All things mandrels
- Thread starter AJC
- Start date
Dusty Stevens
Shiner
With the porter die you can tune your tension in a couple psi increments. The neck turning expander mandrels are just that, and they cost way more in very limited sizes than the $3 pin i can get in less than .0001 steps
Dusty Stevens
Shiner
This doesnt size the neck and is a very precision piece made for the very small percentage of people that varying neck tension affects
FWIW, I tested a number of sizing methods using a batch brass from the same lot that had been neck turned and had the same number of firings with the same load. I used 10 pieces for brass for each method. The aim of the testing was to see which method gave the most consistent inside diameter and smallest neck concentricity. I used pin guages in 0.0005" steps to measure inside diameter.
Methods I tested:
Type S die with various bushing sizes and no expander
Type S die with various bushing sizes and an expander, both standard and carbide expanders
Type S die with various bushing sizes and an expander mandrel
Type S die without a bushing and a lee collet
The expander mandrel was a vermont pin guage from amazon that I had tuned a taper on one end using a belt sander and battery drill. The mandrel was held in a Hornady cam lock bullet puller with an o-ring under the lock ring.
What I found is that all methods could achieve less than 0.0005" difference in inside diameter. However, bushing size diameter was critical when used without an expander, smaller or bigger than the optimum size and the inside diameter consistency increased to 0.001"-0.0015". When the die expander or expander mandrel was used, there was a minimum amount the neck had to be sized down before minimum inside diameter consistency was achieved.
In terms of concentricity, all methods except using the die expander gave less than 0.002" TIR. When using the die expander I got less than 0.004" TIR.
I sure your testing results may vary
Methods I tested:
Type S die with various bushing sizes and no expander
Type S die with various bushing sizes and an expander, both standard and carbide expanders
Type S die with various bushing sizes and an expander mandrel
Type S die without a bushing and a lee collet
The expander mandrel was a vermont pin guage from amazon that I had tuned a taper on one end using a belt sander and battery drill. The mandrel was held in a Hornady cam lock bullet puller with an o-ring under the lock ring.
What I found is that all methods could achieve less than 0.0005" difference in inside diameter. However, bushing size diameter was critical when used without an expander, smaller or bigger than the optimum size and the inside diameter consistency increased to 0.001"-0.0015". When the die expander or expander mandrel was used, there was a minimum amount the neck had to be sized down before minimum inside diameter consistency was achieved.
In terms of concentricity, all methods except using the die expander gave less than 0.002" TIR. When using the die expander I got less than 0.004" TIR.
I sure your testing results may vary
Ned Ludd
Silver $$ Contributor
I've used various methods to size necks, including standard bushing die setups, and expander mandrels. My original thought for using the mandrels was that their use would likely push inconsistencies in neck wall thickness (I don't turn necks) to the outside, and leave them very straight. FWIW - the carbide mandrels available for neck turning purposes are generally held to much tighter tolerances (actual diameter) than the steel ones. Regardless of the price of the Porter die shown previously, the big advantage there is the precision and range of diameters available; something you cannot easily obtain with neck turning mandrels.
My approach with the mandrels has been to use a bushing die first to size the neck, with a bushing that was either .001" or .002" smaller than that which would give me ~.002" neck tension (interference fit). That way, the mandrel would definitely be opening up all the necks in the 2nd step to some degree, presumably allowing for better final diameter consistency than by using a bushing that sized the neck very close to that which the mandrel would open it back up. For .223 Rem and .308 Win, I used .222" and .306" carbide neck turning mandrels, respectively. I typically use a 0.248" bushing with .223 Rem brass (Lapua) and a 0.336" bushing with .308 Win brass (also Lapua). As the first step, I have sized necks with both 0.246" and 0.247" bushings for the .223 brass, and 0.334" and 0.335" bushings with the .308 brass. If you wish to try this method, the size of the bushing used does make a difference.
The point I wanted to bring out with this post, particularly for those that may not have ever tried using a mandrel before, is that sometimes something that seems like a good idea may or may not necessarily offer an advantage, depending on your particular shooting needs. You have to try it to find out. In my hands for the purpose of F-TR shooting, there was really no advantage to using the mandrel. IMO - the necks were not any better or more uniform than I was already achieving using a standard bushing die with half the effort (i.e. one less step). Your results may vary from mine depending on the type of shooting you do.
The other thing I will point out is that you want to take springback into account if you decide to use this approach, especially if you don't have access to an almost unlimited selection of mandrel sizes like the ones from Porter, which I didn't. My thought had been that using a carbide neck turning mandrel of .002" under bullet diameter would give me about the same neck tension that a bushing already known to provide .002" interference fit would give. This was not so, and springback is the reason. When sizing brass necks down from the outside using a bushing, the springback of the brass opens the necks back up just the slightest bit. In contrast, when opening the neck up with a mandrel as the final sizing step, the direction of the springback is opposite; that is, they close up just a tick. The final result is that although you might think the two approaches would give very similar neck tension (at least on paper), in fact they did not. The neck turning mandrel approach gave me between .0005" and .001" greater neck tension than the bushing die already known to give about .002" interference fit. As a result, bullets were noticeably more resistant to seating with the mandrel-prepped necks. Of course, none of that matters if you have access to whatever diameter mandrel you need, as with the Porter setup. However, anyone wishing to attempt this using commercially available neck turning mandrel, just be aware that due to springback, your neck tension will be noticeably greater than about .002", if that's what you have been using previously with a bushing die approach.
My approach with the mandrels has been to use a bushing die first to size the neck, with a bushing that was either .001" or .002" smaller than that which would give me ~.002" neck tension (interference fit). That way, the mandrel would definitely be opening up all the necks in the 2nd step to some degree, presumably allowing for better final diameter consistency than by using a bushing that sized the neck very close to that which the mandrel would open it back up. For .223 Rem and .308 Win, I used .222" and .306" carbide neck turning mandrels, respectively. I typically use a 0.248" bushing with .223 Rem brass (Lapua) and a 0.336" bushing with .308 Win brass (also Lapua). As the first step, I have sized necks with both 0.246" and 0.247" bushings for the .223 brass, and 0.334" and 0.335" bushings with the .308 brass. If you wish to try this method, the size of the bushing used does make a difference.
The point I wanted to bring out with this post, particularly for those that may not have ever tried using a mandrel before, is that sometimes something that seems like a good idea may or may not necessarily offer an advantage, depending on your particular shooting needs. You have to try it to find out. In my hands for the purpose of F-TR shooting, there was really no advantage to using the mandrel. IMO - the necks were not any better or more uniform than I was already achieving using a standard bushing die with half the effort (i.e. one less step). Your results may vary from mine depending on the type of shooting you do.
The other thing I will point out is that you want to take springback into account if you decide to use this approach, especially if you don't have access to an almost unlimited selection of mandrel sizes like the ones from Porter, which I didn't. My thought had been that using a carbide neck turning mandrel of .002" under bullet diameter would give me about the same neck tension that a bushing already known to provide .002" interference fit would give. This was not so, and springback is the reason. When sizing brass necks down from the outside using a bushing, the springback of the brass opens the necks back up just the slightest bit. In contrast, when opening the neck up with a mandrel as the final sizing step, the direction of the springback is opposite; that is, they close up just a tick. The final result is that although you might think the two approaches would give very similar neck tension (at least on paper), in fact they did not. The neck turning mandrel approach gave me between .0005" and .001" greater neck tension than the bushing die already known to give about .002" interference fit. As a result, bullets were noticeably more resistant to seating with the mandrel-prepped necks. Of course, none of that matters if you have access to whatever diameter mandrel you need, as with the Porter setup. However, anyone wishing to attempt this using commercially available neck turning mandrel, just be aware that due to springback, your neck tension will be noticeably greater than about .002", if that's what you have been using previously with a bushing die approach.
Well that was my plan so very good information and timing.
Dusty Stevens
Shiner
You can eliminate the concentricity errors by using good sizing dies on brass shot from a good chamber. Trying to straighten brass at any step in the process is a band aid. Find the point in your steps that concentricity appears and fix it there. If its straight out of the chamber but .003 after sizing then you got die and or brass issues. Fix it there before you move on. The mandrel die isnt for straightening its only for fine tuning neck tension- the last step before seating
I was not trying to correct error, just use good methodologies to prevent causing any. People here got me terrified about that expander ball.
Ccrider
Gold $$ Contributor
The Lee collet die presses the outside of the neck down by by collet to the size of the mandrel, the Porter tool opens the bushing sized neck backb up using mandrels.
Am I still not getting this?
Dusty Stevens
Shiner
You got it but they do 2 totally different things. Think of scrunching it down with that lee die then loading a bullet... or right before you seat that bullet open it up another .0003, or .0005- thats what it does
Dusty Stevens
Shiner
Dont let these forum fobias from the cabin fever ruin your shooting. I remember 15-18 years ago when the scope checkers came out there were guys who wouldnt even go to their first match before they got a frozen scope. And in the end the rube goldberg mounts people were cobbling together caused more issues than a broke scope. Open your calipers to .001 and youll see what keeps a lot of guys from enjoying shooting. Go have fun- throw the concentricity checker in a drawer- youll thank me later
Would that not be directly related to the grind job you do on the end of the pin? Might be a better transition, or where it occurred in the stroke of the ram?
Dusty Stevens
Shiner
You can sure get a big collection of sizes easily with porter’s die. I can change my tension 2psi most times
Ned Ludd
Silver $$ Contributor
You need to determine empirically what neck tension gives the best results. In my hands, approximately .002" interference fit has almost always worked well. That is not to say that the higher .0025 to .003" neck tension I obtained (via springback) using a neck turning mandrel DIDN'T work. In fact it worked just fine. However, for my intended purpose, the precision and velocity numbers were no better than simply using a bushing die. My thought was why go through the extra step if it's not an advantage?
I can imagine if someone had problems with runout using a bushing die setup, that might be one way the mandrel approach could offer a benefit. I can also imagine that uneven neck wall thickness might contribute to excessive ES/SD. If you're using a no-turn neck chamber and don't want to do at least a skim pass, using the mandrel as the final step might also help consistency by pushing material out, rather than in. Neither runout nor poor ES/SD were problems for me. In fact, the very first thing I do with a new sizing die is to remove the expander ball...complete waste to use one IMO. I like to try different approaches in the search for something better, so basically I just wanted to try the mandrel approach and see if it actually was better. Having done so, I am confident in stating that for my purposes, it was not an improvement. However, that might not be the case for everyone, so if you think it may be worth the extra effort, it's not very much cost to buy a mandrel and/or a couple extra bushings to try it out.
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Ccrider
Gold $$ Contributor
So to get a neck size tension range of let’s say .001 to .003 for a 6ppc (.243), allowing for spring back, you would need gages ranging from appx .2425 to .2405?
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