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 POI difference between 55 gr. and 77 gr. 223 bullets
Putter  [Member]
12/14/2007 2:25:50 AM
My AR with a 16" barrel is zeroed at 50 yards, using a variety of different 55 grain .223 ammo (AE, XM193, etc.). I just tried a box of Black Hills blue box ammo with the 77 grain bullet and PPU with the 75 grain bullet, and was somewhat surprised that the point of impact was about 3"-4" lower at 50 yards than with the 55 grain stuff. I expected a lower trajectory, but this seemed kind of excessive. Is this normal, or is something wrong here?
Glacierwolf  [Member]
12/14/2007 2:51:46 AM
Putter,

Heavier bullets will always travel slower and arrive lower. What you saw was perfectly normal for a 50 yard sight in. If you sight in at 100 yards with the 55's you'll find they are a tad high at 50 and the heavier ones are about dead on. If you sight in at 200 with the 55's you'll find them still higher at 50, but, the heavier bullets will be very high and probably an issue.

Most 55's can reach published velocities in a carbine barrel - but - when you read the fine print all the heavier bullets are usually tested on a 20" or longer barrel. So, expect yours to be moving slower than expected - and they will strike lower than expected.

Those heavier bullets were not designed for carbines - they were designed for highpower rifle competition at 200, 300 and 600 yards in 20" barrels. Using them at 50 to 200yards is a waste of money. You won't get a tighter group with them at short ranges because of their design. The positive effects of the higher ballistic coefecients start to make a difference at 200 yards and you can really see the difference at 600.

If you want better stopping power at close range- consider the 55gr Nosler Ballistic tip. It flies really sweet and takes a deer in one round. I have done this. For smaller game - the 55 gr Sierra Blitz works great.

The back of most reloading manuals have all the tables for this, and, there are several computer programs that will help. However - it's all guess work unless you have a chronograph. I'm lucky - I've always had access to a 500 or 600 yard range and didn't need a chronograph to figue things out. But, if you only have a 50 or 100 range handy and need to get an accurate rate of drop at longer distances - you really need to know exactly how fast your bullets are traveling.

Hope this helps. Feel free to email if you have questions.
Putter  [Member]
12/14/2007 3:14:06 AM
That explains a lot. Thanks for the info!
JDW3646  [Member]
12/14/2007 4:52:37 AM
OK, I have a somewhat related question... My Colt has a 1-7 twist and everything I've read advises 62 gr bullets. I do most of my shooting within 50 yds. (that's where my rifle is zeroed at). How much difference would a 55 gr bullet make? The reason I ask is that the seem to be a little more readily available and cheaper.

Thanks,
JoshD  [Member]
12/14/2007 12:00:08 PM

Originally Posted By JDW3646:
OK, I have a somewhat related question... My Colt has a 1-7 twist and everything I've read advises 62 gr bullets. I do most of my shooting within 50 yds. (that's where my rifle is zeroed at). How much difference would a 55 gr bullet make? The reason I ask is that the seem to be a little more readily available and cheaper.

Thanks,


For all practical purposes, none. 95% of the ammo I shoot is 55grn and I also have a Colt 1/7. Most of my shooting is 50yds also due to that being the longest distance I have with basically 0 hassle, and I'm usually lazy
thanegrooms  [Team Member]
12/14/2007 12:17:56 PM

Originally Posted By Glacierwolf:
....... Using them at 50 to 200yards is a waste of money. You won't get a tighter group with them at short ranges ......





Umm... I'm gonna have to go ahead and disagree with you on that one.

In every 14.5" and 16" barrel I've shot, 75 & 77gr shoot a much smaller group compared to a 55gr or 62gr FMJ at 100 yards.
viator  [Team Member]
12/14/2007 12:39:53 PM

Originally Posted By Glacierwolf:

Heavier bullets will always travel slower and arrive lower.





This is not entirely accurate.

When barrel harmonics are factored in, one may find barrels that, at short to moderate distances, will shoot heavier bullets that impact higher than lighter bullets.

As a matter of fact, I have a couple of weapons that do just that.



It is also true that with some weapon platforms one should not be surprised to find that, at short to moderate distances, heavier bullets routinely impact higher that lighter bullets.

While this may at first appear to be counterintuitive, it does in fact occur. Assuming maximum loads, the heavier bullets tend to recoil more. The heavier bullets also tend to be slower. That means that the slower bullet is in the barrel for a longer time, thereby allowing the barrel to rise higher. The angle of the barrel is therefore at a higher angle when the bullet departs. So, the shots tend to impact higher.


I would never claim that heavier bullets always impact higher because of an individual barrel’s harmonics or a weapon’s idiosyncrasies. But sometimes they do. Like they say, you gotta shoot ‘em in your own weapon to find out.


And that is fun.









DevL  [Team Member]
12/14/2007 1:03:44 PM

Originally Posted By Glacierwolf:
Putter,

Heavier bullets will always travel slower and arrive lower. What you saw was perfectly normal for a 50 yard sight in. If you sight in at 100 yards with the 55's you'll find they are a tad high at 50 and the heavier ones are about dead on. If you sight in at 200 with the 55's you'll find them still higher at 50, but, the heavier bullets will be very high and probably an issue.

Most 55's can reach published velocities in a carbine barrel - but - when you read the fine print all the heavier bullets are usually tested on a 20" or longer barrel. So, expect yours to be moving slower than expected - and they will strike lower than expected.

Those heavier bullets were not designed for carbines - they were designed for highpower rifle competition at 200, 300 and 600 yards in 20" barrels. Using them at 50 to 200yards is a waste of money. You won't get a tighter group with them at short ranges because of their design. The positive effects of the higher ballistic coefecients start to make a difference at 200 yards and you can really see the difference at 600.

If you want better stopping power at close range- consider the 55gr Nosler Ballistic tip. It flies really sweet and takes a deer in one round. I have done this. For smaller game - the 55 gr Sierra Blitz works great.

The back of most reloading manuals have all the tables for this, and, there are several computer programs that will help. However - it's all guess work unless you have a chronograph. I'm lucky - I've always had access to a 500 or 600 yard range and didn't need a chronograph to figue things out. But, if you only have a 50 or 100 range handy and need to get an accurate rate of drop at longer distances - you really need to know exactly how fast your bullets are traveling.

Hope this helps. Feel free to email if you have questions.


The 77 and 75 grain ammo is the IDEAL general purpose defensive ammo ammo for carbines. First it is easily twce as accurate at ALL distances than 55 grain FMJ bullets. Second they offer ideal terminal performance on living tissue. The Nosler 55 grain, while EXCELLENT for a 55 grain ballistic tip exhibits its terminal permance in the first 6" of travel with only a small piece of the base travelling out to 11.5-12". If you dont mind the early primary wound channel that is great, but it offers poor results in very hard intermediate barriers like car doors and laminated auto glass. Only the small piece of the base of that bullet passes on after about 3" of tissue because of the bullet breaking up. Still, I would use a Nosler 55 grain or even a 55 grain Silvertip BT over an M193 round ANY day both for accuracy and terminal results.
Molon  [Team Member]
12/14/2007 1:39:34 PM


Originally posted by Glacierwolf:

Heavier bullets will always travel slower and arrive lower.



False. See Hatcher’s Notebook, particularly the chapter entitled “The Theory of Recoil” for an understanding of the interaction between bullet weight, bore dwell time, recoil and point of impact.







Originally posted by Glacierwolf:

If you sight in at 100 yards with the 55's you'll find they are a tad high at 50


False. 55 grain Sierra MatchKings fired from a 16” barreled carbine and zeroed at 100 yards will strike 0.67” low at 50 yards.











Originally posted by Glacierwolf:

If you sight in at 200 with the 55's you'll find them still higher at 50


False again. 55 grain Sierra MatchKings fired from a 16” barreled carbine and zeroed at 200 yards will be dead-on at 50 yards.










Originally posted by Glacierwolf:

If you sight in at 200 with the 55's you'll find them still higher at 50, but, the heavier bullets will be very high and probably an issue.



You just contradicted your first statement in which you said the “heavier bullets will always . . . arrive lower.”









Originally posted by Glacierwolf:

Most 55's can reach published velocities in a carbine barrel - but - when you read the fine print all the heavier bullets are usually tested on a 20" or longer barrel


Most (not all) published data for the muzzle velocities of 55 grain loads tends to be from 20”-24” barrels. No 55 grain load will reach the same velocity as a 20”-24” barrel when fired from a 16” carbine barrel.







Originally posted by Glacierwolf:

Those heavier bullets were not designed for carbines.


Some of the heavier OTM match bullets (eg Hornady 75 grain OTM T2) were designed specifically to work with AR-15 carbines.








Originally posted by Glacierwolf:

You won't get a tighter group with them at short ranges because of their design.



Here’s a 10-shot group fired from an AR-15 from only 100 yards using Hornady’s 75 grain OTM bullet.











Originally posted by Glacierwolf:

If you want better stopping power at close range- consider the 55gr Nosler Ballistic tip



Multiple sources have shown that the 75-77 OTM bullets have vastly superior terminal ballistics compared to 55 grain loads.



5.56 75 grain TAP gel shot





55 grain TAP gel shot






thanegrooms  [Team Member]
12/14/2007 1:55:19 PM
Ta-Da!!! Molon to the rescue!!!!!



Thanks Molon!
Rmplstlskn  [Team Member]
12/14/2007 3:12:38 PM

Originally Posted By Molon:
5.56 75 grain TAP gel shot


Hit at center mass, this is most assuredly a KILL SHOT, probably instantaneously, before they hit the ground.

Rmpl
Glacierwolf  [Member]
12/14/2007 3:18:53 PM
Everyone is right - and - eveyone is still a bit wrong here. LOL. Factory ammuniton bullet accuracy shot from the same rifle is dependent on the commercial load, how it is assembled, and a little less on the component tolerances.

One of the first laws of physics is objects in motion tend to stay in motion. 50 yards is not enough time/distance for any high velocity bullet to show it's true colors. What looks great at 50 yards can give a 18" group at 500. The only way you can determine if a load is accurate without papering it from 50-600 yards is a chronograph where a mean difference of +/- a few fps is ideal and greater than +/- 30fps garbage.

Since each manufacturer has their own costs to incure they make 'deals' on powder and other components - this is pretty self explainatory why Brand X bullets might perform better than Brand Y in your rifle - but not well in your buddies. Internal ballistics is whole new world. The study of this difference is not worth going into for 50 yard shooting.

The biggest difference people will find - especially in military ammo - is the assembly process. Match shooters will ignore some lots and years of Lake City ammo while some lots and years are highly coveted. Lake City re-machines on a set schedule where ammo produced on the new machines have a very small coaxal difference and as the equipment gets older - the coaxal difference becomes much larger giving larger/worse groups.

Coaxal difference is the one thing as a shooter you can control in factory ammo. Ever shoot a near perfect target and get a flier? You fired exactly like all the rest - and no idea how this one strayed into the 7 ring? Coaxal difference. Grab 100 rounds of ammo and measure them on a coaxal gauge and they create a bell curve with 5 rounds at .001", about 18 at .001 to .003, and open up to .005 to .009 and last you'll find some at .018 to .036 difference in how uniform they are seated in relation to the brass. The latter ones are your fliers. If you can just eleminate the latter ones - you'll be happy........... save the .001's for your 600 yard string, next best for 300 and leave the worst for 200.

The relative power of your ammo is measured in foot pounds of energy, bullet weight x speed. If you increase the bullet weight but drop the speed - it's all the same. So a cheap 55gr moving at normal speed has the same energy as an expensive heavier bullet moving at slower speed. Although the heavier bullets are more streamlined and fly with less friction - this advantage doesn't become useful until 200+ yards have passed.

There are four trains of thought on 223 ammo. One is long range highpower rifle shooting 200,300 and 600 yard competition. Then tactical close combat at short distances. Hunting small and medium size game brings in different factors, and last subsonic shooting designed for suppressor use. You cannot take a factor from one of the four types of shooting and bring it into another without blending/merging the good and bad in all the factors.

Those 77gr and 80gr rounds are the heavest and best flying of the 223 family - but - they were designed for single loading at 600yard prone shooting in highpower - if you squish them in so they will fit into the mag you'll get inconsistant ignition...... but it won't be noticeable at 50 yards. Although it might be dangerous. Obviously single loading isn't gonna cut the mustard in tactical shooting - but - might not be an issue if you are deer hunting, have that heavy bullet as a good first round with normal rounds as a follow up if needed.

I fire allot of rounds a month and supervise others shooitng more. I have some ammo for tactical practice, other for subsonics, others for long range, and still others for hunting - but the most important ammo I use is the economical stuff for teaching beginers and punching paper at 100 yards. I have some wonderful rifles and great optics - at that short a distance all factory ammo produces an accurate group for me - just some groups are a bit higher or lower from one brand to another.

What is a huge factor - if you like shooting 55's you'll find sending the ocassional 75gr down range annoying because they fly so much lower compaired to the lighter bullets. If you like 55's then use 68's/69's and you'll be able to wrap your brain around the difference. If you like the 75's then adopt 68/69's or 62gr/green tips as your close in round or economical round.

In rifle I started out as a highpower M1a shooter - 7.62mm/308 Win - 30 years ago. This proved a huge help in Alaskan hunting for me. Kept a Mini-14 in my boat, but, only because I didn't mind loosing it overboard. After facial surgery the military doc's prohibited me from rifle shooting for a year or two - yeah right, - started using a mouse gun a few months after surgery because it was a lower recoil rifle or nothing. 7.62mm shooting is all cut and dry - but - back then the M16 was just starting to make a come back with heavy barrels, faster twists, heavier bullets. Lots of rumors. Lots of mis-information. Mythbusters could spend a whole episode on the M16/M4 rifle. It's important to keep two trains of thought when discussing ammo. First, even a blind squirrel will find an acorn now and then. Meaning sometimes the improbable will work well. Second, exterior ballistics is an exact science. On those few ocassions where the improbable works for you -or you claim Brand X does this or that in your rifle - it's not 'golden information' or useful to anyone else unless it can be reproduced for others to use.

This is where the chronograph becomes so important. One person't experience with an old washed out barrel will be different from someone with a new barrel...... and everything in between like barrel length, manufacturer, tolerances, and age of the equipment that produced the barrel. Unless you know how fast your bullet is traveling, and, what the difference is between travel speed of each round....... you can't prove a damn thing. It's a science thingie.

Last, but not least. You do not want to use any sort of special round or bullet for home or personal defense. Not unless it has a name like Federal's "Personal Defense" or Glaser "Safety Slug". Wound or kill someone in self defense the police may clear you of all wrong doing - but - the survivor or their family can always press civil charges. Use any kind of special round and they will paint you as a vigilante looking to kill somone. Use handloads and you'll be made to look like a killer wannabe not happy with the lethal capacity of 'normal' ammo - a mad scientist hell bent on concocting exceptionally deadly munitions.

Bottom line. Using expensive long range match ammo for 50 yard tactical shooting is like giving grandma a Porche so she can visit the neighbors. You can do it and it might impress your neighbors - but unless you've got tons of money to burn - why do it?

Kevin

Charging_Handle  [Team Member]
12/14/2007 4:11:49 PM

Last, but not least. You do not want to use any sort of special round or bullet for home or personal defense. Not unless it has a name like Federal's "Personal Defense" or Glaser "Safety Slug". Wound or kill someone in self defense the police may clear you of all wrong doing - but - the survivor or their family can always press civil charges. Use any kind of special round and they will paint you as a vigilante looking to kill somone. Use handloads and you'll be made to look like a killer wannabe not happy with the lethal capacity of 'normal' ammo - a mad scientist hell bent on concocting exceptionally deadly munitions.


I disagree with this completely. I'm going to use the best ammunition available to me and not compromise on performance because of this Massad Ayoob type rubbish about civil charges. If someone is worth shooting, they are worth shooting twice. And if shot, they should be shot with good ammo.

I have no problem using 5.56mm TAP. First of all, if a shooting occurs, ammo probably isn't going to be an issue of concern anyway, only the circumstances behind it. I keep hearing people harp about this sort of thing but have NEVER seen a single example given of where using high performance ammo resulted in a successful civil case for the bad guys. Not one.

If there is a need to fire in defense of my life, worrying about a civil trial due to ammunition choice is the last of my worries. My immediate and most important priority is surviving the gun fight. That's why I use an AR carbine for home defense. And that's why I load it with quality OTM loads that offer good terminal ballistics. If my situation justifies me in using lethal force, it makes no difference whether the tool I use is an AR loaded with dum-dum rounds, a .38 special, a knife, a baseball bat or a bastard sword. Lethal force is lethal force. And justified is justified.

And if some schmuck tries to paint me as a "vigilante" and bring me to civil trial over such bullshit, then my defense will be the ammo in question is the same used by many police departments all across this nation.
Glacierwolf  [Member]
12/14/2007 4:42:15 PM
That makes the point. Use the same ammo as your local police and military.

Unfortunatly, I grew up in Massachussetts before entering the military. There was a civil case in the early 1970's where a guy used a hollow point 357 to defend himself in his house. They raked him through the coals in the newspapers because of the 'magnum' designation of the round. Back then - police only had 38 specials.

Shortly aftert this in Mass was the guy who defended his friend at his friends house. This is what created the 'home is your castle' rule'. He was found 'at fault' by a fjury because he wasn't at home when he defended his friend.

Defending your home needs to take into consideration your house's construction and the effect of rounds leaving the dwelling striking neighbors. If you just bought the rifle, ammo, and have no training - no problem. What's your game plan when a round leaves your home and enters a kid's bedroom next door? Then they tout your military record, experience, and all that range time? They read your online postings. In a criminal court it's a shadow of a doubt - BUT - in a civil court it's a 'preponderance of evidence' 49% to 51%. Only have to show - not prove - you might have had an idea - or a common person might have had an idea - the rounds could leave your home and strike others. And you are toast.

Sad day in American. I'm begining to think the ideal defensive weapon is going to become the Lady Wession in Paris Hilton pink.
phoenix27  [Member]
12/14/2007 7:46:21 PM
Some interesting stuff...still, I like those 77-gr rounds.
AR15fan  [Team Member]
12/14/2007 8:07:13 PM
My 20" 1:9 is zeroed for POA at 100M. With 77GN Nosler it hits about 5" low and 3" Right at the same range.
texasyid  [Member]
12/23/2007 7:22:34 PM
My own non educated experience. Colt 6920 shoots tap 75 gr. .223 and 5.56 high about 3" at 100 yds. Black hills 77gr match is dead on remington 55gr .223 is about 5" low at 100yds.
DevL  [Team Member]
12/24/2007 5:19:47 AM

Originally Posted By Glacierwolf:
The relative power of your ammo is measured in foot pounds of energy, bullet weight x speed. If you increase the bullet weight but drop the speed - it's all the same. So a cheap 55gr moving at normal speed has the same energy as an expensive heavier bullet moving at slower speed. Although the heavier bullets are more streamlined and fly with less friction - this advantage doesn't become useful until 200+ yards have passed.

There is a HUGE difference in terminal effects at ALL ranges. Thats why we shoot the heavy OTM stuff. Energy does not incapacitate targets... only tissue damaged matters.

Those 77gr and 80gr rounds are the heavest and best flying of the 223 family - but - they were designed for single loading at 600yard prone shooting in highpower - if you squish them in so they will fit into the mag you'll get inconsistant ignition......

You better share this genious with the guys in Iraq who are issued 77 grain mag fed ammo and are killing people every day with it... they need to know they will have inconsistant ignition. Tell that to the people who shoot Balck Hills 77 grain every day with fantastic results while you are at it.

What is a huge factor - if you like shooting 55's you'll find sending the ocassional 75gr down range annoying because they fly so much lower compaired to the lighter bullets. If you like 55's then use 68's/69's and you'll be able to wrap your brain around the difference. If you like the 75's then adopt 68/69's or 62gr/green tips as your close in round or economical round.

2" at 100 yards is not that much of a difference... most people can deal. Some barrels have harmonics that can have even less shift.

Last, but not least. You do not want to use any sort of special round or bullet for home or personal defense. Not unless it has a name like Federal's "Personal Defense" or Glaser "Safety Slug". Wound or kill someone in self defense the police may clear you of all wrong doing - but - the survivor or their family can always press civil charges. Use any kind of special round and they will paint you as a vigilante looking to kill somone. Use handloads and you'll be made to look like a killer wannabe not happy with the lethal capacity of 'normal' ammo - a mad scientist hell bent on concocting exceptionally deadly munitions.

You have a vivid imagination... care to share these court cases with us? We also have laws against such nonsense in Texas... the family cannot sue here for any reason if it is a justified shooting.

Bottom line. Using expensive long range match ammo for 50 yard tactical shooting is like giving grandma a Porche so she can visit the neighbors. You can do it and it might impress your neighbors - but unless you've got tons of money to burn - why do it?

Kevin



This about the most backward response I have seen on this forum in a while. We use the heavy OTM ammo for its terminal effectiveness both on clothed or light barrier covered targets. You are suggesting that ammo known to have late yaw cycles or shallow penetration, poor penetration of intermediate barriers, etc. are just as good because they are "the same energy" which is beyond ridiculous and is the hallmark of someone with no knowledge of wound ballistics.

We do not shoot this stuff at 50 yards for PRACTICE. We ensure our 75 and 77 grain ammo will be reliable and shoot for groups at 100 yards or more. The rest is saved up or set aside for defensive purposes. We usually sight in for the defensive ammo as the POI difference for 50 yards and in is negligable when shooting the cheap stuff. I use 55 grain ammo for full auto or close range practice and have no noticable POI differences that are even worth mentioning.

There are entire organisations who do nothing but try to dispell these false misconceptions you are trying to perpetuate. Please go to tacticalforums.com and make a post in the terminal effects section that reads "Why heavy match ammo is not needed for 50 yard tactical shooting" and try to say light ammo has the same energy as heavy amtch ammo... it will be an eye opening experience. It may not be stuf to use for 50 yard PRACTICE but it IS what you should use for 50 yard tactical shooting.