Just picked up a Sendero 300 RUM with 200 rounds thru it, throat & barrel checked out good. Gun has muzzle brake on it, glass bedded, 2.5lb trigger, Burris 8-40x scope, everything tight. Shot factory 180 Remington Core Lokt at 100yds, 5/8" 3-shot group from a bipod. Loaded some 212gr ELD-X with Retumbo and US-869 at 3000 fps, loaded 3.900" OAL, Bowler brass, expecting results. Floored that it will shoot no better than 2.80" 3-shot from a bench @ 100yds. I shoot several other rifles well under 3/8" @ 100yds, and these were not fliers, barrel was cool. Ideas?

Wondered if the 212gr is too heavy for the 1:10 twist perhaps? Haven't had opportunity to shoot the factory 180's again but that's first thing I'll do next time out.

It might not be agreeing with the 869. Check speeds but I’d bet till you get around 3100 or better with those 212’s you’re not getting enough pressure to burn well. Try upping the charge

I run the 212’s out of a 1-10 30-06 and they shoot better than anything else I’ve tried. Try some Retumbo or H1000 if you have any. If not, I’d keep ramping it up. I’d bet groups will shrink as pressure comes up.

Thanks for the feedback. Note that I did try Retumbo and had the same result.

Since I posted, I kept thinking that in 1:10 twist with a 308, I've had success with 220 Sierra Match Kings. Hmmm... Thinking more, I went to Berger's stability software and pulled a Berger 210 Hunting in, shows stable, but I noticed that the bullet length was significantly shorter. Plugged in the 212 ELD-X's BC and length, showed marginal.

I think that the long bullet is the problem. I intend next steps to be trying a shorter bullet.

Forgot to mention that US-869 charge is burning cleanly, no residual unburned powder.

Might just be something it doesn’t like. My 300 RUM shoots the 230 Berger pretty well, along with the 220 Scenar. Haven’t tried the 212 in it though.

Good luck with the next tries. It’s almost surprising that it’s not shooting well cause man it shoots like crazy in my old Featherweight.

Your 10 twist is fine, the new IBS 10 shot 1,000 record was shot with a 10 twist 220 Bergers in a 300wsm

Thanks guys, sounds like its maybe something I'm doing. Seat length of 3.900 is within 0.015" of rifling, maybe I'll try off the lands. I know Berger says with their 210 VLD's to seat on the lands, maybe the ELD is similarly sensitive. I've also put an inquiry in to Hornady.

Hornady said 1:10 of faster is required, and stayed that some rifles do not like the long bullet. I'll try seating on the lands and see if that makes a difference. I've tried to find some 200gr Sierra Match Kings, but they're not out there. Closest I could find are some Spitzers, will give them a try. FYI, he US-869 was burning cleanly, had 101.0 gr. in there.

Thanks for the feedback, I know the rifle will shoot, just gotta find what it likes!👍

Solid copper is longer than jacketed bullets like Sierra. Hammer Bullets has a 181 grain that might be perfect for your twist.

According to Berger's stability program and Hornady, the long length is the problem - the longer length takes more twist, so solid copper bullets would make it worse. That's why I'm going to try the shorter traditional Sierras.

Mine had a 10 twist Bartlien and shot 230gr Bergers like a drill with R33. Also used the 200gr LRX with great results. With all bullets I had my best accuracy 50 thou or more off the lands. If the factory stuff shot great I’d take a cue from that and let the bullets have some jump to the lands.

Update on shorter Sierras: i loaded some 220gr Sierra Match Kings with 95.0gr RL33. Shot 0.490" @ 100yds 4-shot group. Only other thing I did was seat the bullets to typical 300 RUM OAL of 3.600" , which buried about half the bullet. Doing more testing this weekend and intend to try 212 ELDs at this length to rule it out. My guess is the 1:10 twist can't handle the ELF length.

Tested this weekend. Sierra 220gr Match Kings worked with several powders. Best results were with 96.0gr RL33. Under 1 MOA 4-shot groups. Nearly identical performance was 24N41. I'd bet that 210gr Match Kings are the ticket, but these looked pretty darn good. Shot some 168gr MKs with 7828, close to 1 MOA. Checking brass yet as it seemed i had boron of the case snug on bolt closure, and that may be causing some variation. All necks were reamed and turned, FL sized, 0.003" press for bullet, using Redding bushing dies.

two hundred gr accubond and 95 gr retumbo.

i have never been able to get anything other than 30 cal 165 gr. interloks from Hornady to group worth a damned in anything else. I woudl try a different bullet from a different manufacturer

The 212 Hornie's stabilize happily in a true 10",at 308 velocities. My biggest 300 Whizzum shoots same in the .3's,at a soft 2800fps in it's 30" spout and a Smooch like everything else. Hint.

Always entertaining to hear all the things folks can't do. Hint.

Laughing!...............

Same here in an 06 P64 at 2700. They don’t seem real fussy either.

Haven't ever seen a Hornie cup/core that began to border on "fussy",save the original Beer Cans that woulda rattled a Juenke off the fhuqking bench.(grin)

Never been difficult to tell who shoots and who don't. Hint................

I'm just providing data while I dial my new combo while some others provide nothing more than hot air....Thanks to those who share load data and relevant information on what works for them. I've been loading for over 35 years in dozens of calibers and rifles. Each is unique, and what works in one doesn't always work in another. When Hornady tells me that their own long 212 ELD bullet is marginally stable in 1:10, I tend to believe them.

Karen,

Some folks unlike you,actually shoot. Read that again. Now one more time. Hint.

Stability is a function of rotational and lineal velocity combined,though you are welcome to any/all Delusions you can concoct. There is no need for you to quantify,how you are an exceedingly sloowwwwwww "learner",as that was/is hardly a "secret". You are too fhuqking Stupid to simply punch the bore and VERIFY twist rate,despite the piece of schit being in your trembling fingers. Hint.

You are the one asking questions and it's funnier than fhuqk,that Ballistics 101 Facts stump you in such a manner and that you are devoid all things bordering a FIRST Fhuqking Clue. Hint.

Bless your heart,for doing your best.

Hint.

LAUGHING!..................

My March scope just showed up in Austin, Tx at my buddy's house. Mine will be a switch barrel-300RUM-338RUM. In the 300 I will start with what I have-215 grain Berger Hybrid Target bullets,. I have my 338 barrel, but waiting on my 3000 barrel and D 'Arcy Echols stock.

Full choke stumpy????

Kchuntis,

Better than .075" constriction,Google it...you "lucky" kchunt. Hint. Congratulations?!?

NorthernLite ain't much greater than receiver diameter,at it's 30"muzzle. Hint.




My S/S Winny Krassick in 300 Whizzum above it,happily stabilizes 212's at 10" too,despite being only halfa foot shorter in spout length. Hint.



Fortunately for you,Imagination and Pretend are free,so you can "afford" to "contribute",as you read my EVERY word and gawk all the Splendid Pixels. Hint.

Bless your heart.

Hint.

Fhuqking LAUGHING!...................

Hey Stick you forgot to spray those rifles down for the wet effect. Makes for more splendid "pixels".

Bacon throat!!! All your ballistic table screen shots, yappin high bc blah blah fuucking blah, why would you build a rifle around a 212 when 225’s and 230’s exist…haha

You poor stupid sonafabitch!! 😂😂

The worst cartridge ever inflicted upon the shooting world!!