300 Rum Load development help needed.

[redchinviking]

So I'm totally new here and could really use some help here in analyzing this load development data. I have an amazing custom rifle from GA precision with Defiance action, 26" proof barrel, T3 Terminator muzzle brake, Manners T5 elite swamp, topped with a 7-35 56 NF Atacr. I finally got this thing after waiting over a year in July of last year and found a great 1/2 MOA load within 100 rnds in nosler brass with H1000 and 210 NLRAB. Fast forward to this season, when I have more time for load development and I decide to try retumbo and 210 VLD's with the new Gunwerks brass. Here's my first load ladder.
Bottom 2 right groups are my old h1000 load in 4th fired neck sized brass, and old h1000 load in new Gunwerks brass. Unnaceptable. Rifle was totally clean and then fouled with old load prior to retumbo ladder. 1st group in ladder at 90 gr is 3 shots in one ragged hole. All loads are .015 off lands. Poi is way low so I adjusted up for the remainder of the ladder. As you can see the high ES/SD groups are one hole. Lowest ES/SD are the worst groups. H1000 old load ES/SD was 5/2.5! But well over 1MOA in the new brass (how does that make sense?). 91 gr has been a consistent 1/2moa on a few ladders now but not good ES/SD. I haven't had a chance to take anything out to yardage but I'm having a hard time deciding what to do next. Anyone else seen this happen where the good groups are the highest ES/SD and lowest ES/SD were the worst?! What load should I pick? I shot the next ladder at 300 but with neck sized only 1st fired brass and the 91gr load was the only charge to stay under 1/2 moa. Hoping to run this ladder again with F/L resize and then tune seating depth from there but not sure what to make of this...

 

[Silly_Ghillie]

if it were me (because I just went through this very same thing switching from 212 ELD-X to 215 hybrids)
When seating your VLD's, do you notice any scraping or dragging on the bullet? I would load one as you previously did and then pull it out and look at the heal and seating surface. If you are dragging at all, you need to address the neck tension.
I just went through this myself. My SD was 5.8 and my ES was 12, but my group was almost two inches. I decided to retry the load and noticed a weird feeling when seating the 215 grain berger hybrid into FC mil brass. The bullet was marred, so I beveled the edges of all of my brass and printed a .7 MOA group with six shots.
the mouth of the brass was scraping into the bullet, causing inconsistent seating and tension. in my case, a couple of turns with the reaming tool on the case neck and problem solved.

 

[Rhovee]

I like 92-92.5. What primers are you using? I have best luck with cci 250's and H1000. Poi of groups and didn't change much.

 

[Silly_Ghillie]

I like 92-92.5. What primers are you using? I have best luck with cci 250's and H1000. Poi of groups and didn't change much.

I swear by H1000 and #250's. From -20 Fahrenheit to 90+ and the combo is very consistent.

 

[redchinviking]

so it's funny you mention the neck tension on that new brass because when I was seating I could definitely tell the tension was greater than I normally feel it. They were also definitely scraping a bit while seating. I normally would debur/bevel case necks but I got my good accuracy and consistency last year in h1000 from fire formed so I was just getting em chamber formed, getting some data in the process, and shooting em fresh out of the box. But a few of those retumbo groups were fabulous! I'm running feds 215M for primers but I do do have some cci's so I'll have to try em with the h1000 again, and try reaming those necks a bit for smoother seating. Just crazy to me that my old load would open that much on new brass. Would really like to stick with h1000 and 210 nlrab cuz all of the sudden retumbo is literally nowhere to be found and I only have 1 lb left:-/ not to mention temp stable and the NLRAB have had fabulous bullet performance on elk and deer over the years and really was only checking retumbo/vld to see if I could find a tighter consistent group. My friend/dad shoot vlds and they always waste so much meat with fragmenting bullets. But consistent one hole groups that go out to yardage would make me a believer.

 

[redchinviking]

Btw I thought 92-92.5 would be the ticket as well but after neck sizing and shooting the exact same ladder out at 300 the 92-92.5 stayed at or above 1 MOA. 91 was the only load that stayed under 1/2 moa. I thought to increase my neck tension closer to that new brass tension so I ordered a smaller neck bushing to try to see if they like tighter neck tension. I was at .335 bushing so I'll try .334 and .333 to see if it makes a difference but maybe the vld likes fresh brass in this gun. Curious to see what FL resize ladder will do to ES/SD and if it will give the same group size/patterns. Will post pics soon...

 

[BallisticsGuy]

How far are you honestly going to take a shot? The answer to your question is in the answer to that question. Modest spreads in velocity may or may not actually matter for your use case.

 

[redchinviking]

Is mid 30's ES spread modest? Out to what distance ish? I think 6-700 yds would be max range for me in most hunting scenarios. Just cause I've seen cross canyon winds and other misjudged variables make some pretty important shots go screwy and at those ranges hunting in central Idaho you can almost always get closer. 800 if conditions were perfect and I had a good spotter with me. But 1000 yds at the range for practice all day long. Gongs ringing out is music to my ears Practice out to 1000 and feel comfortable and confident at 7-8 is my line of thinking.

 

[Mt rummy]

I ran the 93 grains of h1000 for years with the 210 vld. Will drop a bull like a bad habit at a Billy Graham revival service.
I ran 88 grains of same with a 220 eld-x. 30 inch Lilja bbl gives me 3000 fps. Sd is 2 fps and three shot groups at a hundred are over a tenth. 1200 yard I have had many 3 shot groups in the 3 inch area with a 12x 42 nightforce. I am a die in the wool Berger man, but this year I will be doing a change up. I have two 300 rums and would not look back.

 

[BallisticsGuy]

Yes, it is in fact quite modest and will be irrelevant to any of your stated intended purposes. I maintain and publish my own external ballistics app so I have some familiarity with the topic.

At 1000 yards the difference should be within a RCH of 2 inches. That's tiny upside a .5MOA group size which would be about 5.25" (in an ideal world) at 1000yrds. It's inside your existing error margin under the best of conditions.

SD's at or under 20fps across 10-20 round sample sizes is what I tell my long range (up to 1000yrds) students to try for. There's a reason I tell them that. Your measured SD's and ES's are statistically meaningless because you only shot 3 shots of each load. If you want to know how it's performing for velocity then shoot at least 10 shots and 20 would be better.

 

[Mt rummy]

Agree. Sd for me is 5 shot. However, there's a "real world aspect". When your load and platform is consistently popping those balloons at 1k and further...dont look back and over think it. Confidence has a high value in the field. I believe not enough emphasis is placed on shooters form. We all try to buy those little groups. My two cents.

 

[redchinviking]

ok Thanks for the input ballistics guy...prob overthinking the numbers, but it's gotten me this far! I guess it's worth a try to take that 92-92.5 out to 1000 and see if it'll hold together but always heard that SD's should be single digit if you want consistency at 1000. And it has held true for me up to this point. I guess for a hunting round .5 moa that percentage error can be acceptable at higher spreads from what I'm reading. Last year with the h1000/NLRAB nosler brass the ladder work was straight forward with low ES being the best groups. ES/SD went Up and down in the corresponding accuracy nodes. Pretty straight forward. Now this year the opposite is true. Still scratching my head wondering why? I guess barrel harmonics are what they are. Will shoot some longer strings to confirm ES #'s but again I'm having a hard time finding more retumbo which makes me wanna ration it out. Any one know where some is? I'm on a few websites email notify list, but from what I'm hearing it's been picked up by the military and it'll be out for awhile. Last year I had zero luck with h1000 and 210 vlds but maybe because it was still breaking in under 50 rnds. Hard to go back to h1000 now that I've seen this retumbo/vld combo produce such good results. Btw can you guys tell me your brass prep preferences in your 300 RUM? Neck size, partial neck and body, or F/L size? Neck turn or anneal? 1,2,3 thou neck tension? So much to learn from you guys. I don't have nearly any local resources for long range shooting info. You guys are it. Thank you.

 

[Rhovee]

You find me some Lapua 300 Norma brass and I'll trade you some Retumbo.

 

[Mt rummy]

You find me some Lapua 300 Norma brass and I'll trade you some Retumbo.