I'm thinking of doing 1-9 barrel for my next 7mm rifle, talk me out of it.

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bitbythebug

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I just sold my 28 Nosler with a 1-8 twist barrel. It wouldn't shoot the 180 ELD-M's at all. They disintegrated before reaching the target. I was told they were spinning to fast and coming apart, I couldn't refute that. I am building a 7-300prc and am leaning towards the 1-9 twist for it. I did all the calculations on the Berger stability calculator, and it said the 9 twist stabilizes even the 195 Berger's. I was hoping the slower twist wouldn't disintegrate thinner skinned bullets, like the ELD-M. I love the 180's and would like to stay in that area for hunting but would like to be able to shoot the heavier Berger. I can order either barrel from Bartlein. Where am I going wrong with my thinking?
 
as long as you DON'T shoot the 197smk's and what you want to shoot will stabilize, then go for it! i don't remember what the maximum rpm for cup-n-core is within reason (i think it's 437,000 or 347,000?). do you think the 8.4-8.75 is to fast in case of atmospheric changes?
 
xsn10s said:
My new Remington 700 with 1-8" 5R factory barrel shoots 180gr ELDM handloads just fine. My understanding that the rifling (3-4 groove barrels) plays a part in 180gr ELDM's blowing up.
Click to expand...
I never thought that a faster twist was a negative. I instinctively want the 1-8 but the 28 Nosler has me spooked. Maybe it was the rifling's. Would you get the 8 or the 9?
 
bitbythebug said:
I never thought that a faster twist was a negative. I instinctively want the 1-8 but the 28 Nosler has me spooked. Maybe it was the rifling's. Would you get the 8 or the 9?
Click to expand...
I would get a 1-8" to run 180's. Throat condition could cause the bullets to come apart in mid flight too. Which is why I chose a 7mm Rem Mag. I can load it as hot or mild as I want. And with the 180gr ELDM's I let the BC do the work. I'd speak to a good barrel marker like Frank Green of Bartlein barrels on the subject.
 
Interesting post, never ran into an issue with a 28 running 1-8, even with Eld x or Eld M. The 7-300 PRC will be definitely slower than the 28, and probably slower than a 7 rem mag. So I wouldn't for see an issue using that twist rate. If you ever plan on shooting Copper monolithic bullets I would definitely go to an 8 twist. They perform better in a faster twist. Good luck in your choice. Either direction you go it should work just fine.
 
I would look at any of the mono bullets you may consider using if in the future you don't have a choice. If in the future you have to switch to monos and you choose to slow of a twist now you will have to buy a new barrel or shoot something lighter than you would like. Just a thought.
 
I'm collecting part's for a 7 RUM build and have a Proof CF 9 twist in hopes of avoiding the same thing with the 180 ELD-M's and Berger 180 Hybrids.
 
I was just going to say the same about the quarter minute magnum channel. The 1/9 will work and he also stated that one of the great bench rest shooters said the slowest twist that you can stabilize a bullet with will generally be the most accurate. But here is one question if you had a 28 Nosler why didn't you just load it on the slow side of your going to a slower cartridge. I would think if the speed and the twist is killing my bullets then it's easy to slow it down and have probably a really great stable load. Just my thoughts.
 
Someone check my math.

I don't know what velocity you were getting with the ELD-M's out of your 28 Nosler, but just to play games I'll assume it was 3,000 fps. If you had a 1:8 twist, we know that your bullet was spinning 12"/8" or 1.5 times in 1 foot (someone check me please). So at 1.5 revs per foot, times 3,000 fps = 4,500 rps… times 60 seconds is 270,000 rpm. Apply the same to a 1:9 twist and you get 240,000 rpm. Is an extra 30k RPM too much…? 🤔

I have no idea how fast is too fast (I googled it and it seems like none of the smart ppl are willing to put a number on it because there are too many variables).
This was some interesting reading (if this is against the rules I'll happily delete my post).
 
My only question is how many grooves did that 28 Nosler barrel have?
I ask because I know for a fact that there are several bullets, not just ELD-M 7mm, but 25, 26 & 8mm that won't handle 3 groove, and some Ballard style 4 groove barrels shooting really high velocities.
My original 2 224" 7" twist blanks were 3 groove, even a 223 was detonating light bullets, my 22-250AI I built would not hold anything below 85-88g together, even 69g of one manufacturer was detonating about 25 feet from the muzzle.

Back to the original question, I would go 8" twist because you have the better option of running LONG solid copper boolits and not worrying about crappy Hornady bullets coming apart…

Cheers.
 

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