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Why are some calibers more accurate?

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Why are some calibers more accurate?

Old 12-17-2003, 02:20 PM
  #11  
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Default RE: Why are some calibers more accurate?

While I believe that there may be some degree of merit to the argument that some cartridges are better than others, I don't believe that most of the reputation for accuracy some cartridges have can be entirely attributed to the cartridge itself.

The PPC and BR cartridges are renouned for their accuracy, but has anyone considered that the accuracy benchrest shooters achieve with these cartridges might also be attributed to the fact that they shoot them through highly refined, specialized $10,000+ benchrest rifles and not the practical rifles you and I'd take to the field? Or that maybe it's not just the cartridge, but also the time, care and attention to detail the benchrest shooters put in handloading each round so that it is as close to perfect as they can make it? Or maybe also that the benchrest shooters themselves are outstanding marksmen?

Also consider that many of the cartridges known for accuracy are the smaller calibers. One thing I'd consider is that maybe the reputation can be attributed to the fact that the lighter varmint cartridges are usually fired through heavy barrelled varmint rifles, which are almost always going to produce better accuracy than their sporter-weight counterparts in heavier big game calibers. Another thing that might contribute significantly to the reputation of lighter cartridges is that they are much more pleasant to shoot in terms of recoil, which means that the shooter is far less likely to develope a sub-conscious flinch. They will also likely practice more and have longer more productive range sessions because one can shoot a lot of rounds through a 22-250 without needing a chiropracter, but 10 rounds through a 300 Ultra Mag. and most people are done for the day.

I guess my point is that I feel that there is a lot more to a cartridges reputation than the cartridge itself. The 6mmBR may be a preferred benchrest round, but if it were chambered in a typical factory rifle that you and I could buy off the shelf, would it really be noticably more accurate and an identical rifle chambered in .243Win? Same thing goes in reverse, would a $15,000 benchrest rifle in .243 really be that much less accurate than the 6mmBR? Remember that the benchrest matches are won and lost on .001MOA differences in group sizes. But .001 MOA doesn't mean crap in terms of practical hunting accuracy unless you hunt chipmunks out past 1000 yards.

Mike
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Old 12-17-2003, 06:42 PM
  #12  
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Default RE: Why are some calibers more accurate?

I think that its perceived that some cartridges are LESS accurate than others due to extenuating circumstances. If you were to pick the more accurate cartridge between .308 and 7.62x39, most would pick .308. The problem with the 7.62x39 cartridge is not about inherent accuracy, but the fact that the vast majority of rifles that are chambered for it aren't very accurate to start with. Now throw in the fact that different bore/bullet sizes are used by different manufacturers of the cartridge it could be viewed as a less accurate cartridge than the .308. If some spent the money to build a tight fitting rifle for the cartridge, and carefully assembled ammunition from high quality components, the 'accuracy gap' would probably be eliminated.

ANother example is the 30-30, mass produced lever guns aren't always very accurate, but chamber a single shot pistol or rifle in the cartridge, you can get very good accuracy.

One of the biggest reasons why the .308 is seen as more accurate than the 30-06 is due to the rifle its shot in. In the 1950's and 1960's, the M1 Garand was the predominant rifle used for high power rifle competitions. It was found that rechambering them for .308 made them much more accurate. Its not that the .308 is a much more accurate cartridge than the -06, but a weakness in the rilfe that limited the loadings for 30-06. The 30-06 can only be loaded with a few powders and still be safe to use in the garand in terms of not damaging its gas system. These loads are nowhere near the potential for the 30-06 cartridge and consequently mean less than optimal powder loading densities. The .308 could be loaded to the same velocities as the downloaded 30-06 in the same rifle while having its case nearly full of powder.

If you were to use similar quality ammunition in similar quality hunting rifles the whole 'efficient cartridge' theory pretty much disappears.
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Old 12-18-2003, 08:40 AM
  #13  
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Default RE: Why are some calibers more accurate?

Absolutely, I do agree and have said myself there are not accurate cartridges just accurate guns. But, we can't ignore the fact that some cases allow for more consistent ignition of the powder. A smaller capacity case is generally going to burn more consistently than a large capacity case (less material to burn the more consistent it burns), and all else being equal it seems that the powder in a wider case burns more consistently than in a narrow case (more powder closer to the primer). This makes it easier to obtain a load that doesn't vary much from one shot to the next, which can help to make a gun more accurate.

Yes, I agree that a lot of the acccuracy benchpress shooters get is not due to the cartridge. However, I know enough of them to know that they will shoot whatever cartridge they perceive to give them an advantage, and that usually boils down to whicher one is easiest to get consistent velocity from which usually is a shorter fatter cartridge. That is not to say that they can't be competative with larger capacity cartridges, it's just that they are more difficult to get consistent results from than smaller capacity cartridges. And this ease of loading is most likely where the "Accurate Cartridge" theory comes from, people take a 308 and shoot factory loads through it, and since it an easy cartridge to load for the factory's produce good ammo, and as a result they have good accuracy with whatever they shoot through it, hence it's an accurate caliber.

Now how much difference does this make, not much in hunting terms, but in a competition it can make a difference because as someone noted "they measure in .001's of an inch".

Gordon
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Old 12-18-2003, 09:08 AM
  #14  
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Default RE: Why are some calibers more accurate?

Posted by GordonKekko

Absolutely, I do agree and have said myself there are not accurate cartridges just accurate guns
Yup, that about sums it up!
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Old 12-18-2003, 01:20 PM
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Default RE: Why are some calibers more accurate?

Vapodog, I used to do a little Benchrest shooting years ago. I sold off all the guns to help pay for the house and now many years later I'm just getting back into shooting. I haven't done a lot of big game hunting but that's the direction I'm heading. I ordered reloading equipment yesterday based on your advise and will be getting a varmint rifle early next year as well.

This much I feel confident in saying. Any caliber can be a very accurate cartridge, yes, even a .25-35 Winchester, if it gets the craftsmanship and attention to detail that the 6MM PPC gets. I owned a .308 Tight neck on a 40-X and Hart barrel and McMillan stock that normally shot in the .20 range. The reloading was done by a buddy and I never got into that, all I know was the ammo was expensive!

I believe you're absolutely right when you say that there's very little difference in accuracy of different calibers. Certainly none that a big game hunter will ever see.
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Old 12-18-2003, 01:38 PM
  #16  
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Default RE: Why are some calibers more accurate?

So how many of you all ever work up loads chrono'ing each load. I am curious of your results as far as velocity spread is concerned. Would also be curious to know your guys results comparing say a 30-06 and a 308 or maybe a magnum or two.
 
Old 12-19-2003, 08:11 AM
  #17  
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Default RE: Why are some calibers more accurate?

Well, I now chrono every shot when I'm working up pet loads (now that I found a buddy with a Chrono ). And even though I haven't been able to do so for every gun I own here's what I found this spring when working up loads for my 7mm-08 and my buddy's 7mm RUM (this is an extreme case you'll note). But of the three powders we tried in each caliber, I was able to get all three to have and extreme spread of 25 fps or less(one even got to an ES of 14 fps), and I might add all three were among the best performing loads in my gun (not by that much mind you but we only shoot at 200 yards when working up loads). In his 7mm RUM we only found one powder that would get us below the 25 fps ES, and that only got to 23 fps ES. Now keep in mind that both of these guns with the better handloads were shooting sub-moa @ 200 yards, but it seemed to us that both guns seemed to shoot better with the more consistent loads. Now, another thing I noticed was that we tended to get the most consistent burn rate with less than max loads in both rounds. This next spring I intend to play around with this a little bit more, because it is something that we just started working with, and I really want to see if it plays out with my 300 WSM and 257 Roberts. This is just one experiment so it is possible that the results are merely coincidence, but a lot of BR shooters that I talk to seem to agree with what I've found so far, in addition it could be due entirely to the quality of powder available for the super-capacity cases vs the smaller cases, of that I'm not sure, just reporting what I've found.

Gordon
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Old 12-19-2003, 08:20 AM
  #18  
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Default RE: Why are some calibers more accurate?

Well, Gordon, your the first person I have seen get that low of an Extreme spread out of a RUM. I have seen a bunch. I have had two of them and tried a bunch of powders from IMR4350 up to Re25.
 
Old 12-19-2003, 08:28 AM
  #19  
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Default RE: Why are some calibers more accurate?

I can't take credit for that, my shootin' buddy is one of the best handloaders I've ever met! He weighs everything cases, bullets etc. and is very meticulous with his loads (that's why I'm hanging out with him, I'm trying to learn a thing or two). If I remember correctly we got those results with IMR 4350, and it may have been just one of those days, I'd like to head out to the range again to see if we can duplicate the results (that ES is only from a total of 24 shots fired), but with a pregnant wife, my free time is pretty much occupied.

Gordon
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Old 12-19-2003, 08:46 AM
  #20  
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Default RE: Why are some calibers more accurate?

I apologize, I just got off the phone with my friend and he pulled up the data, and we got that ES with IMR 4831. It was 74 Deg. the day we shot it, and when he went out this fall to sight in for Rifle Season, his results were more sporadic (as to be expected according to him) it was 88 degree's and his ES is now around 45 according to his data, so maybe it was just one of those days.

Gordon
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