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 disappear well before the 500-600yd mark. Am I missing something? Thanks for any help-
Sierra 155, 168, 175 MKs
- Thread starter Fatelvis
- Start date
Re: Sierra 155, 168, 175 MKs
what does the wind deflection look like?
It's pretty well understood (IMHO) the 155's are flatter flying, but, as many here, I can range better than I can read the wind(not worth a sh!t in that department). Thus making the 175's preferred.
what does the wind deflection look like?
It's pretty well understood (IMHO) the 155's are flatter flying, but, as many here, I can range better than I can read the wind(not worth a sh!t in that department). Thus making the 175's preferred.
Re: Sierra 155, 168, 175 MKs
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">what does the wind deflection look like? </div></div>
The 155 beats in the 175 in wind also.
I just called Sierra and spoke with Rich Machholz, a ballistician.(Great guy!) He said the 100 fps difference makes a difference because they have the same BC. He said the tradeoff is that the Palma bullet is more difficult to load accurately, due to it's short bearing surface. I asked him if good neck tension (smaller bushing) would help, and he said yes. Due to the tendency for the Palma to tip off it's axis in the neck when hitting the feed ramp, the extra "support" of a tight neck helps. I'm gonna try it!
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">what does the wind deflection look like? </div></div>
The 155 beats in the 175 in wind also.
I just called Sierra and spoke with Rich Machholz, a ballistician.(Great guy!) He said the 100 fps difference makes a difference because they have the same BC. He said the tradeoff is that the Palma bullet is more difficult to load accurately, due to it's short bearing surface. I asked him if good neck tension (smaller bushing) would help, and he said yes. Due to the tendency for the Palma to tip off it's axis in the neck when hitting the feed ramp, the extra "support" of a tight neck helps. I'm gonna try it!
Re: Sierra 155, 168, 175 MKs
2156 Palmas
Varget
LC LR brass
Fed 210 prime
OAL # in the picture is to the ogive. This load rocks all the way out to 1300yrds one of the best bullets in my whole collection of guns/ammo
2156 Palmas
Varget
LC LR brass
Fed 210 prime
OAL # in the picture is to the ogive. This load rocks all the way out to 1300yrds one of the best bullets in my whole collection of guns/ammo
Re: Sierra 155, 168, 175 MKs
The 175 and the 155 (2156) don't have the same BC.
From Litz's testing:
2156 G7 - .229 G1 - .449
175 SMK G7 - .243 G1 - .475
First off, chronograph your loads with a good chrono like a CED M2 or Oehler. Second, with YOUR actual velocities - use a good ballistic program, and use the G7 BCs to generate your drop/wind tables. Litz's BCs are programmed into JBM BTW. Just select the correct bullet, then "Litz" in the drop down with it.
It matters not how things "seem". Unless you are The Terminator, you do not possess the ability to scan and analyze the bullet's shape, track its velocity with your eye, and plot the trajectory table with your internal CPU. Run the math with real numbers and make decisions based on that.
The 175 and the 155 (2156) don't have the same BC.
From Litz's testing:
2156 G7 - .229 G1 - .449
175 SMK G7 - .243 G1 - .475
First off, chronograph your loads with a good chrono like a CED M2 or Oehler. Second, with YOUR actual velocities - use a good ballistic program, and use the G7 BCs to generate your drop/wind tables. Litz's BCs are programmed into JBM BTW. Just select the correct bullet, then "Litz" in the drop down with it.
It matters not how things "seem". Unless you are The Terminator, you do not possess the ability to scan and analyze the bullet's shape, track its velocity with your eye, and plot the trajectory table with your internal CPU. Run the math with real numbers and make decisions based on that.
Re: Sierra 155, 168, 175 MKs
Fatelvis,
If the gun likes 168s, it'll shoot 175s just as well. Never seen one barrel in literally hundreds that I've used over the past 25 years or so that favored one or the other. It'll shoot them, I guarantee it. I'd suggest going right back to basics on this and running about 41.0-41.5 grains of 4895. That's an old standby NM load, and if you've got a gun that won't shoot it, you've got a gun problem. When the M14s were still <span style="text-decoration: underline">the</span> Service Rifle at Camp Perry, there was virtually no such thing as a load work up. Competitors dumped this charge under a 168, and later the 175, and went to the range. Literally, I've never seen a gun that wouldn't shoot this combination beautifully.
Fatelvis,
If the gun likes 168s, it'll shoot 175s just as well. Never seen one barrel in literally hundreds that I've used over the past 25 years or so that favored one or the other. It'll shoot them, I guarantee it. I'd suggest going right back to basics on this and running about 41.0-41.5 grains of 4895. That's an old standby NM load, and if you've got a gun that won't shoot it, you've got a gun problem. When the M14s were still <span style="text-decoration: underline">the</span> Service Rifle at Camp Perry, there was virtually no such thing as a load work up. Competitors dumped this charge under a 168, and later the 175, and went to the range. Literally, I've never seen a gun that wouldn't shoot this combination beautifully.
Re: Sierra 155, 168, 175 MKs
Thanks Kevin. Will the 41-41.5 load beat the rifle? If so, do I need a slotted piston? Thanks-
Thanks Kevin. Will the 41-41.5 load beat the rifle? If so, do I need a slotted piston? Thanks-
Re: Sierra 155, 168, 175 MKs
You'll want to work up to it, but no, it shouldn't be a problem. As I said, this combination used to be <span style="text-decoration: underline">the</span> standard NM load, used in tens of thousands of M14s without a problem.
You'll want to work up to it, but no, it shouldn't be a problem. As I said, this combination used to be <span style="text-decoration: underline">the</span> standard NM load, used in tens of thousands of M14s without a problem.
Re: Sierra 155, 168, 175 MKs
That's definately the best brass to use in an M14, and yes, it'll work in there as well. As I said, start below the top and work up to it if pressure signs allow (and they should with no problem), The LC 7.62 case is thicker than most commercial brass, and loads with these really do need to be backed off a bit. Between that, and teh varying lot to lot differences inherent in powders is why there's a range quoted, but yeah, most will wind up somehwere between 40.5 to 41.5 grains.
Don't know if you've heard this caution before, but I'll mention it anyway; Brass is good for about three firings from an M14. Great guns and I love them, but they're brutally hard on brass. Toss them after the third firing, regardless of what the look like. Another argument in favor LC brass; not only is it well made for autoloaders, it's also fairly inexpensive. Doesn't hurt quite as bad when you have to toss it after that third firing.
That's definately the best brass to use in an M14, and yes, it'll work in there as well. As I said, start below the top and work up to it if pressure signs allow (and they should with no problem), The LC 7.62 case is thicker than most commercial brass, and loads with these really do need to be backed off a bit. Between that, and teh varying lot to lot differences inherent in powders is why there's a range quoted, but yeah, most will wind up somehwere between 40.5 to 41.5 grains.
Don't know if you've heard this caution before, but I'll mention it anyway; Brass is good for about three firings from an M14. Great guns and I love them, but they're brutally hard on brass. Toss them after the third firing, regardless of what the look like. Another argument in favor LC brass; not only is it well made for autoloaders, it's also fairly inexpensive. Doesn't hurt quite as bad when you have to toss it after that third firing.
Re: Sierra 155, 168, 175 MKs
Would a slotted piston help get another firing or two out of the brass, before they need to be scapped?
Would a slotted piston help get another firing or two out of the brass, before they need to be scapped?
Re: Sierra 155, 168, 175 MKs
Nope, afraid not. Frankly, the only thing you can do to extend brass life with an M1A, is trade it for an AR-10. Sorry, but these guns (and the M1 Garands) are just brutally hard on brass. Simply the nature of the beast, and there's really not much you can do about that. Cost of doing business with these rifles, which is why I recommend the LC brass as being some of the best to use in them. Not only are the cases designed to be used in these rifles, but they can also be had at pretty reasonable prices. Doesn't hurt quite so bad when you have to toss them after that third firing. As for some of the benchrest techniques (neck turning, etc., yes, I've actually seen guys advocate this kind of crap for Service Rifles; very bad idea), don't waste your time. Way too much attention and time being spent on what should be a very short lifespan for a case.
Nope, afraid not. Frankly, the only thing you can do to extend brass life with an M1A, is trade it for an AR-10. Sorry, but these guns (and the M1 Garands) are just brutally hard on brass. Simply the nature of the beast, and there's really not much you can do about that. Cost of doing business with these rifles, which is why I recommend the LC brass as being some of the best to use in them. Not only are the cases designed to be used in these rifles, but they can also be had at pretty reasonable prices. Doesn't hurt quite so bad when you have to toss them after that third firing. As for some of the benchrest techniques (neck turning, etc., yes, I've actually seen guys advocate this kind of crap for Service Rifles; very bad idea), don't waste your time. Way too much attention and time being spent on what should be a very short lifespan for a case.
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