Browning X Bolt 6.5 PRC 1:7 twist rate and possible bullet failure per Hornady

[pwdrski]

I purchased a Browning Hells Canyon Speed X bolt in 6.5 PRC. The twist rate is 1:7, which Browning states is to stabilize the longer bullets often used in the 6.5 PRC.
I was listening to a Hornady Podcast on twist rate it was mentioned that Hornady recommends a 1:8 twist rate for the 6.5 PRC.
I reached out to Hornady for their thoughts on a 1:7 twist rate and received the reply that their formula is for twist rate is; muzzle velocity (2960 for Hornady Precision ELD-X 143 grain in 6.5 PRC) times 720 divided by 7 (the twist rate) and if the resulting number is over 300,00, bullet failure MAY result. Using their equation the resulting number is 304,457.
Has anyone experienced bullet failure with an X Bolt in 6.5 PRC with the ELD-X or the CX Hornady bullets.
It seems odd that a major manufacturer would build a rifle that could possibly have poor bullet performance as a result of their twist rate.

 

[wind gypsy]

The jacket is where failure occurs. ELD-m bullets are the one most noted for the failure in recent years. A while back berger created the distinction between hunting and target lines to have thicker jackets on target bullets to handle the fast twists and hot barrels IIRC. I haven't heard much about it happening with ELDx which should have a little thicker jacket and not at all with CX which dont have a jacket at all.

Also, its not like 300,000 RPM is a magical number, just a guideline. What is your actual measured velocity? Precision hunter is based on 24" barrel and there is lot to lot and barrel to barrel variance but Id expect about 50 FPS less velocity with your 22" barrel.

The issue is more notable as a barrel gets hot and gets rougher with firecracking from more rounds through it.

 

[pwdrski]

I'm getting the rifle setup, waiting on my scope and rings order. As a result I have not gotten to the range to chronograph the muzzle velocity My barrel is 24". If my velocity is 2910 chronographed that'll bring it under at 299,314. I have to wait and see as soon as I get my components together and do some range work. I'm heading to Wyoming for Antelope in September, so I want this rifle to be all I envisioned for a medium game rifle.
I did reach out to Browning just for their point of reference on the subject.
I really appreciate your thoughts. Thank you!!

 

[DaleW]

I have a 24" 7.5 twist proof barrel on mine and I've had 0 issues so far, though I mainly shoot the 156 berger. I believe groove count is also something to take into consideration. When I was researching the whole "eldms blow up" thing, alot of people were saying it was less likely if you had a 5 groove barrel. I believe all proof barrels are 4 groove which would be more likely to cause issues but I've shot eldms just fine.

Does anyone know the how many grooves browning barrels have?

Edit: Also, I'm not sure why browning felt it was necessary to go with a 7 twist in the first place.

 

[pwdrski]

It's gonna be a medium sized game hunting rifle, a partner for my .300 Win Mag X-Bolt. So it'll be fed hunting bullets, not the ELD-M, and Wind Gypsy pointed out they, hunting bullets, as a rule have a thicker jacket. I'll also shoot the CX 130 grain as I do hunt NorCal for hogs and Blacktail, but the CX is a monolithic bullet so no issues there. I did reach out to Browning regarding their decision to go with the 1:7 twist, awaiting their response.

 

[nobody]

It's gonna be a medium sized game hunting rifle, a partner for my .300 Win Mag X-Bolt. So it'll be fed hunting bullets, not the ELD-M, and Wind Gypsy pointed out they, hunting bullets, as a rule have a thicker jacket. I'll also shoot the CX 130 grain as I do hunt NorCal for hogs and Blacktail, but the CX is a monolithic bullet so no issues there. I did reach out to Browning regarding their decision to go with the 1:7 twist, awaiting their response.

I had an X Bolt in 6.5 Creed for awhile, it was also a 7 twist. When I asked Browning about that decision, they explained it was due to the increase in ultra high-bc projectiles available now for the 6.5's

Hornady makes a 147 ELDM, Berger Makes a 156 Grain EOL, Hornady also makes their 153 Grain A-Tip, Sierra builds their 150 Grain Match King. Bottom line, there's lots of heavy for caliber, quality projectiles that (contrary to marketing) are very effective at killing game animals, that do benefit from tighter twists. Browning used a 7 twist to take advantage of the availability of those options.

FWIW, my X Bolt Western Hunter was the most accurate rifle I've ever owned. 7 twist shot 140 (NOT 147) grain ELDM's like it was born to do it. Unreal accuracy, unreal. I wouldn't have any issues with a 7 twist in a 6.5 of any flavor personally.

 

[pwdrski]

Thank you for the information!! I'm thinking it's gonna be what I want. My other Hells Canyon X-Bolt in .300 Win is an extremely accurate rifle.

 

[nmarchr]

I have the x bolt speed 1:7 twist prc and that gun shoots the 156 bergers so good. I did try the 143 ELDX and they grouped ok, but the bergers shoot amazing out to 750 yards. sub moa. That's as far as i've tried them.