Rmr 124 mpr short oal Sierra 6th data

[Duck45lc]

Hi all,
Just got 1000 124 mpr bullets and am excited to get some loads developed. Have read every thread pertaining to these bullets so many times my head hurts. Have got a lot of good input on my first thread for some berry’s bullets so I’m dipping in for some more knowledge from people with experience with these. Sadly I am in the club of people that are required to load these at a very short oal. 1.048 is the absolute max that will plunk. So I am looking at a working oal of 1.035-1.040. I have read a lot where people are referring to hornady 124 xtp data so I bought the 11th edition which lists oal of 1.060 for the xtp. I have some cfe pistol powder that I will probably base my starting loads with the hornady data and work up carefully because of the shorter oal. I would like to develop a load using n340 first for the mpr bullets. I have the Sierra 6th manual and for their 125 jhp #8125 they list data at 1.030. The Vv app lists data for this bullet at 1.035. I have a couple boxes of these bullets to compare to the mpr 124. The mpr that I just received measure .545 which is shorter than I have seen reported in other threads here. The Sierra 125 jhp measures an average of .550 so a little longer. The bearing surface appears to be longer on the Sierra as the ogive is a lot sharper angle than the mpr. In my estimation the data for this bullet should match up very close to the mpr. So after all that my primary question is if anyone else has used Sierra 6th data for the mpr or if you all think I’m on the right path. Also posted to possibly help others who are at odds with having to load these beauties really short.

 

[Duck45lc]

Went ahead and loaded some up this afternoon. 124 mpr rem cases cci 500
N340 OAL 1.035.
Sierra 6th start 3.5 max 4.2. At 1.030


Loaded 3 each at .1 intervals.
3.5 they list at 950 from universal 4”
3.8 @ 1000 and 4.2 @ 1050.
Colt competition 1911 5” is what these are feeding. Dual recoil spring that is overkill in my opinion. WWB 115’s just dribble out of this thing. Anyway loaded one in magazine at a time.
3.5 no slide lock and none cleared ejection port
3.6 all 3 made it out only one locked slide back
3.7 same
3.8 all ejected 2 of three locked slide back
3.9 maybe 2 feet ejection all locked slide
4.0 maybe 3 feet ejection cases starting to be noticeably cleaner good slide lock.
4.1 3 feet ejection cases cleaned up more fairly accurate I think, “wind storm tornado watch” but 3-4 inches offhand at 7 yards so ok for now. Going to load more at this level and test accuracy a little more tomorrow ran out of daylight. No noticeable pressure signs so far. Also would like to try some different brass as these were pretty tough seating in the Remington brass a lot of bulging not sure if Winchester or star line would be better just had the Remingtons clean and ready. Not compressed yet but getting close to touching at 4.1. 4.2 is max Sierra lists for standard pressure. Vihtavuori app states 3.7 to 4.4 for Sierra jhp at my working oal of 1.035.

 

[nettlle]

I'm a big fan of RMR MRP 124 grain bullets. I load these for a 1911 4" Commander. I started out with a COAL of 1.065". At this length Had some serious feeding issues at 1.065". Ended up with a final COAL of 1.150". This feeds perfectly and is very accurate. Over 4.4 grains of Bullseye.

 

[Duck45lc]

Frogfur
I’m thinking I’m going to like these bullets too the price is right and quality seems to be top notch. Still working on load development with these not sure about feeding yet. Loaded 20 more at 4.1 n340 will see how they feed for me tomorrow. I wish I could load longer but can’t due to short leade in my barrel. Good news though if I get a CZ I’ll already have loads ready. Damn don’t need an excuse to add another gun.

 

[nettlle]

Frogfur
I’m thinking I’m going to like these bullets too the price is right and quality seems to be top notch. Still working on load development with these not sure about feeding yet. Loaded 20 more at 4.1 n340 will see how they feed for me tomorrow. I wish I could load longer but can’t due to short leade in my barrel. Good news though if I get a CZ I’ll already have loads ready. Damn don’t need an excuse to add another gun.

COAL for a CZ is a whole different animal. Believe me. The 4"1911 Commander is a Dan Wesson (CZ) . And I have two CZ PCR's. When you get a CZ you will have to start from scratch.

 

[Kaldor]

I tried 4.6, 4.8, 5.0, 5.2, 5.4 gr of CFE Pistol with the 124 MPRs. COAL was set for my Sig 226 as it has the shortest throat of all my pistols, cant recall right off hand what it was.
Velocity was 1095 fps SD 22.4 @ 5.4gr, which I am not happy with. SDs were all over the place with all 5 charges which indicates less than ideal load. Zero pressure signs to speak of @ 5.4gr.
I will be trying 5.6, 5.8, 6.0gr of CFE P. My ideal velocity for these is to break 1200 fps for expansion purposes, but also to have an SD that is single digit.
If I see major issue with standard small pistol primers, I will switch to small rifle primers as they take pressure alot better.

 

[Duck45lc]

Good to hear Kaldor. I’ll be testing some with cfe pistol soon as well so it’s nice to see what velocity others are getting. If you get a chance please post your oal. I have the hornady 11th and it lists cfe pistol at 5.3 max for 1150 fps at oal 1.060 for the 124 xtp. Looks like you’re going after some screamers

 

[Otto]

I load MPR’s to 1.08” in a CZ Shadow 2 and they plunk just fine.

 

[lordpaxman]

Vihtavuori app states 3.7 to 4.4 for Sierra jhp at my working oal of 1.035.

VV data tends to be a bit conservative which isn’t a bad thing, and you were right on track to use the VV data for the Sierra 125 JHP. I load a lot longer at 1.120 so I used data from both the 124’s which VV loves to use 1.142” for, and the 125s which are really short. The good thing about the VV powder is it’s well behaved and one of the few I tried at their max values. I don’t have data for the RMR MPR, but I loaded 124 MG HPs, 1.120” 4.8gr N340 to make comfortable minor out of a P226.
I wouldn’t worry or hesitate to use the VV data to it’s max value if you’re looking for the highest V. Good luck.

 

[Kaldor]

Good to hear Kaldor. I’ll be testing some with cfe pistol soon as well so it’s nice to see what velocity others are getting. If you get a chance please post your oal. I have the hornady 11th and it lists cfe pistol at 5.3 max for 1150 fps at oal 1.060 for the 124 xtp. Looks like you’re going after some screamers

My 226 has a 4.6" barrel, so I figure it is a decent average benchmark for velocity for my 9mm pistols which range from 3.1 to 5 inches. Also not a bad firearm to test for accuracy with

 

[Duck45lc]

Thanks for the input guys.
I’ll probably turn them up to the Vv max of 4.4 for the Sierra 125 jhp at 1.035 seeing as they are closely matched to the mpr. The Sierra manual states +p data with n340 at 1.030
Maxing out at 4.5 grains for 1100fps out of 4” universal barrel. So staying within these data points should be safe I would think.
Still can’t wait to get a chronograph so I can post some velocity data from my barrel will be more comfortable pushing things a little more than as well.
Hopefully get a chance to shot a few I have already loaded at 4.1 to check for feeding this afternoon. Then ladder some more up for later.
Can’t believe I have to load shorter than “some” are reporting to work in cz pistols as I have heard they are some of the tightest but as with everything I’m sure there are exceptions.
kaldor, a 226 9mm is on my short list to get so good to hear the report.

 

[Kaldor]

Thanks for the input guys.
I’ll probably turn them up to the Vv max of 4.4 for the Sierra 125 jhp at 1.035 seeing as they are closely matched to the mpr. The Sierra manual states +p data with n340 at 1.030
Maxing out at 4.5 grains for 1100fps out of 4” universal barrel. So staying within these data points should be safe I would think.
Still can’t wait to get a chronograph so I can post some velocity data from my barrel will be more comfortable pushing things a little more than as well.
Hopefully get a chance to shot a few I have already loaded at 4.1 to check for feeding this afternoon. Then ladder some more up for later.
Can’t believe I have to load shorter than “some” are reporting to work in cz pistols as I have heard they are some of the tightest but as with everything I’m sure there are exceptions.
kaldor, a 226 9mm is on my short list to get so good to hear the report.

Sounds like you have a good plan.
My 226 is an SAO Legion. Fantastic pistol

 

[Duck45lc]

Loaded a mag full at 4.2 grains n340 which is the Sierra 6th standard pressure max. Noticeably more accurate offhand 2” at 7 yards cases pretty clean probably 4 foot ejection. This is the same level that I worked up some berry’s hhp 124 bullets at with good results at oal 1.050 for them. Will probably keep going up to 4.4 but want to shoot more at this level first. Hopefully get more loaded later today. Wife acts like she wants to see me today to help with kids. Only have 8 don’t know what her problem is.
Kaldor that is a real beauty. I have a 229 legion 40 in the gray. Love that black finish on yours still pondering sao or da/sa. Thankfully poverty will allow me ample time to mull it over.
Also didn’t mean to bash Remington brass earlier. I increased my flare mor than I normally go and it helped straitened things out was getting some runout in the beginning stages loading the mpr.

 

[Kaldor]

Loaded a mag full at 4.2 grains n340 which is the Sierra 6th standard pressure max. Noticeably more accurate offhand 2” at 7 yards cases pretty clean probably 4 foot ejection. This is the same level that I worked up some berry’s hhp 124 bullets at with good results at oal 1.050 for them. Will probably keep going up to 4.4 but want to shoot more at this level first. Hopefully get more loaded later today. Wife acts like she wants to see me today to help with kids. Only have 8 don’t know what her problem is.
Kaldor that is a real beauty. I have a 229 legion 40 in the gray. Love that black finish on yours still pondering sao or da/sa. Thankfully poverty will allow me ample time to mull it over.
Also didn’t mean to bash Remington brass earlier. I increased my flare mor than I normally go and it helped straitened things out was getting some runout in the beginning stages loading the mpr.

I wanted the grey finish, but the black has grown on me. I do want to put an RMR site on it, but its pretty low priority. If you like 1911s, the SAO is very "1911ish". Not to say the SA/DA is bad, I just wanted something different, and the price was right on this one when I bought in early 2020. Ive got a couple 1000 thru it and it shoots like a dream, even with some of the +P ammos Ive loaded.

Ive never seen an issue with Rem brass either. If you are running into case flaring issues, I highly recommend a Lyman M-die. Its a much more gradual flare that creates a bit of a shelf to set the bullets into, instead of a much more blunt single plug. When using PTX type expander on my Hornady powder drops, I use an RCBS PTX as it creates a flare very similar to the Lyman. Trust me, youll thank me later. I have an M-die for almost every rifle and pistol caliber I load, its just a fantastic piece of kit.

 

[MH81]

I use these in my CZ SP-01 and have them loaded at 1.040, with 5.4 grains of Power Pistol. That gets me an average velocity of 1125, with a ES of 37 and SD of 16. Nice solid recoil, no pressure signs, great accuracy. Of course, that's in my pistol with my barrel, so others may have different experiences. Overall, RMR bullets are my go to!

 

[Duck45lc]

Sorry for the delayed update been bogged down at work. Overall happy with 4.2 grains n340 oal 1.035. Loaded some at 4.3 and 4.4 which is the max loading on the VV app. At 4.4 I’m getting some primer cratering from a sloppy firing pin hole but primer edges are good and round. I get some of this with factory 115 fmj ammo as well so I’m not too concerned with it. But as good as the 4.2 loading is performing I’ll just stay at this level until I get a chronograph to see if I need more velocity for expansion. Again 4.2 is the max standard pressure loading in the Sierra 6th. MH81 Good to see someone else’s results loading these bullets really short. Just for reference Sierra 6th lists power pistol at 4.2-5.0gr for standard pressure at max 1100. +p listing is 4.6-5.7gr for 1200 FPS from a universal 4 inch barrel. They list 5.4 with their 125 jhp running at 1150 fps so it looks like your results are right in line with the manual. Thanks for posting.