Reloading the .223 Remington/5.56 NATO Cartridge

[Nickle]

Put your questions and comments about the .223/5.56 in this thread.

[1shot]

Greetings!

I myself have never reloaded, but I am starting to get into reloading, and plan on reloading 5.56 soonly.  Fortunately, I have at hand an expert reloader with pistol and .308, who has a chronograph, and will be helping me every step of the way.

I am posting to bring folk's attention to the following link:

http://www.eskimo.com/~jbm/calculations/traj/traj.html

One, for it's utility, and two, to ask resident experts how useful it really is.  It's a trajectory calculator that takes all potential effective data concerning a round, and produces a trajectory analysis in inches and minutes of drop (or windage, if you add wind into the mix).

What I have been doing here, is entering all relevant data (sight height from barrel, round weight, etc) and then fiddling with muzzle velocity to create a "best match" for MOA drops at X, Y, and Z distances with the clicks on my rear sight elevation.  Then checking against different sites (such as AR15forums) that post reload data, to match my desired muzzle velocity to a 'proven' load to get the specs I would need to reload to to reproduce said trajectory.

(Thank you RWVA and Appleseed - without learning MOA from you, I would not have had even the concept to do this sort of thing)

I have had to revise the parameters recently, after learning that the 80 grain 5.56 I had really wanted would have a seat length extending beyond my magazine length, requiring single loading that was just not practicable.

So I went down to 77 grain and re-fiddled with the muzzle velocity to make a match, and wound up with a load that (while not matching the numbers on my rear elevation wheel) allows me to get POA-POI sighting from 100 yds to 850 yds from a 5.56

The PLAN I have, is to load a 55 grain target round to a muzzle velocity that gives me perfect POA-POI trajectories at KD's 100, 200, 300, 400, and 500 -- and then load a 77 grain "battle" round that lets me reach out to 850-900 yards settling "clicks" on my elevation according to 12 yard increments.

Basically, I am looking to spur a discussion on how ballistics and trajectory figure in to reloading, and to discuss how accurate sites such as the above mentioned

http://www.eskimo.com/~jbm/calculations/traj/traj.html

really are.


I am assuming, of course, that once I have some test-sets of both my "battle" round and my "target" round, I would need to take them to a KD range and fire groups to verify trajectory, then going back to the reloading bench to fine-tune, finally returning to the range with the final product and then fine-tuning my sight adjustments.

Since I have never reloaded before, i am simply looking for someone to help by critiquing my methodology and giving me further ideas to go with.

Many thanks, and Semper Fi!

Glen

[Nickle]

1shot, I haven't checked the utility yet, but I will tell you that sometimes when you change loads, the windage and elevation both change.

I'm not sure why this is so, but suspect it has some to do with barrel harmonics, and the time from firing until the bullet exits the barrel, and the exact moment in the harmonics that the bullet exits the barrel.

Kind of complicated, to say the least, but, the bottom line is the POI may change in ways you don't expect, such as windage.

And, I expect you to be suspicious, as it didn't ever make sense to me, either, but it is like I said.

[Buckshot]

Glen,

I agree with Nickle, I have even seen POI changes on different years of otherwise identical ammo (different years of LC M2 Ball, for example) and different countries manufacture of "supposedly" completely identical and interchangeable ammo like 7.62 X 51 NATO Ball, M80.

Your sights should have been set for either M193 ball or M855 Ball.  I would start out by reproducing THOSE loads and work on the more exotic stuff lately.

I also think you are pushing the 55 gr. bullet expecting it to work at 500 yards.  The Army didn't use it past 300 yards on KD ranges like the SAFS at Camp Perry.  With the old M16A1 and Ball, M193 we fired at 200 yards and 300 yards only at the SAFS, and this was held on Viale Range which has positions and is usable right out to 1,000 yards, so it was NOT a range facilities limitation.

Some on this list say it is good to 400 yards.  I have never tried it, so I won't say they are wrong, but from what I see the velocity is going to be too low to get any terminal action out of the bullet and it is just going to punch holes like a nail gun.

Buckshot

[Nickle]

I have used M193 Ball at 400 meters, from the M16A1, and I will say it gets there, and knocks the silhouettes down (it did when I went to Boot Camp in 1972). I don't think I would trust the terminal ballistics, though, specifically the wound ballistics.

[1shot]

Yes, I know 55 gr knocks the 480yd popups down at the home range, which is why I'd feel comfortable with it for a target round.  My battle round will be 77 grain. 8-)

[Nickle]

Yes, I know 55 gr knocks the 480yd popups down at the home range, which is why I'd feel comfortable with it for a target round.  My battle round will be 77 grain. 8-)

Sounds like the smart way to go. Just remember you will have to reverify zero when switching ammo, and you'll be all set.

[Muddogg]

62 grain is the proper weight for rifle with a 1:7 twist, right(e.g. M16A2)?

When I can do a lot more reloading in my free time(and money to buy all the equipment), I plan on Reloading for my Colt Sporter AR-15. I really like the performance of the Remington 62 gr Core-Lokt HPBT ammo.

[Nickle]

62 gr BT bullets are said to be the best choice for the 1-7 twist. I recommend them, for sure. You should have better luck with them than the 55 gr in that twist.

[1shot]

To my understanding, the 77 grain rounds actually work better not only precision at range, but also in terminal ballistics and damage done.  62 grain has been the military standard since the 1:7 was introduced, but many of the SF units using M16A2's in country are pulling strings to get the 77 grain rounds, although more expensive, according to reports does a better job at doing the job.

I myself have a 1:7 twist, and have experienced decent performance with the 55 grain knocking down popups and punching holes in paper at 480 and 500 yards.  I am sure that 62 grain would be more accurate at 400 and 500 than the 55 gr, but the margin can't be too awful great since I was hitting the 480 popups without difficulty.

The best accuracy at 500 and beyond - not to mention the force of impact at long range - will obviously be with the 77 grain.

Black Hills Gold is providing 77 grain match rounds to units OIF in Iraq and Afghanistan today.  From what I have heard, it's doing a significantly better job than the M855 62 gr.

I do believe, also, that there is an M designation for the new 77 grain 5.56 round.  I don't know it offhand, but it is quite new.


edited to add:  I really REALLY wanted to go with the 80 grain for my battle round - given that I could get it FMJ as opposed to HP - but discovered through my reloading research that you can't seat the 80 gr projectile deep enough to load in a magazine and I would have to single load.  So I compromised to the 77 grain projectile being introduced OIF in Iraq and Afghanistan.

[Buckshot]

To my understanding, the 77 grain rounds actually work better not only precision at range, but also in terminal ballistics and damage done.  62 grain has been the military standard since the 1:7 was introduced, but many of the SF units using M16A2's in country are pulling strings to get the 77 grain rounds, although more expensive, according to reports does a better job at doing the job.

I myself have a 1:7 twist, and have experienced decent performance with the 55 grain knocking down popups and punching holes in paper at 480 and 500 yards.  I am sure that 62 grain would be more accurate at 400 and 500 than the 55 gr, but the margin can't be too awful great since I was hitting the 480 popups without difficulty.

The best accuracy at 500 and beyond - not to mention the force of impact at long range - will obviously be with the 77 grain.

Black Hills Gold is providing 77 grain match rounds to units OIF in Iraq and Afghanistan today.  From what I have heard, it's doing a significantly better job than the M855 62 gr.

I do believe, also, that there is an M designation for the new 77 grain 5.56 round.  I don't know it offhand, but it is quite new.


edited to add:  I really REALLY wanted to go with the 80 grain for my battle round - given that I could get it FMJ as opposed to HP - but discovered through my reloading research that you can't seat the 80 gr projectile deep enough to load in a magazine and I would have to single load.  So I compromised to the 77 grain projectile being introduced OIF in Iraq and Afghanistan.

1Shot,

What powder are you going to use for the 77 gr. bullet and what velocity are you projecting?

Buckshot

[KY Gungeek]

Couple of comments here (I'm coming from lots of fiddling with reloading and a little & growing background in NRA High Power).

1) As a target round, 77's work great in a 1:8 twist to 600 yards (this is a standard for a High Power Service Rifle).  I've personally shot them there and shot with lots of others doing the same.

2) Windage does change with distance.  The path of a bullet is not a 2-dimensional arc, but rather a 3-D arcing corkscrew.  If you've ever seen trace through a spotting scope, or a tracer, you can observe this.  The cause is that the bullet is not exactly lined up with the flight path (yaw) and that mis-alignment is not the same all the time - it rotates around the flight path like the axis of a wobbly top (term is precession).

3) I think the original question is on the accuracy of sites such as the one above.  Couple of observations I have about this.

• The information (trajectories) are based on a mathematical model (duh) and they are sensitive to numbers input for BC (ballistic coefficient)
• The basic models don't hold very well
• The more complex models require very accurate figures for BCs
• The numbers published are off enough to make your calculations off - this is because their BCs are calced at a particular temp, humidity, and altitude, phase of the moon...
• BCs are different for different velocities - check out Sierra's for figures on SMKs
• If you really want to explore this, you need to get an average BC by determining velocity drop over a known distance.  The BC will be different for different distances.  You do this by placing your chrono down range and shooting through it with loads for which you already know a muzzle velocity.  There's software that will do this.

Sounds complicated, and it can be.  I read an article in the last issue of Shooting Times, written by Ken Oehler (Oehler Chronographs) that discusses how to get around some of this.  Let me see what I can dig up...

There is a different approach - typical of accuracy shooters such as bench resters and High Power competitors.  High Power guys live and die by sight adjustments at KDs.  However, they generally look for a load that is the most accurate out of their gun (and above a minimum velocity so that it doesn't take too many clicks).  They are looking for the smallest group size.  Then they shoot at distance and record the come-ups.  You'll see lots of notes in a book, and sometimes taped to the rifle, about mechanical zero, then come-ups for distance. 

Point is, they don't try to do fine mathematical predictions about sight adjustment.  They go for accuracy (repeatability), then observe and record adjustments under real conditions.  Since you are handloading and using bullets that don't have a standard military designation (i.e. bullet weight and velocity), this might be a better approach.  If you find a model that fits your observations (i.e. MOA at KD), you might use it to predict unknowns...

[KY Gungeek]

Sounds complicated, and it can be.  I read an article in the last issue of Shooting Times, written by Ken Oehler (Oehler Chronographs) that discusses how to get around some of this.  Let me see what I can dig up...

Found my mag articles - Shooting Times, June 2007.  This is a quote from Ken Oehler's column "Oehler on Ballistics".  Page 21.

"...there is no assurance that the bullet's behavior is actually described by G1 at other velocities.  Matter of fact, we know that G1 doesn't fit modern long-range hunting bullets or the very low drag bullets.

How do we know which of the published drag functions to use with a particular bullet?  We know that the long range results from most ballistic programs do not fit the observed shooting results."

Oehler goes on to explain that the military uses doppler radar (or other methods) to determine a much more accurate description of a particular round's trajectory.  Not a mathematical prediction, but an observation of the actual path. 

G1 is a mathematical model of the drag which is how the trajectory is calculated.  There are several others.  The quote above appears just after a discussion about how difficult it is to get good measurements of BC.

Oehler ends this article with a teaser about how we can use G1 (and other models) to get better results...

[Swampfox]

The stuff the Navy supplied us for match shooting is 5.56MM LR MK 262 MOD 1.   It's a 77gr HPBT match bullet, and it's great stuff.  I scored 182  (out of 200) at 1000yds at Quantico last year with it (that didn't hold a candle to what the Army and Marines were doing -- But it was pretty good for me and my AR15 for our first go ever at 1000yds!).

I've heard rumors that it's identical to the Black Hills 77gr match ammo, and that they make it for the military.

Swamp

[1shot]

The stuff the Navy supplied us for match shooting is 5.56MM LR MK 262 MOD 1.   It's a 77gr HPBT match bullet, and it's great stuff.  I scored 182  (out of 200) at 1000yds at Quantico last year with it (that didn't hold a candle to what the Army and Marines were doing -- But it was pretty good for me and my AR15 for our first go ever at 1000yds!).

I've heard rumors that it's identical to the Black Hills 77gr match ammo, and that they make it for the military.

Swamp

I've heard that not only are they identical, but further that Black Hills are the folks who actually make MK 262 Mod 1 for the military.  I can't rightly remember though, what the difference was between Mod 1 and Mod 2.  I'll have to go back and re-research -- I think I remembered wanting Mod 2 more than Mod 1, but I can't really remember why at this point...

[BELT FED JASON]

This does not follow the direction this discussion is heading but it works well for me.

21.5 grains of Accurate Arms 2460
Either pulled 55 or 62 grain proj. from Pats and Hightech ammo
Winchester small rifle primers. 
Dillon 550b to fill em

Out of 4 different rifles, two colt's, a dpms, and a frankfort arsenal,  this load all grouped 2-3 inches at 100 yards.

YMMV

Jason

[1shot]

1Shot,

What powder are you going to use for the 77 gr. bullet and what velocity are you projecting?

Buckshot

I've calculated 24.2 grains of VARGET powder with a cartrige seat length of 2.255" delivering approx 2700 fps from a 20" barrel AR.

I did all my ballistics calculations for the 80 grain, so I have to recalc for the 77 grain bullet to come up with a more refined target muzzle velocity.  I'm guessing I'll be looking for a muzzle velocity between 2730 and 2750 to achieve desired performance (approx 27 MOA drop at 950 yds).

Unfortunately, the ballistics calculator is not responding at the moment.  I'm thinking it's getting hit too hard right now.

[Old Dog]

1Shot, load for accuracy, not velocity.  There are a lot of things to keep in mind and "watch" for:
1  you don't want too much pressure so start with a powder charge that is on the low end of the scale (as listed in a chart for that powder/bullet - very obvious signs of high pressure is the primer.  I don't want the rounded edges looking flat, nor do I want the primer metal to start trying to flow back into the firing pin hole in the bolt.  I've never measured the brass diameter before or after so I can't give advice there.
2  watch the overall length, it's got to feed out of the mag. and chamber reliably.  The heavier the bullet the longer the bullet the farther down in the case it has to go the less volume available in case the higher the pressure.  You also need to check to make sure the bullet is not contacting the riflling when the shell is chambered as that can also increase pressure
3  magnum primers increase pressure and old literature says they can decrease accuracy when used in a non-magnum cartridge
4  I used to start with 10 shells with the same powder charge and shoot two 5 shot groups at 300 yds. (this was a .308, you've seen it) I had several sets of 10 rounds with powder charges varied about .2 grn. (I never went anywhere near the max loads as most of the time the most accurate load ends up being a lower velocity/lower pressure load).
5  The promising loads were repeated and shot at 300 yds. again.  If they repeated performance I reloaded and shot out to 600 yds.
6  With my rifle a couple hundred fps slower (if that's what it was) was not and issue if the group was good
7  When you start finding the right combinations of powder, primer, bullet and "build" for your rifle you will be amazed at the difference between "factory" and your reloads
8.  (left this one out by accident the first time) the loads need to reliably function in your semiauto.

As with anything new to you.  Read everything you can get your hands on about it (I bought 4 reloading manuals as I was starting out).  Go slow, don't allow distractions, double check your work, insure the cases chamber fine prior to installing the primer, powder, bullet and again once you get the loads "built".  No sense going to the range with a bunch of shells that won't chamber.  All of this should be assured if you set up the resizer right and went through the OAL set up right. 

This will sound funny after everything I just wrote, but be careful who you listen to when you get advice.  Your rifle is different than just about every other one that looks like it.  What works for someone else probably won't work exactly the same for you (close maybe, but not exactly).  Also, you're working to make something that will operate at pressures in the range of 50,000 psi.  You can't afford to make a mistake - so back to the part above about lots of reading from reliable sources, not hearsay and no distractions while you are "building" those loads.  Good luck.  The right load can reduce your group size by 50% or more.  I've seen it in more than one rifle.

[Nickle]

Powders that work well in the .223 are 4320, H322, BL-C 2 and 4895. There are others, so don't be afraid to try more than a couple of them.

[catch223]

Here are my secret sources for bargain M855 clone reloading:

Powder:  Powder Valley Ramshot TAC - 8lb jugs for 78 bucks!

Bullets:  GI bullets - Pulled M855 bullets, $35/1000!  Looks like RVO is out of biz.  Now I'd go here:  Ammunitionstore.com

Brass:  GI Brass has it for .05/round when he has it.

Primers:  Powder Valley again for Wolf or CCI primers (.018 and .021 respectively)

I've also ordered powder and bullets from Hitech but they're out of most of it at the moment.

Right now I'm using 26.5 grains of WC844 from Hitech to replicate M855 velocities.  I'm also on about the 5th reload of Radway Green brass, which has surprised me with its durability and general "good-for-reloading-ness".

[Buckshot]

1Shot,

I have a question about your "special ammo" the Mk 262 Mod. 0 or Mod. 1 clone.

Is this ammo that you can afford to pass, along with your rifle, to a newbie as loaners at an Appleseed, or is this a specialty ammo?

Do you have an affordable M193 or M855 clone (like Catch223 mentioned above) for things like the 25 meter stages at an Appleseed?

Not implying anything at all, just wondering.  I know at least one guy at our club who made himself some "super ammo" for long range, but he could not afford to shoot a National Match Course with it, per him, it wasted too much money!

Just wondering how you handle this kind of situation.

Buckshot

[Morguns1cam]

   Ive been loading ammo for about 25 years now, lots of pistol, rifle and shotgun loads. But just started reloading for auto-loading rifles, namely M1A's and AR15's in the last few years. When loading for these type rifles you must understand "Headspace" as it relates to your rifle and ammo. Also be able to measure your reloaded ammo to be sure it is correctly headspaced for Your rifle. You rifle and your buddy's identical rifle will be slightly different in terms of head space. For example if your rifle is headspaced on the long end of the scale and you full-length resize your fired brass back down to minimal specs, the brass may have to expand several thousandths of an inch to properly seal the chamber. If this is the first  loading (new brass) it probably wont be a problem, but if this process is repeated a few times (sometimes just a couple times) the brass gets over worked and the casehead separates or worse. Ideally what you want to do is resize the brass to 1 or 2 thousandths of an inch (.001"-.002") smaller than your chamber headspace. This gives room for the brass to expand when fired (a must) but doesnt overwork the brass prematurely. Measuring the overall length of you cases isnt enough when youre loading for a semi-automatic gun. You must be able to measure the case's headspace which is from the case base to the case's chamber bearing surface which is somewhere on the shoulder.
        What I do is take a once-fired casing from my rifle and measure the headspace (I use a RCBS precision mic), realizing that after the case was fired, it expanded to fill the rifle chamber then contracted back (spring action of the brass) around a thousanth of an inch.
I then set my resizing die to bump the case shoulder back another 1 thousandth of an inch which gives me a case that is .002" smaller than my chamber. These rounds chamber well and function well.
       Another gotcha I found reloading the .223 is that the case necks are very fragile and thus very easily bulged when crimping the bullet, resulting in failure to chamber in the rifle. To get around this I just didn't crimp at all for awhile and this worked fine, later I discovered the Lee factory crimp die which doesn't depend on case length but gives a good crimp without bulged case necks!
                          Happy Loading!

[Buckshot]

Morguns1cam,

You can do the same thing without all the measuring hassle by taking a case fired in that rifle and resizing it until it will chamber again with only light finger pressure, no spring pressure.  Then turn the die in 1/4 more turn.

That is how we did it back in the late '70s before all the fancy, expensive tools were so common.

You just have to have a sizing die for each rifle, or take the time to find the rifle with the smallest chamber in that caliber and reload ALL rounds like they were for that rifle.

Buckshot

[Old Dog]

I'm not an expert by any means.  I suppose I've just been lucky with my reloads (as well as other things).  I began reloading .223 for my M700 Rem. VS.  Later when I got my mini14 it digested the same reloads with no issues.  I thought I was setting the die up for a minimal amount of resizing (leaving a small oily ring around neck right where the neck and shoulder meet.)  The only issue with the mini14 was that the twist rate of the barrel was too fast for some of the thin jacketed varmint bullet I was using (the blitz and sx bullets they used to make).

I only had one .308 so no resizing issues there from gun to gun.

I started reloading 30.06 for my US Enfield and my father in laws 742 Rem.  Again, resizing to leave that little oily ring those reloads fired in both of those rifles and later when I added the other bolt action WW1 30.06's they worked fine in all of those.

I think if you have a problem you're better off spending the time to really figure out why than to just accept what someone who hasn't fired your rifle, prepared your brass and reloaded your ammo for you "guesses" might be wrong from the comfort of the internet.  This isn't to say you shouldn't ask for advice as many times the varied advice you get can contain the answer you're looking for. 

The bottom line is you knowing what caused the problem is better than trying different things till something works and then accepting "common wisdom" about why it worked.

Have a good one and good luck with your reloading - but better than luck is lots of reading about reloading in reloading manuals and workg out your issues and coming to a workable solution for you rifles.

[Oohrah]

OK, I had a very weak moment and knuckled under to
owning a black rifle.   The Bushmaster 16" HB, 1 in 9" barrel
with adjustable stock and removeable carry handle arrived
yesterday.   Main question is what bullet weights will this
twist handle, and what range of wts are ideal for that twist?
   What accuracy can I expect out of the box without tweaking
it with a floating forearm and such.   I plan on using some form
of hollow point or expanding with the thought in might give an
edge for unimpressive military ballistics of the full jacket.
   Goal is to provide energy pressure to reliably fuction the AR
action, and to ring out as much accuracy out of this as is in it's
form of A4 type Carbine.
   One Shot, I don't know when you served, but in the early
sixties, the M16s were pure junk due to a number of factors
from design,  bullet wts did not match twists, dirty powder
that would vomit it back through the action, and it would
plain quit running when ya didn't want it to.   After many
modifications, I guess with proper maintenance, it has been
much improved.   At least I hope that I won't be disappointed!

[Joe]

Oohrah
You should be able to shoot any bullet from 50 to 75 gr. The heavier bullets you will have to push a little harder to get them to stabilize well. If you push the lighter or varmit bullets too fast they will blow up or your accuracy will go to hell. Varget or Reloader-15 will do excellently for powder. IMR4895 works well too but is harder to meter & dump in the case. Load to magazine length. If you get a good tight neck sizing you do not need to crimp the bullets. Load to magazine length. This will be the recommended OAL in most manuals. Don't push for max. velocity. I've found best accuracy for a given load is roughly around 10% less than max. One of the big keys to accuracy is to follow Bushmasters included instructions to break in your barrel. (Also on their website) If you reload carefully it is very possible to consistently get sub MOA groups. A friend of mine recently bought a 1-9 20" flat top and put a big Nightforce on it. He is getting 1/2 MOA at 600 yds with the Hornady 75 Ballistic tips & 23.5 gr Varget.

[Muddogg]

OK, I had a very weak moment and knuckled under to
owning a black rifle.   The Bushmaster 16" HB, 1 in 9" barrel
with adjustable stock and removeable carry handle arrived
yesterday.   Main question is what bullet weights will this
twist handle, and what range of wts are ideal for that twist?
   What accuracy can I expect out of the box without tweaking
it with a floating forearm and such.   I plan on using some form
of hollow point or expanding with the thought in might give an
edge for unimpressive military ballistics of the full jacket.
   Goal is to provide energy pressure to reliably fuction the AR
action, and to ring out as much accuracy out of this as is in it's
form of A4 type Carbine.
   One Shot, I don't know when you served, but in the early
sixties, the M16s were pure junk due to a number of factors
from design,  bullet wts did not match twists, dirty powder
that would vomit it back through the action, and it would
plain quit running when ya didn't want it to.   After many
modifications, I guess with proper maintenance, it has been
much improved.   At least I hope that I won't be disappointed!

1/9 rifling in a .223 bore prefers 55 gr. bullets, I have a chart back at school that says exactly what twist goes with which size bullet(going off the length of the bullet). That's not to say other sizes will not work well, but from my knowledge(I'll have to double check) that information is correct.

[Nickle]

Muddogg, I disagree with that.

1/9 should prefer a much heavier weight than 55 gr.

I'm thinking 62 gr would be good, and not over 69 grain.

Folks, if you think you're going to shoot 77 gr bullets out of a 1/9 twist AR, and get good accuracy, you are wrong. 77 gr bullets are for "1/8" (actually is 1/7.75) or 1/7 twist barrels.

I do know that optimum twist for .223 type velocities and a 52 gr HPBT or 53 gr flat base match bullet would be 1/14 to 1/15. I've used both, usually with a .219 Donaldson Wasp or .22 PPC (I hate the PPC). Those both have the same velocity, plus or minus a little, that the .223 has.

I would say a 1/12 twist should be optimum for the 55 gr bullet.

[wcmartin1]

Muddogg, I disagree with that.

1/9 should prefer a much heavier weight than 55 gr.

I'm thinking 62 gr would be good, and not over 69 grain.

Folks, if you think you're going to shoot 77 gr bullets out of a 1/9 twist AR, and get good accuracy, you are wrong. 77 gr bullets are for "1/8" (actually is 1/7.75) or 1/7 twist barrels.

I do know that optimum twist for .223 type velocities and a 52 gr HPBT or 53 gr flat base match bullet would be 1/14 to 1/15. I've used both, usually with a .219 Donaldson Wasp or .22 PPC (I hate the PPC). Those both have the same velocity, plus or minus a little, that the .223 has.

I would say a 1/12 twist should be optimum for the 55 gr bullet.

Agreed.

[Oohrah]

Many thanks Joe.   A ray of hope that perhaps that a kill
with accuracy, rather than performance is possible.   No
instructions on barrel break in  were sent with the rifle.
The only experience loading was for a Mini 14 that was
pretty much ho hum with 55 gr of anything.   Picked up a
bolt gun with loading information with it, for lt. weight bullets
(favorite 40 gr Noslers) that I suspect is a 1 in 12 twist.
This 1 in 9 picks up the higher end gap.
   Unless varmits, I don't feel much over 300yds. I would opt
for a larger caliber to increase bullet energy.   MOA at 300
I could live with.   Appears I do have some work cut out to
my energies toward the bolt gun that I have a start, and the
Bushmaster that will be a new experience from the get go.
All of the gas guns have certain perimeters that allow them to
operate well.   None I have worked with were ever at their best
with max loads.   Great info Joe
Semper Fi