what does ammo do?

[omega21]

So I have some ammo questions that are driven by my general lack of technical knowledge in this area. I purchased a KAC LPR and am now thinking about what optics and ammo to purchase for a 300-500 meter shooting session. Obviously the scarcity of ammo these days makes this a little more challenging, but so does my ignorance in this area.

I understand the inverse relationship between barrel twist rate and bullet weight. The 1:7 rate on the LPR is a better match for heavier bullets in the 69-77 gr range. Although this makes me ask, why is standard mil issue ammo 62 gr then?

So I’m looking to get some match 77 gr ammo and most of what I am finding is .223 not 5.56. The 5.56 match ammo I’m finding is in the 62 gr range. The LPR is chambered for 5.56 so wouldn’t putting in .223 ammo negate any advantage I have with the heavier 77 gr ammo? (Because I am assuming .223 wont seat exactly right in the 5.56 chamber)

So am I better off going with 62 gr weight but a 5.56 case, or can I “settle” for a .223 case with the heavier 77 gr round? I guess the basic question is what contributes/detracts more from long range accuracy – chamber to case fit or bullet weight.

I realize this may be an academic discussion as “effect size” of 77 vs 62 gr or .223 in a 5.56 chamber may be negligible at 500m. Fundamentals like the shooter and quality of ammo and optic probably have more to do with it, but I am curious as I want to buy some ammo now and spending all my money on the LPR doesn’t leave me with much left over for ammo at this point.

[ForTehNguyen]

its best to try out a variety of brands and weights. Each gun shoots different and performs better with certain loads. For my Remington 700 I bought about 10 boxes of various match ammo to try out and I eventually decided on one based on price and performance.

[bp7178]

Twist works to stabilize bullets. Faster twist rates stabilize longer bullets, which may or may not be heavier. The 1-7 twist is meant to stabilize the very long tracer bullets. 1-7.7 is the optimal twist for 77gr projectiles.

There are generally no differences in the cases between 5.56 and .223. There can be a slight capacity difference, but this would effect re-loaders, not so much you and your question.

5.56 has a greater peak pressure and will generate slightly more velocity. This will give you less drop at longer ranges, and very slightly longer fragmentation ranges.

You are better off getting more accurate ammo, then worrying about all of that. Generally speaking, two loads one at 5.56 and the other at .223, the .223 will have a slight nudge in the accuracy department.

If I were you, I would buy some factory loaded rounds that use the 77gr. SMK bullet and see where you are at.

[Airhasz]

Shoot a variety of .223/5.56 ammo and see where you are at, as others have stated.

[Failure2Stop]

The LPR generally performs the best with high quality match grade .223.



Typos brought to you via Tapatalk and autocorrect.

[omega21]

ok, I posted in the technical discussion forum because I want more detail and info then "Shoot a variety of .223/5.56 ammo and see where you are at..." but thank you.

bp7178 - you say that "There are generally no differences in the cases between 5.56 and .223." You are correct - I misspoke in my OP and really meant to convey that the chambers are cut differently between these two calibers.

Failure2Stop - you are saying that the LPR performs best with .223. Is that because it doesn't have a "true" 5.56 chamber? A 5.56 chamber has a longer leade than 223 so rifling engagement is not as immediate. Is the chamber in the LPR cut with better proximity between the mouth of the cartridge and the point at which the rifling engages the bullet (since it's a match barrel)? So the bullet has to 'jump' less before engaging the rifled portion of the barrel. Not asking you to give away any trade secrets ;)

[bp7178]

There are quite a few chambers designs that are safe for 5.56 without any inherent accuracy loss. The 5.56 SAM-R, .223 Wylde, Noveske's NMod0, etc.

IIRC the LPR uses a Kreiger made barrel, but I don't know who does the final turning.

From KAC's site,
The LPR utilizes an 18” Match Stainless Steel barrel with a Custom Match chamber

So realistically, its some version of a .223 but 5.56 safe chamber.

You are very much splitting hairs when worrying about the downrange difference between the two.

If you have a rifle that is safe to shoot 5.56 with, as yours seems to be, for short range blasting ammo you'd be well served with some XM193.

If you are trying to develop your marksmanship skills, I would buy as much .223 pressure 77gr Sierra BTHP loaded cartridges that I could. Measure and record your group sizes. When you are consistent the numbers will show it, regardless of the maximum possible smallest group, which for 300-500m will more than likely be with a 77gr bullet.

After you achieved consistent results, spread some money around and try different stuff.

More Indian less arrow.

[Magelk]

.

There are generally no differences in the cases between 5.56 and .223. There can be a slight capacity difference, but this would effect re-loaders, not so much you and your question.


.
There really isn't. At least not between 5.56 and .223. I've weighed hundreds of cases and have never found a difference between them although there are still tons and tons of people who believe it. I even had one jackass tell mee he could tell the weight difference in his fingers between lake city and 223 stuff.

OP, this is an ok read about 223 vs 5.56 http://www.luckygunner.com/labs/5-56-vs-223/

[omega21]

OK, took your advice and ordered some Hills Ammunition 223 77 Grain and 69 Grain Sierra MatchKing Hollow Point and some Colt Match Ammunition 5.56 55 Grain Sierra MatchKing HPBT, and some Federal 77 grain Gold Medal Match Sierra Matchking BTHP and lastly some ADI OutBack 69 Grain BTHP Sierra Matchking Ammo. Let's see how it goes. Thanks for all the feedback. Oh, one more question! Why are there ammo choices with only a few grains of difference in the bullet weight? I saw 69 gr and 68 gr of the exact same ammo. Same with 77 gr and 75 gr. Are these weights specific to certain barrel types? Thanks!

[omface@yahoo.com]

5.56 is a very popular round. That is because of its accuracy and magazine capacity. Once the military switched to 1:7 in order to improve results of the tracers others followed soon to test the range. Some small differences are just because of different manufacturers. Keep in mind mil rounds have steel penetrators 62gr so the same size round in lead is 68-69gr depending how the jacket is made. Others are hollow points for aerodynamics some have plastic tips to do that. Others are boat tailed to make them more stable. Depending on your twist rate, barrel length, gas system, distance shooting and purpose you might choose a specific type. If you need to knock down metal targets with 55.6 then go with a 75gr Sierra if your doing target practice at the range stick to 68 either fmj or spire point or soft point. The best way to tell what you need is a controlled test fire at whatever desired range and target. Then choose the best.

[omface@yahoo.com]

Also different bullet manufacturers have online apps that can show you the accuracy of different rounds being shot from various rifles. Most you can adjust range and conditions. Winchester has one for the IPhone that works well. I like using it to test my own accuracy and reloads.

[WC 2-3]

The reason you saw 68, 69, 75 and 77 grain bullets is because those are different bullet manufacturers. Nosler and Sierra match bullets are 69 and 77. Hornady is 68 and 75.

[bp7178]

OK, took your advice and ordered some Hills Ammunition 223 77 Grain and 69 Grain Sierra MatchKing Hollow Point and some Colt Match Ammunition 5.56 55 Grain Sierra MatchKing HPBT, and some Federal 77 grain Gold Medal Match Sierra Matchking BTHP and lastly some ADI OutBack 69 Grain BTHP Sierra Matchking Ammo. Let's see how it goes. Thanks for all the feedback. Oh, one more question! Why are there ammo choices with only a few grains of difference in the bullet weight? I saw 69 gr and 68 gr of the exact same ammo. Same with 77 gr and 75 gr. Are these weights specific to certain barrel types? Thanks!

I'm going to bet the FGMM and BH will be the most accurate. If you're testing at 100 yards, the 69gr may have a slight nudge. At your requirement of 300-500, the 77gr. will buck the wind better.

Small differences, ie 69gr. vs 68gr., the 69gr. is a Sierra bullet, the 68gr. is a Hornady. But be advised, there are over seas manufacturers that list the same weights, but they aren't as consistent.

I had developed a load with 55gr. Hornady FMJ-BT bullets that was amazing. Just switching to Priv Part. 55gr. and it went from hovering around 1 MOA to 3 MOA.


There really isn't. At least not between 5.56 and .223. I've weighed hundreds of cases and have never found a difference between them although there are still tons and tons of people who believe it. I even had one jackass tell mee he could tell the weight difference in his fingers between lake city and 223 stuff.


The capacity difference is a few grains of H20, but if you're at the upper end you can go from a nice load to ejector swipes and popped primers. I ran into this going from LC 09 cases, larger capacity to some HSM .223 stamped ones.

[omega21]

you guys are brilliant! Really appreciate the input and wisdom!

[danpass]

CMP and NRA Highpower full course matches are 200 standing, 300 sitting rapid, 300 prone rapid and 600 prone slow.

A lot of guys use 77 Sierra Match King bullets in their reloads 'across the course', which is what I do. Others use 80smk for the prone slow. I may start doing that for kicks lol.

I would be comfortable using any factory match rounds based on a 77smk.

[Magelk]

The capacity difference is a few grains of H20, but if you're at the upper end you can go from a nice load to ejector swipes and popped primers. I ran into this going from LC 09 cases, larger capacity to some HSM .223 stamped ones.

I have no hsm cases to compare, but there is no difference between LC, PSD, FC, Winchester,Remington, etc etc etc.There may be subtle differences but there isn't, in my experience with case capacity. The only differences in case capacity I've ever found, and this includes all the headstamps I've ever used, is so negligible it's not even remotely worth worrying about. If you have cases with "a few grains" capacity difference, you're buying some ****ed up cases.

[Magelk]

Disclaimer, maybe a benchrester would worry about what I was talking about but thats about it.

[bp7178]

Anyone working at the upper end of load development would worry about it.

Again, you go from a nice comfortable warm load to excessive pressure signs.

http://www.6mmbr.com/223rem.html

.223 Rem Case Weight vs. Capacity

Case Manufacturer Case Weight* H20 Capacity**

Lake City 06 92.0 30.6
WCC99 95.5 30.5
Sellier & Belloit 92.3 30.5
Remington 92.3 30.4
PMC 93.5 30.4
Hirtenberger 93.7 30.4
Lake City 04 93.0 30.4
Federal 96.3 30.2
Hornady 93.9 30.1
IMG (Guatemalan) 95.4 30.1
Lapua (new lot) 93.4 30.1
Winchester 93.9 30.1
Olympic 97.4 30.0
Radway Arsenal 96.1 30.0
PMP 104.5 29.9
FNM 93-1 97.3 29.8
Lapua (old lot) 104.0 28.0

So the extremes;

LC 06 92.0 gr. and 30.6 gr. H20 (capacity)

Lapua 104.0 gr. and 28.0 gr. H20 (capacity)

2.6 gr. capacity is a HUGE difference.

[Magelk]

An old lot of lapua is the only one that has that big of a deviation. Eliminate it from the list and what I was saying is completely true. Keep it on the list and your point is completely true. My advice, use the lapuas separately and then don't sweat it.

[bp7178]

Dude even some of the other ones can vary by a grain.

If you're working up loads at the upper end, and you're right on headspace, you're going to have issues switching brass.

Even 1/2 grain can change things.

[aklaunch]

May i recommend Patrick Sweeny's AR-15 volumes 1-4

If the power goes out in your home, and you have a candle you can find some great information.