300 Norma Mag Build
- Thread starter vbirddogs
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AKShooter
Silver $$ Contributor
Well, still waiting on barrel. But this is what I did. Stiller tac338 action. Ended up getting a cadex chassis in the deal, so going to run that for awhile. Went with a pretty light barrel, 5-sporter plus I believe. The idea being I can run it at the range at about 16-18 pounds. But have a way to get it down to hunting weight if I elect to hunt with it by putting it in a different stock. Not much more $ than a normal custom.
Not a comp gun, will be slow fire. So think I'll be okay with the lighter barrel. Going to put a area 419 brake on it. Straight 300nm too, mainly because that's what my smith has, but also plenty of horse power to run the 215's I'm planning on shooting. And no fire-forming, and the forster dies work well with reamer. He has built 4-5 of these rigs, one which he owns so going with a proven system
We will see, maybe have a few weeks on the barrel. Krieger 1-9 4-groove.
Check out the 300nm improved thread here. Thats another great options, and he is stocking rifles, or has parts on hand. That was a very close second!
Not a comp gun, will be slow fire. So think I'll be okay with the lighter barrel. Going to put a area 419 brake on it. Straight 300nm too, mainly because that's what my smith has, but also plenty of horse power to run the 215's I'm planning on shooting. And no fire-forming, and the forster dies work well with reamer. He has built 4-5 of these rigs, one which he owns so going with a proven system
We will see, maybe have a few weeks on the barrel. Krieger 1-9 4-groove.
Check out the 300nm improved thread here. Thats another great options, and he is stocking rifles, or has parts on hand. That was a very close second!
Thanks for the reply. Yeah, I'll definitely be going with the same barrel you've chosen. I'm looking harder at the MDT - ESS Chassis now. I do like the looks of the Cadex ones though too. I'll look into that Stiller action. I was thinking of a Mausingfield action though. I'm not too concerned with weight, I probably won't hunt with it. And yes, I've heard a lot of good things about the 300 norma mag improved.
I have instock rifles and parts on the shelf ready to ship depending on what route you wanna go. I even have a big Surgeon 1581 XL and chassis sitting on the shelf. For stocks I have manners eh1 and XLR magnesium chassis. If a guy doesn't want the instock rifles and wants something slightly different the lead time is 6 weeks or less right now as long as parts are instock.
That's all I use in my 6.5 now, the Lapua and Petersen Brass. Like them both.
I built mine on a 338 RPR. The factory barrel is 1.200" so I bored the handguard spacer to clear 1.250" and enable the use of standard barrel blanks. It'll still work with factory barrels.
I've had the best luck with the Lapua brass. The Peterson I tried was 6-16 thou short of my go gauge at the headspace datum. I necked it up to 338 and back down to 30 to put a false shoulder in it. No more 300 Norma brass from Peterson for me. How many firings the Norma brass will last depends entirely on the reloader. If you want it to last as long as the Lapua brass, it'll have to be 50 fps slower though.
I went with a 1:8 twist and the performance is amazing on our 2300 yard target.
I've had the best luck with the Lapua brass. The Peterson I tried was 6-16 thou short of my go gauge at the headspace datum. I necked it up to 338 and back down to 30 to put a false shoulder in it. No more 300 Norma brass from Peterson for me. How many firings the Norma brass will last depends entirely on the reloader. If you want it to last as long as the Lapua brass, it'll have to be 50 fps slower though.
I went with a 1:8 twist and the performance is amazing on our 2300 yard target.
I went with the 8 twist also but for some reason my 9 twist shot better at all ranges. I have no idea why???? Must be the way it was chambered??? Do you have any idea why that could be?
Lapua brass has been great for me as well. I shot 225 gr. ELDMs
Thanks,
H
Might be luck of the draw on the barrels. Might just be I started with the 230 Hybrids and they'll always have an advantage when I test them against other bullets because the loads are more developed. They fell pretty hard the first time I tested them against the ATips though.
I haven't tested the 225 ELDm in awhile, and I understand that they were recently redesigned, but they've never shot very well at long ranges from my 30 cals from 300wm through 300 Lapua Improved. I've tested them several times against length sorted 230 Hybrids trying to get away from so much bullet handling, but the vertical was always better with the Hybrids.
I've been using 1:8 for awhile. I think with 1:10, the best bet is going to be the 215 Hybrid, but I have enough altitude that even the 230 Hybrids have worked pretty well. Sometimes I see circular reasoning when guys are selecting twist. If you already have a 1:10, the 215 works the best, but that doesn't mean your next barrel should be 1:10.
I think 1:9 was the keep your options open twist. It worked well with the 230s, but was probably the best for the 215s. The 230 ATips are significantly longer than the ELDm or 230 Hybrids. A 1:9 only gives a 1.46 stability factor with the ATips. I try for 1.8-2.0 with jacketed bullets shooting deep into the transonic. That's similar to a 300 grain 338 caliber with a 1:9.3 twist, which nobody thinks twice about. 1:8 puts the 230 ATips at 1.85.
The 198 Flatlines take a bunch of elevation out of the turret, but I haven't been able to get them to actually outscore the jacketed bullets with 1:8. I'm trying a 1:7 with them next, with and without the nose ring.
I haven't tested the 225 ELDm in awhile, and I understand that they were recently redesigned, but they've never shot very well at long ranges from my 30 cals from 300wm through 300 Lapua Improved. I've tested them several times against length sorted 230 Hybrids trying to get away from so much bullet handling, but the vertical was always better with the Hybrids.
I've been using 1:8 for awhile. I think with 1:10, the best bet is going to be the 215 Hybrid, but I have enough altitude that even the 230 Hybrids have worked pretty well. Sometimes I see circular reasoning when guys are selecting twist. If you already have a 1:10, the 215 works the best, but that doesn't mean your next barrel should be 1:10.
I think 1:9 was the keep your options open twist. It worked well with the 230s, but was probably the best for the 215s. The 230 ATips are significantly longer than the ELDm or 230 Hybrids. A 1:9 only gives a 1.46 stability factor with the ATips. I try for 1.8-2.0 with jacketed bullets shooting deep into the transonic. That's similar to a 300 grain 338 caliber with a 1:9.3 twist, which nobody thinks twice about. 1:8 puts the 230 ATips at 1.85.
The 198 Flatlines take a bunch of elevation out of the turret, but I haven't been able to get them to actually outscore the jacketed bullets with 1:8. I'm trying a 1:7 with them next, with and without the nose ring.
The unavailability of Retumbo is what's cramping my 300 Norma style at this point. I built it because Lapua started making brass for it, but it was 18 months before I found any.
I have N570 loads for it, but avoid temperature sensitive powders during the summer months. I might give H1000 a try because I know as soon as I get that worked out Retumbo will reappear.
I have N570 loads for it, but avoid temperature sensitive powders during the summer months. I might give H1000 a try because I know as soon as I get that worked out Retumbo will reappear.
shoot4fun
Gold $$ Contributor
Not to brag but I have just over 8 pounds of Retumbo, 3 of RL26 and a couple of H1000. Retumbo already has to feed my 6.5PRC and my 300 Win Mag so it won't last a long time.
It must be the altitude I am at (~5,000 feet) bc Shooter Ap says that a 1:9 twist gives me 1.75 SG with the 230 Atips at 1.764 length and the 225 ELDMs at 1.655 for length says 2.08 for SG.
I wouldn't think altitude would affect SG to THAT degree...? I was reading about "spin decay" at long long range that was a concern with the 9 twist.
I shot the Flatline 198gr. as well and I couldn't get them to group well at all with the 9 or 8 twist. Funny thing, they shot about 6 min lower at 100 yds than the heavier ones. No idea why.???
Thanks for your feed back.
Elevation is your friend. If you plug 29.92 inHg, 59 F, and pressure is absolute or 0 ft for altitude, the SG will drop to the level I posted. The SG is the ratio of an approximation for the gyroscopic forces to an approximation for the aerodynamic overturning forces. The aerodynamic forces drop as air density drops. You can see from the change in absolute pressure that the air density drops pretty quickly with altitude. With some bullets, altitude will increase the resistance to tumbling out of proportion to the increase in stability factor.
The term spin decay is usually used in the discussion about SG being the lowest at the muzzle. The velocity decays faster than the spin rate. Like altitude, but working on the other term, the SG increases as the bullet slows down because the aerodynamic forces are dropping faster than the gyroscopic forces. Its sometimes used as a justification for slower twist rates.
The problem is many who shoot ELR have migrated towards relatively high stability factors because they give better scores. The Berger twist rate calculator now targets 1.5 as the "Optimum" SG, up from 1.4 as the "Minimum" a few years ago, but when Litz supplies a 375 Cheytac rifle it comes with enough twist to give an SG of 2.5+ with the longest bullets used. Cutting Edge is both active and very successful at the KO2M. They recommend 1-2" faster than the minimum twist if the bullets are going to be shot far enough to reach transonic velocities. On the other hand, there are a lot of 22 caliber varmint rifles out there that shoot small flat based bullets very well at SGs well below 1.4.
There are 2 reasons for these contradictions. The first is the SG was an approximation to start with and the second is dynamic stability is different than gyroscopic. One way to look at dynamic stability is the ability of the bullet to self correct yaw. It's primarily the result of the bullets shape, but faster twist rates do help some bullets. The lower density and length of solids used for ELR makes them need all the help they can get. Short lead cored flat based 22s don't need any help at all.
Lately, it's become public that BC variations dominate the dispersion problem at distances beyond a mile. Some of us figured this out awhile ago after being disappointed when very low velocity spreads didn't help as much as hoped. Many who didn't figure out the actual mechanism figured out that 100 yard groups don't have a lot to do with 2000 yard groups. Bullets that self correct yaw well give lower shot to shot BC variations. Testing bullets and twist rates beyond a mile is the only option.
At 5000' its somewhere between possible and likely you'll get results from bullets and twist rates that won't be duplicated at sea level.
Could you be more specific on the action? Which Kelbly?
Can you specify which Defiant action?
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