BC increase

[Jeff Von Rosenberg]

To those much more intelligent than myself! What % increase in BC can I expect by tipping my bullets? ( maintaining the max velocity for that load). I hope I am not showing my ignorance!!please help. I am pointing 7mm 180 hybrids, 168SMK's and 106 grain .6mm Matrix. And others but these are the majority. I do measure bearing surface and trim meplats prior to tipping. Thanks a BUNCH for the help!!!! JVON

 

[bward]

Around 3-5% depending on what the meplat looks like before tipping.

 

[Steve Blair]

I compared several Berger bullets that I trimmed and pointed with stock bullets. The differences in elevation at 300, 600 and 1000 yards were used to back into and estimate the G7 B.C. This is not the most accurate method but should be fairly close as the estimates agreed closely at all three distances. The bullets estimated were: 6mm 105 Hybrids, 7mm 180 Hybrids and cal. .30 230 Hybrids. Pointed and unpointed were fired at the same time and with the same load. A Viper SS 6BR was used with the 105 and BAT 3LL rifles were used with the 180 and 230. [br]
6mm 105 Hybrid - Litz G7: .278, est. G7: .297 - difference: 6.8%
7mm 180 Hybrid - Litz G7: .345, est. G7: .377 - difference: 9.3%
Cal. .30 230 Hybrid - Litz G7: .380, est. G7: .410 - difference: 7.9%

 

[Laurie]

Interesting results, Steve, and higher than I would have expected. Bryan Litz says 3-7% and that partly dependant upon calibre, partly upon the original meplat width, most Bergers running around 0.06 to 0.07-inch. The smaller the calibre, the greater the potential gain as any unpointed meplat of a particular dimension is a greater % of a small calibre bullet's frontal area than for a large calibre example. As they tend to have similar widths for any particular make as they come out of the forming die irrespective of calibre, and are reduced by the same amounts by home-pointing, you might get double the benefit from pointing a .22 cal bullet compared to a .30 cal model.

I'm a very cautious 'pointer' as I prefer to under-do the process but run nil chance of stressing the bullet. I assume a 3% BC improvement on my 0.308 Bergers, and 5% on 90gn 0.224" VLDs for .223 Rem. This seems to tally pretty well with what the ballistic program calculates and what happens on the range in terms of elevation adjustments needed for long range matches.

 

[CatShooter]

YOU can't judge an increase from someone else's estimate.

You need to shoot the bullets un-pointed, and then shoot them pointed, same day, same weather, same everything - there is NO other way to do it.

 

[Laurie]

YOU can't judge an increase from someone else's estimate.

You need to shoot the bullets un-pointed, and then shoot them pointed, same day, same weather, same everything - there is NO other way to do it.

Yes, did that with 90gn .224 Berger VLD at ~2,910 fps MV at 1,000 yards. The elevation increase was in line with a 4-5% BC improvement.

 

[Steve Blair]

It was initially surprising. But I've shot many matches where the rifle was zeroed at 300 yards and calculated elevation used. It's rare that third or fourth shots are off more than ±1/2 MOA at 1000. Friday, I'll shoot at Ben Avery in the Arizona Palma Championship. I have no data for 800 and 900 at their altitude and it is forecast to be pretty cool. I'll run a cheat sheet before I leave and am confident that it will be close. [br]
Another aspect is that the B.C. increase percentage is a little misleading. The pointed 105 Hybrids impact ~13-14" higher at 1000, 180 Hybrids ~10-11" and 230 Hybrids ~8-9". The difference in drop seems not directly related to the numeric percentage. [br]
The right way to do this is with a Weibel Doppler system and firing a generous series of pointed and unpointed bullets to obtain a sound basis. As soon as I find a unit to borrow, I'm all over it.

 

[6BRinNZ]

Interesting results, I had decided not to bother with pointing the 6mm Hybrids as they already have a small meplat...but ~6% isn't to be sneezed at.

The results for the 7mm 180 Hybrid might not be that far off the mark. Below is an excerpt from Brian Litz web site about the bullet.

The special secret of this bullet is that since it has a wider than average meplat, the drag reduction that’s possible from aftermarket pointing of the meplat is much more than average. Typically the drag can be reduced (BC increased) by 2-4% for most bullets that already have small meplats. However, since the meplat of the hybrid is so wide to begin with, it’s BC is increased by 8% when pointed!

 

[johara1]

I trim and point... and at the set up i mic them at the shank and at the pressure ring 90 degrees apart, before and after pointed and make sure there is no expansion. After the pointer is set i will randomly check them. then run all over the Juenke machine to sort and look voids …… jim

 

[Rtheurer]

Im thinking I should develop a tiny wind tunnel to sell so everyone so they can place there pointed bullets inside to see if there pointing die is set up correctly!
I think Im on to something here.... Ha!

Hope this thread finds you well.

RT

 

[normmatzen]

Donovan,
I agree 100% with you.

I don't tip my Berger Hybrids. I don't do any measurements on new bullets as I have found the variations are so much less than other brands that it isn't worth the time. That said, I am not so sure now so I may start sampling new lot codes.

But, I believe that for a first order effect, proper tuning (I do have tuners on my bench rest guns) is more important than tipping as with proper tuning, not only do you allow for deviations in tip shape, but you correct for many other velocity variables.
I am not sure of second order effects though. I guess I will worry more about that when I finish in the nationals high enough to believe my skill is then a second order effect instead of a first order effect!

 

[johara1]

I think it boils down to how bad you want to win or just show up . If you condemn something and not given it your best shot is wrong,how you trim and tip them takes time to do it right. I know i don't want jacket separation, so i'm careful not to let them expand a .0001 and the juenke will let you know the rest. My ES is down to 3 from trimming and pointing and they shoot 14" flatter at 1000 yds. and they are better in the wind. This just part of it,a very important part of loading. Berger 105 hybrids can be super and next lot pure garbage,i have had both.I had some that were .2439 in diameter and were 15 divisions on the Juenke but i had one lot that were 3 divisions. So shoot them right out of the box but what ever bullet you use i would still check them, and if you want to shoot small trim and point…….. jim

 

[Laurie]

My ES is down to 3 from trimming and pointing [johara 1]

I can understand how trimming and pointing reduce retained velocity spreads at long ranges and hence improve elevations all other things being equal. I can also understand how careful bullet measurement and batching might reduce MV ES when coupled to meticulous case preparation, charge weighing, and loading procedures.

However .... I cannot see how trimming and pointing on their own can affect MV ES.

 

[johara1]

Laurie, The bullets are then the same length from the ogive to the nose, also the over all length of the bullet is a lot closer. You are right that is just part of it,GD 503 helps as constant seating depth. Consistent neck tension is a plus also,bearing surface length held to +- .0005 is very helpful. It seems to me people write off steps in loading for time,cost or just plain lazy.
I tested freezing barrels, it cost 40.00 @ barrel that is cheap for the life of the barrel,but i still hear it doesn't work. If you look at the finish of the chamber verses one not frozen that is worth it by itself. The barrel doesn't walk when heated, what is that worth?I shot more 50's in light gun and more hundreds in heavy with a light gun. Did the freezing help, the best part they are average barrels,now i have frozen hummer ……… jim

 

[mysticplayer]

In my experience, there can be deterioration to pointing, when pointing to aggressively/excessively, do to bullet deformation of the boat-tail (which can happen very easily in small amounts that many will not detect or even look for), and can hurt uniformity of bullets that are of good uniformity already.
I point bullets, but only bullets that I find to not have uniformity of the meplat only, and do it limited to the amount to not cause deformation.

I point to uniform the BC and feel the gains to uniformed BC is an accuracy increase more so then trying to squeeze out the most BC, which is only a ballistic increase.
I still gain BC as well, but it is not the focus or reason why I point. Uniformity with increased BC is why I point and not just trim, but the uniformity is what prevails on the target. At least as I see it....


My 2-cents
Donovan Moran

Yep, you can make a good bullet junk by over pointing. Don't ask me how I know...

From my testing out to 300m, couldn't see much of any gains but out beyond 800yds, YES!!!!

Again, I am not too worried about BC increase as I miss much further then any bullet can save. What I found when pointing a bucket of Berger 30cals was how different the bullets FELT when pointing. Some needed more force then others and I can relate that to the overall shape of the nose which includes the tip.

When done, they visually looked more consistent. I don't have the tools to really measure this small stuff well but it is obvious to the eye.

Shooting way out there, no doubt much improved for vertical. The pointed bullets just shoot more consistently. Big change, no but it's the little bits of confidence that help me so I will continue to point.

I didn't notice a big change in my drop at distance but it was improved for the pointed bullets.
Jerry