Looking for something that will give me a bit more range with a long zero without adjusting sights while still lethal as all get out.

Shooting from a 16" carbine.

LF

IMI  5.56 77gr otm razor core  lr mod 1

Thanks.

Have MV for that ammunition.  I did look it over but could never get an MV for it from a 16" barrel.

That said, I'm awaiting the delivery of my first chronograph.

LF

All sorts of velocities from my rifles....

http://www.ar15.com/forums/t_3_16/676005_Various_Chronograph_results____16_Middie_and_20_Rifle_.html


And my suggestion is the Black Hills 5.56 77gr TMK.... it is fast and has a better BC then the 77gr SMK.

Agreed, definitely the BH 77gr TMK

I really enjoyed and appreciate the work you put into those MV studies.  It must have been an incredible amount of work.

The BH TMK figures prominently in my scheme to find a effective long-range lethal round.  I own some and have been impressed with it, especially its terminal ballistics.

But the MV is less than I'd like out of a 16" barrel and, with the zero I like (300m long zero), it has a trajectory with an almost 7" bullet rise within 300 m.

Now, that's not unworkable.  But I'd much prefer a lesser bullet rise within 300 m.  Any suggestions?  What could be done without reloading to increase the MV and flatten the trajectory without having to go to a shorter zero which would result in diminished long-range trajectory?

Maybe nothing but for custom reloading?

LF

Well... you'll have to compromise somewhere.

You want fast out of the gate? You want heavy weights for better terminals? You want flatter/faster? You want slower/heavier?

Maybe you'll be better served with another caliber like 22-250.

This ^... You can not get to where your thinking is taking you. There is a reason 55grn has been the go to for years. It is all a trade off somewhere.. If energy delivered to target is goal then heavy. If flattest trajectory is goal then light.
@ what distance is the question ?

I would get some of the tipped match king loads.

I'm beginning to believe you guys are right about trade offs, although was hoping it wasn't so.

BTW, I was also beginning to believe, as the above poster points out, that there is a relationship, an inverse relationship, between projectile weight and muzzle velocity.  True?

Is that relationship hard and fast?  Is there a physical principle at play here that I'm unaware of which makes it so in small bore rifles?  Or, is it just experiential, a matter of observation and experience?

LF

Yes, there is generally an inverse relationship between muzzle velocity and bullet weight.  



It takes more energy to accelerate the heavier bullets, given the maximum pressure the system can handle you can safely accelerate lighter bullets to higher velocities.



If you want more velocity while still retaining a high BC you might look at the 69gr Black Hills Tipped Matchking.  They are 125fps faster and still have a better BC than standard 77gr projectiles.



http://www.black-hills.com/shop/new-rifle-ammo/5-56mm/

Yep, the heavier the bullet, the lower the muzzle velocity. Trying to push a 77 TMK noticeably faster than what Black Hills does would likely result in being over pressure.

The heavy match bullets have high ballistic coefficients. They retain their velocity and buck the wind better. The heavy match bullets will have less drop at extended ranges, even though they start at lower velocities.

A 69gr TMK will get you slightly less holdhold under. If you want to minimize hold under, something like 50-55gr TSX or 55-62gr bonded soft point will work depending on the max range you have in mind.

How far are you looking to shoot and what are you shooting at.  A hold under of 7" isn't a huge deal unless you're shooting ar small varmints.

OK, on inverse relationship.

Before I saw the above post I thought I could determine if such a relationship existed by using the data contained Bufoosh06's link above.  Indeed, there is an inverse relationship as shown below:



I've drawn a linear trend line through the data points, but, one could easily imagine that whatever mathematical equation describes the relationship is a negative exponential.  But that sort of apparent curvature in the graph is determined largely by extremus (the two extreme points on the graph).  So, it's a bit much to infer a negative exponential on the basis of two extreme points.

Still, the inverse relationship is apparent.  My next question was, is the inverse relationship the result of physics or is it an artifact of the loads ammunition manufacturers choose to arbitrarily produce.  The above post suggests that it's a physical limitation due to chamber pressure limitations and I accept that as reasonable and likely the case.

So, the compromises you guys suggest are required appear to be required.  Pity.  One cannot have excellent MV (which I take to mean flat shooting) and excellent accuracy and lethality at long range.  

I was going to run ballistic curves on all of Bufoosh06's data and determine if there's a load that's an outlier and gave good flat shooting and excellent long range lethality.  But I've now read enough both on this board and off of the board that the only reasonable choice (compromise) is BH TMK in heavy bullets, 69 or 77 gr.  And, that's based on its excellent terminal ballistic performance and accuracy due to its considerable weight.

So, no sense over-analyzing just for the sake of analysis.

To those of you who've been engaged in shooting commercial ammunition for a long while, what I'm about to point out is probably something you've known implicitly for some time.  But I've only been in this game for a few months and all my previous experience 45 years ago was with issue rifles and issue ammunition.

Anyway, it's a surprise to someone like me with so little contemporary experience that there is so much difference in MV for ammo with the same weight bullet, notably the 55 gr. ammo.  But then that data probably contains ammunition loaded for NATO chamber pressure and non-NATO chamber pressures.  My rifles will shoot either.  But I now know to be picky and pay attention to MV on the package.

Thanks guys

Maximum effective range of my 16" AR which I take to be 500m and shooting only at human-size target simulants.

Was trying not to adjust sights over that range.  But now that doesn't look doable if I choose ammunition with the best terminal ballistics and lethality at long range.

LF

Are you using irons or a scope?

given that the primary objective above all else is to hurt something, the 77gr OTM of TMK (my preference) is probably something you want to stick with and work around.

You're problem IMHO seems to be your resistance to glass which really is your answer. Any decent 1-4x scope with honest to god MOA or Mil marks will get you as far as you want to go as accurately as your abilities allow with any load you want or scavenge without having to touch a knob with any zero you care to use.

IMHO

Irons and RDS.  No magnified optics.

LF

Noted and thanks.

LF

You can readily use basic holdovers / unders to adjust for range and trajectory.... granted it will not be pin point accuracy, but it is far easier then most people realize.

Study your trajectory for your bullet choice and try it at a 300yd ish range.... a lot of people get "nervous" ( not quite the right term ) about longer range shooting... but a change in your RDS position on target is an easy adjustment.... as long as you know approximate distance and your projectiles trajectory.

Or...... buy a scope with a good ranging reticle.... which is what I have done.

This reticle does most of the thinking for you.... just make sure you install the scope level with the rifle. As long as it is level ( the scope) all you do is "read" the reticle and bang away.





From this scope.....

https://www.primaryarms.com/Primary_Arms_4_14X44_FFP_Scope_with_308_p/pa4-14xffp308.htm


I know you said irons and RDS.... but.... ( they also have more compact versions... I just prefer the Front Focal Plane )

I did look at magnified optics with mildot and milradian reticles and also some with BDCs when I first got the rifle (had a problem with a contractor and needed it right away).

I like the mil/mil scopes a lot and I liked the more capable reticles too (Horus).  I saw some very impressive videos of the use of those reticles for near instantaneous aimpoint correction after the first round is fired.  But with kids in college they were way too expensive.

I know some of the scopes (PA and SWFA) have BDCs and given that I'm not interested in shooting varmits, but rather, human sized targets they don't have to be exactly dead on at range.  And, the one you point out is relatively inexpensive at less than $300.  So, that's a possibility.

But I've been concerned that the BDCs are calibrated in one or a few loads and would tend to limit my choice of ammunition.

Hey, here's an idea...if holographic sights project an image onto a screen including BDC why not insert a memory chip to which any ballistic trajectories could be uploaded and which would modify the BDC to conform to the ballistics of any load and any rifle barrel length. Then if you switched loads or rifles you'd download different BDC data.  Or, because the amount of data to set the BDC is small then put lots of load's data on the chip and have a way to select the appropriate BDC right on the scope for whatever load and rifle you're using at the moment.

Fantasy?

Having just dropped a couple of hundred plus for a Votex RDS and having lots of college student debt to pay off from my kids it's probably going to have to wait until the next gun (a 20" or 24" rifle in 5.56, I think).

Anyway, thanks so much all you guys for putting up with my questions and for your guidance.  I've learned a lot.  

Best,

LF

A friend who built my rifles suggested that because the LOA had to be the same the heavier bullets were probably longer and that their additional length then limited the amount of propellant powder that could be loaded into the casing.  He attributed the lower MV of heavier loads to this.

Hmmm.  I'm not so sure.  I've never broken a 77 gr. TMK apart to see if it was full to brimming full as his idea suggests.  But I'm not so sure it wouldn't have a lot of space remaining.

So, I thought I'd mention here his explanation.

LF

What good is faster if the groups stink? A heavier bullet with a high BC will typically be more accurate than a lighter faster bullet, especially long distance.

Sierra 77 SMK  or TMK.

Many loads are compressed and it wouldn't surprise me if the Black Hills loads are a compressed powder charge. In the end it's pressure that is the limiting factor.

 

Boy, are BDCs run down by posters on the Precision forum.  If you read their posts you'd never buy one.

Their principle complaint is that the BDCs are produced for particular loads and particular MV (barrel length).  And, that as loads and rifles aren't standardized anywhere but in the regular armed forces, excepting the SOF, then they're wrong 99% of the time right out of the box.

Put a chip in 'em.

LF

This isn't rocket surgery.  

You shoot your BDC/load combination at different ranges, and figure out how it correlates.  Maybe your 300 yard mark is on at 315, maybe your 400 is on at 387, it doesn't matter because  in the real world your target is rarely going to be at an exact distance with a  00 on the end.

Now for maximum precision, knowing your dope and turning the knobs is going to be better, but for fast and dirty a BDC is fine.

BTW, a red dot at 500 yards is retarded.  How are you going to dope wind?  Even with a good scope and 77gr TMK, doping the wind at 500 with a 16" 5.56 takes some serious skill.

Here is some good reading for those interested in this thread:

http://www.thenewrifleman.com/is-the-sierra-tipped-match-king-the-flattest-shooting-223-ever/

I'm not trying to start something here, just relaying what I've read and being thankful for your input.  I guess I see truth both sides of the argument.  Some emphasize precision, some emphasize good enough to get the job done.

I also say computerize the darned BDCs and also the reticle projected and all the controversy goes away as BDCs become precision optics.  And, there'd probably be 100 fold the sales of BDC's in America in 5 years time.  Even "Irons Dave" (me, Longfisher) would buy one, or, two of them.

Heck, we've computerized watches.  Why can't we computerize holographic sights?

LF

Yep.

I'm new to the AR15 world.  But early on I identified the TMK's as pretty awesome projectiles out to 400 - 500 yards.

It's not that I'm smart.  One doesn't have to be smart to see the obvious.

Pricey, though.

Still, in a perfect world it would shoot as flat as the XM193 55 gr loads.  Sadly, ours is not a perfect world.

LF

They exist, and are very expensive for shooting at such a short distance.  You still need to know the range anyways, which means a BDC/holdover will be much quicker.

If such forces were not proportional, an ant could kill you.

Besides, XM193 is only flat for the first 300yrds, its crappy BC causes it to drop quickly.

BH 77grain TMK

This.

LF

Does a tighter twist rate also decrease MV?

I generated some chronograph data recently (Magnetospeed Sporter Chrono) using two 16" AR15s one with a 1 x 9 and another with a 1 x 7 twist and the MVs of the same ammunition were reproducibly a few percent lower in the carbine with the tighter twist.

Round55 gr. XM193 1 x 9, BC 0.338 (fps)62 gr. XM855 1 x 9, BC 0.307 (fps)55 gr. XM193 1 x7, BC 0.338 (fps)62 gr., XM855 1 x 7, BC 0.307 (fps)
1                       3081                                                      2985                                             3091                                               2972
2                       3097                                                      2994                                             3068                                               2965
3                       3078                                                      2992                                             3047                                               2986
4                       3095                                                      2988                                             3041                                               2970
5                       3065                                                      2978                                             3051                                               2970
Average               3083                                                      2987                                             3060                                               2973


LF

Ordered 200 rounds of BH 69 gr. TMK.  Let's see how it shoots.

LF

Where did you find it?



 

Searched forever, it seems, but finally found it in stock here:

Triad Tactical

Will be here by Wednesday.

Old Virginia also has it but wouldn't break up a 500 rd. box to sell me a couple of hundred, although they have done so in the past for BH 77 gr. TMK and OTM.

Best,

LF

My testing with 1:14, 1:6 and 1:5 twist 5.56 barrels showed very little difference. All of these were shot on the same day with identical profile barrels. The 1:6 twist barrel has ~400 more rounds through it than the 1:5 and 1:14 barrels.

 






I originally posted this in the Green Mountain test barrel thread.