Substituting plated RN bullets for JHP bullets

[lewmed]

 With my favorite Precision Delta 124 gr JHP bullet being impossible to find right now I've decided to save my last few thousand for serious shooting and replace them with RMR 124gr RN plated. I had already decided to change my old stand by powder for Sport Pistol so I needed to start all over and work up new loads. I started with twice fired Federal brass Federal standard primers 3.6 gr of SP at an OAL of 1.135" it took 3.8 grains to cycle in all my guns and all the way to 4.2 gr before it became accurate with 4.3 being to most accurate so far. My old load with the PD 124gr JHP was 4.2 gr of 231 with a velocity avg. of 1077 fps fired from my SP01  this new load feels much softer with no signs of excessive pressure with an avg. velocity of 1105 fps. but most data is showing 4.3 to be a near max load. I thought I would ask here if anyone is loading the same bullet and powder combo and what their results were.

[George16]

I had been using RMR’s 124 Gr plated as my practice ammo and use Precision Delta’s 124 Gr JHP for matches. I load them both with 4.0 Gr of SP @ 1.120-1.125” OAL. Both have the same recoil impulse and about 128-130 PF.

Accurate enough for USPSA.

[Wobbly]

RMR generally uses a more "blunt" ogive shape on their RN and JHP, so most CZ users report shortened OALs in the range of 1.060" after subtracting the 0.015" setback.

So in my humble opinion, you are much more likely to need a velocity re-test due to the foreshortened OAL rather than the jacket material.

 

[lewmed]

 This last batch of 4000 124gr plated RN bullets I just received from RMR isn't the old blunt fat round nose and they look to have a very thick plating and have a rounded base.

[George16]

This last batch of 4000 124gr plated RN bullets I just received from RMR isn't the old blunt fat round nose and they look to have a very thick plating and have a rounded base.

Same here. I think they got this batch of plated somewhere. It’s not their own plated bullets because the plating is thinner and the bullets are more pointed instead of the usual blunt bullets.

It’s great for practice but not much as match ammo.

[lewmed]

 Thank you George16 I think I'll follow your lead and shorten my OAL to 1.125" and back off my powder charge to 3.8gr of SP and start over.  My old chronograph with the 5.7X28 bullet hole still works but has been giving some odd readings I'll use my friends new one for this test he shot mine I think it's my turn to shoot his.

[George16]

@Lewdmed, a friend of mine shot his Prochrono while trying to chrono his .224 Valkyrie loads. It still works but sometimes shows “err” but always goes back to reading velocity after turning off and then back on. He ended up buying a new Labradar to minimize his chances of shooting it  .

3.8 Gr is a good weight to start with. Just make sure the bullets go straight into the cases to minimize chances of damaging the thin plating.

[lewmed]

 @George16 do you know how thick RMR's plating is I melted the core out of one of these new ones and measured the plating at about .008" I also used a micrometer to measure the diameter of a handful and found them a bit over size .3565" I think your right RMR is selling whatever they can get their hands on during this shortage. It's no big deal they will still make okay range ammo but I wish I had ordered more PD 124 gr JHP bullets when they were $75 per 1000.