Same bullet weight different bullet and POI

[mccraggen]

How much difference does it make if you use 2 different companies bullets yet identical weights?

 

[DrMike]

Point of impact can be changed significantly. Maximum chamber pressure can be raised or lowered significantly, and hence, velocity can be changed dramatically. Though weights may be similar (or even identical), metallurgy can differ, bearing surface can be quite different, etc.

Perhaps one would not have a significant difference; however, there is a good chance that a number of parameters will be changed in ballistic calculations.

 

[mjcmichigan]

I routinely see different POI if I switch bullet brands at same weight.

Also see this with boxed ammo. Dr. Mike listed a lot of the reasons. I’d add seating depth too.


Sent from my iPhone using Tapatalk

 

[c. schutte]

I can see different POI's using a different lot of the same thing. It would probably be an accident if two different bullets from two different manufacturers actually hit the same place and I can't ever remember it happening to me. I've used a lot of factory ammo over the years and it always means accounting for different types of ammo. Of course, having said this watch all the examples of those who have experienced it differently come in. :>)

 

[ethmoid1999]

I always back off the load I'm using when changing bullets and then work up. I have always seen a change in POI although some might be suitable for big game not suitable for a varmint rifle. In my limited experience, the change has been worse with small diameter bullets than in larger ones.

 

[Elkman]

Lots of difference, don't ever do it. My 300 WM puts 180 gr. Nosler Partitions several inches to the right of 180 grain Sierra. My Mashburn is not quite as picky but the difference can be measured in inches. I always practice with Sierra or Speer bullets, and then check my POI for the Noslers prior to hunting season

 

[ShadeTree]

I have an 06 that will amazingly put 150 gr speer hot cor's at virtually the same POI as 180 grain hornady's. On the other hand 180 grain Sierra's will impact significantly to the right of both. So yes, bullet design, bearing surface, etc, can and does at times change impact considerably.

 

[PJGunner]

The rifle, a Winchester XTR push feed with 24" barrel. It's pet load pushes the 150 gr. Sierra Game King at 2880 FPS and groups run .75" on average. For spits and grins I ran some 150 gr. Partitions with the same charge and no real change in POI. A six shot group, three Sierras and three Partitions made a one inch group. I shot the same sequence up at Raton New Mexico at +14* and no change in POI and groups still right at one inch. Brass was Winchester with standard WLR primers. Powder was the long discontinued WMR of which I have a large supply. I'll have to try them in a couple of other .270's I have to see if it'll hold true.
I have a good load for the .300 Win. Mag. using the 200 gr. Speer Hot Core. I just may try the 200 gr. Partition with that load in the .300. Powder is again WMR. Dunno why Winchester dropped it but it has been just about perfect in the .270 and .300 Win. mag. I just also found out it's a sleeper in the .280 Rem. yet will not work at all in the 30-06. By not work I mean crappy accuracy, erratic velocity and strange pressure problems. A long as it makes my .270, 280 aand 300 Win. happy, then I'm happy.
PB

 

[longrangehunter]

I've done it with 30/06 200 gr. Oryx's and 220 Woodleigh FMJ's; 375 H&H 300 TBC's and 300 FMJ's; 458 Lott 500 Speer AGS, and Woodleigh FMJ's.

Some can be done with the same powder, like the 30/06 and RL-22, IMR-4064 in the H&H, I'd have to look up which two I used in the 458 Lott, but I know it was VV N135 for the 500 Speer AGS.

Some if it is seating depth, and nothing in common with velocity. I just look for POI to form in the center bulls eye, and no matter what the velocity is just skip it and run with it!

 

[Charlie-NY]

You might be surprised at just how consistent different bullets of the same weight could shoot. I have a very accurate load for my 338RUM which I have been shooting at 400yds using a 250 AccuBond. I decided to give the Berger 250 Elite Hunter a try using the same load. The Berger has a longer boattail and sharper/longer nose profile. This makes the bearing surface shorter.
3 shots from each load at 400yds printed 2 overlapping groups. The Berger shot into a bit smaller group but not enough to pull me away from the 250 AccuBond which has been a reliable performer on game animals.

 

[NYDAN]

I have experienced vastly different P.O.I. within the same bullets weights.

I don't think I have the targets to prove it but I believe that I have different P.O.I. if I shoot from a dirty barrel that has been sitting for awhile vs a clear barrel. Well, I may have the targets if I look back through my notebooks. Why else would I believe that?

Dan

 

[Cleveland48]

I have had rifles that shot way different with different bullets of the same weight. I do have a 6.5 CM that shooting 120 TTSX at 2920 fps impacts exactly the same as my 140 gamekings at 2840 fps. This rifle actually shoots practically everything within an inch or two of each other, why I don’t know. This is the only rifle I’ve ever had do this, all my others sometimes have drastic differences in POI.


Sent from my iPhone using Tapatalk

 

[DrMike]

Each firing system (rifle, cartridge and components, shooter) is an entity unto itself. Certainly, there are exceptions to the rule. My 7RM will deliver both 175 grain Sierra GK and 175 grain Nosler PT to the same POI and at similar velocities. However, I nearly blew up a .356 when I had worked up a load with 250 grain Hornady IL and then tested a 150 grain ABW Kodiak. The fact that I had dropped back by 5% saved my bacon (and the rifle). The fact remains that there are usually enough variables that it would be most unusual for two bullets of similar weight to have the same POI.

 

[JD338]

I have found that the AB and BT loads in my rifles
can use the same powder charge but shoot to a different POI. In my 257 Roberts, the 100 gr BT, PT, and the 115 gr BT, PT all hit to less than an inch POI.
Every gun is different.

JD338

 

[SJB358]

I’ve messed with this a couple of years now since I use quite a few Bitterroots in different rifles. My plan is usually to work up a good accurate load with a Nosler, then keeping everything else the same, I use a BBC with the same charge. I don’t mess around any closer than 250 yards and would rather do everything at 300. I actually try to match the speed on the BBC to the Partition which seems to put them in the same group as Partitions at distance. I don’t have a ton of BBCs so I stole the load work up procedure from ol Bob Farese and Bill Steigers. As long as the rifle isn’t sick and completely fussy it hasn’t taken much work to get them working together. Most of the time the BBC takes a little less powder than a Partition since it has a pure copper jacket but otherwise Ballistically it is very similar out to 500-600yards.

 

[Desert Fox]

Very rarely you gonna find two different brand of bullet with the same weight that would have the same point of impact. Even the same brand but of different lot. In all my years of shooting I only experienced it once when I switched my 6MM Remington load of 87 grain Hornady Match with 87 grain Hornady V-Max. I didn't even bother to adjust the seating depth. My rifle didn't noticed the change at all.

 

[Polaris]

The difference can range from nearly insignificant to surprisingly large, and may change in both X and Y axis. The only way to find out what your particular combination will do is to load and test fire. As eluded to above, follow all applicable safety precautions, you are changing a component and may change internal ballistics into the red zone.

In general, I've found mostly small differences when changing similar styled bullets in a given weight. Would make a difference to a serious target shooter or perhaps on game at ranges in excess of 200 yards. The differences do seem to amplify with different bearing surfaces /profiles. For example, my M1 Garand shifts significantly to the right with a 150 gr Sierra FB spritzer vs. Hornady 150 FMJBT. Elevation difference is negligible to 200 yards, after that point, I suspect the external ballistics of these 2 loads would come into play and introduce some significant deviation. These 2 bullets have significant differences in profile and bearing surface. Happy shooting!