Ballistician needed for confused 98

[Depreacher]

At the range this morning, my K98 8x57 was shot at 100 yds. It is sighted dead-on at this distance for 16gr. 2400/Lee 170gr. boolits. Using 150 gr. J______ spirepoints (yes, I sinned) ahead of 50 gr. of AA4350, the rifle printed 4 1/2" low. To me this was normal, and expected after almost 50 yrs. of 8mm and 30-06 experience. Next, I shot some 1942 Canadian sterile military rounds with 154gr. spirepoints. Rounds were very powerful, and kicked like demon possessed bay mule. Expecting the rifle to shoot even lower, I was surprised to see a 5 shot 1 13/16" group forming 11" HIGH and 3" right from POA. HIGHER????? As Nicodemas said "how can this be". Master ballistician, thy humble servant lieth prostrate at thy feet, awaiting thy glorious revelation. cbp ps. Second group was a disappointing 2 1/4", while last group (a 10 rounder) was a sick 3 1/4".

[Scrounger]

Maybe the shooter was affected a little because of the recoil?

[SharpsShooter]

You imply higher recoil and higher velocity. It seems that the barrel harmonics (circular vibration pattern) with that hot load are significantly different and the barrel is at the high point of the circle when the bullet exits the bore. While it does not follow the usual "rule of thumb", it is not unheard of at all. I had a siameese mauser 45-70 that did similarly when I ran the velocities hot.

[Bass Ackward]

At the range this morning, my K98 8x57 was shot at 100 yds. It is sighted dead-on at this distance for 16gr. 2400/Lee 170gr. boolits. Using 150 gr. J______ spirepoints (yes, I sinned) ahead of 50 gr. of AA4350, the rifle printed 4 1/2" low. To me this was normal, and expected after almost 50 yrs. of 8mm and 30-06 experience. Next, I shot some 1942 Canadian sterile military rounds with 154gr. spirepoints. Rounds were very powerful, and kicked like demon possessed bay mule. Expecting the rifle to shoot even lower, I was surprised to see a 5 shot 1 13/16" group forming 11" HIGH and 3" right from POA. HIGHER????? As Nicodemas said "how can this be". Master ballistician, thy humble servant lieth prostrate at thy feet, awaiting thy glorious revelation. cbp ps. Second group was a disappointing 2 1/4", while last group (a 10 rounder) was a sick 3 1/4".

CBP,

I am no ballistician, but I'll give er a wack if you can accept an over simplified explanation.

Cast tend to offer less friction than jacketed. Less friction less barrel vibration and at lower frequencies. So different velocity loads tend to exit a lot closer to each other. Thus your only real effect is seen with more velocity climbing on the target based on how high you are above line of sight at a particular range.

Jacketed present more friction. They cause wilder barrel vibration and at higher frequencies. So smaller velocity changea are needed to change impact point based on where the bullet leaves the barrel. If your barrel oscillates from 10 oclock to 4 oclock you print on that line. If it is oval, then you can end up anywhere. Add that change to the line of sight effect described above, and you get the results you experienced.

My guess is that the last load you fired had tight bullets for your bore or they coppered pretty good. But that is just a guess.

[StarMetal]

Gernerally I've found that if you adjust the sights for cast the jacketed loads shoot higher. Most "all" the rifle I own shoot cast low if the rifle was sighted for jacketed loads. I would say the jacketed load you handloaded wasn't no ways near the velocity of the Canadian stuff, thus shot lower then it.

Someone said you might have been affected by the recoil of the hot Canadian stuff. I don't think so with the very good group you shot with that. If you are affected by recoil you flitch and that doesn't produce a group.

Joe

[BOOM BOOM]

HI,
My experance is the same as STARMETAL's.

[Tom Myers]

As was stated before, YOU are probably not affected by the recoil, but your rifle certainly is.

When calculating impact points for artillery rounds, a factor refered to as the "Angle of Jump' is incorporated into the equations that are used to calculate the ballistic trajectory-impact point and this value is unique to each different projectile and loading for a particular gun.

The same is true for a sporting firearm. The trajectory path for a certain projectile launched at a certain velocity will generally remain the same. The only difference is that the Angle of jump is not referred to, but is unique to a particular firearm and is only implied in the zero range sight setting.

The Angle of Jump is unique to each firearm and load. It is a product of many variables, a few of which are, projectile barrel time, combustion pressure, barrel friction, position of projectile at peak pressure, acceleration rate while in the bore, muzzle velocity, etc, etc.

It would be folly to try and predict an accurate sight setting or impact point from a known trajectory path without an initial zero sight setting unless the actual Angle of Jump for that particular loading and firearm is known. Since the Angle of jump is implied in a zero range sight setting and then if the trajectory of a round is known, downrange sight settings may then be somewhat accurately predicted.

Hope this Helps,

Tom Myers
http://www.tmtpages.com

[David R]

I am far from a ballasitcian, can't even speel it.

My 1917 enfield shoots lead lower than the J stuff. It also shoots em FAR to the Left. My front site is on the edge of the dovetail. If I crank up heavy lead boolits, they shoot more to the right than the "normal" lead loads. So the hotter the load in MY gun, the more it shoots higher and to the right.

It will shoot tighter groups with lead than I have seen with J.... Boolits, just not the same point of impact. Barrel is free floated.

Every gun has its own personallity. Figuring it out is part of the fun.

David

[mike in co]

maybe some 8mm machine gun ammo.....hot stuff...

[stocker]

8 X 57 was never used by our military to my knowledge. Standard service cartridge was of course 303 Brit. in that era. Do you have any idea what purpose it was made for? I haven't tried to research Canadian military ammo so perhaps there was some in service application for it that I don't know of. I can't even think of an Allied force that we may have been supplying ammo to that used it.

I am curious to know.

Thanks

[Jumptrap]

8 X 57 was never used by our military to my knowledge. Standard service cartridge was of course 303 Brit. in that era. Do you have any idea what purpose it was made for? I haven't tried to research Canadian military ammo so perhaps there was some in service application for it that I don't know of. I can't even think of an Allied force that we may have been supplying ammo to that used it.

I am curious to know.

Thanks

Did the Bren use 303? For some reason, I was thinking when the Brits copied the Czech gun, they kept the 8mm caliber...because it is rimless.

And of course, anything the Brits do, the Canucks ape. Never could figure that out either. Here the Canadians sit next door to the worlds greatest military power and the freest society on Earth, yet they insist on miming the Brits.....politically and militarily. Yes, I think it's always been an 'in your face' attitude towards the US. We bled white chasing the goddamned British out and our neighbors have played open host to them ever since. I think they feared being taken over by the USA more than being a British lackey...so they remained in the Commonwealth of Nations....har, what a ****ing joke.

Oh back to guns and ammo......perhaps Dominion or whoever makes ammo up north had a miliatry contract to supply the ammunition.....and I am almost sure British MG's were in 8 mm, if they used a rimless case.

[StarMetal]

Jump

You're right about the Canadians aping the Brits, but then did have an M16, still might, I believe they called it the C7 though.

Joe

[StarMetal]

Stocker

From what I've read the Canadians converted some Ross rifles to 8x57 Mauser but that was back in WWI

Joe

[Depreacher]

THANKS GUYS, From barrel friction, to barrel harmonics, to angle of jump I am seeing it is a matter of many factors. Your input was really appreciated, and I understand things better now. The military ammo was bought from the old Marshall Hyde company in 1968. It was advertised as being produced by dominion, in sterile form, for the WW2 chinese forces (what little there were) who were armed with 8mm rifles. SUPPOSEDLY!!!! Anyhoo, wern't the old chinese mausers in 8mm??? Were they called Chang Kai Chek (spelling?) Mausers?? The boolit weighs 154gr. and the powder looks like 4895. When I bought the ammo I was a healthy young 25 year old buck. Shooting 50 or so rounds in a short period didn't bother me one bit. Now at 62, and after two bouts with Lymphoma cancer, the ammo produces a lot more "kick" than it used to. I have also noticed that people make stairs much more steeply than they used too. THANKS AGAIN for the info. cbp