Range Report 230 grain RMR FMJ FP

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Range Report 230 grain RMR FMJ FP

Postby Rklenke » Thu Jan 18, 2018 1:37 pm

I'll start with the obligatory reloading statement: These worked with my rifle, make sure you do your own work-up. That being said, I did follow TexasSheepDogs advice, starting low and not exceeding 42 grains LilGun.

I recently bought some Rocky Mountain Reloading MHI bullets as cheap plinkers in the 450. I've had tons of trouble with extraction using the 300 grain bullets, so I figured I'd try something new. I was only testing for pressure signs, velocity, and ability to cycle, I promise I'll get some accuracy testing done at 100 yards in the future when I get more time. All the rounds were shot standing off hand, 10' from a the chrono at a distance of 25 yards.
Rifle: 18" mid gas, no brake
OAL: 2.07
Taper Crimp: I started at .476" and reduced to .475" after the first string up to 39 grains. I may decrease even more to .474 due to multiple bullets "setting back" when not cycled properly
Powder: LilGun

36 2066
36 2104
37 2192
37 2047
38 2156
38 reference picture
39 2231
39 2302
39 2174 .475" crimp here on out
39 2180
39.5 2305
39.5 2345
40 2378
40 2343
40.5 2325
40.5 2531 WHAT?! had to forcefully extract with charging handle, but no other pressure signs
40.5 2364
41 2376
41 2490
41 2431
41 2337 (shortened OAL due to bad cycle)

Trends: I noticed that every round extracted with one exception. Almost all the brass dropped directly to my feet when I had a good cycle. From 38-40 grains, if I loaded 2 in the magazine, the first would extract and jam with the second (reference picture). Recoil was pretty mild. I never noticed a flattened primer, ejecter or extractor mark. With the very limited amount of rounds per powder weight, I think I will begin at 40 grains for the 100 yard testing and tighten down the taper crimp to .474. Either I started shooting better or the groups started tightening up as the powder load went up, no way to tell, but I'll put pictures up anyway.

Lastly, if you haven't checked out RMR, DO IT! I've ordered tons of bullets through them, they are an awesome small business that treats their customers right. I've never got a bad product from them. Shameless plug over.

tgt1.jpg
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tgt2.jpg
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tgt3.jpg
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tgt4.jpg
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Re: Range Report 230 grain RMR FMJ FP

Postby Rklenke » Thu Jan 18, 2018 1:40 pm

These bullets look pretty cool
MHI.jpg
MHI.jpg (70.97 KiB) Viewed 941 times


This happened on multiple occasions. Almost like the extractor let go of the case while halfway extracted. When the last round was fired, the bolt locked all the way back every time.
double feed.jpg
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This happened on the 38 grain load. Needs more crimp to be safe.
setback.jpg
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These bullets are pretty soft lead. These were pulled from a stump and are sitting next to a 180 grain hard cast with almost no deformation (1250 vs 2300 does make a difference though)
soft lead.jpg
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Re: Range Report 230 grain RMR FMJ FP

Postby Hoot » Thu Jan 18, 2018 3:10 pm

I'd wager that the one that flew hot, suffered some setback when chambering. That'll jack up the pressure = velocity. IMHO, having to force a spent case out with some serious charge handle action is a sign of excessive pressure in itself. I've had to pry some out over the years, even pound a few out with a brass rod. Before you resize that case, check it for growth right where the web ends and the case wall begins. I'm betting it is fatter than the rest of that charge weight group.

Think about it this way. During ignition, as the pressure rises, the case walls expand out to where they are stopped by the chamber walls. That allows them to cling to the chamber wall, seal off and not push too hard back on the bolt head. Once the bullet breaks the muzzle seal on its way out, the pressure drops and the case contracts back to only slightly greater diameter than when they are resized but enough to allow easy extraction. We're talking a game of thousandths of an inch change, but that's enough to allow them to pull out. In the presence of extreme pressure, the case gets driven into the pores of the chamber wall at a microscopic level and that causes it to adhere to the chamber wall, preventing it from shrinking back once the pressure drops. On the rare occasions where that has happened to me, I mark the problematic case with a sharpie right there at the range and I throw it into the recycle box when I get home. No telling how it may have been weakened and I for one, do not want a case head separation then next time out. The cost of a piece of brass is not worth risking damage to my rig or me.

If you didn't segregate your spent brass, it wont be hard finding the one that seized up. It'll be fatter than the rest. Again, a game of thousandths. I segregate my spent cases during a range session, based upon charge weight. That allows me to check them for casehead growth before I resize them. It helps determine at what charge weight, I'm venturing into the excessive pressure zone. A much better determining factor in an AR based rig, than primer condition. Obviously, if you're flattening primers, that's another excessive pressure sign, but not the only sign.

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Re: Range Report 230 grain RMR FMJ FP

Postby Rklenke » Thu Jan 18, 2018 3:21 pm

After I got that serious set back bullet I double checked the next chambered round each time as I do value my fingers and eyes. The one that shot hot wasn't set back, and I verified each charge between my digital and balance scale. I'll see if I can get some calipers on the hot brass when I get back.

I'm pretty excited to get to the 100 yard range and see how these do. Maybe I can get a camera on my ejection port while firing to see what the double feed issue is now.
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Re: Range Report 230 grain RMR FMJ FP

Postby Texas Sheepdawg » Fri Jan 19, 2018 9:26 pm

What’s the twist on this barrel?
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Re: Range Report 230 grain RMR FMJ FP

Postby Rklenke » Fri Jan 19, 2018 9:34 pm

Texas Sheepdawg wrote:What’s the twist on this barrel?


1:24

I also discovered that my extractor is a "modified" extractor for the 450. I swapped it out for a standard one, hand cycled a bunch of rounds fine, and will see if it cures some of my issues.
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Re: Range Report 230 grain RMR FMJ FP

Postby Texas Sheepdawg » Fri Jan 19, 2018 10:36 pm

Okay. Yeah. Those velocities look similar to mine in my 20” 1:24 twist AR. I think the key to my success was applying the LeGendre side crimp.
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Re: Range Report 230 grain RMR FMJ FP

Postby Rklenke » Fri Jan 19, 2018 10:44 pm

Texas Sheepdawg wrote:Okay. Yeah. Those velocities look similar to mine in my 20” 1:24 twist AR. I think the key to my success was applying the LeGendre side crimp.


Without a cannelure, the side crimp would come in handy. Is 0.474" taper crimp good enough in a .451 bullet?
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Re: Range Report 230 grain RMR FMJ FP

Postby Texas Sheepdawg » Sat Jan 20, 2018 5:09 am

Rklenke wrote:
Texas Sheepdawg wrote:Okay. Yeah. Those velocities look similar to mine in my 20” 1:24 twist AR. I think the key to my success was applying the LeGendre side crimp.


Without a cannelure, the side crimp would come in handy. Is 0.474" taper crimp good enough in a .451 bullet?

Works for me. I wouldn’t go any tighter though. Might deform the bullet or case and or cause headspace issues.
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Re: Range Report 230 grain RMR FMJ FP

Postby Rklenke » Sat Jan 20, 2018 7:42 am

Texas, I noticed your OAL with the fmj is a bit longer than mine. Did you base your seat depth off the ogive and lands? For mine I tried to compromise between the above and having the bullets diameter seated in the case (which is impossible).
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