Mini MPR & BE-86

Status
Not open for further replies.

Lee Q. Loader

Member
Joined
Jan 30, 2018
Messages
440
The following post contains load data that was safe for me in my gun. Please work up your own loads.
I've read here that some of you are finding the best accuracy in your 9mm carbines with lighter bullets. I've only shot 124 MPR's through mine, but decided to try the 115 and see how it shoots.
I've had great results with the 124's.

I loaded 8 rounds each of 5.6, 5.8 and 6.0 with BE 86 at an OAL of 1.07. The indoor range had a max distance of 15 yards. All three loads shot one ragged hole at that short distance as you may expect, but the 6.0 gr load shot a smaller ragged hole of 8 rounds. I'm going to load up some more at 6.0 and have them ready to try at 25 and 50yards when I get a chance. No need to go higher on the charge. Max is 6.3, but I do have a shorter OAL.
Looks like I'm going to really like these bullets too.
 
I'll bet those are moving along pretty well. Be careful.

From the Alliant PDF.
115-gr JHP
BE-86
Fed. 100
Federal
1.120
6.3
1238
Different bullet, shorter OAL which can make a rally large difference in the small 9MM case. Able to chrono these?
 
RMR MP JHP

I feel like I'm in the army, again... with initials for everything.

Different bullet, shorter OAL which can make a rally large difference in the small 9MM case.

I agree. When I first started loading 9mm for my BHP (...see? More initials!) I didn't really adhere to the OAL spec in the manual, it never really made that big of a difference in .45ACP, so why waste my branepower with it in 9mm? What I got was some rounds that cratered the primer and allowed the hammer to follow the slide back into battery, and others that barely cycled the slide. There may have been other factors... that was a long time ago... but those results, and hindsight, make me tread a little more carefully when loading a small capacity high-pressure round like the 9mm, particularly near max.
 
I'll bet those are moving along pretty well. Be careful.

From the Alliant PDF.

Different bullet, shorter OAL which can make a rally large difference in the small 9MM case. Able to chrono these?
Walkalong,
Sounds like you think I maybe borderline overpressure with the 6.0 loads? I certainly would defer to you and many others here that have much greater experience than I.
I do not have a chronograph. The primers on the 6.0 loads looked ok, but I know that isn't always a good measure of too hot loads.
Do you think I should back down to the 5.8 or 5.6 loads, given that I don't have a way to chrono these? 5.6 grains with the 124 MPR is my other load, also at 1.07 OAL.
Thanks for your help.
 
My experience with BE-86 is it likes to be pushed a bit to gain max accuracy, but every gun is different!

I'd probably give 5.9gr a try and see what you get for accuracy.
 
Walkalong,
Sounds like you think I maybe borderline overpressure with the 6.0 loads?
I think you may be at max for sure, hard to tell and primers lie. I'd be interested in the velocity.
5.6 grains with the 124 MPR is my other load, also at 1.07 OAL.
I ended up at 5.7 with the 124 Gr MPR @ 1.105 to 1.110 OAL. I went up to 5.9 (1238 Avg FPS from a 5" 1911 @ 90 degrees), but was much more comfortable at 5.7 Grs (1224 Avg FPS from a 5" 1911 @ 90 degrees). Only gaining a few FPS for the last .2 grs is a clue for me.
index.php
 
Different bullet, shorter OAL which can make a rally large difference in the small 9MM case. Able to chrono these?
The big difference is the diameter. RMR will be 0.3555" where the bullet referenced in the Alliant load data will be 0.3550". I would stop at 6.0gr. for that reason alone. I agree this is where a chrono can help.
 
The big difference is the diameter. RMR will be 0.3555" where the bullet referenced in the Alliant load data will be 0.3550". I would stop at 6.0gr. for that reason alone. I agree this is where a chrono can help.

The BIG difference is OAL or bullet seating depth.

How did you arrive at your precise measurements down to 0.0005" difference?
RMR lists their bullet at .355"
They make great bullets but I doubt tolerances can be measured down to.0005"??

Speer (Alliant" also lists at 0..355
 
How did you arrive at your precise measurements down to 0.0005" difference?

RMR lists their bullet at .355" They make great bullets but I doubt tolerances can be measured down to.0005"??
FYI, according to my .355" pin gage verified calipers, current production (bought earlier this year) of various RMR 9mm in-house jacketed bullets measure .355"

I do believe RMR sizes their in-house jacketed bullets slightly larger than .355". Perhaps Jake could verify.
 
Last edited:
All RMR in-house bullets are .3555-.3557. Thats what we keep as our tolerances. Relatively speaking, there is almost no variance at all in diameter with our bullets. I believe the MPR is right at .3555" Also, we've had some pressure testing done and there is no recognizable difference in pressure between a .355 and a .3555 bullet. The biggest thing that may determine pressure is OAL. I've been loading the mini MPR at 6.1 grains of BE86 and getting over 1300 fps from my 6" barrel. Granted, my oal is 1.135. I do not believe that to be a good load at 1.07. It might be, but you're probably venturing into +p pressures. BE86 has proven to be the safest powder tested when trying to get good +p loads. That said, don't do anything stupid. You can really get some high velocities but at risk of shooting higher pressure.
 
FYI, according to my .355" pin gage verified calipers, current production (bought earlier this year) of various RMR 9mm in-house jacketed bullets measure .355"

And?? What is your point? I said they are listed at .355?? Have you measure (Alliant)Gold Dots down to .0005 variance and what lot number?

The whole jist was that decreasing the available case volume will raise pressure in a 9mm. Then the obscure .0005 bullet thickness was mentioned?
 
And?? What is your point?
Many factory barrels, and even aftermarket match barrels are oversized at .356"+ groove-to-groove diameter and can benefit from slightly larger sized diameter bullets.

IIRC, Zero 115 gr FMJ was one of several projectiles Atlanta Arms used during the component shortage to produce their Elite 115 gr FMJ Match AMU ammunition that must produce five 10 shot groups smaller than 1.5" at 50 yards - https://atlantaarms.com/products/9mm-115gr-fmj-match-amu.html

I measure Zero 115 gr FMJ at .356" and Hornady HAP at .355" (For many, HAP is accuracy reference for match grade bullets).

So I did a comparison range test in this thread of HAP, Zero and RMR - https://www.thehighroad.org/index.php?threads/thoughts-on-rmr-bullets.847718/#post-11054234

Comparison 25 yard groups with adjustable stock

index.php


Comparison 25 yard groups with fixed stock (Larger sized .3555" for RMR and .356" for Zero produced smaller groups than .355" sized Winchester 115 gr FMJ bullet)

index.php


After these initial range testing, RMR became my preferred choice of bullets for accuracy reference testing

index.php
 
OP here, Thanks to everyone for your responses. Looks like maybe I went into territory I probably should stay away from until I get a chronograph.
1.07 has to be my OAL for the carbine, so I'm going to do some more testing and comparison. I'll stay below 5.8 grains of BE-86 with the RMR Mini MPR.
 
Lacking a chronograph, what I used to do when conducting load development with bullet different than listed in published load data was to conduct initial powder work up from start charge (If using significantly shorter OAL/deeper bullet seating depth, reduce start/max charges by .2-.3 gr).

If start charge reliably cycled the slide, extracted/ejected spent brass and accuracy was good, I would WORK DOWN until slide would barely cycle and then WORK BACK UP towards published max while looking at accuracy trend (Reduced max charge if using shorter OAL/deeper bullet seating depth).

With faster burn rate powders (Faster than W231/HP-38/Sport Pistol), I often got accuracy at start to high range load data. With moderately slower burn rate powders (Slower than Unique/Universal/Power Pistol/BE-86/WSF), I often got accuracy at mid-to-near max load data.
 
The biggest thing that may determine pressure is OAL. I've been loading the mini MPR at 6.1 grains of BE86 and getting over 1300 fps from my 6" barrel. Granted, my oal is 1.135. I do not believe that to be a good load at 1.07. It might be, but you're probably venturing into +p pressures. BE86 has proven to be the safest powder tested when trying to get good +p loads. That said, don't do anything stupid. You can really get some high velocities but at risk of shooting higher pressure.
Words of wisdom. Thanks Jake. :thumbup:

1.07 has to be my OAL for the carbine, so I'm going to do some more testing and comparison. I'll stay below 5.8 grains of BE-86 with the RMR Mini MPR.
Sounds good. Keep us posted.
 
Many factory barrels, and even aftermarket match barrels are oversized at .356"+ groove-to-groove diameter and can benefit from slightly larger sized diameter bullets.

IIRC, Zero 115 gr FMJ was one of several projectiles Atlanta Arms used during the component shortage to produce their Elite 115 gr FMJ Match AMU ammunition that must produce five 10 shot groups smaller than 1.5" at 50 yards - https://atlantaarms.com/products/9mm-115gr-fmj-match-amu.html

I measure Zero 115 gr FMJ at .356" and Hornady HAP at .355" (For many, HAP is accuracy reference for match grade bullets).

So I did a comparison range test in this thread of HAP, Zero and RMR - https://www.thehighroad.org/index.php?threads/thoughts-on-rmr-bullets.847718/#post-11054234

Comparison 25 yard groups with adjustable stock

index.php


Comparison 25 yard groups with fixed stock (Larger sized .3555" for RMR and .356" for Zero produced smaller groups than .355" sized Winchester 115 gr FMJ bullet)

index.php


After these initial range testing, RMR became my preferred choice of bullets for accuracy reference testing

index.php

Good Grief! You are off on another tangent that has nothing to do with the the statement of Ray15: The discussion was about pressure in the 9mm case.
"The big difference is the diameter. RMR will be 0.3555" where the bullet referenced in the Alliant load data will be 0.3550". I would stop at 6.0gr. for that reason alone. I agree this is where a chrono can help."

Your testing free hand with a oh so accurate JR carbine and it's accuracy was not the issue. Plus the "Peanut Gallery" (your words) would find error in that testing. But I suppose a measurement of pressure with bullets of ,0005 greater diameter will need to me measured next somehow
Why make it all so much more than it needs to be?

The Minutia just continues. The End.
 
Good Grief! You are off on another tangent that has nothing to do with the the statement of Ray15: The discussion was about pressure in the 9mm case.
Oops, you are right.

I got my response crossed.

Sorry (Need to work on reading comprehension for retirement :rofl:)
 
And?? What is your point? I said they are listed at .355?? Have you measure (Alliant)Gold Dots down to .0005 variance and what lot number?

The whole jist was that decreasing the available case volume will raise pressure in a 9mm. Then the obscure .0005 bullet thickness was mentioned?
Good Grief! You are off on another tangent that has nothing to do with the the statement of Ray15: The discussion was about pressure in the 9mm case.
"The big difference is the diameter. RMR will be 0.3555" where the bullet referenced in the Alliant load data will be 0.3550". I would stop at 6.0gr. for that reason alone. I agree this is where a chrono can help."
It wan't so much a discussion, just you claiming we couldn't possibly know how the diameter of a bullet and then lowering your sights when it proved we did. I do find diameter of jacketed bullets to matter. I have loaded thousands of RMR-produced jacketed bullets of various types and regardless of OAL I reach max velocities with them with a few tenths less powder than with the actual 0.3550" bullets the load data uses. This factor is easily ignored when you are using really long OALs that depend on a healthy leade to chamber, as the loads tested in generating the published data are going to chamber without leade.

Comparing OAL isn't really telling you much. You have to take it to the seating depth before you are comparing anything functional. I agree seating depth matters, but so does diameter.

upload_2019-6-6_19-32-44.png

And no, you can't compare these OALs - one is a hollowpoint and one a RN. A thousandth in diameter makes a BIG difference, and I do not believe a half-thousandth can't be noticed in carefully controlled pressure testing. The tighter the fit, the less pressure it's going to leak, physics being somewhat inflexible. Have a different view? You are welcome to it.
 
Last edited:
No doubt a .3555 bullet will produce more pressure than the same exact bullet at .355 at the same seating depth etc.

I believe the question is does it make more difference than seating depth. Of course how much deeper in the case the bullet is will tell the tale, but I think people are much more apt to get into trouble with too short a seating depth than using a .3555 bullet. A lot of 9MM groove diameters are at least that.

Many years ago I bought Zero brand 9MM (#162 .355) and .38 Super (# 161 .356) 124 Gr JHPs. After some testing I stopped buying the "9MM" bullets and used the .356 ".38 Super" bullets in my 9MM and my .38 Super.

I think we need to worry about seating depth more than bullet diameter in 9MM. Shortening seating depth in the small high pressure case pushes pressure up fast.

One of our favorite things to tell/show new reloaders about is the Speer warning in their manual.
 

Attachments

  • Speer 9MM .030 Deeper Warning.jpg
    Speer 9MM .030 Deeper Warning.jpg
    57.8 KB · Views: 23
No doubt a .3555 bullet will produce more pressure than the same exact bullet at .355 at the same seating depth etc.

I believe the question is does it make more difference than seating depth.
That, I believe also depends on groove diameter of the barrel. ;)

I think we need to worry about seating depth more than bullet diameter in 9MM. Shortening seating depth in the small high pressure case pushes pressure up fast.
Yes. :thumbup:
 
Status
Not open for further replies.
Back
Top