Seater Die for RMR 124 MPR

[Lee Q. Loader]

As my screen name would indicate I'm a big fan of Lee products. I use the 4 die pistol set to load 9mm. After loading over 1000 rounds of the RMR 124 hollow point MPR. I realized that the standard plug in the seater die doesn't fit that bullet well and will sometimes allow it to seat slightly crooked. I realized this when I found the slight bulge in the brass at the base of the seated bullet was only on one side of the case. After going through my inventory I realized this happened about half the time with the Aguila brass and about 1 in 20 times on other brass.

I went to the Lee website and ordered the "custom bullet seating plug". I sent them a bullet, as they request and paid the $8.

I was very disappointed when the new plug came in the mail and they sent me the exact plug that comes with the 4 die set. I believed they were going to take the bullet I sent them and "custom" fit a plug for me.

I hate to bash on one of my favorite companies, but that was pretty poor on their part.
So, sorry for the long story to lead to this simple question:
What seater die would you recommend for the RMR 124 MPR?
I have about 4000 of these bullets and I don't really care about cost to get them seated correctly. Thanks

 

[LiveLife]

I was very disappointed when the new plug came in the mail and they sent me the exact plug that comes with the 4 die set. I believed they were going to take the bullet I sent them and "custom" fit a plug for me.

Have you tried the new plug?

 

[LiveLife]

Lee ... 4 die pistol set ... RMR 124 hollow point MPR ,,, standard plug in the seater die doesn't fit that bullet well and will sometimes allow it to seat slightly crooked. I realized this when I found the slight bulge in the brass at the base of the seated bullet was only on one side of the case.

To prevent bullet tilting, make sure there is enough flare that will allow the bullet base to be inside the case mouth when the bullet is set and ensure bullet stays straight up without tilting as it enters the die mouth.

I do not use FCD for reloading 380Auto/9mm/40S&W/45ACP and seat/taper crimp in the same station (In my new Auto Breech Lock Pro with 4 stations, I am testing 9mm seat and taper crimp in separate stations using 2 seat/taper crimp dies but so far no significant difference I can tell).

Keep in mind, tilted bullets can affect OAL variance. Using factory seater plug with RMR 124 gr jacketed FMJ and FP (Match Winner) bullets, I get .003" OAL variance with mixed range brass and .001" OAL variance with pre-resized brass using factory seater plug that comes with the seat/taper crimp die - https://www.thehighroad.org/index.p...progressive-press.833604/page-2#post-10779806

Note no one-sided bulge on case necks.

 

[Dudedog]

Both my stock Lee and Hornady seaters work fine with the MPRs.
I like to use the FCD with 9mm, some people like it some people don't.

I would contact Lee and ask them about the seater they sent you.
Could just be that someone dropped the ball, while not good they messed up the first time, I believe any company should be given at least 1 chance to make things right.
(now 3, 4... tries are a completely different story)

 

[Lee Q. Loader]

Yes I did try the new die just to be sure. I have also tried increasing the case flare.
the thing is if I remove the seater plug and just place it over the nose of the bullet it doesn't fit snuggly. The bullet can move around a bit. This is not the case with other bullets I have on hand, namely 124 grain Berry's round nose and 115 grain XTP.

 

[LiveLife]

Have you tried the new plug?

Yes I did try the new die just to be sure. I have also tried increasing the case flare.

the thing is if I remove the seater plug and just place it over the nose of the bullet it doesn't fit snuggly. The bullet can move around a bit.

RMR 124 hollow point MPR ... I went to the Lee website and ordered the "custom bullet seating plug". I sent them a bullet ... they sent me the exact plug that comes with the 4 die set. I believed they were going to take the bullet I sent them and "custom" fit a plug for me.

I think they sent you the same seater plug as factory because that's the correct seater for RMR 124 gr MPR bullet.

Below picture is seater plug out of my Lee die. Notice the hole where the tip of FMJ/RN bullet would go and the curved profile that would follow the RN bullet profile. The seater plug makes contact with the bullet further down from the tip (look at below comparison picture of FMJ RN/MPR, essentially MPR is FMJ RN with tip cut off).

Below picture shows two 9mm seater plugs resting on RMR 124 gr FMJ and MPR. Notice the contact points further down from the nose tip (Since MPR bullet base is longer, if you account for similar profile above case mouth as shown in above picture, plug would be pushing on the same part of MPR as FMJ RN).

As long as bullet length and nose profile (ogive) construction are consistent, finished OAL and bullet seating depth will be consistent. RMR 124 gr FMJ/FP bullets are more consistent than many other jacketed bullets and produced .001" OAL variance from different headstamp brass (with pre-resized brass that removes reloading variable of shellplate tilt from resizing) which illustrates the consistency of RMR bullet lengths and nose profile bullet-to-bullet - https://www.thehighroad.org/index.p...progressive-press.833604/page-2#post-10779806

 

[LiveLife]

if I remove the seater plug and just place it over the nose of the bullet it doesn't fit snuggly. The bullet can move around a bit. This is not the case with other bullets I have on hand, namely 124 grain Berry's round nose and 115 grain XTP.

This is interesting. If the seater plug works with Berry's RN and XTP, the plug should work with RMR MPR as shown in my picture.

Could you take some pictures of your plug and MPR bullet?

 

[Walkalong]

A flat seater stem works great with the 124 Gr MPR JHPs.

 

[Lee Q. Loader]

Here are some pics. The new plug is on left with the rmr. Berry's on the right. The plugs are identical.

 

[Lee Q. Loader]

Well the pic didn't post the way I thought. I'm sure you can figure it out. The RMR is on the top Berry's on the bottom.

 

[YBOT]

I’ll sure follow this thread as I’ve started to build some loads using the RMR 124 gr JHP MPRs with resized mixed range brass and using my new Lee four die set and the bullet plug that came with them. (Looks like a RN plug.) Have not seen this issue. I use a Wilson 9mm chamber checker on each round. I do assume the Wilson checker would catch this anomaly.

Hope you get to the bottom of this quickly. Lots of great help and suggestions here.

P.S. I use the Wilson guage after resizing and before the next step. Then after the round is complete.

 

[CrankyCraig]

I’ve had no. Issues whatsoever using lee seating dies with match winners, MPR’s or round nose. Following.

 

[9mmepiphany]

What seater die would you recommend for the RMR 124 MPR?
I have about 4000 of these bullets and I don't really care about cost to get them seated correctly.

While I think the service that LEE offers is one of the better values in reloading, you could also go the route I went with the Redding (.38Spl) Competition Seating die: (the one in the middle)



Before I'm accused to elitism, I'd like to say that I got mine at 50% off and that I switch between different bullet profiles quite a bit

 

[Walkalong]

and that I switch between different bullet profiles quite a bit

I use mine to seat all but one of my .38 Spl and .357 Mag loads. Everything from .38 WCs to .357 SWCs. It is very handy to just be able to dial them all in quickly. I use one sizer for both calibers as well. I did make a flat seater stem for it from an extra factory stem.

I would like another one or two of the seaters, but they are so dang proud of them these days, and I still have a little bit of a grudge against Redding as well.

 

[Doublehelix]

I use those bullets almost exclusively, and seat them without issues with my Redding Competition Seating Die.

 

[tightgroup tiger]

Redding or RCBS dies should fix you up. RCBS carbide die sets (gray box) comes with both seating stems, round and flat nose. Better value.
I really like the Redding dies I have but RCBS carbide dies have treated me really well over my 46 years of reloading until it comes to Redding's dual ring resizing dies then RCBS takes a back seat in the pathetic few calibers that Redding offers them in.
I must say it is really, really nice to have a mic sitting on top of the seating die. I'm guilty also, but it is not absolutely necessary. The seating stem must fit the nose profile first.

I use mine to seat all but one of my .38 Spl and .357 Mag loads. Everything from .38 WCs to .357 SWCs. It is very handy to just be able to dial them all in quickly. I use one sizer for both calibers as well.

If Redding has it down with this seating die, then It's money well spent. My micrometers are on my rifle dies.
Mics on pistol dies? you guys are teaching me expensive habits. Hmmm, that gives me another dial to play with. I love dials. I will have to check these out.

My wife will not be happy and I will blame it all on you, of course.

 

[9mmepiphany]

...until it comes to Redding's dual ring resizing dies then RCBS takes a back seat...

Yup, these are great if they are offered in calibers that you reload. I am using one for my .38Spl (no combo dies for these) and likely will be getting one in .45ACP

Mics on pistol dies?

These have been great for my .38Spl loading, because I hate the process of Adjust, Measure, Guess, Adjust, Measure, Repeat until you get it just right. With the mic dies it's just measure once and adjust...well, I did confirm by measuring again the first time.

I only have them in .38Spl and 9mm so far. I'm likely to get another for .45ACP, but I'm fighting the temptation to get the Micrometer Crimp die also

 

[Walkalong]

My "micrometer" crimp dies. I adjust the crimp die for a heavy crimp, then use whatever spacer is needed to get the crimp I want. Log that and I am good to go the next time. Never have to move the lock ring, just screw the die out of the bushing, put the spacer on, screw it back down finger tight.