Sinclair Expander Mandrel Die Test

[Greasegun]

I surprisingly didn't see me difference in runout, as shown, between my mandrel sized brass and brass sized with a standard die. I'm comparing the two methods with the chronograph and for groups to see if there's a noticeable difference.

My problem was being caused by the redding expander button being crooked on the stem, bending the necks. Redding sent me a new one and it was junk too. For now Im just using the mandrel die until I switch to a different FL size die.

 

[Jud96]

My problem was being caused by the redding expander button being crooked on the stem, bending the necks. Redding sent me a new one and it was junk too. For now Im just using the mandrel die until I switch to a different FL size die.

Yeah that's not good. One thing I should note, my bullets all felt way better when seating with the mandrel sized brass opposed to my standard sized brass. Even if there's not any noticeable difference in my tests, I think I'll continue using the mandrels just in case I run into an issue like you had.

 

[Greasegun]

Yeah that's not good. One thing I should note, my bullets all felt way better when seating with the mandrel sized brass opposed to my standard sized brass. Even if there's not any noticeable difference in my tests, I think I'll continue using the mandrels just in case I run into an issue like you had.

I would imagine that the expander mandrel your using is a larger diameter than the button in your size die, leaving less neck tension. The real test is which one shoots better?

 

[Jud96]

I would imagine that the expander mandrel your using is a larger diameter than the button in your size die, leaving less neck tension. The real test is which one shoots better?

Actually with the expander ball/button I was getting around .002 neck tension, with the mandrel I'm getting 0.003. That in itself can change things, but we will see what does the best on paper and over the chronograph.

 

[338 dude]

I recently decided to buy a Sinclair Expander Mandrel die and test it out compared to the standard dies I've been using. Today I compared concentricity of loaded rounds, 16 were sized with a standard Hornady full length sizing die with expander ball and then bullets seated with a Hornady seating die. The other 16 had just the bodies sized and shoulder bumped with the Hornady sizing die with expander ball removed and then had the necks expanded with a 0.282 mandrel.

The reason I tested such a random number of each, is because I already had 16 rounds loaded using just the standard die, so I loaded the same number with the mandrel die to have the same sample size. I measured concentricity with a homemade setup that I thought up. Later I'll build my own proper concentricity gauge, but that's a project for another day. I've used a setup like this before and have seen others do it as well. It takes a little practice getting use too but it's fast, simple, and precise nonetheless.

I added two pictures of notes I copied down showing the Total Indicated Runout (TIR) for each round I measured. The first list is from the standard sizing die, the second is with the mandrel die. This was with my .284 ammo, I'll do this exact test with my .308 Norma ammo in the near future as well. Please stay tuned for updates, more testing, and more data on the Sinclair Expander Mandrel Die. So far the results are pretty neck and neck, with the mandrel die taking the lead by just a smidge. I hope you all enjoy and find this as interesting and cool as I do haha. I love this stuff!


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I like your improvised concentricity tool it looks like it would do very well

 

[Muddyboots]

Many years ago (probably before most on forum were born), a neighbor of mine was bench guy and he passed along a tip to me on runout. He was adamant in the necessity to rotate the round during seating even to extent of marking on case body an index point so he could at least rotate the round 1/3 to 1/3 of the bullet length being seated while seating the bullet. He measured the distance of the bullet being seated into the case and divided by 3 so he had index marks on the bullet as well. I couldn't stop laughing when he told me to do that for my hunting loads to get better runout reduction. I do rotate during seating the bullet and I do believe it helps runout from numbers I have run off his gauges but NO I do not go the length he does. Let me clarify, I don't rotate, the bullet does.

 

[Jud96]

Many years ago (probably before most on forum were born), a neighbor of mine was bench guy and he passed along a tip to me on runout. He was adamant in the necessity to rotate the round during seating even to extent of marking on case body an index point so he could at least rotate the round 1/3 to 1/3 of the bullet length being seated while seating the bullet. He measured the distance of the bullet being seated into the case and divided by 3 so he had index marks on the bullet as well. I couldn't stop laughing when he told me to do that for my hunting loads to get better runout reduction. I do rotate during seating the bullet and I do believe it helps runout from numbers I have run off his gauges but NO I do not go the length he does. Let me clarify, I don't rotate, the bullet does.

I actually do rotate my ammo when seating bullets. I don't get too serious with it, I just seat the bullet half way then spin the case roughly 180 degrees and finish seating. I've been told it helps with runout and I load every round like this since my Dad taught me to do this when I was a little kid haha.

 

[Jud96]

Update on the Sinclair Mandrel Expanding die. I did some testing today and it looks like my .284's barrel has sped up 30fps or so since last time I chronographed it. I have about 180-200 shots down it now and I haven't chronographed it since I had about 150 through it. This is around the same round count the Bartlein sped up on my .308 Norma and threw me off. I'm outside my velocity node so I'm going to have to redo this test in the future after I get back in the 2850fps node I was in before. I still wanted to show my results from today just for reference.

 

[Josebigsky]

Hey Judd,

Thank you for doing all this testing and sharing it. I was thinking of going to mandrels but wasn't sure it was worth the effort, especially for a hunting round. What did your impacts looks like down range? I realize you were out of your node for velocity but curious anyway!

 

[Jud96]

Hey Judd,

Thank you for doing all this testing and sharing it. I was thinking of going to mandrels but wasn't sure it was worth the effort, especially for a hunting round. What did your impacts looks like down range? I realize you were out of your node for velocity but curious anyway!

Honestly I don't pay attention to my groups when the Magnetospeed is strapped on the barrel. I just was shooting into a 50 yard berm at a target that was there from before. I just got on the center of it and touched it off. I had two ragged holes at 50 yards though from the rounds I fired. I'm going to group them after I redo my chrono testing.

 

[Josebigsky]

Thanks for the quick reply. This is an interesting topic for sure. Keep up the good work.

 

[Mikecr]

16 were sized with a standard Hornady full length sizing die with expander ball and then bullets seated with a Hornady seating die. The other 16 had just the bodies sized and shoulder bumped with the Hornady sizing die with expander ball removed and then had the necks expanded with a 0.282 mandrel.

Are you saying here that you FL sized case bodies and necks the same, with only neck expansion method changed?
Was the brass tested here fire formed or new?

 

[Jud96]

Are you saying here that you FL sized case bodies and necks the same, with only neck expansion method changed?
Was the brass tested here fire formed or new?

Yes that is correct. And brass was all fired and shoulders bumped .002

 

[Mikecr]

My assessment:
Runout that high is beyond what mere expansion method can improve.
You must be heavily FL sizing with considerable chamber clearances.