9mm 115 versus 147

[augdog]

Which of the two 9mm or 147 will have the higher POI at 7yds and 20yds

 

[DadSmith]

That depends on your sights. If you have fixed sights you will need to find the ammunition that shoots to the poi you desire. If you have an adjustable rear sight you can adjust it to the poi you want with whatever you are shooting.

 

[Twangbanger]

Are you trying to raise the poi of a fixed sight gun? The easiest way is to shoot them both and find out. I suspect the difference will be negligible, but actual shooting will tell you more than the internet ever will.

I wouldn't order a case of 147s until you know your gun will feed them.

 

[BugI02]

Using typical muzzle velocities for 115 grain and 147 grain and ignoring any velocity drop out to 7 yards, the 115 grain will drop 0.064 inches below bore axis while the 147 grain will drop an additional 0.02 inches due to its slightly longer time of flight

Reviewing some ballistic data, 9mm loses between 5 and 10% muzzle velocity by 25 yards. So using a 5% drop off as the average speed over the 20 yard interval as a back of the napkin estimate, the 115 grain would drop about 0.58 inches below bore axis at 20 yards. The 147 grain would drop about 0.766 inch below bore axis at 20 yds

Providing you did not introduce a parabolic path with sight adjustment, the 115 grain would always have a higher POI, with the difference being essentially unnoticeable at 7 yards but a bit more than 1/6 of an inch lower at 20 yds but still less than half the width of the bullet itself. All other things being equal, the 147 would almost go through the same hole as the 115

 

[Leo]

What about 124's ? They seem to shoot point of aim in anything I ever tried.

Are you an accomplished pistolero that holds tight groups at 20 yards? The bullet drop at 20 yards is less than most group sizes. When I was OCD about things, I had a Ransom rest for testing pistols. You could see bullet group drop with that, but free hand, not so much.

 

[rooster]

Without getting super scientific I would say drop out of a full size 9mm pistol is irrelevant up to at least 50 yards.

A quick google confirms that shooting a torso sized target gets you hits even at 100 yards without any holdover with 124’s.

9mm Ballistics Chart & Coefficient (Luger) GunData.org

This is a 9mm Luger ballistics chart (external) generated using our ballistic trajectory calculator. It tracks the movement of the bullet in zero wind conditions, and out to 100 yards. If you want to go further or apply wind resistnece then use custom seetings with our ballistic calculator. All...

gundata.org

 

[johntheplinker]

Another thing to take into consideration is barrel dwell time. A 147 will be in the barrel longer than a 115 so recoil and muzzle rise are more apt to cause it to print to a higher POI, in theory anyway. I haven't tested it but then again I'm not a good enough shot with a pistol to tell if it makes any difference.

 

[Bigtanker]

Another thing to take into consideration is barrel dwell time. A 147 will be in the barrel longer than a 115 so recoil and muzzle rise are more apt to cause it to print to a higher POI, in theory anyway. I haven't tested it but then again I'm not a good enough shot with a pistol to tell if it makes any difference.

I can verify this. I had a 3rd gen with fixed sights. It always shot 115 low. Switching to 147, it brought the POI up about 2 inches (@ 30 ft.) Still lower than the sights but the POI went up.

 

[johntheplinker]

I can verify this. I had a 3rd gen with fixed sights. It always shot 115 low. Switching to 147, it brought the POI up about 2 inches (@ 30 ft.) Still lower than the sights but the POI went up.

Thank you for confirming this. I usually shoot just one type of ammo at a time so next time out I may shoot some 115s then follow up with some 147s on the same target.

 

[KokomoDave]

147s sre generally subsonic so if you are running a suppressor , take that in account of no ballistic crack.

 

[Gingerbeardman]

This sort of thing is fascinating to me. So the bullet drop data seems to support the 147 impacting lower, but then the dwell time seems to support higher impact. Is that influenced by the shooter? Would shooting from a rest change the results?

My own two cents would be to shoot different weights, pick the one you prefer and then train enough to have poi where you want it. However, I love the scientific discussion!

 

[Trapper Jim]

Another thing to take into consideration is barrel dwell time. A 147 will be in the barrel longer than a 115 so recoil and muzzle rise are more apt to cause it to print to a higher POI, in theory anyway. I haven't tested it but then again I'm not a good enough shot with a pistol to tell if it makes any difference.

Yes this true. For me, and for the heavier bullet I prefer, A tailored cartridge to a gun with properly set up sights will print at 6 O’clock on a small target at 15 YDS. Fixed sights not regulated to this is a mis built gun and needs repaired to be right and I will not put up with a sub standard gun.

If we are using the adjustable sight model, the criteria is the same. For me to own, the rear adjustable sight will be all the way down and centered perfectly, along with the front sight of correct height and centered as well. Again, for a 6 O’clock hit on a 4 inch square at 15 yards.

I set my irons up on my rifles the same way except for 100 yard zeros. With a properly built gun, one has all the elevation room available for longer shots. And again, favoring the heavier bullets per caliber.

Being set up perfectly for me, this method allows enough sight adjustment to compensate for impact differences with lighter, faster loads.

In a perfect world quality gun manufacturers aim for this but in fact mis the mark in production as they know the return rate is low from a consumer pool. I have had to send a few S&W and Rugers in for factory correction and never have had to send in any CZ’s.

Service pistols are a different standard for gun makers as minute of man seems to be within specs.

Having said this, the optic nerve, brain routing and other contributors to eyesight to POI contains many variable among the race and will change in one’s lifetime.

For sight alignment, recoil, Ballistic performance and reliability, I would consider 147 first and work down in bullet weight from there For your sweet spot.

See you on the range,

Trapper

 

[gregkl]

I have loaded up all my 125 gr rounds and I have some 115gr projectiles. I have a load I have shot in the past but maybe I should try a few recipes to make sure they land at the same place as my 125's do.

I certainly don't want a round to land lower than my 125's. When I error, I am usually low.

 

[gmcttr]

Fed HST 124gr (12 shots) on left and 147gr (14 shots) on the right. Shot with a CZ P-10S, hands rested on a bag with a 6 o'clock hold at 50'. Cleary shows the 147's printing lower in this case. If you're going to talk barrel dwell time, you need to consider recoil impulse and things I don't know about as well.

 

[russc2542]

This sort of thing is fascinating to me. So the bullet drop data seems to support the 147 impacting lower, but then the dwell time seems to support higher impact. Is that influenced by the shooter? Would shooting from a rest change the results?

My own two cents would be to shoot different weights, pick the one you prefer and then train enough to have poi where you want it. However, I love the scientific discussion!

Yes.

It really comes down to testing your load in your gun in your hands. There's math, physics, and trends but it really comes down to how those things play together including (especially) the nut behind the wheel, in automotive terms.

 

[BugI02]

This sort of thing is fascinating to me. So the bullet drop data seems to support the 147 impacting lower, but then the dwell time seems to support higher impact. Is that influenced by the shooter? Would shooting from a rest change the results?

My own two cents would be to shoot different weights, pick the one you prefer and then train enough to have poi where you want it. However, I love the scientific discussion!

From a math perspective, the initial explosion of the powder and acceleration it imparts to the bullet is very chaotic. Most barrel dwell time formulas (which are predominantly used for rifles) only consider the final 85% (7/8ths) of the travel because that is thought to exclude the chaotic initial acceleration

That said, a typical 147 MV is 1000fps and a typical 115 is 1150fps (factory ammo).
even ignoring the chaotic part and utilizing the whole length of a 5 inch barrel (full size 1911) time to transit the barrel is .00042 seconds or so for 147 and .00036 for 115. Without digging into it mathematically a whole lot more I can't say for sure, but my quick and dirty approximation is that the bullet is long gone before any difference in force transmitted to your hand and arm can make a difference