Sierra 155Palma, 168MK, and 175MK


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Fatelvis
December 6, 2012, 11:29 AM
I wanted to use 175SMKs in my M1A, after reading how they fly better at longer range than the 168s, and also my scope is calibrated for them out to 900 yds. Unfortunately, my rifle hates 175s, but loves 168s. The BDC lines in the scope would coincide with the 168's trajectory pretty well until about 500yds, but then falls off, making the BDC inaccurate. I had an idea: Try the 155MK Palmas, and see if they would be a closer match, due to their higher velocity. I plugged all three bullets into my Sierra program, using 2600fps for the 175, 2650fps for the 168, and 2700fps for the 155. The 155 shot flatter than BOTH of them all the way out to 1000yds! What?? The 155's BC is lower than both of the others, and it would be moving just a little faster. I would like to believe it, but it doesnt seem logical. I would think it's lighter weight, and lower BC would make the velocity advantage discappear well before the 500-600yd mark. Am I missing something? Thanks for any help-

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SlamFire1
December 6, 2012, 11:53 AM
I have never shot 155's at 1000 yards, I have done so with 168's and 175's. The 168's keyhole. The 175's at least put a circular hole on paper.

I do not believe that you can push a 155 fast enough in a M1a, at least without damaging the gas system, to keep the bullets supersonic.

At the last match, I think I over heard long range shooters saying they were pushing their 155's to 3200 fps.

A Palma shooter can tell use exactly what velocity is needed.

I really don't believe in the numbers from computer programs, I have plugged in numbers then compared to my 1000 yard zeros and found things don't work out at the range the same as the programs predict.

Like the amount of elevation you will need. I needed a lot more.

USSR
December 6, 2012, 12:02 PM
I do not believe that you can push a 155 fast enough in a M1a, at least without damaging the gas system, to keep the bullets supersonic.


+1. The Palma boys, who are pretty much restricted to this weight bullet, drive them at well over 2900fps in bolt guns with LONG barrels. You simply will not get enough velocity with this bullet in your M1A to make it a viable option for shooting at 1k. Just MHO.

Don

dannewberry
December 6, 2012, 05:46 PM
There are 168's with higher BC's than the Sierra bullets. The Hornady 168 AMAX is a good option to consider.

Swampman
December 6, 2012, 06:54 PM
Actually the BCs for the PALMA 155s are considerably better than those of the 168s and compare pretty favorably with the 175s, especially when you consider how much faster you can push them. In my experience, the difference is significantly more than 100 fps.
YMMV.

From the Sierra website.

http://www.sierrabullets.com/index.cfm?section=bullets&page=rifle&brandID=1&displayAll=1

155 grain Palma MatchKing.
.504 @ 2700 fps and above
.470 between 1800 and 2700 fps
.430 between 1500 and 1800 fps
.380 @ 1500 fps and below

168 grain MatchKing.
.462 @ 2600 fps and above
.447 between 2600 and 2100 fps
.424 between 2100 and 1600 fps
.405 @ 1600 fps and below

175 grain MatchKing.
.505 @ 2800 fps and above
.496 between 2800 and 1800 fps
.485 @ 1800 fps and below

I suspect that you may have looked at the ballistics for the older style Sierra 155 grain MatchKing.
.450 @ 2600 fps and above
.443 between 2600 and 1800 fps
.417 @ 1800 fps and below

The 155 Palmas shot OK in my M1a, but not quite as well as the SMK 168s or Lapua 155s. Since the longest range within a reasonable driving distance from my house is only 600 yards, I generally just use the 168s.

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