How much off center does it take....

[roysha]

I ask this because of a couple threads discussing HPing a mold at home.

Using a more or less average range of 25 yards and normal handgun calibers, (38 Spec, 44, 45ACP, etc.) how much would an off center HP effect the accuracy of a bullet?

I realize that many factors enter into this question such as diameter of projectile, nose shape, length, length/depth of HP, diameter/shape of HP and what all, but it seems to me that the room for error, under most hobby shop set ups, would be rather large and the resulting off center HP would effect the accuracy to some degree or another. Obviously. I'm not talking about 10-15 thousandths, perhaps 1-3 thousandths which could very easily happen.

On the other hand, I have seen some very distorted noses of bullets that seemed to shoot into the "group" as well as the rest.

[wiljen]

I think a minor imbalance probably does not have time to manifest itself much at 25 yards from the muzzle. It would be interesting to test but I think the fact is other variables would account for as much of the result as the imbalance and make it virtually impossible to draw accurate conclusions. As ranges get longer, it would be easier to see the difference but those same other factors would also be magnified by a proportional amount. I've seen bullets that leaded like crazy that shot reasonable groups at 15 and 25 yards which leads me to the conclusion that at that range they simply dont have enough time to depart substantially from the median of the group. Conversely, I don't think I've ever seen a 100 yard "group" fired with a boolit that leaded substantially. At that range I think the term pattern might be better used to describe the results.

[paul h]

What is your accuracy standard at 25 yds? To me an accurate handgun shoots 1" groups at 25 yds, and I'd expect a hp being off center a few thousandths to open up a 1" group. I've seen changing lubes open up groups. If you're talking 2-3" groups at 25 yds, it probably wouldn't be as noticeable.

I can't imagine modifying a mold to hp it with anything less than a lathe or a mill and zeroing the mold cavity to the best of your ability. I've modified a few molds over the years for myself and others and that was done by zeroing the mold in a 4 jaw chuck with a 10ths indicator and getting as close to 0.0001" runout as I could and wouldn't settle for anything less than 2 tenths. I found out most molds aren't truly round and I'd have to compensate for the out of round condition.

[runfiverun]

I done a test a while back involving a drill bit a seater die and some loaded 45 colt ammo I rigged a drill press over my reloading press and used different drill bit's and different depths.
and eyeballed everything somewhere near the center.

I had to really take some lead out of the nose [15-20 grs] and at a heck of an off center angle to notice the boolits not in a 50 yd group.

now the ones I did get centered the best did shoot a better over all group [it may have been me making it happen though]

[Bret4207]

I don't recall if it was this board or another version of it, but we had quite a discussion on this. With a HP there are as many factors working for you as against you that it seems to cancel the bad stuff out. A HP moves the CG rearward and that's a help usually. The HP cavity itself being closer to the center of rotation decreases the effect relative to, say, an entirely off center nose or a big divot missing from one side of the outer section of the nose. It will all add up of course and it's not something you try to have happen, but as I recall the consensus was that 1-3 thou in the HP mattered a lot less than 1-3 thou elsewhere, or in runout for that matter. Not sure that helps you, but that's how I remember it.

[DeanWinchester]

I dunno about a HP but I have a 255g RCBS mold I use for .45 Colt that the nose is off center to the body by .030. Its bad enough you can actually see it.

.......It shoots dead nuts! I've balked at getting rid of it a few times. It just shoots SO well.

[Wayne Smith]

Mann's The Bullet's Flight has some significant data concerning nose damage and accuracy. Not the same issue but very directly related. You will be surprised how much nose damage it takes to ruin a pistol boolit.

[Harter66]

I read a magazine artical some yrs ago reguarding bullet damage. One test group was shot w/the noes ground off center by the full width of the SP w/the related divot. At the test range ,100yd I think,groups opened only fractions of an inch. Base damage was much more critical . I will agree w/the others in the HP centering being less critical.

[Boolseye]

I can offer a little practical experience with drilled HPs using a Forster tool with both a drill press and a hand drill.
All the pistol bullets I've HP'd in this way have been as or more accurate than their solid predecessors.
I found no appreciable difference in accuracy out to 25 yds shooting offhand, two-hand or on a rest.
-BE