Long range shooting question

[kestak]

Greetings,

Rifle: LMT MV308
Barrel: 18 inch
Caliber: 308
Bullet: Sierra 168 grains 2200 (Matchking)
Powder: WC844 41.5 grains
Velocity: 2610 ft/sec
Scope: Monarch X 1.8 inch over barrel. 4 clicks for 1 MOA

Verticals:
200 meters 2.0U (8 clicks)
300 meters 5.0U (20 clicks)
400 meters 8.5U (34 clicks)
500 meters 12.5U (50 clicks)

My questions:
- On a benchrest with bipod: I get a group 1 inch at 100 meters, 2.5 inches at 200 meters, 6 inches at 300 meters and 10 inches at 300 meters. Is the problem my shooting ability or my load? I have the same result with variations with Nosler bullets 168 grains HPBT, I4895 powder, CCI primers, Federal primers. I got lucky 1 week ago and got a string of 4 groups of 4 to 6 inches inches at 400 meters with 41.5 grains WC844, Sierra 2200 bullets.

- With a full wind from the right 8-10 miles per hour, I get a drift to the left of 12 inches (center of the 10 inches group with a 20 shots group. Is it a normal wind drift deviation or my zero sounds a tad on the left?

Thank you

 

[theblakester]

http://youtu.be/H7bOIB2Zk-E

Be sure to watch the other sniper videos in sequence (when you have time). Tons of long range shooting information. Hope it helps... Or you at least find it interesting. Good luck

 

[jim243]

It sounds like you are using "pull down powder" (surplus). Since it is simular to H-335 I would recomend that you try H-4895 or IMR 4350 for that weight bullet at long range shooting. A slower powder will develop a more consistent pressure build up and should do you better for those long range shots.

Just my 2 cents.
Jim

 

[wanderinwalker]

I too would assume you could get a bit better results with something like off-the-shelf H4895 or Varget or RL-15 versus pull-down powder.

Next, is that 2610-fps truly chronographed from your rifle?

Sounds like 100% normal wind drift to me, depending on the range. I've never calculated drift specifically to windspeed, but more by watching the mirage on the range. Note: this only works until the wind gets fast and takes the mirage away, but I've never shot in those kinds of conditions. My last time at Camp Perry I was shooting between 2 and 2.5 minutes of wind at 600-yards on my .223 (12-15" of drift) but I can't remember the wind speed. Probably sub-10mph.

Also, I've heard and read of strange things happening shooting with bipods on hard surfaces. Possibly shooting prone from the grass or using sandbags instead of the bipod would help tighten those groups. And the "ballistic cone" isn't always a linear progression. A 1-MOA group at 100-yards don't always translate downrange into 1-MOA at any given range. Some bullets will flock tighter further out, some drift further off center. You don't know what you'll get until you actually put holes in paper and see the results.

 

[helotaxi]

What is your standard deviation and extreme spread on those loads? Are they opening up vertically or horizontally? Velocity deviation can easily explain your diverging group size as the range increases. Variability in the wind that you can't detect won't help either.

 

[taliv]

if it holds 1" at 100, the only thing that would make it magically open up at greater distance would be wind.

so my suspicion is your scope. are you adjusting parallax? can you see the target clearly at that distance? using the same sight picture? try a different target where you can get a better sight picture?

are the groups at each distance circular or strung vertical or horizontal?

 

[Blackrock]

That 18" barrel ain't helping you much. Plus a change to either H414, Varget or RL15 could help. You will need the fastest burn rate that bullet will take to get the optimum fps out of that short barrel. IMO a .308 needs a 24" barrel to have any chance at long range accuracy.

 

[kestak]

Measured with a chronograph about 10-12 feet in front of muzzle.
The spread is pretty good. I did the test with 50 rounds. If my memory serves me well, I had only 2-3 that were +-70 ft/sec and the remaining was int he 2590-2630 (plus or minus a few ft/sec)

The tight groups I had in the past were a nice "circle" group (as much as you can get with 5 shots). The one I got with the wind drift was almost a perfect Oval. I just went into the garage to register my shots fired with that rifle and I shot 44 rounds in a 11.5 inches x 7.5 inches group at 400 meters (not 20 like I write in my first msg).

I just did the math in my mind with my rule of thumb "scientific kentuky windage" 30-06 Garand wind drift (distance/100xwind speed/10) and it is 4 clicks. I also used my little ballistic app on my ipad and it says 4.5 MOA with that kind of wind. Those are consistent with themselves but not consistent with what I see.

(still watching the videos BTW.... )

 

[helotaxi]

if it holds 1" at 100, the only thing that would make it magically open up at greater distance would be wind.

Velocity and wind variation have increased effects as the range increases so a high shot-to-shot velocity spread would open groups up more as the range increases.

 

[taliv]

Yeah that is true. But it would have to be a HIGH variation

 

[kestak]

Hmm....No one answered that question. Is it possible my zero is a tad bit left and it does not show much at 100, 200, 300 but at 400 it shows way much?

I just talked to a guy who shoot at the same range than me and he said with his Remington 24 inch barrel, 308, 175 grains bullets, he does not need to do any correction to hit "the plate" up to 500 meters with the kind of wind we had yesterday. with my deviation, I would have missed the plate (10w x 24h) certainly.

 

[1911 guy]

Things that come to my mind, maybe you're already doing some of them:

Make sure all your cases are the same headstamp. Thicker/thinner case walls affect pressure from shot to shot.

I happen to like Varget for .308, but there are other good powders. In any case, I'd switch powders to something that is A) in the mid range of the burn rate for .308 and B) takes up the most case capacity for your load.

Start at the Min load, load ten rounds, increase 1/2 grain for another ten rounds. Work up to Max load. Go to the range on a dead calm day and shoot. When you find "The Load", go home and pull the bullets on the rest of them.

Try another bullet. Some rifles, even two made the same day at the same factory, will shoot differently.

 

[WYOMan]

A 40 fps spread is high for longer ranges. My load for my hunting rifle has a ES of 12.99 fps. My long range bolt rifle is less. Also wind is tricky even for experienced long range shooters. It is not a single constant speed. Also the terrain over which the bullet is travelling to the target is a factor, unless its perfectly flat. The range where my brother and I used to shoot long range matches had 6 wind flags from the line to the 1000 yard targets, and they NEVER all reacted exactly the same. Also there were 2 draws and a small ridge with a pond for watering cattle along the way. The draws were like wind tunnels. If you want to see how much your affecting your accuracy try shooting from sand bags on both the forearm and butt stock, to try and minimize the movement your bringing into the equasion. I would find a more consistant load first.

 

[helotaxi]

That 18" barrel ain't helping you much. Plus a change to either H414, Varget or RL15 could help. You will need the fastest burn rate that bullet will take to get the optimum fps out of that short barrel. IMO a .308 needs a 24" barrel to have any chance at long range accuracy.

That's silly. You don't choose rifle powder based on barrel length because barrel length has no bearing on powder suitability or the pressure curve of the cartridge.

taliv- with the 168SMK a max velocity spread in the region of 50fps in the velocity range that the OP is working in results in a vertical impact difference of 0.2 inch at 200yds, 0.8 inches at 300yds, 1.6 inches at 400yds and 3.1 inches at 500yds. 50fps isn't a huge max spread by any means.

 

[taliv]

Heh ok well 50fps is pretty huge for me

Your zero won't change your group size

 

[C-grunt]

Could also just be your shooting. If you are using a bipod get off the bench and go prone with a rear bag. If you want to shoot from the bench use a front and rear bag.

 

[Detritus]

Heh ok well 50fps is pretty huge for me

Yeah, but because of what you do for at least part of your "fun", you're a bit more critical of stuff like that.

Most of us are not ever, or in some cases are not yet, going to be that hairsplitting about max spread.

 

[ms6852]

You need to perform a ladder test to see which load will be best for your barrel. The harmonics of the barrel have a lot to do at longer distances. It is best that you use 300 yards to perform this test if not 200 yds will do. At a hundred yard the distance is not that great where environmental conditions could make a difference. You no longer shoot moa at 200 yds. but I wonder how much of that is your doing. If you can find someone who you know is a better shot than you, (no offense intended) that could shoot for you a group at several distances would also help you pinpoint your problem. Remember that a 3 inch spread at 300 yds. and a 6 inch spread at 600 yds. is still shooting moa.

 

[wanderinwalker]

keystak, your range friend with the 24" barrel has more velocity and a better BC than you have. It's well within expectation for his wind drift to be less than yours. For fun punch your 168gr load into a ballistic calculator and then run the numbers for the 175gr bullet at the same speed. BC trumps pure bullet speed.

 

[kestak]

I just bought an ipod and shooters ballistic. It looks like the wind drift group was within the normal per that application...

Range(yd) Path(in) Path(moa) Drift(in) Drift(moa) Velocity(fps) Energy(ft-lbs) TOF(s)
1400 -1301.7 U88.8 -333.0 R22.7 883.5 291.1 3.111
1350 -1162.1 U82.2 -308.2 R21.8 900.6 302.5 2.942
1300 -1033.8 U75.9 -284.3 R20.9 918.9 315.0 2.777
1250 -915.4 U69.9 -261.0 R19.9 938.8 328.8 2.615
1200 -806.9 U64.2 -238.5 R19.0 960.4 344.0 2.456
1150 -708.0 U58.8 -216.9 R18.0 983.7 361.0 2.302
1100 -618.3 U53.7 -196.2 R17.0 1009.2 379.9 2.151
1050 -536.8 U48.8 -176.3 R16.0 1037.7 401.6 2.004
1000 -463.5 U44.3 -157.4 R15.0 1069.9 427.0 1.862
950 -397.8 U40.0 -139.5 R14.0 1106.9 457.0 1.724
900 -339.3 U36.0 -122.7 R13.0 1149.5 492.9 1.591
850 -287.4 U32.3 -107.1 R12.0 1198.1 535.5 1.463
800 -241.5 U28.8 -92.6 R11.1 1252.8 585.5 1.341
750 -201.1 U25.6 -79.4 R10.1 1312.9 643.0 1.224
700 -165.7 U22.6 -67.4 R9.2 1378.6 708.9 1.112
650 -134.8 U19.8 -56.6 R8.3 1449.3 783.5 1.006
600 -108.1 U17.2 -47.0 R7.5 1524.3 866.7 0.905
550 -85.3 U14.8 -38.5 R6.7 1602.8 958.3 0.809
500 -65.8 U12.6 -31.0 R5.9 1681.9 1055.1 0.718
450 -49.3 U10.5 -24.5 R5.2 1763.8 1160.4 0.631
400 -35.7 U8.5 -18.9 R4.5 1848.6 1274.7 0.548
350 -24.5 U6.7 -14.1 R3.8 1936.4 1398.7 0.468
300 -15.7 U5.0 -10.1 R3.2 2026.3 1531.6 0.393
250 -9.0 U3.4 -6.9 R2.6 2118.1 1673.5 0.320
200 -4.3 U2.0 -4.3 R2.1 2208.3 1819.1 0.251
150 -1.3 U0.8 -2.4 R1.5 2300.4 1973.9 0.184
100 0.0 0.0 -1.0 R1.0 2394.8 2139.3 0.120
50 -0.2 U0.4 -0.3 R0.5 2490.6 2313.8 0.059
0 -1.8 0.0 -0.0 0.0 2590.0 2502.2 0.000

 

[jaimeshawn3]

+1 with ms68. Do a ladder test to determine exactly what is the best powder charge for your barrel. I'd also recommend trying a heavier bullet with a better balistic coef.
Maybe move up to 200gr Sierras.

 

[Mobuck]

In my estimation, WCC844 is too fast to give a 168 grain bullet optimum velocity from an 18" barrel. WCC846 would likely be a better choice. This is what I use with 155 grain HPBT out of 24" bores. As for the group size, small variances in shooting form become magnified as range increases.

 

[kestak]

WC844 is at the position 81
H4895 is at 87
I4895 is at 89
TAC is at 86 (many long range shooters in 308 at my range are using it)

With 41.5 gr of I4895 I get 2480 ft. secs same bullet, same case, same primer.
With 41 gr of WC844 I get 2590 ft. secs same bullet, same case, same primer.

I don't mind to change powder to TAC or I4895. I'll ladder it at 200-300 yards and see the results...

 

[Walkalong]

if it holds 1" at 100, the only thing that would make it magically open up at greater distance would be wind.

so my suspicion is your scope

Yep, so if it isn't a scope problem, learn to read wind better.

Loads that shoot 1 inch at 100 yards, do no keep opening up at longer distances unless outside forces are working against it.

I used to shoot better at 200 than 100, simply because I was more comfortable doing so. I tried to be too fine at 100.