Using 168's and 175's need help.

[doctordoctor]

I have searched and searched and have asked others for help but no results....

I recently purchased a new Rem 700 XCR long range tactical (24" barrel) and I qualified for a precision rifle course at Front Sight, NV. I in haste and in stupidity purchased several hundred rounds of 168's SMK's. This is fine and dandy but I will be shooting from 300 to 1k. The problem I quickly learned is that I will need 175 SMK's for 800+... SO I am sheepishly and with much ridicule from my wife will be buying some more ammo in 175.

Anyhow my question..... Is there a way to lessen the pain in the pocket book by using both grain ammo using my 168 zero??? I was hoping that there is a way to compensate with my nightforce nsx scope for the ballistic/trajectory change/difference. I really don't have the $$$ as an ER resident to buy more ammo, but really want to hit steel at 1k.

I was hoping or thought that I could simply adjust for the difference in trajectories by using my 168 zero and adding the difference in MOA to it for the 175's. thus accounting for the heavier bullet. I hope this makes sense. BASICALLY I am pretty sure I will not have time to re-zero (which I KNOW is the best way to go) before I shot 800-1k. I have 400 rounds of 168 that I don't want going to waste.

So my question in a nutshell is if there is a way to accurately shoot 175's using a 168 zero compensating with MOA? I will re-zero after i blow through my 400 rounds of 168's FGMM.

Your help will be greatly appreciated! really it will be accepted GREATFULLY

Dr. B

 

[Minesweeper3433]

I would print out 2 drop charts for both rounds that can be verified by yourself at the corse and adjusted. The primary round you will use should be zeroed just learn where the second round hits in relation at a set distance and learn 2 different tables from the same zero. At least until you use up all your ammo then just go back to 1 table.

 

[Bob3700]

you might try using a ballistics program and compare your two bullets and loads.

Give it a try.

Bob

 

[doctordoctor]

okay so it is a plausible idea that I had... brings a smile to my face! Boy has this been an expensive mistake!

 

[expiper]

shure...it is no different than using two different handloads at differnt ranges (or the same distance..)....just do the ballisitcs and/or record the turret settings for the various distances and shoot your sighters....go from there...Roger

 

[necchi]

Another option;
Sell the 168's on this forum,,There a section below just for this activity.
It's a very busy section of the forum, it's a simple and productive way to meet your goals.
http://forum.accurateshooter.com/index.php/board,11.0.html

 

[DaveWhite]

You will be fine with the 168's out to 600 or perhaps 800, but not beyond. It is not the end of the world to tear that ammo apart and reload them with the 175 or even 190 grain pills. You will have to work out your zeros for the new loads.

There was a Forum string earlier this month on a similar issue with a short barrelled .308 and how to get it to work on 1k targets. The answer is the heavier bullet; it has a bit more thump, but will get the job done. Most LR shooters will advise against the use of the 168 grain bullet, but feel free to use them at the short line. It might be easier to stick with one load and just set aside the 168's, or has been suggested sell them to help finance your purchase of the 175's.

Most clubs organize bulk purchases of Sierra bullets, and the discount is substantial. That may not help your immediate need, but is a good long term strategy to save some $$.

If you have bullet puller, you can simply unload those 400 rounds and set them up with the heavier bullets (might even save you some powder!).

Good luck and hold center!

 

[bozo699]

I guess I just can't take it I haven't said anything stupid yet today so here goes,..
Why can't you shoot the 168's at 1000 yards? I know the 175's would be more ideal but I have shot with guy's using the 155 smk's and scenars at 1K I am not a .308 nut but I have a couple and just goofing around I have hit my steel gongs with it using factory federal gold match 168's at 1048 yards. I just had two friends that attended a precision rifle course in central Washington state both were shooting tactical rifles, 20" Tikka T3 and a 24"Sako both in .308 both shooting 168 SMK's in factory ammo, forgot the brand. The targets were randomly placed from 100- to over 1200 yards, Brian was on the 20" and was able to hit the 18" gong that was just a few feet shy of 1K but was unable to hit past that and he had never shot past 300 yards in his life. I say shoot the 168's up then go from there.
Wayne.

 

[navyrad8r]

Hey doc,
talk to front site and see if they would cut you a break on a "trade in" of som of your 168s for sumpin heavier. while your at it ask them about the come ups too. they are the ones teaching the class. maybe their range is a wind tunnel and you could shoot 155's?? or if they have tough wind maybe you need some 185-190 (or more) class projo. Most facilities have ammo for purchase, or can give you reccommendations. i hope this helps... IMHO i would find out the powder and charge in those cases, pull the bullet and simply "mexican match" new bullets on top of the powder charge as long as the recipe is safe.

PUBLIC SERVICE ANNOUNCEMENT:
***the mexican match term was not meant to slur and or insult mexican, latina, hispanic, or any other group in our society.***

Best of luck and enjoy your class!!
cheers,
doc

 

[people]

Selling them is a good option but you will probably take a loss on them.



mexican match have not heard that term for a long time.

 

[doctordoctor]

Yeah selling would not make financial sense plus it was like pulling teeth to explain the last ammo purchase! I sure wouldn't want to try and explain another one! pick and choose my battles... The mexican match idea isn't a bad idea... Thank you so much you have all been very helpful.

Dr. B

 

[DaveWhite]

here is a detailed answer on why the 168 is not the pill for 1k, regardless of what some others might say. Laurie's post is from the competition forum and it is worth printing and putting someplace where you can read it several times.

.308 @ 1k F-TR
« Reply #7 on: 12:59 AM, 06/07/11 »ReplyQuote

The people who've warned you off 168s really are your friends, at least so far as the Sierra MK model and those that are fairly close copies - the Hornady BTHP Match, Speer Gold Match, and Nosler Custom Competition - are concerned. They are superb short-range performers, but not only have relatively low BCs, are fundamentally unsuited for very long-distance use thanks to an over-steep boattail angle of around 13-degrees. The ideal angle is 7-9 degrees for long range bullets and going into double figures risks the airflow separating from the boat-tail walls and causing turbulence at transonic velocities leading to both a rapid loss of speed and instability. This also applies to the 180gn Sierra MK and to a lesser extent to all .30 cal Hornady A-Max models, the superb 208gn excepted. With .308 Win 168gn / 180gn bullet MVs, instability kicks in around the 900yd mark.

Berger's 168s are a very different matter and are all designed from the off as long-range bullets (unlike the others, the SMK launched 50 years ago as the 168gn International for 300 metre shooting - a role it was and still is superb in).

I agree with the advice given here by others, but you only hint at the shooting you're doing and that affects your choice. If you're sling shooting in a true Palma match run according to international Palma Federation rules, you're limited to .223 Rem / no bullet weight limitation or .308 Win loaded with a bullet of "less than 156gn weight" (hence the apparently strange choice of 155.5gn by Berger looking to squeeze the last ounce of performance out of the envelope). If run under local / US 'any bullet weight rules', you can load what you like and many shooters opt for heavier, higher BC models to reduce the effects of wind changes.

There are two potential downsides to this practice - the heavier the bullet, the heavier the recoil. The 175gn Berger BT Long-Range is a popular 'any bullet weight' choice as it gives substantially reduced wind drift compared to the 155s, but tolerable recoil in a 13lb sling gun. The 185gn Berger BT Long-Range is superb ballistically in .308W, but many shooters find the recoil too heavy with it.

The other argument against the heavies in this context is getting practice in wind reading. If you are going to shoot a lot of 'Palma Rules' matches, you may benefit from using the Palma bullets throughout to gain the experience and wind reading judgment with the 155s and avoid having to mentally switch between coping with two sets of bullet behaviour at long ranges.

If you're going to shoot F/TR, you go for the best ballistic and grouping combination that your rifle and bullet can deliver. Many F/TR competitors stick with the 155s because they do tend to group very consistently, but others have gone for 185s, and the 210gn VLDs. Some use both deciding which ammunition they'll shoot according to the conditions on the day. See the table below of 1,000yd wind drift in a 10mph true crosswind for a range of bullets at equivalent MVs (same muzzle energy).

The point behind all this is that as you've already discovered in your three-distance matches is that .308 Win is a very good 800yd cartridge but a marginal 1,000yd performer unless everything is optimised for this range - a bullet that groups well, has a suitably high BC and is shot at the highest velocity you can squeeze out of your rifle safely and consistent with good accuracy.

Incidentally, you are rather pessimistic in your belief as to what 1-12" twist will stabilise. The 190gn Sierra MK is a short bullet for its weight and this rifling twist works fine in all reasonable temperature and atmospheric conditions. You can also happily stabilise the 185gn Berger BT L-R, but the new 185gn Hybrid is a longer bullet and is marginal for this twist rate, really needing 1-11".

155gn (original Sierra Palma MK #2155) 3,000 fps 106.8" drift
155.5gn Berger 3,000 fps 91.1"
168gn Berger Hybrid 2,886 fps 82.0"
175gn Sierra MK 2,828 fps 97.1"
175gn Berger BT L-R 2,828 fps 85.8"
185gn Berger BT L-R 2,750 fps 81.4"
190gn Sierra MK 2,714 fps 90.0"
200gn Sierra MK 2,645 fps 86.0"
210gn Sierra MK 2,581 fps 77.5"


The other thing you are looking for is a retained velocity at 1,000yd that is not only still supersonic, but is as far above the speed of sound (1,122 fps under standard weather and pressure conditions) as possible to avoid transonic turbulence effects. The best of the 155s at 3,000 fps MV are running around 1,300 fps at this distance, the 185gn Berger at the equivalent 2,750 fps MV has another very useful 50 fps or so velocity. Your 175 and 190gn Sierra combinations are predicted to be travelling at 1,191 and 1,226 fps respectively under standard conditions, the 175gn value getting decidedly 'iffy' as strange things can happen as you approach the speed ofr sound under some conditions.

The worst pickle to be in is some bullets being supersonic and some subsonic as they approach the target and that's possibly what you were getting with your 175gn Sierra MK load. This bullet is VERY susceptible to this issue (been there, got that T shirt!); conversely, the 190gn SMK is famous for its transonic and subsonic stability, why it was long a favourite with British Commonwealth Match Rifle shooters who shoot .308W at 1,000-1.200 yards.

All data in the table is based on G7 BCs from Bryan Litz's book Applied Ballistics for Long Range Shooting 2nd ed and the PC ballistics program supplied with it. Using the G1 BC figures and tables / programs supplied by the bullet companies other than Berger Bullets are OK for shorter distances (up to 600yd), but can be seriously misleading (over-optimistic) for .308W at 1,000yd. Berger Bullets quotes both G1 and G7 BC for its longer range bullets on its website and also has a little free ballistics program that runs G7s for download.

Laurie,
York, England

 

[bozo699]

Dave,
Thanks for the explanation.
Wayne.

 

[DaveWhite]

Thank Laurie, it was his thoughtful response. That man knows his onions!

 

[bozo699]

Thank Laurie, it was his thoughtful response. That man knows his onions!

I know that.
Wayne.

 

[navyrad8r]

Doc,
i was shuffling along in service rifle working forever on a 600yd load. One of my mentors told me to mexican match our 77GR black hills match ammo with either 75gr or 80gr amaxs. that way you save powder and are on same powder too! 7thou jammed and shoot it at 600. the gun will tell you which one it wants. Mine was the 80 Amax and of course the big box has 600 instead of competitors 500. midway gave me a birthday coupon and wife saw me savin money! still married and went distinguished that year. if you mex match just make sure you pull the bullet square and carefully so you dont goof up your necks on the brass or mar the jacket. i use the Hornady cam puller and it works great very gentle on the jackets!! I might even be able to help you get some Berger 190 VLDs or i have ALOT of the older Hornady 190's (treat like SMK's). we could discuss a reasonable price and get them to you quickly in case if you don't need a whole box and want to load only a few for the 900/ 1 k...send me a pm if interested.
Cheers
doc