Why isn't everyone loading 200gr+ pills for .308?

[dbooksta]

I was playing with Robert Meijer's excellent "BfX" Excel ballistics calculator and compared Hodgdon's published max safe loads from a 24" .308" bbl using 168gr (muzzle velocity 2828fps) and 200gr (muzzle velocity 2582fps) BTHP bullets. The 200gr dominates in every measure I think a shooter would care about down the range past 1000 yards:

<ul style="list-style-type: disc">[*]More retained energy[*]Less wind deflection[*]Less spin drift[/list]

In the mid-range the 200gr trajectory does drop by 1 MOA more than the 168gr, but by 900 yards it has caught back up and is flatter through 1000 yards.

I suppose for shooting under 500 yards the only significant factor is retained energy, and maybe that's not worth the marginal cost of heavier bullets. But for anyone who loads .308 with the intention of long-range shooting why isn't 200gr or 220gr the standard instead of 168gr or 175gr?

 

[Anchor Zero Six]

Re: Why isn't everyone loading 200gr+ pills for .308?

Why isnt everyone running short barrels?

Cant answer eith question but I'm running a 20" 300WM and working up a load for 230 Bergers.

 

[squirrel_slayer]

Re: Why isn't everyone loading 200gr+ pills for .308?

I too am curious about jumping on the heavyweight bandwagon (208gr a-max flavor) i'm just unsure if I can push it fast enough to make it worth while out of a 16" gas gun.

 

[1lnbrdg]

Re: Why isn't everyone loading 200gr+ pills for .308?

Shhhhhh, Dont let everyone in on this secrete . . . .

I'm likeing the 185 / 190 gr pills myself. Can't seem to get the velocity out of the 200(+) bullets to make them worthwhile though.

 

[dbooksta]

Re: Why isn't everyone loading 200gr+ pills for .308?

I have also considered the barrel length issue -- I shoot both 16" and 26" .308s. The benefit of the longer barrel is obvious: More velocity and energy produced from the same load, hence more "ballisticly efficient."

But when considering heavy vs. light bullets it doesn't look like barrel length matters: Max loads are going to produce roughly the same muzzle energy for all reasonable bullet weights (for .308 call that 145-220gr), but the heavier bullets, with their higher ballistic coefficients, will retain more energy downrange.

 

[Bill Larson]

Re: Why isn't everyone loading 200gr+ pills for .308?

200+ pills don`t shoot in most .308`s with 12" twist.
short barrels take bullet speed down... a disadvantage at LR.
bill larson

 

[D Miller]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"> Why isn't everyone loading 200gr+ pills for .308? </div></div>


Not all 308s will shoot them well. I watched a 308 during load dev with the 208s that was marginally better than a 12ga with 00. I think it was a 11 or 12 twist.

 

[Anchor Zero Six]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bill Larson</div><div class="ubbcode-body"> 200+ pills don`t shoot in most .308`s with 12" twist.
short barrels take bullet speed down... a disadvantage at LR.
bill larson </div></div>

Didnt realize folks still used 1:12 barrels do those load from the front with a ramrod

Just kidding you are absolutly correct that twist will be a factor. For point of reference the side of the box on the Berger 230 OTM's state in bold letters to use 1:10 twist.

As for the velocity loss I have found only a loss of 50 FPS from 26" to 20" barrel pushing 190SMK FGMM ammo. We are speaking in the reloading section so it should go without saying that a few grains can easily compensate for a measly 50 FPS and still remain within safe pressure ranges.

Dont have chrono data for the 230's yet but the velocity difference between short and long barrels has been consistant enough for me not to be worried about them falling to the deck 10' from the muzzle.

 

[Bob 964]

Re: Why isn't everyone loading 200gr+ pills for .308?

I shoot the 208 Amax, but my barrel has a 1:10 twist and will spin and stabilize the 208 appropriately. Barrels with 1:12 twist have difficulty spinning the 200+ grain bullets fast enough to effectively stabilize them, so most shooters with 1:12 twist barrels will shoot a 155, 168 or 175 (or similar) weight bullet.

A few years ago, Don Miller developed a formula for calculating the stability of a given bullet in flight. Based on a bullet's caliber, weight, length, barrel twist, muzzle velocity, and some environmental conditions, Mr. Miller calculates the "Gyroscopic Stability" (SG) for any given bullet. To achieve an adequate level of stability (and accuracy), the SG should be at least 1.40 and should not exceed 2.0.

An article in accurateshooter.com entitled "Calculating Bullet RPM — Spin Rates and Stability" (June 2008), has a link to Mr. Miller's formula in an Excel spreadsheet that permits you to calculate SG for any given bullet.

To put this in perspective, my friend Greg has a barrel with a 1:12 twist. Using the Lapua 155 Scenar in .308, his round needs to generate a muzzle velocity of 2950 fps to achieve an SG of 1.40. In my gun, which has a 1:10 twist, the 155 Scenar will generate an SG in excess of 2.0 at only 2900 fps.

So... if Greg and I were both shooting the same 155 Scenars at 2925 fps, his accuracy would suffer because his gun is not spinning the 155 fast enough to properly stabilize it. My accuracy would suffer because my gun is spinning the 155 too fast to properly stabilize it.

 

[memilanuk]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">But for anyone who loads .308 with the intention of long-range shooting why isn't 200gr or 220gr the standard instead of 168gr or 175gr? </div></div>

Because there is only so much range of adjustment in a scope, and a .308 needs a lot of it. The heavier the bullet, the more drop you'll have to deal with, and the more precise your ranging and subsequent elevation corrections will have to be.

And in my opinion... if you're shooting beyond 1000yds with a .30 cal more power to ya, but there are better choices than a .308 Win regardless of what bullet you stuff in it. It can be done - BTDT - but there are better choices.

 

[High Binder]

Re: Why isn't everyone loading 200gr+ pills for .308?

Why stop at 200gr why not go 500gr or a 1000gr? Why doesn't everybody run Nightforce/USO scopes?

Every gun/owner is different and there is a breaking point where you enter the realm of negative returns.

 

[dbooksta]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: memilanuk</div><div class="ubbcode-body">Because there is only so much range of adjustment in a scope, and a .308 needs a lot of it. The heavier the bullet, the more drop you'll have to deal with, and the more precise your ranging and subsequent elevation corrections will have to be.</div></div>

One might think, but like I said, if you look at the trajectories a 200gr .308 drops at most 1MOA further than a 168gr for any range, so danger spaces are practically the same out to 1000 yards (... at which point the 200gr has higher retained velocity).

 

[dbooksta]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: High Binder</div><div class="ubbcode-body">Why stop at 200gr why not go 500gr or a 1000gr?</div></div>

For .308 you will get the same muzzle energy out of bullets in the range of about 140-220gr for reasonable loads to the same peak pressure. Above 230gr (at least using copper and lead-core bullets) the cartridge dimensions reduce the muzzle energy you can produce at max pressure.

So perhaps I could rephrase my original question as follows: <span style="font-weight: bold">Given the ballistic advantages, why don't rifle shooters who intend to work up loads for long ranges always use the heaviest bullets they can that (A) spin-stabilize in their barrel and (B) achieve peak muzzle energy for their chosen cartridge?</span>

 

[JoshcBoucher]

Re: Why isn't everyone loading 200gr+ pills for .308?

I'M shooting 168s,as I work up to 600, when I go to "that" range. I always thought that IF I wanted energy at 1000,or further, I'd move to the 300 Mag. 95% of the time, I'm just shooting paper, so energy isn't an issue.Bullet drop is more of a concern, so I'd focus on FPS, and wind effect.

 

[dbooksta]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: joshboucher</div><div class="ubbcode-body">I'M shooting 168s,as I work up to 600, when I go to "that" range. I always thought that IF I wanted energy at 1000,or further, I'd move to the 300 Mag. 95% of the time, I'm just shooting paper, so energy isn't an issue.Bullet drop is more of a concern, so I'd focus on FPS, and wind effect. </div></div>

It's not just muzzle energy: Yes, you give up 1MOA in drop in the middle ranges, but right from the start the heavier bullets' higher ballistic coefficient give you less wind drift. Granted there isn't a big difference at short ranges, but even at 600 yards the 200gr will have 1MOA less deflection from perpendicular 10mph winds. And I'm assuming that it's a lot harder to dope wind across a course than distance.

 

[JoshcBoucher]

Re: Why isn't everyone loading 200gr+ pills for .308?

I'm just a "casual shooter". I shoot a 5 shot group in about a minute and a half. I figure wind is a constant, in that time frame, and adjust for my second group. If I was that worried about it, I'd get a 50 cal. But they cost so much, to shoot.Again I'm just a "casual, hobby shooter". I shouldn't have said anything, I guess.

 

[High Binder]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: High Binder</div><div class="ubbcode-body">Why stop at 200gr why not go 500gr or a 1000gr?</div></div>

For .308 you will get the same muzzle energy out of bullets in the range of about 140-220gr for reasonable loads to the same peak pressure. Above 230gr (at least using copper and lead-core bullets) the cartridge dimensions reduce the muzzle energy you can produce at max pressure.

So perhaps I could rephrase my original question as follows: <span style="font-weight: bold">Given the ballistic advantages, why don't rifle shooters who intend to work up loads for long ranges always use the heaviest bullets they can that (A) spin-stabilize in their barrel and (B) achieve peak muzzle energy for their chosen cartridge?</span> </div></div>

Yeah, I tend to agree with your underlying point. My post was more to the point of why people do inexplicable things. I personally only shoot 168s and 155s as 175s weren't available in bulk when I was in the market and I've never even tried anything over that because I have great success with 168/155 bullets. Now if 175+ had been available in bulk when I was in the market I would no doubt be shooting those.

 

[Fuzzball]

Re: Why isn't everyone loading 200gr+ pills for .308?

Why isn't everyone loading 200gr+ pills for .308?

1. Not a lot of .308s can stabilze such heavy bullets.
2. Precious few people shoot to or passed 1K yards.
3. It's bloody hard to get everyone to do anything.

 

[Anchor Zero Six]

Re: Why isn't everyone loading 200gr+ pills for .308?

Lol well said on point #3

 

[Cegorach]

Re: Why isn't everyone loading 200gr+ pills for .308?

I would imagine magazine constraints also have something to do with it.

 

[scotharr]

Re: Why isn't everyone loading 200gr+ pills for .308?

There is an optimal bullet weight for each cartridge. Many would argue that the 308WIN does not have enough powder capacity to push the heavy bullets fast enough to make any difference versus the lighter bullets. If you really want to get the benefit of a 200 grain bullet, then move up to 30-06 or bigger.

 

[YAOG]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">I was playing with Robert Meijer's excellent "BfX" Excel ballistics calculator and compared Hodgdon's published max safe loads from a 24" .308" bbl using 168gr (muzzle velocity 2828fps) and 200gr (muzzle velocity 2582fps) BTHP bullets. The 200gr dominates in every measure I think a shooter would care about down the range past 1000 yards:

<ul style="list-style-type: disc">[*]More retained energy[*]Less wind deflection[*]Less spin drift[/list]

In the mid-range the 200gr trajectory does drop by 1 MOA more than the 168gr, but by 900 yards it has caught back up and is flatter through 1000 yards.

I suppose for shooting under 500 yards the only significant factor is retained energy, and maybe that's not worth the marginal cost of heavier bullets. But for anyone who loads .308 with the intention of long-range shooting why isn't 200gr or 220gr the standard instead of 168gr or 175gr? </div></div>

People already tried that, it's called 30-06. But people got tired of hurting themselves for no good reason.

But now that you mention it if you loaded up a 30-06 with some modern components like a Hornady 178g Match bullet over 54.0g of RL-17 at 2,800fps you would have a decent performing round. It would approach 300WinMag performance range wise and only use 60% of the powder of a 300WinMag.

 

[Griffin4590]

Re: Why isn't everyone loading 200gr+ pills for .308?

I've been playing around with new loads for my .308 and looked long and hard at the 208gn amax but when it came down to it 175smk gets me to 1k and anything over that is the reason I own a 300.
Thats my reason for not shooting a 200+gn pill

 

[asbestosglove]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: memilanuk</div><div class="ubbcode-body">Because there is only so much range of adjustment in a scope, and a .308 needs a lot of it. The heavier the bullet, the more drop you'll have to deal with, and the more precise your ranging and subsequent elevation corrections will have to be.</div></div>

One might think, but like I said, if you look at the trajectories a 200gr .308 drops at most 1MOA further than a 168gr for any range, so danger spaces are practically the same out to 1000 yards (... at which point the 200gr has higher retained velocity). </div></div>

You are looking at a table and challenging a person who has experienced more shots at 1000 than most. Do what you want, you obviously don't really want any answers.

AG

 

[wrhunter]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cegorach</div><div class="ubbcode-body">I would imagine magazine constraints also have something to do with it. </div></div>

This... If I stick a 208 in my 700 at 2.80" coal there isn't much room to get it up to 2500+ fps in a 20" barrel. Single feeding would be a different story.

 

[dbooksta]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Scooter-PIE</div><div class="ubbcode-body">There is an optimal bullet weight for each cartridge.</div></div>

That's another way of posing my original question: How does one determine the "optimal" bullet weight for each cartridge? What are the criteria? (My proposed criteria were "heaviest bullet possible that achieves max muzzle energy and spin-stabilizes.")

 

[Chanonry]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Squarenut</div><div class="ubbcode-body">I shoot the 208 Amax, but my barrel has a 1:10 twist and will spin and stabilize the 208 appropriately. Barrels with 1:12 twist have difficulty spinning the 200+ grain bullets fast enough to effectively stabilize them, so most shooters with 1:12 twist barrels will shoot a 155, 168 or 175 (or similar) weight bullet.

A few years ago, Don Miller developed a formula for calculating the stability of a given bullet in flight. Based on a bullet's caliber, weight, length, barrel twist, muzzle velocity, and some environmental conditions, Mr. Miller calculates the "Gyroscopic Stability" (SG) for any given bullet. To achieve an adequate level of stability (and accuracy), the SG should be at least 1.40 and should not exceed 2.0.

An article in accurateshooter.com entitled "Calculating Bullet RPM — Spin Rates and Stability" (June 2008), has a link to Mr. Miller's formula in an Excel spreadsheet that permits you to calculate SG for any given bullet.

To put this in perspective, my friend Greg has a barrel with a 1:12 twist. Using the Lapua 155 Scenar in .308, his round needs to generate a muzzle velocity of 2950 fps to achieve an SG of 1.40. In my gun, which has a 1:10 twist, the 155 Scenar will generate an SG in excess of 2.0 at only 2900 fps.

So... if Greg and I were both shooting the same 155 Scenars at 2925 fps, his accuracy would suffer because his gun is not spinning the 155 fast enough to properly stabilize it. My accuracy would suffer because my gun is spinning the 155 too fast to properly stabilize it.

</div></div>

and if you run the numbers on the 208 AMAX in a 1:10 then at lower velocities and in 'cold' conditions the stability COULD be marginal. To the extent that in some conditions I take a couple of shots with the moderator off to check stability. Don't want to 'lose' it down range.

In the wrong conditions and with possible errors in MV, twist rate, weight etc it could go horribly wrong.

 

[scotharr]

Re: Why isn't everyone loading 200gr+ pills for .308?

Dbooksta, I think most people here agree with your statement: heavier bullets are better ballisticly than lighter bullets. Next, you have to put that in the context of cartridge case capacity. Every cartridge will reach the point of diminishing returns where the bullet becomes too big for the case to propel "well." A lot of grizzled veterans will tell you 200grs and up is too big for the 308WIN (for long-range shooting). Feel free to do your own research and, who knows, maybe a new 200 grain bullet will break this "truth." The best "laboratory" is your local 1K Palma or F-TR match.

Regarding the "ideal" long range bullet for 308WIN, the current consensus among top long range F-Class shooters seems to be on the 185gr Bergers or something similar. Some people shoot 155s exclusively because they are just that darned good now. Others shoot 155s on mild days and save their 185s for windy days when they need the extra inch or two benefit it provides at 1K.

Also remember recoil is not your friend and you definitely don't want the increased recoil of heavier bullets if there is no measurable ballistic benefit.

We could have the same discussion about the 223REM, why don't more people use the 90gr pills for maximum advantage? Well, because many really good shooters have already tried it and found it difficult and tedious to get good performance out of a 223REM case....maybe that will change when the next gee-wiz 90gr pill is released.

 

[dbooksta]

Re: Why isn't everyone loading 200gr+ pills for .308?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Scooter-PIE</div><div class="ubbcode-body">
Also remember recoil is not your friend and you definitely don't want the increased recoil of heavier bullets if there is no measurable ballistic benefit.
</div></div>

Just to make sure the discussion isn't muddied with errors: From the same rifle recoil should be the same because muzzle energy is the same. In fact, on the margin recoil should be lower with heavier bullets loaded to same muzzle energy because internal ballistics are more efficient (which would show up in the "rocket-effect" component of recoil).

[Correction: Internal ballistics are more efficient for the heavier bullet, but recoil is indeed higher because it's proportional to momentum, not energy.]

 

[clmayfield]

Re: Why isn't everyone loading 200gr+ pills for .308?

The fundamental issue comes down to chamber dimensions. As has been mentioned, people say "heavy," but what they mean is "long." A chamber needs to be speficially reamed with a long leade to allow you to seat that bullet far enough forward to get it out of the case. As was mentioned above, OAL is a factor as well. You are not going to get into a normal magazine with a 200+ grain bullet that is seated far enough out. I don't even have a detachable mag, but a 185 gr Berger seated for accuracy will not fit in my magazine. Sure, I could seat it deeper and deal with a compressed load.

Add in the twist rate issue and you really need a gun that is dedicated to heavies if you want to shoot them. I got a 1:10" twist with my rifle, and in hindsight, that was a mistake. I can stabilize a 200+ gr bullet, but given my chamber, it won't work. For a typical tactical rifle, 1:11" is plenty of twist to stabilize the projectiles that will work in the rifle. Nobody loads tactical rifles single shot.

For an F-TR gun, plenty shoot 200+ grain bullets. They are loading single shot and have chambers and barrels built around that bullet. They key is to build the rifle around that bullet. With a long action, you could probably build a tactical rifle around 200+ grainers, but they would probably jump to far to shoot 7.62 NATO or factory 308 WIN ammo well.

From a purely ballistic point of view, yes, those heavier bullets are superior at 1,000 yards. It is just that people don't feel like spending money on a tactical rifle that will not shoot factory ammo well.

 

[dbooksta]

My favorite answer

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Carter Mayfield</div><div class="ubbcode-body">The fundamental issue comes down to chamber dimensions. As has been mentioned, people say "heavy," but what they mean is "long." A chamber needs to be speficially reamed with a long leade to allow you to seat that bullet far enough forward to get it out of the case. As was mentioned above, OAL is a factor as well. You are not going to get into a normal magazine with a 200+ grain bullet that is seated far enough out. I don't even have a detachable mag, but a 185 gr Berger seated for accuracy will not fit in my magazine. Sure, I could seat it deeper and deal with a compressed load.

Add in the twist rate issue and you really need a gun that is dedicated to heavies if you want to shoot them. I got a 1:10" twist with my rifle, and in hindsight, that was a mistake. I can stabilize a 200+ gr bullet, but given my chamber, it won't work. For a typical tactical rifle, 1:11" is plenty of twist to stabilize the projectiles that will work in the rifle. Nobody loads tactical rifles single shot.

For an F-TR gun, plenty shoot 200+ grain bullets. They are loading single shot and have chambers and barrels built around that bullet. They key is to build the rifle around that bullet. With a long action, you could probably build a tactical rifle around 200+ grainers, but they would probably jump to far to shoot 7.62 NATO or factory 308 WIN ammo well.

From a purely ballistic point of view, yes, those heavier bullets are superior at 1,000 yards. It is just that people don't feel like spending money on a tactical rifle that will not shoot factory ammo well. </div></div>

Thanks -- wish this forum had "Helpful/Unhelpful" buttons for each post to identify most helpful answers.

 

[Chanonry]

Re: My favorite answer

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Scooter-PIE</div><div class="ubbcode-body">
Also remember recoil is not your friend and you definitely don't want the increased recoil of heavier bullets if there is no measurable ballistic benefit.
</div></div>

Just to make sure the discussion isn't muddied with errors: From the same rifle recoil should be the same because muzzle energy is the same. In fact, on the margin recoil should be lower with heavier bullets loaded to same muzzle energy because internal ballistics are more efficient (which would show up in the "rocket-effect" component of recoil).</div></div>

don't think so, I think that it is a conservation of momentum issue. So as bullet weight goes up so does recoil. Could be wrong...

There is definitely a ballistic benefit in going to 208 AMAX which may make the recoil compromise worthwhile

 

[dbooksta]

Re: My favorite answer

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chanonry</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">Just to make sure the discussion isn't muddied with errors: From the same rifle recoil should be the same because muzzle energy is the same. In fact, on the margin recoil should be lower with heavier bullets loaded to same muzzle energy because internal ballistics are more efficient (which would show up in the "rocket-effect" component of recoil).</div></div>

don't think so, I think that it is a conservation of momentum issue. So as bullet weight goes up so does recoil. Could be wrong...</div></div>

My key observation is that muzzle energy for max loads is roughly the same across a range of bullet weights, which means that heavier bullets leave the muzzle at lower velocities.

Momentum is proportional to velocity, but energy is proportional to the square of velocity. Since (apparently) momentum is the dominant factor in "recoil," <span style="font-weight: bold">the heavier bullets will have <span style="font-style: italic">less</span> recoil than lighter bullets with equal muzzle energy!</span>

[<span style="font-weight: bold">Correction</span>: I get an F in Physics here -- if two bullets have the same energy the heavier one has <span style="font-weight: bold">more momentum</span> than the lighter one. Sorry!]

 

[Fuzzball]

Re: My favorite answer

"Since (apparently) momentum is the dominant factor in "recoil," the heavier bullets will have less recoil than lighter bullets with equal muzzle energy!"

If you test that theory on the range I suspect you'll change your mind.

 

[memilanuk]

Re: My favorite answer

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">Since (apparently) momentum is the dominant factor in "recoil," <span style="font-weight: bold">the heavier bullets will have <span style="font-style: italic">less</span> recoil than lighter bullets with equal muzzle energy!</span> </div></div>

Dunno about equal muzzle energy, as nobody I know loads to a specified ME, but most people do load workup looking for a target MV.

Plugging some real-world numbers thru JBM yields the following:

Berger 155.5BT @ 3000fps, 48gn powder, 17.5lb gun (actual numbers from my F/TR rifle last year):

Recoil Velocity: 5.6 ft/s Recoil Energy: <span style="color: #FF0000">8.7</span> ft•lbs
Recoil Impulse: 3.1 lb•s

Berger 230 Hybrid @ 2550fps, 45 gn powder, 17.5lb gun (load values from someone I know running the bigguns in his F/TR rifle):

Recoil Velocity: 6.5 ft/s Recoil Energy: <span style="color: #FF0000">11.5</span> ft•lbs
Recoil Impulse: 3.5 lb•s

Yes, at those velocities with those bullets the 230 retains a whole *hell* of a lot more muzzle energy @ 1k... but again, if you're looking for retained ME @ 1k, you should be looking for a different cartridge. As far as target shooting... you cut wind drift (in theory) by about a third, in exchange for upping the recoil energy by about a quarter.

Lower wind drift is always a Good Thing, but many (most?) people shoot better with lower recoil in my experience. For my target guns where I can't use a brake or a can to soften the blow, and there is a hard limit on the overall weight... it becomes a balancing act between wind drift, recoil, and accuracy.

Definitely an interesting discussion (in a good way) !

 

[dbooksta]

Recoil vs bullet weight

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: memilanuk</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">Since (apparently) momentum is the dominant factor in "recoil," <span style="font-weight: bold">the heavier bullets will have <span style="font-style: italic">less</span> recoil than lighter bullets with equal muzzle energy!</span> </div></div>

Dunno about equal muzzle energy, as nobody I know loads to a specified ME, but most people do load workup looking for a target MV. </div></div>

In order to have a useful discussion on the trade-offs of different bullet weights I assumed that one loader for a particular rifle would tend to load to the same pressure levels. E.g., loaders who like to shoot "hot" will (hopefully) stop around the max pressure regardless of which bullet they're working up. So I pulled up Hodgdon's loads for .308 and for each bullet weight took the highest muzzle velocity published for the "do not exceed" load. I don't think there is any better way to eliminate external variables than to use Hodgdon's test data for a particular pressure peak. Obviously if you load different bullets to different pressures you don't have a sound basis for comparison.

Anyway, the useful observation from those data is that muzzle energy is pretty much constant for bullets between 140-200gr loaded to the same pressure levels.

Of course loaders tend to measure and talk in terms of muzzle velocity, but the useful "invariant" for this question is energy = MV^2 * bullet weight.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: memilanuk</div><div class="ubbcode-body">
Plugging some real-world numbers thru JBM yields the following:

Berger 155.5BT @ 3000fps, 48gn powder, 17.5lb gun (actual numbers from my F/TR rifle last year):

Recoil Velocity: 5.6 ft/s Recoil Energy: <span style="color: #FF0000">8.7</span> ft•lbs
Recoil Impulse: 3.1 lb•s

Berger 230 Hybrid @ 2550fps, 45 gn powder, 17.5lb gun (load values from someone I know running the bigguns in his F/TR rifle):

Recoil Velocity: 6.5 ft/s Recoil Energy: <span style="color: #FF0000">11.5</span> ft•lbs
Recoil Impulse: 3.5 lb•s
</div></div>

The load you quote for the heavier bullet has 7% more muzzle energy and 25% more muzzle momentum, so of course it will have more recoil by either measure.

My observation is that, all else equal, heavier bullets (within a reasonable range for the caliber) loaded to the same peak pressure (which is the benchmark safe reloaders follow) produce the same muzzle energy.

There seems to be some disagreement as to whether "felt recoil" is proportional to energy or to momentum. If the former, than heavier bullets produce only slightly less recoil than comparable lighter bullets due to reduced rocket-effect recoil. If the latter than heavier bullets produce significantly less recoil.

 

[Chanonry]

Re: Recoil vs bullet weight

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">[

My key observation is that muzzle energy for max loads is roughly the same across a range of bullet weights, which means that heavier bullets leave the muzzle at lower velocities.

Momentum is proportional to velocity, but energy is proportional to the square of velocity. Since (apparently) momentum is the dominant factor in "recoil," <span style="font-weight: bold">the heavier bullets will have <span style="font-style: italic">less</span> recoil than lighter bullets with equal muzzle energy!</span></div></div>

that's not consistent with the results predicted by online recoil calculators such as JBM though, nor my experience on the range. 155 has a hell of a lot less recoil than the 208.

 

[dbooksta]

Re: Recoil vs bullet weight

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chanonry</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body">
My key observation is that muzzle energy for max loads is roughly the same across a range of bullet weights, which means that heavier bullets leave the muzzle at lower velocities.

Momentum is proportional to velocity, but energy is proportional to the square of velocity. Since (apparently) momentum is the dominant factor in "recoil," <span style="font-weight: bold">the heavier bullets will have <span style="font-style: italic">less</span> recoil than lighter bullets with equal muzzle energy!</span></div></div>

that's not consistent with the results predicted by online recoil calculators such as JBM though, nor my experience on the range. 155 has a hell of a lot less recoil than the 208. </div></div>

I just noticed and reported that there is a problem with JBM's "recoil energy" calculator. [EDIT: Actually to first order the JBM calculators are correct. They aren't incorporating variations in propellant velocity, but that's a second-order effect.]

[Deleted erroneous reasoning based on conservation of energy instead of momentum] -- I made an error in my previous statements: All else equal, including muzzle energy, the heavier bullet has <span style="font-style: italic">higher momentum</span>, which translates to higher recoil.