extend the ram any farther when I lean on the handle.

 

[jlow]

6BRinNZ - I think we are on the same wavelength. I think most of my problem is with the resizing although the annealing most likely contribute.

I have a reasonably good touch and generally can seat bullets to within 0.001” with the same press but the headspace thing is much more finicky and appears to also depend on the brass which is where I think the annealing comes in. Unfortunately with a gas gun, you cannot get reliably operation bumping to the longest length, the general recommended bump is 0.003”. I am now working more as you say with technique with the press and dwell time – it’s good advice. Will look out for those dead horses too. Will probably still go with an annealing machine to as you say get that consistency which I do think I am also lacking.

Thanks again for your time and advice – it is much appreciated.

Boyd – I think we are seeing the same thing. As mentioned above, I think it is both the force/dwell on the final part of the down stroke plus my inconsistency in annealing which is landing me in hot water. As for just extending dwell time, my guess is that it does matter but I have not done it enough and with enough care to tease this out. But what I can see both force and dwell appears to matter – thanks again!

 

[JRS]

I finally tired of fighting with the same problem, and chose to go a bit different route. I use the Al Warner designed and manufactured "BIG DIE", and changed over to a non cam over press. The Lee Classic Cast. Measuring my sized brass, I find the dimensions virtually undetectable. I believe the cam over changes with time and use. Having used dies made by every manufacture, to include custom dies, I can honestly say the WTC die is without question, the most consistent I have ever used. Expensive, but worth every dime.

 

[BoydAllen]

I don't know if I mentioned it earlier in this thread, but just to make sure, I checked my Rockchucker (with a .001 dial indicator) to see if the ram pulls back at the bottom of the handle travel. It does not. It goes up all the way, and then stops. I find that I like it this way. If you are going to play with dwell time, I think that it is important that the press have this characteristic.

 

[jlow]

JRS – Wow, that is a beast of a die. No price and so a sticker shock might be on the way! LOL! Thanks regardless for giving me the tip of this option. Will definitely keep it in mind if my current strategy goes south….

Boyd – Sounds like an interesting idea. I have a dial indicator on a magnetic mount. Was thinking of taking a reading off the bottom of the ram but I can’t quite figure out where to mount the puppie. How did you do yours? Inquiring mind needs to know?

 

[JRS]

I suppose what I should have stated was this: if the cam over was measured each time, I would be willing to bet it does not happen at the same place, with the same amount of force each time. Using the Lee press, I have found the feel of the handle on each stroke much more consistent than having to rely on the bottoming out of the cam over. Something in the linkage has to wear over time and use. Without the cam over, I can actually feel the amount I am sizing each and every time. It works for me, and I have no reason to deviate.
A good example of the cam over would be a compound bow. If one were to place the bow in a mechanical firing jig, and measured each pull with a scale, each time that string was pulled, you would find a different reading on each pull even though you are pulling the same length. The cam will not consistently break over at the same point each and every time. You might cam over at 70# the first pull, then cam over at a higher or lower poundage with each additional pull. How would one know that their press is caming over at the same place each time simply because it cams over?

 

[jlow]

I think you are right and I agree that it might be hard to get the same pressure each time which is when I thought a torque wrench might have a place here. Did a quick Google search and ran into this puppie.

http://www.precisionaccuracycompany.com/leechbrlopr.html

Now it is made to produce a consistent crimp using a Lee Crimp die but apparently Richard Lee thinks it is also the perfect tool to get that 25 ftlbs of pressure we are suppose to use with the Lee Crimp die. I am thinking I could use it for that plus that last bit of resizing when the shoulders are bumped? Regardless, one is in the mail together with my Bench Source….