Expanding mandrels..... neccessary?

[Creedmoor shooter]

Hey guys, I'm always looking to improve my ammo and accuracy. Currently I neck turn and run bushing dies and shoot for .002 neck tension with a .001 shoulder bump. My loaded ammo on average has .002-.003 run out. I'm looking at expanding mandrels and wondering if I could improve my ammo even more? Seems alot of guys use them with great results. What's every ones thoughts?

 

[milo-2]

Hey guys, I'm always looking to improve my ammo and accuracy. Currently I neck turn and run bushing dies and shoot for .002 neck tension with a .001 shoulder bump. My loaded ammo on average has .002-.003 run out. I'm looking at expanding mandrels and wondering if I could improve my ammo even more? Seems alot of guys use them with great results. What's every ones thoughts?

The best thing to do would be to try find out just where the runout is being imparted into your operation.
Theoretically brass coming from a fired chamber will be as true as it can get. Check runout on your necks. Some gauges you can get dial indicator inside of a the necks also.
Then size your brass and recheck.
Then seat a bullet and check neck and bullet.

Seems to be a common theme that running a mandrel down a neck pushes inconsistencies to the outside, then you seat a bullet in the magical hole created.
My train of thought is wouldn't seating a bullet also push the inconsistencies to the outside.

 

[Jud96]

I too am interested in going to the mandrel method of sizing. I've been hearing more and more about it lately and everyone says it either helped them or they didn't notice much. I haven't heard anyone say it made their ammo, groups, or consistency any worse. It's also not super expensive to get into. The mandrel die is like $33 and each mandrel is $10 for each caliber.

 

[bigedp51]

I'm with milo-2 and checking to see where the runout is happening.

Bushing dies work best with tight neck chambers and neck turned brass. And the Redding bushing die FAQ tells you if you do not neck turn and the neck thickness varies .002 or more then use the dies expander. This requires using a bushing .002 to .003 smaller and using the expander to push the neck thickness variations to the outside of the neck.

Tech Line & Tips (FAQs)
https://www.redding-reloading.com/tech-line-a-tips-faqs

I use the Redding neck thickness gauge below, and with one turn of the wrist it tells you the neck thickness variations and average neck thickness. NOTE, neck thickness variations can also cause neck runout/bullet runout.

 

[loonie]

I use Mandrels a lot and like them but I find the bushing is usually the culprit for runout. I use Widden non bushing FL dies made with my desired neck size, and run out is non existent!!!

 

[bigedp51]

Very good point by loonie above, the video below by the 6.5 Guys brings up the same point about runout and bushing dies. I also prefer using the Forster non-bushing full length dies with their high mounted floating expander. The neck of the die holds and centers the neck when the expander enters the neck and reduces neck runout.



Below Forster benchrest sizing and seating dies.

 

[DUSTY NOGGIN]

mandrels push through easier when the necks are thinner . which i think helps smear the brass more evenly

wish they made one that you pressed through a tight tolerance die body opening . that might center the axis without having to fire form ..

like a body/shoulder only die with a precision centered hole at top that fit an expander shoulder tightly . some sort of an expander with a camover action to guide in there while the brass is locked into the press

or like a redding comp sleeved expander die

 

[aushunter1]

They are a better option than using the standard stem expander/ball in most dies.

I have Redding bushing dies & the stems are always out f alignment.

 

[Creedmoor shooter]

Like I said, I currently neck turn and use the bushing die with the expander ball removed. Just wondering I'd the expanding mandrel is better overall

 

[DUSTY NOGGIN]

yes i think they will help . but what i think they dont do ( but wish they did ) support the body while doing it


you know how the redding body support sleeves work , right ?? if they had a die with a support sleeve similar to that . and then expanded at end of throw while supporting the body .. it may acyually hold the body side to side while centering and expanding at the same time

expanders basically just open up a smaller hole larger .. no matter if the neck and body axis line up or not

so now, you have to neck turn, fire form. full or full bushing size then ... it should be very close to centered now, then expanding

the die i wish they had would skip the fire forming step

 

[wonderman4]

I have been using standard RCBS FL sizing dies for decades. The case body is fully supported in the die as it is sized (obviously) but I always leave the stem loose so that it can float just a little. I have no problem getting 0.000-0.002" runout and most of the time the runout is 0.000-0.001".

 

[milo-2]

Like I said, I currently neck turn and use the bushing die with the expander ball removed. Just wondering I'd the expanding mandrel is better overall

What brand of dies are you using? My runout was cut in half switching from Redding type S dies to Whidden bushing dies. Before that I had made gains getting away from a T-7 press and running Forster coax's, though minor.
What accuracy are you achieving now? If not satisfactory, what is the goal? Just say you do cut your runout in half, will you see gains in your rifles?
You don't read much today on just what amounts of runout affect accuracy, but unless you are shooting BR or maybe F class, I cannot see .003" runout causing that much issue.

 

[Creedmoor shooter]

What brand of dies are you using? My runout was cut in half switching from Redding type S dies to Whidden bushing dies. Before that I had made gains getting away from a T-7 press and running Forster coax's, though minor.
What accuracy are you achieving now? If not satisfactory, what is the goal? Just say you do cut your runout in half, will you see gains in your rifles?
You don't read much today on just what amounts of runout affect accuracy, but unless you are shooting BR or maybe F class, I cannot see .003" runout causing that much issue.

I can generally average a .4 moa 5 shot. Sometimes .3s but mostly .4s. Really looking to get close to that .25 moa mark. I'm using redding type s

 

[bigedp51]

They are a better option than using the standard stem expander/ball in most dies.

I have Redding bushing dies & the stems are always out f alignment.

Below a modified Forster expander and spindle assembly installed on a Redding FL .243 die. The spindle was cut to the correct length and a rubber o-ring installed under the lock ring.