Anyone ever over rpm a bullet

[ebb]

Early Berger 30 caliber 210 match bullets in a Remington barreled 300RUM 10 twist. The tech said "too much twist, too much speed , and way too rough of a barrel."

 

[Bart B.]

Three instances come to mind.

When Sierra introduced its 168 grain HPMK 7mm match bullets, its thinner jacket (compared to hunting bullets) was engraved enough by lands that hotter loads spun with 9 inch twists oft times flew apart. Conventional rifling weakened jackets too much. Boots Obermeyer started his 5R rifling shape for 7mm match barrels which solved this problem.

Sierra split a production lot of their 30 caliber 168 HPMK bullets shipped to the US Army International Rifle Team and the US Navy Rifle Team. Navy team rebulleted 7.62 M118 match ammo with them; several flew apart shot from Garand's 1:12 twist barrels. Army Int'l team put theirs in reduced hand loads for their 1:12 twist barreled 300 meter free rifle's 308 Win ammo. Sierra replaced the USN's bullets and offered to do same with the Army's 168's. Army said no thanks, they were the most accurate 168's they ever had.

I was shooting Norma 26 caliber 139 grain match bullets in 264 Win Mag ammo in a 600 yard match. My scorekeeper watched 2 more of them fly apart at close range after seeing one of my early record shots fly apart about 50 yards downrange.

 

[Bart B.]

When the British Empire started using 7.62 NATO M80 ball ammo in their fullbore matches, they soon learned their 12 twist 30 inch long barrels spun the 147 grain bullets too fast leaving about 3000 fps for best accuracy at any range up to 1000 yards. The best lots of ammo had bullets a bit better made but still enough unbalanced to cause accuracy problems. Their barrel makers started making 1:13, even 1:14 twist, barrels and decent accuracy happened.

The 30BR cartridge shoots bullets around 120 grains leaving about 3000 fps and uses 17 or 18 inch twist barrels for best accuracy. Faster twists degrade accuracy with the very best match bullets.

Best accuracy happens with any bullet spun just fast enough to stabilize it. One reason the 7.62 NATO was designed with 1:12 twist 22 inch barrels shooting the same bullets 100 fps slower than 30-06 ammo did from 1:10 twist 24 inch barrels.

Bullet spin rate in rpm equals velocity (in fps) times 720 divided by twist (in inches). Spin rate slows down about 10 to 15 percent over 1000 yards.

 

[johnfred1965]

Faster twists degrade accuracy with the very best match bullets.

Good thing I don't use the very best match bullets in my .243. It will shoot about 1/3 MOA at 300 with the 105 class bullets, but it will also shoot 1/3 MOA with 55gr Btips.

The accuracy lost from over spinning a good match bullet is negligible compared to all the other variables involved.

 

[Ggmac]

I have a 7 twist 243 that is doing funny things at 1k yards. Im running 3260fps so thats 335,000 rpm. Has anyone ever had similar rpm cause odd things to happen? The e targets say that 400fps slower rounds hit 1/2mil high. Thats not logical!!! Also the 400fps is not logical, you could get better ES loading powder with a damn coffee spoon!!!!But if it was for lack of a better idea melting or wobbling then maybe????

Look into the British SMLE at 1000 yds . It in the precesion shooting set .
It was called compensated I think . Slower bullets hit the same as faster , all having to do with vibrations , slower bullets left the barrel as it was pointing up , faster bullets as the barrel was pointed down

 

[CTanM]

Ive blown a few up with my 6 AI

1/8 28” kreiger

Currently shoots 107 matchkings and 105 amax

Running 3400 FPS

I’ve never seen a failure in either bullet.

75 vmax will grenade by 50 yards

If you’ve never had a failure at 100 yards I don’t think your bullets are exploding farther down range, but that’s just me.

Anything I’ve ever spun apart has been before it made it to a 100 yard target

And there’s also no “I wonder what just happened”..... it poofs and floats along in the wind.

If you can’t get your recoil under control then bag your rifle up POINTED AT THE BERM lol and shoot a few free recoil looking over your scope. If they are vaporizing you can’t miss it.

I would just think that the bullet would fail when really revving at max rpm.... not at 3-400 yards. By then your well under 300,000 rpms.

But if thats what’s going on. Just shoot a matchking

 

[DOGCAPPER]

I have had quite a few over rev shooting 50 grain in a swift. They puff up between 10 and 30 yds.

The 50 grain hornany did come with a warning not to fire over 35 3600.

 

[Shawnba67]

I would just think that the bullet would fail when really revving at max rpm.... not at 3-400 yards. By then your well under 300,000 rpms.

But if thats what’s going on. Just shoot a matchking[/QUOTE]
I have a hard time wrapping my head around this statement. I cant believe that the rpms would be affected very much no matter what the distance.
Can you point me towards evidence that it does? I would love to know more.

 

[Eric Leonard]

why did you want a 7 twist bbl to start with,,it seems with a 243 case an 8 should be plenty and maybe an 8.5 would be better for 105s at those speeds

 

[ljc300]

Early Berger 30 caliber 210 match bullets in a Remington barreled 300RUM 10 twist. The tech said "too much twist, too much speed , and way too rough of a barrel."

Yup... Sierra 50 gr Blitz out of a 220 Swift! Bang Poof!

 

[74Bronco]

I've shot the berger 105 hybrids thru a 7.5 twist at 3400 with poof, but they shot better at 3100-3200 for me and the 7.5 loves the 110-115 grainers just as much at 3100 fps, shot a .390 5 shot group at 200 yards off bipod and no bag with the berger 115 vldh. That 7 twist should be running the 110 or a 115 grainer , the 105 doesn't need the extra twist at those velocities your running

 

[DTubb]

The stress cracked throat of your barrel is the biggest contributor to your bullets demise. Yes twist rate and jacket thickness are important but throat smoothness trumps them both.
Many times a treatment 8-10 TMS bullets cures the problem but it can reappear.
Dtubb

 

[spaniel]

I've blown bullets, but typically I order my barrels with the appropriate twist for the heaviest bullet I want to shoot. When I ordered the barrel for my precision AR the maker questioned why the slow twist, I said because a 60gr VMAX was the heaviest I'd ever shoot from it.

You can also damage but not blow a bullet. I was shooting a 243AI at prairie dogs, and the round count by the end of the day was pretty high. Shooting 600 yards at a hillside I had 3 out of the last 50 rounds impact significantly low. I figured the bullets were damaged and had increased drag.

You're shooting the velocity of my 243AI out of a standard 243...