Pro's & cons between .30 & .357

[Mod90]

Ok guys, I have some questions & know some of you guys have the big bore aspect of air gun shooting down to a science, & thought maybe you all can donate some enlightenment to me on this topic.

What are the advantages & disadvantages in long range shooting out to 200 yards between the .30 & .357 if both calibers are using cast bullets of similar design, besides the obvious weight & size dimensions.

How much better or worse would one fare over the other accuracy wise when considering wind drift?
Is the only advantage of the .30 possibly higher muzzle velocities?
What about BC & energy retention capabilities of both calibers at longer ranges? How do they compare?
Which caliber would be easier to make more efficient  use of air per shot?

I know if the answers are any where, they gotta be here 

[PakProtector]

You're gonna love this: you tell me.

http://www.gatewaytoairguns.org/GTA/index.php?topic=57828.0
http://www.gatewaytoairguns.org/GTA/index.php?topic=73197.0
http://www.gatewaytoairguns.org/GTA/index.php?topic=55930.0
http://www.gatewaytoairguns.org/GTA/index.php?topic=72024.0
cheers,
Douglas

[Mod90]

Thanks for the links Doug.

Methinks this is gonna take me a while to soak up

[rsterne]

The first link above has the most answers to your questions regarding the bullets.... Here are the Coles Notes:

Sectional Density of the bullet (basically weight) governs how heavy a bullet you can sling with a given pressure and barrel length....
As caliber increases, for a given SD the bullets get shorter and fatter.... bullets of the same shape have a higher SD in a bigger caliber....
Ballistics Coefficient for a given shape is dependant on the SD.... so for a given shape, the larger caliber has the edge in BC....
Whatever the caliber, best to stick to a limit of about 950 fps to get the least wind drift for a given bullet....

So assuming 3000 psi and a 24" barrel (and don't forget you have to consider the pressure at the end of the shot string, not the fill pressure), you are limited to a maximum SD of about 0.17 to have ANY hope of reaching 950 fps.... That is a bullet of 113 gr. in .308 and 152 gr. in .357.... If you go heavier than that, you will want more pressure or barrel length or have to accept that your velocity will be lower.... In similar shapes, that .308 bullet would have an edge in BC.... On the other hand, if you compare that 113 gr. .308 bullet to the same weight in .357, then the .308 will have a big edge in SD and therefore BC and wind drift.... In this respect, airguns are no different than PBs....

You mention shooting out to 200 yards, so I will assume you are not talking deer or hog hunting here, but varmints or predators.... If that is the case, I personally don't see the point in a .357, I would say the choice would lie between .257 and .308.... For the gun above, and the same SD in .257, the bullet would weigh about 80 gr., and have better ballistics than the .308.... At 950 fps, that works out to 160 FPE in .257, 226 FPE in .308, and 304 FPE in .357.... All of those are pretty stout numbers, you won't be doing them with any less than a custom rifle.... Since the amount of air you use will be in direct proportion to the FPE, you can do anything with the .257 that you can with the .357, with better ballistics, for half the air.... with the exception of delivering FPE....

Bob

[Mod90]

Well Bob, I was thinking about adding the .257 as well to the equation, but that might have made things a bit more complicated. My only concern with the .257 is that due to the ideal weight it would need to be at to maximize SD & efficiency as well as to deliver enough energy downrange at those distances, it would actually be a pretty long bullet. That would limit the guns that could be used to either single shots like the Airforce guns, or the Korean Sumatra's or Evanix AR6

So right now I'm thinking the ideal configuration would be the .30 cal with a 28" LW barrel to make use of the expanding air as much as possible & 100% bore sized TP inlet to reduce the shock wave produced from the rush of air as it exits the valve, using bullets cast a little fat at about .303 and sized down to .301
How does that sound to you so far?

[rsterne]

I don't think you will pull the power you want out of a Korean gun (although I've never had one), but I know that dyotat100 (and others) are doing exactly what you want to do starting with Condors, so PM him and drag him in here to pick his brain.... Not sure what you are targeting at 200 yards to need over 150 FPE, but I can understand the dilemma regarding bullet length.... Unfortunately, for a given SD and bullet shape, the length is almost fixed regardless of caliber.... A typical bullet with an SD of 0.17 will be about 5/8" long.... Therefore, you will find that BC is roughly proportional to bullet length as well, again regardless of caliber.... You mention single shot guns like that isn't what you want, and that will really hamper your attempt to reach out if you restrict yourself to repeaters with short magazines, regardless of caliber....

Beyond that, the choice you have for a barrel length and caliber (assuming you can match up bullet diameter to the LW barrel) is a good one.... According to the LW website, their .30 cal barrel is 0.306" groove and 0.298" land, which seems to me in between everybody else.... I know Tim@Mac1 couldn't get that barrel to shoot pellets, and bullets are generally 0.308-0.309" so unless you get a custom mold made you would have to size them a lot (maybe more than you can with one die?).... If interested in .308 cal (for the availability of bullet molds) I would look to TJ's, they have them in 10", 14" and 20" twist, priced by the inch.... I assume you know that arigun barrels (eg. FW and Daystate) are .300 cal, made for the JSB pellets (and vice versa), not the standard .308 cal used for PBs (and hence lots of molds available).... Since you are interested in bullets, not pellets, I would definitely go .308, not .300 (or .306)....

Bob

[WECSOG]

This is slightly off topic, but another advantage of using 950 fps for a velocity goal (besides killing power and accuracy) is that it makes fpe calculations very easy: just double the projectile mass in grains!

[WECSOG]

...bullets are generally 0.308-0.309" so unless you get a custom mold made you would have to size them a lot (maybe more than you can with one die?)....
Bob

Using pure lead would help in that regard; not only would it be easier to size but would also have a smaller as-cast diameter since pure lead shrinks more on cooling than the harder alloys that cartridge-gun bullet moulds are designed for.

[rsterne]

It's not the difficulty in moving the lead around that is the problem (unless the bullet is very hard), it's where it goes when you do so.... leaving that lead as flashing/distortion on the sized bullet if you try an go too far.... Mind you, even a pure lead bullet would be difficult to size 0.005" or more.... A 0.308" mold (and many are 0.309") won't drop small enough even with pure lead to fit an LW 0.306" barrel properly without sizing, IMO.... However, custom mold makers will allow you to specify the diameter to match your barrel....

Bob

[Mod90]

If going .257 or .30 route,  I would definitely need to be casting my own ammo. Not enough variety available on the market to try in either caliber btill I find one that shoots well  to make buying ammo an option

[Tofazfou]

Now, when you say 30, are you saying the EUROPEAN 30 which is about .300-.303?  Or are you saying the American .308.  Because here in the states, we call .308 the 30 cal.

If you mean 308 then that is preferred over the 357 for your choices of shooting distance.

If you simply mean .30 and your are referring to PELLETS then i say HECK NO.  HECK NO TO BOTH CALS

BUt if you mean .303, then that is a caliber more suited to long range.

The 357 is NOT a 200 yard projectile.  EVEN IN THE 357 MAGNUM cartridge.

Now, you can shoot 158-200 gr 358 pills but that's in a MAGNUM PB pistol.  Not in an airgun.

[rsterne]

There is no such caliber as .303 in airguns.... The Daystate is CALLED that to take advantage of the calibers popularity in England, but it is 0.300" and the 50 gr. Daystate pellets, made by JSB, measure the same as the 45 gr. that FX uses, and they both measure 0.300" at the head.... The skirts are of course larger, just like any airgun pellet.... Interestingly, the .303 cal in PBs is actually .311-.312.... and there are a few bullet available for that (but no pellets)....

However, Cedric is correct, if you want to do long range shooting with a .30 cal, go .308 NOT .300.... Same thing in .25 cal, you want .257, NOT .250 which is the airgun size.... Can you get bullet molds for .300 and .250?.... Yes, but they are custom made, all the standard molds are .308 and .257.... (with the exception being the 70 gr. BBT which I designed to work in the .300 cal barrels, and a couple of molds in .250, but they are all too light for 200 yard work)....

Bob

[PakProtector]

Now, when you say 30, are you saying the EUROPEAN 30 which is about .300-.303?  Or are you saying the American .308.  Because here in the states, we call .308 the 30 cal.

If you mean 308 then that is preferred over the 357 for your choices of shooting distance.

If you simply mean .30 and your are referring to PELLETS then i say HECK NO.  HECK NO TO BOTH CALS

BUt if you mean .303, then that is a caliber more suited to long range.

The 357 is NOT a 200 yard projectile.  EVEN IN THE 357 MAGNUM cartridge.

Now, you can shoot 158-200 gr 358 pills but that's in a MAGNUM PB pistol.  Not in an airgun.

I suspect that a 180 gr, .357 will do quite adequately at 200 yards....going with rough proportionality, that would be about a .70-long BBT. Getting to 950 fps would ov course need 360 FPE...and that is not a trivial amount of energy. It puts a 500cc bottle gun into the 5-shot string neighborhood...less if you go faster.
cheers,
Douglas

[Mod90]

Biggest I'm going is .30 Doug. I'm not looking to need to recharge after every 3-5 shots. I'd like to get at least 7-10 shots before needing a refill, & that should be easily doable.


Cedric, I'll be using a LW 28" 30 cal bbl. Their site states it's not choked 28" & .298 land, .306 groove, I will have to slug the bore first to see if those dimensions are accurate. Then it's just a matter of casting & sizing the ammo that would best suit the barrel, & lots of shooting to see what size & weight it would yield optimal results.

Hopefully with any luck I can start getting all I'll need for this by the end of Jan. next year, then all I'll need to get would be the molds, sizers, lube & press

[PakProtector]

Biggest I'm going is .30 Doug. I'm not looking to need to recharge after every 3-5 shots. I'd like to get at least 7-10 shots before needing a refill, & that should be easily doable.


 

That is why I am building a 308...with a 250 Bar tank of 500cc. A 7-8 shot string with tight velocity spread should be within my reach. A hunting plinker...LOL
cheers,
Douglas

[Mod90]

Seems we're thinking along similar lines 

[rkr]

I actually started thinking of converting my .357 evanix to .30 but after thinking it through it just doesn't work. I need magazine fed bullets and would like closer to 200 fpe but in reality those two requirements rule the .30 out as a choice of caliber.

[Bruce]

200 fpe is very possible in .308  look at Extreme Airguns http://www.extremebigboreairrifles.com/

well over 200fpe possible with that gun

Bruce

[dyotat100]

Yes with 30+" barrels and 4500 psi fills you can make a lot of power.

I have a 32" condor with a 1-14 TJ barrel. Makes right around 300 fpe with 171 gr slugs. I like to shoot 112-118 gr slugs. It  Is around 230-250 fpe with the lighter stuff. All this on 3000 psi fill.

When you down size a guns caliber you will be surprised how much fps you lose. Larger bullet is easier to push.

[rsterne]

mod90, in addition to a custom mold, if you decide to size you will need a custom sizer for a .306" barrel.... Fortunately, they are available at reasonable cost....

http://www.doughtyent.com/Pages/SizingDies.html

Bob