500 Yard Rifle

[Bart B.]

.308's with 22 and 24 inch 1:12 twist bullets weighing 180 and 190 grains have won a lot of matches and set some records, too. 1:10 twist .308 Win barrels aren't needed unless bullets weigh more than 200 grains or the barrel's shorter than 22 inches.

[Metal god]

Hey Bart what do you think of the yaw factor in spinning a bullet to fast . The Berger 30 cal 175gr VLD recommends a 1-13 twist or faster . Would 1-10 out of a 24" barrel be to fast ? Is there a chance the nose of the bullet will yaw at the longer ranges as velocity drops off . I hope yaw is the right term . I mean the nose of the bullet wants to lift up or stay up rather then follow the trajectory path

[mwells72774]

Im building a mauser for half that cost. Cant beat a mauser action, ask the remington 700 guys

Got a beater mauser 98 for around 150. Get a shilen barrel for 250, hogue pillar bedded stock for 90, leupold mount and rings for 50. Doing as much of the work you can yourself will save tons of $

[Gmony.308]

I hope yaw is the right term . I mean the nose of the bullet wants to lift up or stay up rather then follow the trajectory path

Metal God: I think you're referring to YeeHaw not yaw! I can tell you this the velocity of the thing-a-ma-jig propelled out of the whatcha-ma-call-it multiplied by the speed of rotation is proportionally relevant to the force of impact on the kanorbitz, but only after accounting for friction and heat expansion of the thing-a-ma-jig against the increase, or decrease in atmospheric conditions dependent upon elevation, wind direction, humidity, and polar alignment of the stars.

Sorry to kidnap the thread guys, for the most part it's been interesting reading.

[csmsss]

I hope yaw is the right term . I mean the nose of the bullet wants to lift up or stay up rather then follow the trajectory path

Actually, that's pitch, or vertical deviation from the intended path. Yaw is lateral/horizontal deviation from the intended path.

[Bart B.]

I think Metal god's referring to as yaw is actually the coning motion of the bullet's nose about the trajectory axis. As the bullet's spin axis is always parallel to the trajectory, its nose will always be a tiny bit above the trajectory; so will the center of its tail. That happens when the bullets are not perfectly balanced about their form axis. As 99.9% of all bullets are not perfectly balanced, each one will have a bit of coning motion, or nutation as it's sometimes called, about the trajectory axis. The more nutation a bullet has, the more drag it has. More rpm's caused by fast rifling twists causes more centrifugal forces that cause that nutation. Which means the BC will be less than those perfectly balanced ones. The center of that coning, or nutation, will be above the trajectory axis.

Most of the best bullets will have up to a 1% spread in BC at most, but it's still enough to open up groups non-linearly as range increases. When this adds to the velocity spread's effecting bullet drop, it's no wonder long range groups do not subtend the same MOA value the ammo had at short ranges. Those well balanced bullets leaving at the lowest velocity can strike the same point on target as a bullet a bit unbalanced leaving at the highest velocity. The opposite happens when things are reversed; bigger groups.

There is some evidence that when bullets are spun way, way too fast, they tend to stay more paralled with the bore axis and do not nose over like passed footballs do enroute to the receiver. At this extremely high rpm rate, the normal unbalance of bullets will then cause disasterous effects on accuracy.

Sierra Bullets' has had excellent info on this stuff in their reloading manuals. Even time of flight measurements showing how different twist rates for the same load change the bullet's BC.

Short range benchresters shoot their bullet with the slowest twist possible for best accuracy. They'll adjust the powder charge a tenth or so for temperature changes; cold air's thicker than hot air and bullets need to be spun a bit faster to stabilize them so they add a tenth (or one click on their powder measure). 120-gr. bullets in the .30BR shoot great from 1:17 and 1:18 twist barrels.

A 1:10 twist from a 24" long .308 Win. barrel's a bit much for any bullet lighter than 200 grains, in my opinion, for best accuracy. In sub zero weather, however, it may be about perfect.

csmsss says that's pitch, or vertical deviation from the intended path. Do you mean the bullet takes a higher or lower arc to the target than normal?

[Bart B.]

While Mauser actions are the basis for so many others, I think they've got two shortcommings.

One is their trigger. An aftermarket one will greatly improve that area.

The other is lock time. Way too long for precision shooting. It turns a centerfire rifle into a rimfire 22; you have to hold it still for 3 times as long as other modern actions. However, a titanium firing pin and extra strong spring, it will be much, much better.

Both mods is what some folks did with their single shot FN Mauser target actions. Once upgraded in these areas, they were as good as Win. 70's and much better than any Rem. 7XX action.

[jimbob86]

Guys, I'm looking for a rifle to punch out to 500 yards. I plan on target shooting &you possibly deer.

Whatever you choose, if it's going to be shot at deer @500, it needs to be fast and efficient, and not just for a flat trajectory, but for time of flight: you need to be reasonably sure the animal will not move between the time the bullet leaves the gun and the time it arrives at the target animal.

A 168 gr .308 Win SP bullet leaving @ 2800f/sec will take more than .6 sec to reach 500 yards. Unless it's laying down, you can't be reasoanbly sure the animal won't take a step in that time, no?

[chadstrickland]

My bad. Had a moment.

[Metal god]

Thanks Bart , yea that's what I was getting at . If I understand you correctly from what your saying . For the cheaper bullets with less quality control . You really don't want to over spin them . Not that I plan to shoot cheap bullets long distance , just saying .

[Bart B.]

jimbob86, do you think a 168-gr. bullet leaving a .308 Win. case then going out the muzzle at 2800 fps can do so with normal, safe 52,000 CUP (62,000 PSI) peak pressures? That fast seems a bit too much to me for 22 or 24 inch barrels.

[allaroundhunter]

Originally Posted by Bart B.

jimbob86, do you think a 168-gr. bullet leaving a .308 Win. case then going out the muzzle at 2800 fps can do so with normal, safe 52,000 CUP (62,000 PSI) peak pressures? That fast seems a bit too much to me for 22 or 24 inch barrels.

That is about the speed I am getting from max charges and a 26" barrel. I would be hesitant to try to push them that fast from a shorter barrel, but if you work a load up to that point without pressure signs then I wouldn't disagree with its use.

[jimbob86]

jimbob86, do you think a 168-gr. bullet leaving a .308 Win. case then going out the muzzle at 2800 fps can do so with normal, safe 52,000 CUP (62,000 PSI) peak pressures? That fast seems a bit too much to me for 22 or 24 inch barrels.

That was what Speer claimed for a comperessed load of RL15 out of a Rem 700 w/ a 22' barrell ..... Optimistic, probably.

The point remains valid, and even more so using a more realistic MV, though: With a .308WIN time of flight is too long for 500yd shots at game unless the animal is bedded..... and not even then, unless the shooter knows his range, wind dope and trajectory exactly.....

[Bart B.]

Just how accurate/exact are "pressure signs?"

What standards or specs are there for them?

I've shot hundreds of 7.62 NATO proof loads (65,000 CUP) and none of their fired cases looked any different than the same case, powder charge and primer used in standard loads (50,000 CUP). Standard load used a 147 gr bullet, proof load used a 172 gr bullet.