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Old 04-09-2011, 14:55   #31
Buffalobob
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For the 308 or any other caliber, each increase in muzzle velocity of 100 fps is only going to give about a 50 yard increase in range.
For BC if you increase it by 10% then you get a 10% increase in range. For a given cartridge both muzzle velocity and BC have practical limits on the amount you can increase them. One should keep in mind that BC is tied to sectional density and muzzle velocity is tied to weight.

What Litz has done is change the shape factor without sacrificing either BC nor sectional density and gained large increases in yardage out to whatever range the shooter and spotter have the skill to achieve with the equipment they have available.
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Old 04-09-2011, 16:06   #32
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Quote:
Originally Posted by Gene Econ View Post
BO:

Any of the match grade 155's are excellent bullets. Note they were designed very specifically for Palma shooting. Generally they use a 1 turn in 13 inch twist, 30 inch long barrel in order to stabilize that specific bullet and to get the 2950 plus FPS needed to ensure it is above the speed of sound at 1K. International Plama rules demand a bullet of 155 grains or lighter and 7.62 / .308 cartridge. US Palma lets you shoot any bullet weight but it must be .30 caliber and I believe is restricted to the .308 cartrdge. Understand that Palma rifles are also restricted in weight.

So, in a way you see why those bullets were designed the way they are. To feed a very specific need of a very specific sport. Would they be fine for military purposes? I don't think so because you don't see 30 inch long barrels on M-24's and you need that speed for that shorter and lighter bullet to stay above the speed of sound.

Personally and for military applications I see .30 caliber bullets weighing in the 170 - 180 grain range is about ideal to maximize danger space given 20 inch + - barrel lengths, a requirement to keep the bullet length down to maximize available cartridge capacityand magazine seating, while allowing for a fast enough velocity for performance to practical combat ranges -- which I see as 600 meters or less but the Army sees as 800 meters or less.

Another thing you need to consider is recoil effects. The higher the recoil, the more negatively it affects the shooter. A 155 Palma load is very hot -- too hot to blast regularly from standard receivers but its recoil is still noticeably less than a round of 118 shot from a 24 or 110. That means a-lot when talking about blasting those antique 190's and 220's.

Oh yes, note I did not get into BC comparisons. Although they are of value in decisions on ammunition that shooters make, you will never see them become the primary factor. Accuracy, velocity, and terminal effects are generally the primary issues going into a decision on some sort of cartridge and bullet. Those three get mixed up in priority based on the specific need but those are generally the three issues involved with decisions. BC's get involved after initial decisions are made and a guy has narrowed down his potential choices. Even then, they may not mean anything.

As a general rule, from the barrel to 300 the BC has very little meaning. From 300 - 500 it has some meaning and from 600 out it does have meaning you can actually see in reality. But only when you are looking at equal velocities and BC differences of at least 5 %.

Gene
Thnaks for the info. You mentiond the recoil and that is why I was thinking the 155 in 308 vs the 300 WM and 338 Laupa with their punishing recoil etc. but I see your point on the 30 in bbl.

My personal preferance is the 06 since it has better ballistics than the 308, years of load data, not as much recoil as the 300 WM and can handle up to 220 gr bullets if need be but that would be another round in the system and logistic wise a possable problem.

I have a 155 gr load a guy give me that is a top shooter I am thinking of trying in my match 308. The results will be intresting I just have to get the time to load it and trigger time not to mention $$$.
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Old 11-17-2011, 14:41   #33
Buffalobob
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I ordered a box of the bullets for my 308. Here are a couple of pictures of the box and then there is a picture of two Sierra 175 MK on the left and two Berger 175OTMs on the right. It was misting rain at the time of the picture.
Attached Images
File Type: jpg Bdr 175OTM.jpg (64.2 KB, 37 views)
File Type: jpg Bdr 175OTM (1).jpg (37.6 KB, 37 views)
File Type: jpg Bdr 175OTM (3).JPG (127.5 KB, 73 views)
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Last edited by Buffalobob; 11-17-2011 at 14:58.
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Old 11-17-2011, 14:57   #34
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Deer season starts Saturday after Thanksgiving so I needed to go to the rifle range to check some zeros and took along some loads for the OTMs to test for accuracy. I normally shoot 43.4 grains of Varget in RWS cases for competition with the Sierra 175 MK and on calm days that will group about 0.3-0.4 for three shots. For this test I am using Winchester cases that have about 1 grain more volume than RWS but are less consistent in quality. It was gusting wind up to 5mph today so groups were a little more open.

First picture is of the standard 175MK loads where I am adjusting the zero between the top 3 shot group and the bottom 3 shot group. Aim point is the upper right corner of the tape.

Second picture is the Berger 175 OTMs with three different charges of Varget and 5 shot groups instead of 3 shot groups. All three groups go just under 0.5 for five shots. This is acceptable accuracy for me and this particular rifle.

I think I will try them out on deer this season and see how they work.
It will probably be a long time before I get to test past transonic ranges so don't be holding your breath waiting on it.
Attached Images
File Type: jpg 175SMK (1).jpg (27.4 KB, 66 views)
File Type: jpg `175OTM.jpg (17.6 KB, 73 views)
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Old 11-18-2011, 18:23   #35
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The second edition of Litz' book is very good and fairly easy to understand. There are a few errors but he gives a good explanation of the difference between secant and tangent ogive bullets and the ballistic differences between shorter and longer boat-tailed projos.

I am guessing but Litz and Berger have done extensive recent original art designing "Hybrid" bullet profiles, melding what they consider the best of both tangent and secant ogives. I assume that's what they've done with the 175.

My experience with 300-grain .338 Lapua Magnum projos has Sierra Match Kings running out of steam around 1600 Meters (they definitely do NOT fly true transitioning thru trans-sonic); Bergers around 1800; and Lapua Scenars right about 2 klicks (all using the same primer, brass, and powder charges).

RUAG (Switzerland) has a new proprietary 300-grainer they are adding to their Swiss-P line that is aimed at meeting USSOCOM's 1500-meter PSR spec as well.

Last edited by Sinister; 11-18-2011 at 18:26.
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Old 11-18-2011, 21:05   #36
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Quote:
Originally Posted by Sinister View Post
----- My experience with 300-grain .338 Lapua Magnum projos has Sierra Match Kings running out of steam around 1600 Meters (they definitely do NOT fly true transitioning thru trans-sonic); Bergers around 1800; and Lapua Scenars right about 2 klicks (all using the same primer, brass, and powder charges).

RUAG (Switzerland) has a new proprietary 300-grainer they are adding to their Swiss-P line that is aimed at meeting USSOCOM's 1500-meter PSR spec as well.
OK - Slightly off topic but you've got my undivided attention. Have you had an opportunity to look at the Hornady 285gr .338 Bullet yet?

PS - You coming to Bragg next month for the sniper competition?
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Old 11-19-2011, 09:10   #37
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I've looked at the Hornady 285s but not shot a bunch (maybe 20 rounds). I have a photo somewhere with sectioned Hornady 285, Scenar, and Match King or Berger side-by-side. The Hornadys are interesting in that the nose of the projo is hollow (like a 308 155-grain Scenar) while the jacket is nearly the same length as the 300-gr Scenar, pushing the center-of-gravity towards the rear.

We're getting to Fayetteville on Wednesday night (the 7th).
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Old 11-25-2011, 11:14   #38
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Brush- I have a Rem 700Mlr in .338 Lapua. It is just a factory rifle with a stock muzzle brake. It has much less recoil than my son's M70 .300 Winmag. It is not as bad as people make it out to be. I have only had it for about 8 months. I use the 300gr SMK with good results. Now I have to buy a better rangefinder, though....

I should add that I am a rookie at this and no where near the class of the other QP's commenting on this thread. My comment was on the recoil remark only...

Last edited by mark46th; 11-25-2011 at 11:31.
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Old 04-19-2012, 07:01   #39
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As I mentioned in post #34 I would try to test the transonic stability of the bullet. This has finally happened and as luck would have it the test weather conditions were pretty raggedy but I shot anyway.

Because I do not have access to a 1500 yard range I decided to develop a reduced velocity load that would go subsonic at about 700-750 yards. One of my loading manuals had a starting load for 175 grain bullets and Varget so I put together a load with a muzzle velocity of 2250 fps. This load was tested for accuracy at 100 yards by firing two groups from the bench. Groups size CTC was less than 0.4.

Ttransonic stability was tested during a F-class match at R4 Quantico USMC. There was the worst headwind I have experienced in the last six or seven years. It was about 20 mph and varying from 10:00 to 2:00. During the unlimited sighter stage at 800 yards the rifle was zeroed for the 155.5 Berger (MV= 2800fps) that I normally compete with and also the 175 OTM (MV-2250fps). The 800 yard stage was fired with the 155.5 Berger and produced an average per shot score of 9.3 which was probably the best score I have ever gotten at that stage. The “open” rifles were averaging about 9.0. But what I got was a period of wind that stayed at 11:00 so I didn’t have the direction switches that are so damaging to the score. So the test was off to a bad start being as I had shot about 5 points better than normal under some of the worst conditions.

At 900 yards I used the 175 OTMs and got a per shot average of 7.3 being as the wind was back to switching direction. At 1000 yards I went back to the Berger 155.5 and got a per shot average of 6.75. Those of us shooting “FTR” (308) were recording misses off of both sides of the target because the wind was so unpredictable. The interesting thing is that the subsonic, slow moving 175 OTM produced a higher per shot score than the faster supersonic 155.5 Berger at the 100 yards difference --- 7.3 vs 6.75. This is about a half MOA difference.

So I conclude that the 175 Berger even when it is well below the transonic zone still retains very good accuracy.

For those who forgot, I tested terminal performance of the 175 OTM at normal velocity on a deer in this thread.


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