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 POI change between 180gr and 150gr bullets?
#4897678
01/09/14 01:25 AM
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Joined: Sep 2009
Posts: 1,403
tx outlaw
OP
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My .30-06 was sighted in for 180gr Core-Lokts, but I have recently decided to switch over to the 150gr Core-Lokts. How much of a POI shift should I expect to see and is there a particular direction I can expect the POI to move? Asking because I may not have time to go re-sight in my gun before my next hunt. If there is a possibility of a big change in POI, though, I will make time to get to the range between now and then.
Thanks.
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4897686
01/09/14 01:28 AM
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Joined: Dec 2008
Posts: 41,179
J.G.
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Down and right is my prediction. Heavier bullet, leaving slower.
I would definitely re-zero!
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4897689
01/09/14 01:30 AM
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Joined: Apr 2007
Posts: 60,489
BOBO the Clown
kind of a big deal
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kind of a big deal
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Could be a bunch, 150's will shot much lower most likely. Need to re sight in. Remember when sighting in you want to chase the bullet. Bullets hits 3" below the bull you want to dial to the bullet hole
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4897691
01/09/14 01:30 AM
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Joined: Aug 2008
Posts: 769
wetduck
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Tracker
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never know till you you shoot them for certain. i would buy a box of 180 just to make sure
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4897692
01/09/14 01:31 AM
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Joined: Dec 2009
Posts: 712
Wader
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Shoot 'em and find out. Of my two 30-06s one will not shoot for crap with 150gr bullets, but 180s rock.
-ww
A thousand reasoned opinions never equal to one case of diving in and finding out.
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Re: POI change between 180gr and 150gr bullets?
[Re: Wader]
#4897751
01/09/14 01:58 AM
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Joined: Dec 2008
Posts: 41,179
J.G.
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Shoot 'em and find out. Of my two 30-06s one will not shoot for crap with 150gr bullets, but 180s rock.
-ww It probably has a 1:10" twist rate.
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Re: POI change between 180gr and 150gr bullets?
[Re: J.G.]
#4897879
01/09/14 02:47 AM
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Joined: Dec 2010
Posts: 38
drake_taker
Light Foot
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Light Foot
Joined: Dec 2010
Posts: 38 |
Assuming all things otherwise are equal....which we shouldn't.......but...
If you sighted your rifle at 100 yard, with a scope height of 1.5 inches over bore, using a 180 gr bullet at 2700 fps:
Without adjusting your scope, and holding the crosshairs on the target at 100 yards:
A 150 gr bullet traveling 2900 fps would strike 0.3 inches above point of aim at 100 yards.
At 125 yards, the 150 gr bullet would hit at the crosshairs, while the 180 gr bullet would hit 0.5 inches low.
At 200 yards the 150 would drop 1 inch less (hit higher) than the 180 gr (3.2 inches vs 4.2 below crosshairs)
at 400 yards the 150 would drop 1.6 inch less (hit higher) than the 180 (33.5 inches vs 35.1 below crosshairs)
Last edited by drake_taker; 01/09/14 02:50 AM.
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Re: POI change between 180gr and 150gr bullets?
[Re: BOBO the Clown]
#4898221
01/09/14 05:07 AM
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Joined: Dec 2010
Posts: 8,841
DocHorton
THF Trophy Hunter
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Could be a bunch, 150's will shot much lower most likely. Why would it hit lower? It will be traveling faster and a lighter bullet....wouldn't it drop less at a given distance? My guess is it would hit higher than the 180's at distance.
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4898310
01/09/14 10:10 AM
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Joined: Jun 2006
Posts: 8,342
Dave Davidson
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Without a sense of urgency, nothing ever happens.
Boy, if I say "sic em", you'd better look for something to bite. Sam Shelley, Rancher Muleshoe Texas 1892-1985 RIP
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Re: POI change between 180gr and 150gr bullets?
[Re: DocHorton]
#4898313
01/09/14 10:47 AM
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Joined: Sep 2006
Posts: 32,516
kmon11
junior
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junior
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Could be a bunch, 150's will shot much lower most likely. Why would it hit lower? It will be traveling faster and a lighter bullet....wouldn't it drop less at a given distance? My guess is it would hit higher than the 180's at distance. quit guessing and go try it, in most cases I have seen the same as what Bobo wrote. the slower heavier bullet will have more recoil than the lighter bullet and be in the barrel for more time for the recoil to have an effect on the bullet path.
Last edited by kmon1; 01/09/14 10:53 AM.
lf the saying "Liar, Liar your pants on fire" were true
Mainstream news might be fun to watch
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Re: POI change between 180gr and 150gr bullets?
[Re: DocHorton]
#4898399
01/09/14 01:05 PM
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Joined: Dec 2008
Posts: 41,179
J.G.
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Could be a bunch, 150's will shot much lower most likely. Why would it hit lower? It will be traveling faster and a lighter bullet....wouldn't it drop less at a given distance? My guess is it would hit higher than the 180's at distance. He had a typo? 
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4898477
01/09/14 02:04 PM
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Joined: Sep 2009
Posts: 18,954
ChadTRG42
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If there is a possibility of a big change in POI, though, I will make time to get to the range between now and then. This^^ Go re-verify your zero. It could easily be a few inches off. POI shift vs bullet trajectory are 2 different things. In my experience, the lighter bullets have a POI shift higher than the heavier bullets, and to one side. But unless someone knows the exact barrel harmonics of your barrel, it's simply a guess. Go shoot it to know.
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4898883
01/09/14 04:25 PM
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Joined: Aug 2010
Posts: 1,147
RickC
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If I didn't have time to re-zero, I would continue to shoot 180 until I had the opportunity to sight in 150s. you may find your rifle doesn't like the 150s as previously stated.
NRA Life Member
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4899079
01/09/14 05:38 PM
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Joined: Sep 2011
Posts: 1,756
okjhutch
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i have heard and read that the .30-06 was original designed to shoot the 180 gr, so i am guessing for the most part stick with the 180's but i know every rifle and people are different and it may like the 150's you just need to make time to shoot both and evaluate. I have tryed this with the 2 i had and they both like the 180's best, and they were much easier to find anywhere i went, i dont remember the drop of drift, its been alot of years since then. good luck
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Re: POI change between 180gr and 150gr bullets?
[Re: kmon11]
#4899102
01/09/14 05:48 PM
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Joined: Dec 2010
Posts: 8,841
DocHorton
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Could be a bunch, 150's will shot much lower most likely. Why would it hit lower? It will be traveling faster and a lighter bullet....wouldn't it drop less at a given distance? My guess is it would hit higher than the 180's at distance. quit guessing and go try it, in most cases I have seen the same as what Bobo wrote. the slower heavier bullet will have more recoil than the lighter bullet and be in the barrel for more time for the recoil to have an effect on the bullet path. Interesting....Fireman, Chad and myself predict the 150's will hit higher and Bobo and Kmon predict they will hit lower than the 180's. I admit I don't fully understand all of the physics behind bullet ballistics but I can't see how a heavier, slower object will not drop faster out of the barrel of a gun. I know in my other rifles the heavier grain bullet typically drops more quickly. I'm curious to see the actual results.....
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Re: POI change between 180gr and 150gr bullets?
[Re: DocHorton]
#4899131
01/09/14 05:58 PM
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Joined: Dec 2006
Posts: 766
beech96w
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I admit I don't fully understand all of the physics behind bullet ballistics but I can't see how a heavier, slower object will not drop faster out of the barrel of a gun. I know in my other rifles the heavier grain bullet typically drops more quickly.
Ignoring BC and SD... The force of gravity is constant. A 150 and 180 will drop the same in a given ammount of time. The 180gr projo will leave the muzzle slower, and take longer to get to the impact point. More time... drops further.
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4899137
01/09/14 06:00 PM
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Joined: Sep 2009
Posts: 18,954
ChadTRG42
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Doc, remember, POI shift is totally different than the trajectory. If the 180's are sighted in at 100 yards, the 150's (I'm predicting), will have a POI shift high, and to one side. This has to do with the barrel harmonics, not trajectory. It is simply a POI shift due to the different bullets being used.
Now, the 150 will shoot flatter at a given distance than the 180 (if both are pushed to top speeds).
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Re: POI change between 180gr and 150gr bullets?
[Re: ChadTRG42]
#4899163
01/09/14 06:13 PM
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Joined: Dec 2010
Posts: 8,841
DocHorton
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Doc, remember, POI shift is totally different than the trajectory. If the 180's are sighted in at 100 yards, the 150's (I'm predicting), will have a POI shift high, and to one side. This has to do with the barrel harmonics, not trajectory. It is simply a POI shift due to the different bullets being used.
Now, the 150 will shoot flatter at a given distance than the 180 (if both are pushed to top speeds). That makes sense.....I am thinking trajectory and I guess the 150 will drop less at a certain distance because it is lighter and faster but not necessarily equivalent to POI shift because of barrel harmonics. By the way....the .308 subs you loaded for me are awesome and shoot great! Super quiet with my can!
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Re: POI change between 180gr and 150gr bullets?
[Re: J.G.]
#4899227
01/09/14 06:40 PM
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Joined: Apr 2007
Posts: 60,489
BOBO the Clown
kind of a big deal
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kind of a big deal
Joined: Apr 2007
Posts: 60,489 |
Could be a bunch, 150's will shot much lower most likely. Why would it hit lower? It will be traveling faster and a lighter bullet....wouldn't it drop less at a given distance? My guess is it would hit higher than the 180's at distance. He had a typo? Nope. Did same thing with my old 300win mag two months ago Same thing happens with my 257wby(115/110/100/80), 243(80/100), 25-06(100/115) and 270wsm(130/150) i shot two weeks a go. Heavier hits higher. 100tsx and 80gr tsx two in vertical, inch vertical for 110ab and 100 tsx/sp.
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4899292
01/09/14 07:05 PM
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Joined: Feb 2010
Posts: 447
Strongbad
Bird Dog
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Bird Dog
Joined: Feb 2010
Posts: 447 |
It's not about the drop. It's about the arc. The 180's will be higher at 100.  Decided to edit and elaborate. Obviously gravity is a constant. Here's where it should start to make sense. If you're zero'd at 100, with the 150's for example, your bore should not be level with the bullseye at 100. If it was, you'd miss it every time. The time to target, however small/slight will still result in the bullet dropping. The bore must be aligned higher than the bullseye, creating an angled trajectory/arc. The 150's will get to the target faster... resulting in a shorter less pronounced arc. The 180's will be slower, resulting in a longer more pronounced arc. This changes as the range increases of course, but generally speaking for rifles at 100 yards the above will be the case. The same thing happens with pistols at short range.
Last edited by Strongbad; 01/09/14 07:32 PM.
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4899488
01/09/14 08:18 PM
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Joined: Aug 2011
Posts: 545
Loaded
Tracker
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Tracker
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Posts: 545 |
A heavier bullet leaving the barrel slower can also leave later in the recoil impulse, meaning the barrel may have risen ever so slightly more with the heavier bullet than the lighter one at the moment the bullet leaves it. This could mean a higher POI for the heavier bullet.
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4899492
01/09/14 08:21 PM
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Joined: Apr 2007
Posts: 60,489
BOBO the Clown
kind of a big deal
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kind of a big deal
Joined: Apr 2007
Posts: 60,489 |
I have no idea why just reporting my experience
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Re: POI change between 180gr and 150gr bullets?
[Re: Strongbad]
#4899531
01/09/14 08:37 PM
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Joined: Dec 2010
Posts: 8,841
DocHorton
THF Trophy Hunter
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It's not about the drop. It's about the arc. The 180's will be higher at 100. Decided to edit and elaborate. Obviously gravity is a constant. Here's where it should start to make sense. If you're zero'd at 100, with the 150's for example, your bore should not be level with the bullseye at 100. If it was, you'd miss it every time. The time to target, however small/slight will still result in the bullet dropping. The bore must be aligned higher than the bullseye, creating an angled trajectory/arc. The 150's will get to the target faster... resulting in a shorter less pronounced arc. The 180's will be slower, resulting in a longer more pronounced arc. This changes as the range increases of course, but generally speaking for rifles at 100 yards the above will be the case. The same thing happens with pistols at short range. So based on what you are saying.....for the arc the 180's may be higher at 100 but would eventually "catch up" and drop below the arc of the 150's at some point? Like maybe the 180 is 2" high at 100, 1" high at 175, even at 250, and starts dropping below past that? Or will the 180 arc always be above the 150? Just trying to understand how it works....
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4899551
01/09/14 08:49 PM
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Joined: Apr 2007
Posts: 60,489
BOBO the Clown
kind of a big deal
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kind of a big deal
Joined: Apr 2007
Posts: 60,489 |
Doc, lets just go to elm fork tomorrow and see what happens
I need to shoot my 243 on last time before I send it to the hack shop
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Re: POI change between 180gr and 150gr bullets?
[Re: tx outlaw]
#4899552
01/09/14 08:49 PM
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Joined: Dec 2010
Posts: 492
Time Killer
Bird Dog
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Bird Dog
Joined: Dec 2010
Posts: 492 |
He never said the distance, did he?
So, who knows. Haha
Shooting 800 yards and 100 yards will likely give us a different answer..
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