Why are Hollow Point bullets more accurate?

[mugsie]

I was having difficulty shooting tight groups with my 223's, one bolt and one AR. The groups were decent, under an inch for the bolt, but I thought they needed to be better. I was using 55g FMJ and 55g SP from Remmington, with 27g of H335. I tried 50g hollow points and now my groups are touching (26g of H335 with CCI small rifle magnum primers), which is the way I always thought they should have been. Of course this is benched, since shooting off hand I'm able to put them all through the same hole making it difficult to judge!

So, why are HP's typically more accurate then other bullets?

 

[strat81]

You've discovered the OTM phenomenon, OTM meaning open-tip match. Hollow-point sounds too evil for target shooters, I guess! Generally, I avoid soft point bullets for target work since the tips deform more easily than FMJ or OTM bullets.

So I didn't answer your question. It involves ballistic coefficients, physics, astronomy, astrology, and El Nino. I'm interested in the answers, and I'm sure some will say "Go to your local library..."

ETA: I'm not a huge fan of bulk Remington bullets. They are scary inconsistent. For blasting, I'll go with Winchester or Hornady. Check out ar15.com's reloading section, they have more .223 info than anyone.

 

[ChristopherG]

I think someone smarter than me explained it to me this way at one point:

Concentricity.

A perfectly accurate bullet needs to be perfectly concentric, though of course no bullet is; but the always-present, slight deviations from concentricity have less of an effect--create less 'wobble'--if they are further from the axis of rotation. So, the tip of the bullet is the most crucial bit, concentricity-wise; and the effect of a hollow-point is to move the mass at the tip out away from the axis of rotation, reducing wobble.

 

[alucard0822]

OTM do not normally function like a hollow point pistol round (to aid controlled expansion) It is a result of the manufacturing process where lead is swaged into the jacket, and the ogive is formed around the core. The center of gravity is moved rearward twards the bearing surfaces, while allowing better quality control of the boattail and base. A longer bullet increases BC(ballistic coefficient) but also requires higher rpm in flight to stabilize, reducing the weight in the front minimizes this. Many of the new generation VLD bullets place a polymer tip into the hollow point to increase the BC even further as in the a-max.

BC is basically a measure of aerodynamic drag, the higher the number, the lower the coefficient of drag vs weight, and the better that bullet can maintain velocity over distance

 

[Jim Watson]

The varmint hollowpoint and "open point match" bullets are more accurate because:

The bullet base is more uniform.
The center of gravity is farther back.
The whole thing is made more carefully than FMJ military bullets and SP hunting bullets.

By the way, alucard, whose VLD has a plastic point? I haven't seen any but I have only tried Berger and JLK. Note: The commercial bullets with colored plastic points from Nosler, Sierra, and Hornady are NOT true VLDs.

 

[USSR]

The bullet base is more uniform.

+1. A bullet can be made with either the base open to insert the lead (FMJ), or the tip open to insert the lead (HP). Since the base of a bullet is more critical to accuracy, the solid, closed base on hollowpoint bullets will generally give you more accurate bullets.

Don

 

[rjohnson4405]

My offhand shooting seems to go through the same holes as well, either that or I only hit the target once per clip, but I'm pretty sure it's the same hole...

 

[jwr_747]

most test run by bullet manufactures shows that the bullet base being undamaged is the deciding factor on accuracy.bullet nose can be beat to crap,as long as the base is intact accuracy doesn't suffer. jwr

 

[wcwhitey]

Were the new bullets plain based or boat tails and at what distances. For 100 yard shooting or less, I use plain based bullets. They settle down faster than the boat tails. Now over 100 yards all bets are off. I often shoot at a close by 50 yard range (nice people, small place) and have found that the plain based bullets shoot better at those distances in my AR. Groups reduced almost 1/4" at that distance. This was Sierra vs. Sierra product BTW. For bulk I liked the Winchester 55 FMJ's (Winchester 748, Win SRP's and Winchester and Lake City Brass).