75 gr .224 RMR bullets

[buckey]

Been playing around with Rocky Mountain Reloading .224 75 gr bullets in 5.56. Have tried Tac, H335 and Acc 2520 powder and so far I can't seem to get better then 1.5 3 shot groups in a Ballistic Advantage 1X8 18" barrel. Any one else tried these bullets?

[Shadow9mm]

Looked at them a few times, never tried them though. Having tried other budget match bullets in the past, I have found it better just to buy SMK's and save myself the time and headache...

[Unclenick]

I got some of their 69-grain bullets awhile back. They shoot as well as any of several others at 100 yards, but I have not tried them at enough distance to sort out subtle performance differences.

In 308, I found I had to go to some extra trouble to get 2520 to ignite consistently enough for best accuracy. I had to deburr flash holes and use magnum primers, but doing so cut groups 40%. H335 is the canister grade version of WC844, a military propellant for M193, but military primers are magnum level, which some of these older spherical powder formulations need.

I would suggest trying a stick powder that's known to give good accuracy with heavy bullets in 223. You can do worse than IMR4895 or H4895.

[surveyor]

I havent tried them, but my 77 smk match load is a cci 450 lc case and varget

[FrankenMauser]

Haven't tried them.

3-round groups are a waste of time. They lie.
Bump that number for a better view of actual performance.

[jetinteriorguy]

I have the same barrel and with RMR 62gr and 69gr bullets get sub MOA with both H4895 and Varget with the H4895 edging out the Varget by a hair. Generally 1/2-5/8” groups are what it shoots. I think I could do better with a scope that has a finer reticle but I’m plenty satisfied as is and the slightly heavier reticle is easier to pick up in dim light.

[Rimfire5]

I haven't tried the 75 gr RMRs yet and probably won't.
Not because they are RMRs but because my rifle doesn't seem to shoot 75 gr bullets very well, although 73 grain ELD-Ms have the best average overall at 100 yards for 5-round groups.
I have tried RMR 69 gr bullets and they shot reasonably well.
They averaged 0.300 for 35 5-round groups with 4 different powders. Best powder was Varget with an average of 0.286.
69 gr SMKs (essentially the same shape) averaged 0.274 with the same 4 powders. Best powder was Varget with 0.233.

Best overall was 73 gr ELD-Ms with an average of 0.243 with the best powder being Varget with 0.216.

The reason I won't try the 75 RMRs is that 75 ELD-Ms average 0.375 and Berger 75 LDMs average 0.353.
I don't expect miracles when I reload.

[buckey]

Interesting, Thanks for the feed back!

[Rimfire5]

IMO, every barrel has different preferences so you may find that in your barrel, the 75 gr RMRs shoot great.

I have two Savage 308s with the same 24-inch barrels.
One shoots best with 150 grain bullets and shoots 168 well but doesn't shoot 175 gr bullets and above well at all.
The other shoots 175 gr through 200 grain bullets extremely well, 168s well but doesn't shoot 150 or 155 gr bullets well at all.

That has always proved to me the fallacy of asking for 'favorite loads' since there is no way to identify a particular rifle's preferences without trying different combinations in a particular rifle and there is no guarantee that anyone else's rifle will perform like yours.

[buckey]

So true, So true !!!

[NWPilgrim]

I get best accuracy in my ARs and heavy bullets with stick powders. Varget and 8208xbr followed by H4885. The best ball powders I’ve tried with the 77 bullets are CFE223 and BLC-2. H335 does best for me in the 62-69 gn range. It really drops out with the 77s for some reason.

[Sevens]

3-round groups are a waste of time. They lie.
Bump that number for a better view of actual performance.

Haha, I kind of agree! However in this case, if his three round group is disappointing him, it’s a better choice than a 5 or 10 round group, no? Saves time and components.

[tangolima]

For final "qualification" of a load, I shoot no less than 10 shots, and calculate the 50 and 90 percentile group sizes. During working up the load, for example COAL test, I even shoot 2-shot groups. If it looks promising, I will fire more shots to confirm, or I will move in to other configurations. Not ideal, but have to strike a balance between ideality and practicality.

If only extreme-to-extreme group size is measured, it is indeed no point shooting more as the group can't shrink.

-TL

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[NWPilgrim]

https://youtu.be/oTWDUZ8Awig?si=3QH1fMQsbtdkfek_

This is a good discussion with Dan Newberry, the inventor of the OCW method and Erik Cortina (sp?) an F-Class champion. Who also interviewed ballisticians who insist on large data groups of 30-100 shot groups.

The video is painfully slow moving but the content is great. I listened at 1.5x speed. The transcript is also available at the link.

From what I can gather:
Three shot round robin groups can absolutely identify an accuracy node that can be further tuned with seating depth or barrel tuner. But exact precision can only be confirmed by large group data sets.

For instance, OCW can help you to efficiently identify that 45.6 gr is the accuracy node regardless of bullet or barrel. But only 30+ shot groups can determine the true precision of the load when you get to fine tuning.

I thought this was a good perspective that statistics and small group ladder methods like OCW are not at odds. They are used for different purposes. I liked Erik’s comment that small shot groups are necessary to preserve precious barrel life. If a precision barrel is only good for 2-3k shots you can’t be shooting lots of 30 round groups to find a an accurate combination. Likewise once you find an accuracy node it is silly to claim a three shot group indicates 0.4” precision.

[Unclenick]

Three-shot groups can give you useful information if you shoot several of them and combine them (overlap them). The OCW method looks for three such groups, or 9 shots, to identify a load. You can also use a running average of three of the three-shot groups (so you are really looking at 9-shot groups). The main limitations of three-shot groups are that they average about half the size of the average for 100 shots, so you want to allow for that in your thinking about where you can count on the bullet going, and the standard error for three shots is high enough that they don't precisely locate your point of impact. Averaging the center locations of three of them, though, will frequently get your POI center located within the limits of the resolution of your sight adjustments. Unfortunately, that high standard error also means you will occassionally get misled evaluating OCWs and may need to re-fire one.