When to use expander mandrel on semiauto

[CST]

I have a AR that is denting the heck out of the necks of the brass causing a lot of runout. I just picked up the Sinclar expander mandrel....
When should I use it? right before I put the brass into the Redding FL bushing die or afterwards? I found that the expander ball in the die is contributing to too much runout..

 

[Danco411]

It depends on what you want your case neck tension to be. If you are using a collet "S" type die then I would run the expander first then size with my chosen neck collet for tension. If you rising a standard die then the tension may be too high so I would run the mandrel through after you size but then I would certainly do a light crimp with a LFC die.

Why do you think the expander ball is causing excessive runout? I don't worry about runout on my AR's. I believe the bullet slamming up the feed ramps will cause more runout than any expander ball.

 

[SWThomas]

I would use it after. You can use it to set your desired neck tension while you're rounding out the mouths. I polished mine down to 0.220 and it gives me plenty of neck tension and I don't need to crimp.

 

[InfScout1/69]

Why would you use the expander ball in a bushing die ? All it's doing is negating what you did with the bushing in the first place. Take it out

 

[CST]

i have a redding bushing dies. the necks get pretty beat up on this precision rifle.. when I load em up with the expander ball in place i get excessive run out. i figure I give the mandrel a run to smooth out the dented necks..i just dont know if I can use it before I run it thru the FL bushing dies or after.

 

[gstaylorg]

How "good" does the load need to be? First, using a bushing-type die may help alleviate your issues with runout caused by the ball-type sizing die. However, if you have significant flat spots on the case necks, simply resizing with a bushing die may not totally remove them. Even if it looks like they are gone, you can still detect the flat spot with a concentricity gauge. The best remedy is to use an expander mandrel prior to FL resizing. The mandrel will remove a fair amount of the flat spot and allow the resizing die to take care of the rest more efficiently. Not sure whether you will be able to see any improvement with a semi, but it's really not that much extra work to run the expander mandrel through the cases first, then resize.

 

[BLDTYLRY]

I would start by looking at your gas system. Dented Necks and/or shoulders is caused by over gassing. Either install an adjustable gas block or heavy buffer to increase the dwell time.

 

[Victor N TN]

Why would you use the expander ball in a bushing die ? All it's doing is negating what you did with the bushing in the first place. Take it out

I agree. Take the expander ball off the decapping rod. If you need to use the mandrel to "iron out" the dents, use it FIRST. That way your bushing die brings the neck back to where it should be.

 

[Victor N TN]

How "good" does the load need to be? ...

I don't know about everyone else on here. But if I'm going to load an empty case, I want it to be THE BEST I can make it.

I admit I may not trim ALL the brass after each firing. But if I don't, I at least lock a set of calipers and gauge them. If you have a rifle that is capable of shooting 1/2 or better MOA why settle for ammo that does any less.

That's just not the way I was taught to do things.

 

[gstaylorg]

Regardless of what is commonly posted on internet shooting forums, there are plenty of semi-autos that simply aren't capable of shooting much (if at all) under 1 MOA, regardless of how well-prepared the ammo is. You aren't going to find many people that are more rigorous in their reloading practices than I am, for the exact reason you stated. However, I'm shooting my hand loads out of custom bolt guns in competitions out to 1000 yd. I probably wouldn't choose to spend my time going to the same lengths reloading for a >1 MOA semi auto, particularly if I just want it to go bang every time and be able to hit a paper plate at 100 yd. There is little chance that the extra effort could ever actually be seen on the target. My comment was for the OP's benefit because there was not enough info in the original post to say anything meaningful about the accuracy/precision of the rifle or intended shooting purpose. I'm sure he can decide for himself whether extra effort will be worth it.

 

[Victor N TN]

I shoot from 100-200-300 benchrest to 1,000. I have 2 guns for each. I have an old M1 Carbine that shoots 2 1/2" at 100. I don't do quiet as many steps for it that I do for the rest. But the care with the set up, powder and inspection and checking are the same.

 

[gstaylorg]

Agreed...I think we do things very similarly. I just hate sending someone down a path that takes extra effort and might not help them without pointing out the possible limitations.