[Bead Drawer]

I'm interested to know why the 155 grain "Palma" match load for the .308 isn't used in sniping. Palma matches are very demanding long-range events. Why is the 175 grain .308 preferred over the 155 grain for sniping? I'm referring to the Federal Gold Medal Match cartridges in both weights.

Thanks in advance.

Practice, Practice, Practice, and shoot true.

 

[Jeff_850]

probably something to do with the bullet weight might produce less momentum and less penetration that way?
it starts out with a much higer velocity and actually more energy but has a BC of .450 instead of .496 (Federal Gold Medal 175)
but i think it still out paces the .308 just im too lazy to calculate this when the ballistic changes at differnt velocities
accuracy is great ive herd some people say recoil is less... i cant tell the differnce... thier velocities are higher i can notice a differnce between Aussie surplus 144 grain for example kicks like a .223 not that any of these .308 loads kick that much (cause its a ligher bullet at probably similar velocities)
now then accuracy is comperable and they both out pace 168 grain (federal gold medal match) yet 168 gr does better at 100-300y id say
my rifle likes 175 grain a lil better but its hard to say for sure its close

 

[Dan]

Bead,

Jeff is on the right track. I ran some of the numbers on Sierra's ballistics software. Even though I'm not a real competition shooter, I couldn't pass it up when I saw it in action at the '04 SHOT show. I set the velocities equal so you could see the entire picture.

Sierra 155 gr. HPBT Palma Match
Velocity: 2500 Ft./sec. (very low for this weight)
Drop @ 1000 yds. (inches): -512"
Energy (ft/lbs.): 433 ft./lbs.

Sierra 175 gr. HPBT
Velocity: 2500 Ft./sec. (very good for this weight)
Drop @ 1000 yds. (inches): -471"
Energy (ft./lbs.): 577 ft./lbs.

All it takes is another 100 ft./sec. on the 155 gr. Palma Match to get the drop even with the 175 gr. (-471"), but the energy remains lower. When the drop is equal, the 175 gr. still hits with 110 ft./lbs. more energy. Using the numbers as a guide, my opinion is the heavier bullet is used in a sniping role because it hits harder and resists wind drift better. I'm not a sniper, but hopefully that's more than an educated guess.

 

[mele]

I'm glad someone brought this up, because it brings up some interesting points.

Lets look at the raw data for the three (3) federal .308 match loadings. And then I'll try to explain why the palma is not used

Here are the three loads
168gr at 2600fps
175gr at 2600fps
155gr at 2950fps

At 1000 yards the total drop and energy for the three loads are:
168gr 456" 537 ft-lbs
175gr 437" 609 ft-lbs
155gr 356" 604 ft-lbs

Um, I would have to say that for 1000 yard .308 shooting, the 155 palma load is clearly superior. Its drops 100 full inches less then the 168gr, and 81 inches less then the 175gr and the energy is nearly identical. Well, 350fps is a whole bunch faster at the get go, and is why it does so much better. The 155 gives up some in BC, but the extra velocity more then makes up for it. These numbers were computed using a copy of the free "Point Blank" ballistics/reloading software. Its not as good as sierra or others, but the numbers are close enough. (you'll see very similar results from other software, numbers maybe slightly different).

So, why is the 168 and 175 used? The sectional density is a little better on the heavier bullets (allows better penetration), but thats not something that clearly dictates bullet selection. The big reason is because humans are creatures of habit. The 168 was the first real match loaded cartridge to hit the market, and is now ingrained as the de-facto. The 175 has gained inroads because it is better then the 168, but mainly because the military adopted the m118LR with the 175 gr. This, coupled with most all BDC (bullet drop compensators) being set to the ballistics of the 168 make it very difficult for the 155 to make any progress.

I do plan to start doing some evaluations with the 155 and see just what its sniping potential may be. Stay tuned on the site.

MEL

 

[Jeffvn]

I will not disagree with mel, but have one piece of information to add that changes the picture substantially. I was asking this same question not too long ago, when I was testing the 155 Lapua Scenar (BC of .508), which is considerably lighter than the 175 SMK, but has a higher BC than that bullet. (when you hold one in your hand you know it flies like crazy sharp sleek nose, very little curve to the ogive.)

What the box of 155 SMK Federal Gold Medal ammo does not tell you is that the 2950 fps muzzle velocity is based upon use in a 30 inch barrel. The 2,600 fps for the 175 and 168 is based upon a 24 inch barel. If you want an accurate comparrison between the two you need to compare the 155 at approximately 2,825 fps (at least according to my QuickLoad software). At 2,825 fps, the 155 and the 175 are traveling at virtually the identical speed at 1,000 yards, but the 175 holds much tighter (nearly 20% less drift over 600 yards) into the same amount of wind.

Don't get me wrong, my 155 Lapuas eat the 175SMKs for lunch when I shoot the Lapus at any velocity above 2,800 fps and nearly any range up to and potentially beyond 1,000 yards. But then again my Lapua 155 Lapuas also kick butt on the 155 SMK at every yard line that I've ever shot them (the Lapua BC is nearly 20% higher).

 

[Bead Drawer]

hmm,

This is all very interesting. Thanks for the responses everyone, and I look forward to seeing the evaluations and the potential for the 155.

 

[mele]

Jeffvn,

Thank you for that information! You are absolutely correct that it changes everything. I'm surprised that federal does not mention the 30" barrel, as it is critical. This particular load loses most all of its luster if it only 2825 from a 24" tube.

MEL

 

[Bead Drawer]

I was looking at Federal's website, and the 155 grain load has a few inches more wind drift in a 10 mph crosswind at 500 than the 175, at 1000 yards though, I couldn't say.

I don't think I would attempt a shot in a 10 m.p.h. crosswind at that distance though.

 

[Jeff_850]

Mel:
they mention 24" barrel in the catlog
why i dont know maybe an error

but it is still a nice accurate round from a 26" barrel
be interesting to see how the 22" barrel on your Bravo handles it, and what speed it spits it out at, if ya want to try a pack of it and see how it does

 

[Jeffvn]

Mel

I hear you. I was really disappointed (and told the rep at Federal as much) when he told me its was based upon a 30 inch tube (can you say palma and tubes that look like pole vaulting sticks).

When I reduce that load using Quick Load, I get 2,882 fps from a 26 inch tube, but everything is indiviualized.

IN any event, I can rund my Lapua 155s at roughly 2,875 using IMR 4895 from my Patriot Arms 24" tube and be conservatively safe on pressure. An easy 2,800 and use most any powder. At 600 yards (using a 300 yard Zero) with my Lapuas running 2,875 fps, I'm a full 2 MOA flatter than the 175 SMK. I have not yet shot the 155s Lapuas beyond that range, as the 1,000 yard range South of Houston at Bayou Rifles has not yet opened. Still 2 MOA at 600 is pretty amazing.

 

[Scatch Maroo]

I was asking this same question not too long ago, when I was testing the 155 Lapua Scenar (BC of .508), which is considerably lighter than the 175 SMK, but has a higher BC than that bullet.

What's BC?

Scatch Maroo

 

[Bead Drawer]

It is worth noting, that in the Gun Buyer's annual #30 (the latest one) the Federal Palma load is run out of a 24 inch barreled Howa custom, and measured 2903 f.p.s. over a PACT Chronograph.

Upping the barrel length to 26 inches, as on the Remington 700P, should improve velocity a little bit, bringing the speed of the round very close to Federal's published figures out of a 30 inch barrel.

Palma shooters routinely use barrels even longer than 30 inches, and it is doubtful they are gaining much extra speed for the extra few inches, as the .308 loaded in any configuration is done burning powder long before the 26 inch mark.

At the risk of offending someone, which I apologize if I do, I submit that a 26 inch barreled rifle will produce speeds very close to Federal's figures, close enough to ignore the importance of the 30 inch barrel, thus giving plenty of reason to compare the 175 and 155 grain rounds.

I would very much like to see such a comparison done, if only to satisfy curiosity.

 

[morpheus]

What's BC?

BC is Ballistic Coefficient. BC is a rating system based upon a bullet's weight, shape, and ability to retain velocity. The higher the rating(expressed in decimal points) the higer the bullet efficiency at long range.

It basically means that a bullet with a high BC will have better ballistics than one with a lower BC.

 

[Jeff_850]

Scatch:
bc stands for ballistic coefficient, its a coefficient to determine how much velocity degredation is at various distances, how much a bullet will drift in wind and all too

Bead Drawer
im probably about 100 fps short but i havnt used a chronograph so dont quote me on this, just judging by the bullet drop that i have had out to 600
its about a full minute higher either that or im too stupid and cant count 1/4 minute clicks from where it was and where i thoguht it would be

 

[mele]

I will take up the challenge! If the local gun shop has the 155 federal, I will chrono it compared to 175. I have a patriot arms rifle on the way here right now for evaluation, which I will use if I can get 155 locally, if not, I'll have to order in a box of 155 and will test it in the 22" tube bravo.

MEL

 

[Jeff_850]

Mel:
www.ammoman.com has Federal GM 155 gr for $19/free shipping (last i checked)
when i order i have it in no more than 3 days, last order, 5000 rounds of .22 LR ammo came in 2 days, 40 lbs of ammo free shipping

velocities arnt hurt with your 22" barrel with the 168/175 grain if i recall correctly will be interesting to see if thats true for a 155 grain bullet
speaking of the Bravo when can we see a pic of that put in the gallery section

 

[mele]

$18 per box, $100 minimum order to get free shipping. I'll get some ordered.

In regards to the bravo: I was wondering when people would start asking me for gallery pics of what I got... perhaps I'll have to start trickling them onto the site, though my collection is not nearly as nice as many of the listers.

BUT, for pics of the bravo, you'll have to be patient, its down at tac-ops right now getting the suppressor fitted and test fired. I hope to have everything back to me in a couple of weeks. I'll post some pics of it with suppressor attached

MEL

 

[Jeff_850]

well what do you have?

its a couple of weeks when will i see your stuff in the gallery section?
soon???

do you have a class III or how do you get the supressor there
and do you have to 'explain' to the government what you 'need' one?

 

[mele]

Dang, you guys don't forget anything!!

The bravo gets here this week from tac-ops. I do not have a class III, so I have to get the tax stamp like everyone else. But since I am a dealer I have the option of a getting an agent letter which means I'm an agent of the manufacturer and will sell/evaluate their products. I will do that and then handle the tax stamp for my permanent suppressor.

I also am finishing up my review of the Patriot Arms Genesis rifle this week. After that, I'll start posting some pics of what I own

MEL

 

[SpEcTeR]

Mel,

I'm really interested in you Patriot Arm's review due to the fact that I'm seriously considering having Jered rebarrel and stock my 700. I've been getting information from their website, articles, testimonials and from Jeffvn and it seems like a worthy venture up until now. Jeff tells me that he is pretty fair priced considering the amount of work he performs and quality of course.