Bullet Length VS Stability

[gunboat57]

I recently bought a Handi Rifle in 22-250 with a 24" fluted bull barrel, 1 in 14 twist. Some reloads with 55gr Hornady V-Max bullets came with it. At 50 yards I was getting groups just under 2" which I was not happy with. I also noticed the bullet holes weren't round but slightly oblong. So the bullets weren't flying perfectly point first.

The reloads were at the low end of the recommended powder charge so I decided to increase the charge by one grain. I thought maybe they needed a higher rotational speed to stabilize. I also did a quick calculation with the Greenhill formula and figured my V-Max bullets were just at the point of being too long for my 1 in 14 twist barrel.

So I loaded up 5 rounds with the higher charge weight, and 5 more rounds with the higher charge weight and I snipped the plastic tip off the bullets to make them shorter.

The ordinary V-Maxes again formed a 2" group with oblong holes. The snipped bullets made a ragged hole with one flyer. Holes were perfectly round.

I guess I'll just have to use up my 55gr V-Maxes by snipping the tips. I don't think the varmints will notice the difference at 200 yards.

Oh yeah, I also loaded 5 rounds with Hornady 55gr SP bullets. They also shot a tight group with round holes. Amazing what a little difference in bullet length will do.

 

[ironworkerwill]

Usually the base of the bullet has more to do with accuracy than the tip. OTOH, being a boat tail, I'd figure the V-max would have shot funny with the nose snipped off.

I like your findings and your approach.

 

[RPRNY]

As you found, 55 grs are just at the outer limits of stability according to Greenhill. The formula suggest a 0.54" max bullet length for a 1:14 twist. Your solution is well reasoned and admirable.

 

[dagger dog]

"THE BULLET" for the 22-250 is usually a 40 grain.

 

[243winxb]

Barrel twist vs Bullet length

Length of bullet is more important then the weight.

[/URL][/IMG] Then comes bearing surface.

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[mtrmn]

LENGTH, not weight, if I understand it correctly. It just so happens that the heavier the bullet for a given caliber, the LONGER the bullet is. I'd say with conventional jacketed lead bullets you probably would not want to go over 50 grain with that twist. If you were shooting Barnes copper bullets I'd guess more like a 35 gr max. JMO

 

[jmr40]

It is my understanding that it is the length of the bullet in contact with the rifling, not the entire bullet length, that matters. That is why some bullets perform OK even though you'd think they are too heavy. If I'm right then snipping the tip off had nothing to do with it. But I've been wrong before, and I'm not 100% sure here.

Regardless, I'm betting you will do better with lighter, shorter bullets.

 

[gunboat57]

Ironworkerwill, all my bullets were flat based. I might try some boattail bullets some day and see what they do. It looks like almost all the 224 Hornadys under 55 gr are boattail.

The 55 gr Hornady SP bullets I used (which were stable) were "borrowed" from my son-in-law. He reloads for an AR in 223 with a 1 in 9 twist. I bet his AR will stabilize the 55 gr V-Max bullets nicely. If I don't keep snipping my bullets I might just swap bullets with him.

 

[Haxby]

gunboat57 -
The stability calculator at jbmballistics.com seems to agree with your calculations. They have a list of bullet lengths, too.
I'd be curious to know how much shorter the snipped bullets are.

 

[Kp321]

The calculations for rate of twist and stability have nothing to do with the bearing surface length of the bullet. However, real world performance does.

 

[gunboat57]

Here's a visual summary of what worked and what didn't. 55 gr V-Max on the left, 55 gr Varmint on the right, snipped V-Max in the middle.

 

[dagger dog]

delete

 

[gunboat57]

Just for an update, I sighted in today with 55gr SP bullets. I'm about 1" high at 100 yards with bullet holes round and touching. So my zero should be at about 200 yards. This gives me a +/- 1" from POA zone from 25 yards to 225 yards. Works for me!
I also shot some 40 gr plastic tip boat tail bullets just for comparison. They grouped about 2" low and a bit left at 100 yards. Holes were touching and round.
I think after using up my 55 gr loads I'll switch to the 40 gr bullets since I'm not after anything bigger than groundhogs and the 40 gr load shoots a bit flatter.