Twist rate question

C

cdoc42

New member
I have a Browning X-Bolt Stalker with 26" barrel in 6.5mm Creedmoor that I purchased in 2017. I'm looking for the twist rate and a review of rifles on the Browning website shows the "new" X-Bolt Pro Long Range that appears to differ only in the name, having a twist rate of 7".

A question is raised because the data on the boxes of Hornady ELD-Match created it.

Two lot numbers differ in BC numbers and twist rate recommendation, leading me to question if I should bother working up loads for them, assuming my twist rate is 1:7".

Lot #1
Twist rate 1-8"
G1BC .646
G7BC .326
I measured the base to tip: 1.385"
I measured the base to ogive: 0.762

Lot #2
Twist rate 1-8"
G1BC .697
G7BC .351
Base to tip: 1.458"
Base to ogive: 0.814

I would appreciate any suggestions.
 
First, bullet twist rate is the minimum recommended. Faster twist barrels are ok.

Barrel twist rate is what you actually have. It can accept bullets that listed as that min twist or slower. Your bullets should be fine.

That said, is there anyway to get about 200 or so of the exact same bullet. 2 different bullets will likely not shoot into the same group at most distances.
 
Thanks, Nathan. Yes, I can get out to 1000 yds, but I must have had what I call an "age-related mentals deficit."

The Cabela's store in my area has a ton of Hornady bullets, mostly 30 calibers, but they are all stacked in proper caliber sequence on one long shelf except for the 6.5mm. They are stacked together so 140gr ELD-M is mixed with 147gr ELD-M. I purchased the 147gr when what I really needed was to replace the 140gr that I had been using and I never looked at the weights as I just put them away, after I posted above. That explains the differences in BC and measurements.

It's fun getting old. Sometimes.
 
It's fun getting old. Sometimes.
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I here you. Just did a job that takes like 2 hours in a day! When I was 40, I just dropped to the ground and bounced back up. At 49, it is much harder…..less bounce.
 
If memory serves me correctly, Browning used a 1 in 8 twist until 2020. Either way, the 1 in 7 twist will work well for both of them. In my experience, the 140 grain ELD Match bullet is more consistent than the 147 grain as far as the BC is concerned. I have experienced more consistent results at distance with the 140. Both bullets work well. My Browning with 1 in 7 twist shoots both very well. The 140 grain do shoot a bit better for me though.
 
I would think the 1:7 twist might be better for the new 150 grain bullets that are now available for the 6.5mm CM. 150 is marginal for a 1:8 twist.

I have three 6.5mm CMs (all 1:8 twists) and two of them shoot the 147s very accurately - equal to the 140 and 142 grain bullets. The third shoots 130 and 140 grain bullets better.

As one of the posters mentioned, the actual barrel twist is barrel specific, so you might find one barrel that is faster or slower than the twist rating.
 
Nathan said:
I here you. Just did a job that takes like 2 hours in a day! When I was 40, I just dropped to the ground and bounced back up. At 49, it is much harder…..less bounce.
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Nathan, wait until you hit 80. I was still able to change the plumbing under my daughter's kitchen sink but twisting, looking up, and mostly, getting back out from under convinced me to tell her she needs a plumber the next time.
 
Kilotanker and Rimfire, thanks for the information. I did well with the 140 so far out to 1000 yards, I have not yet tried the 147.
 
Cdoc42,

Measuring twist with a dry patch on a cleaning rod can be done and is a good idea to confirm matters. If you have a borescope you can also follow a land and count it's turns after finding the distance from throat to muzzle. Rifling has tolerances, too.

Note that the base-to-ogive measurement requires stating what tool you measured it with. The Hornady and Sinclair tools hit the ogive at different diameters, and therefore give different distances from the base on the same bullet. Same with the dial indicator tools for this purpose.

The 147 looks like it should be plenty stable if perfectly formed and aligned in the bore. Indeed, it looks, if I am guessing the length of the plastic tip correctly, like 8.5" would be close to an ideal twist for it from a 26" tube in an ICAO standard atmosphere. So in your gun it is spinning faster than is strictly necessary for full velocity loads, unless you plan on cold weather shooting. Since longer bullet jackets are harder to draw with perfect symmetry, perhaps Hornady's process is coming up against it's limits and a slower twist might cut the wobble enough to improve accuracy a little. But that's speculation on my part. Other explanations are possible. If your seating die tends to seat the 147 with more runout than it does the 140, that could do it, for example.
 
Nathan, wait until you hit 80
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You're awesome! I'm in my mid-sixities and have brain farts non-stop. I don't even have confidence I'll make it as far as you have. Keep shooting and posting results. ;)
 
To expand on a bit of what Uncle Nick mentioned,

for a rough measurement of your rifle's twist rate, a patch, cleaning rod, sharpie marker and a ruler/tape measure are all you need.

Easiest done from the muzzle. The patch is so there is enough of a tight fit that the rifling turns the rod. Put a reference mark on the rod with the sharpie so you can see one full turn of the rod.

insert the rod until you feel the bite (it turns with the rifling)
Mark the rod at the muzzle. Insert slowly until you get to one full turn of the rod, then mark the rod again, at the muzzle.

Remove and measure the distance between the muzzle marks on the rod. That's your twist rate, one turn in "X" inches. its quite simple actually.

No, its not precise down to three decimal places but it will give you a number good enough to use.
 
Hey, guys, thanks for the info! A long time ago I read how to do what 44 described, but in the interim, I lost-and forgot -it. I definitely will do that with other rifles but I just finished reading an email from Browning reporting my twist rate is 1 in 9" and 1 in 7" wasn't done until the newest rifles were produced. (Mine was purchased in 2017).

So my guess is 1 in 9 is better than one in 7 when the recommendation is 1 in 8 or 8.5
 
stagpanther said:
You're awesome! I'm in my mid-sixities and have brain farts non-stop. I don't even have confidence I'll make it as far as you have. Keep shooting and posting results. ;)
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Stagpanther, be optimistic!! There's no benefit to pessimism. I was buying something the other day and the saleslady was having super trouble with the computer-assisted register and I told her, "I hope there's not this much trouble getting into heaven; if there is, I'm going right to hell." That made her day.
 
cdoc42,

Alas, I was a little optimistic about the tip. Litz has the 147 ELD-X in his book of measured bullet characteristics, and by including tolerance errors and different atmospheric conditions, he found the 1-in-9 just did not get it stable enough. It never went fully unstable, but it is marginal enough that he recommends a minimum of 8.2" twist for it. He recommends 8.5" for the 140. In warm summer atmospheric conditions, the 9" may work for both, but don't be surprised if the 140 groups tighter.

So this brings us back to measuring. As I mentioned, even pitch has tolerance, and we've had folks measure claimed rifling pitch to be off as much as half an inch, with a quarter inch of error not being uncommon. So I would still go ahead and measure it.
 
A dream come true? :confused: Like Murphy's law, pessimism can either be a look on the glum side or it may be used to anticipate problems to better prepare to handle them. Half empty or half full? Like everything else, it depends on what you do with it.
 
Although out of place, I just have to add this one: As I get older I find there is still a lot to learn. So I forget frequently to make room for the new stuff.
 
Unclenick said:
cdoc42,

Alas, I was a little optimistic about the tip. Litz has the 147 ELD-X in his book of measured bullet characteristics, and by including tolerance errors and different atmospheric conditions, he found the 1-in-9 just did not get it stable enough. It never went fully unstable, but it is marginal enough that he recommends a minimum of 8.2" twist for it. He recommends 8.5" for the 140. In warm summer atmospheric conditions, the 9" may work for both, but don't be surprised if the 140 groups tighter.

So this brings us back to measuring. As I mentioned, even pitch has tolerance, and we've had folks measure claimed rifling pitch to be off as much as half an inch, with a quarter inch of error not being uncommon. So I would still go ahead and measure it.
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I guess that explains why Browning changed the twist rate. The "new" 1:7" stalkers are called "pro" but look just like my 1:9. I'll soon compare both the 140gr and 147gr to see what's up, but I know the 140's work. After I adjusted 15 inches to the left for wind, I hit a 12-oz spray paint can dead center at 1000 yards. But a fellow shooter outdid me by hitting a baseball.
 
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