Dillon .40 decapping/sizing die for 9mm Mk7 press?

[BiknSwans]

I having trouble with decapping 9mm range brass.  Occasionally a spent primer gets sucked back into the primer pocket and the Mark 7 Evolution jams up when the case and spent primer are in the swaging station.

 

I first tried the Mighty Armory decapping die that came with the Evolution. ThenI tried installing the MA spring upgrade, but the shock from the strong spring flipped new primers over and I got sideways primers being seated.  Then I tried a Lee Universal decapping die.  Finally I removed the spring from the MA die and filed the pin tip to a wedge shape.  So far, this has worked the best, but not good enough.

 

My friend has a .40 Dillon decapping/sizing die that he can ship to me.   The Dillon die has a spring that isn't as stiff as the MA spring, so maybe this setup won't flip over primers being seated.  Using the .40 die on 9mms won't resize the case, so it will be similar to a universal decapping die.

 

Does anyone have any experience with trying a Dillon .40 decapping die on the Mark 7 Evolution set up for 9mm?

[mikamarj]

After enough fighting, my solution to the same problem was that I bought a second toolhead only for decapping and sizing.

[dansedgli]

I accidentally used a dillon 40 resizing die to try and resize 357 sig cases a month or so ago, I had done it in the past. It trashed about 400 cases because I turned the press on and walked away (1050 with mark7). The inside of the case gets sized too so it will wreck the 9mm cases. 

 

After realising what happened I remembered that I had used a 40 cal push through die for this previously, not a sizing die. 

Edited June 26, 2020 by dansedgli

[ELK-K]

I had the same problem with decapping 9mm and tried all the usual advice floating around the internet without success. This problem has plagued my reloading for years. Recently I made a small modification to the standard Dillon size/decap die and it has worked wonderful for the last ~20,000 rounds. I have only had two or three primers get sucked back in over the course of these last 20k whereas before I would have 5+ suck back in for every 100 rounds I loaded. I experienced the same problem on my 1050 and my Revolution and this mod fixed the issue on both machines. I’ll try to post some pictures this evening with a description of the modification.

 

Here are some pictures of the modification I made to the standard Dillon decapping/sizing die. I essentially modified the assembly to allow the spring to compress approximately 0.100” before pushing the primer out. After the primer is pushed out, the spring snaps the assembly back by the 0.100” with a significant amount of force and it launches the primer off the end of the decapping pin. There is a very audible “snap” each time a case is decapped.  The primer is shot off with such force that often the spent primer will bounce out of the primer catcher on the 1050.  This modification has completely solved the problem for me!

 

I tried a version of this using the original snap ring design at the top of the assembly but I kept breaking the snap rings about ever 2,000-3,000 rounds. This is why the end of the assembly has been turned down to the base of the snap ring grove and then drilled, tapped, and reassembled with a threaded fastener and washer.

 

Also, I have found that the standard decapping pins from Dillon have just enough variability in the diameter that some are so large they get stuck in the flash hole and don’t snap back easily.  This prevents the new design from functioning correctly.  Therefore, I measure the pins and turn off a few thousandths from the big ones and problem solved.  This could be done with sandpaper and a drill if you don’t have a lathe... it doesn’t take much and they don’t all need it.

 

A lathe is required to make the modification.  If you don’t have access to one or have a friend with one, any machine shop could make these mods in about 5 minutes and would probably only charge about $20.

 

If you want a video of the modified die running on the Revolution, PM me your email address and I will send it to you (it is too big to post).  Let me know if you have any questions.

Edited June 27, 2020 by ELK-K

[BiknSwans]

Thanks guys.  I haven't figured out yet how ELK-K's modifications would work, but in the meantime, I'm going to try the .40 sizing/decapping.  My friend decapped 150 9mms this morning using the Dillon .40 die, there were no sucked back primers, and the cases were not re-sized.  I'm hoping the less aggressive spring won't mess up the priming system on the Mk7.

 

Buying another toolhead and decapping and swaging only in the first pass is probably faster than what I'm doing now.  I try to watch for the spent primer going down the tube.  If I don't see it, I listen for the primer to drop into the plastic container.  But I can't hear that if either the case feeder or bullet feeder motor is running.  Then I manually check the case to check that the primer has been removed.  Very slow, but otherwise this process works well.  

[BiknSwans]

I tested the use of the .40 Dillon sizing/decapping die yesterday on my Mark 7 Evolution.  Seating the primer into the second round failed, and I quit using it.  The primer was sideways, just like using the Mighty Armory universal decapper with the spring upgrade.  The 5 cases I decapped were decapped just fine.  I finally figured out how the Dillon decapper works and ELK-K's modifications, but for the Mark 7, less spring power would probably be better.

 

I'm almost positive I'm going to buy another toolhead and use a 2 pass process.  I'm not sure if want to to swage or not on the first pass.  As a slight bonus, I'll have clean primer pockets when I wet tumble with pins after decapping.

 

I might have tried the FW Arms™ Auto-Case Centering Decapper/Deprimer, which claims to be almost pull-back proof, but they are out of stock.  Also, I can't find many user reports about the FW die.

 

Thanks to all for your help.

 

 

[Thetimb]

13 hours ago, BiknSwans said:

I tested the use of the .40 Dillon sizing/decapping die yesterday on my Mark 7 Evolution.  Seating the primer into the second round failed, and I quit using it.  The primer was sideways, just like using the Mighty Armory universal decapper with the spring upgrade.  The 5 cases I decapped were decapped just fine.  I finally figured out how the Dillon decapper works and ELK-K's modifications, but for the Mark 7, less spring power would probably be better.

 

I'm almost positive I'm going to buy another toolhead and use a 2 pass process.  I'm not sure if want to to swage or not on the first pass.  As a slight bonus, I'll have clean primer pockets when I wet tumble with pins after decapping.

 

I might have tried the FW Arms™ Auto-Case Centering Decapper/Deprimer, which claims to be almost pull-back proof, but they are out of stock.  Also, I can't find many user reports about the FW die.

 

Thanks to all for your help.

 

 

Buy these lock rings. You lock them in around the die so you can easily remove and swap

out dies and put them back exactly as they were before with zero hassle. 
 

https://www.amazon.com/Hornady-044606-Sure-Loc-Lock-Ring/dp/B001OPTMU4

 

It will save you the price of a another tool head.