Bullet Length

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sandytye

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Does anyone have or know where to look for bullet length of nosler partitions, TSX or MRX.

i'm looking for a new bullet for my 7mm and it only has a 1:9.5 twist.

i'm hoping to run some numbers for the 160 / 175gr variety to see if they will have a remote chance of stabilising:confused:

this would be a lot easier on the pocketbook if i didn't have to buy a box of each to find out.
 
Bullet length has little to do with what you are trying to achieve.
It has more to do with bore contact length.
Round nose bullets tend to have more for example.
A short fat roundnose will likely have significantly more contact length than for example a boattail.
 
If we have a cylindrical bullet which is in contact with the bore along it's entire length, the bullet is as short as possible within caliber and weight. Once we taper the nose and base of the bullet, we can lengthen the bullet out, making it's bearing surface very short, yet the bullet much longer than the cylindrical bullet of the same weight. The shorter bullet will stabalize in a slower twist than the longer bullet of the same weight.

Because the discussion began with 7mm bullets, the following is the relationship between twist and maximum length of a 7mm bullet.

Twist Length
1:8 .... 1.51"
1:9 .... 1.34"
1:10 .... 1.21"
1:11 .... 1.10"
1:12 .... 1.01"
 
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In theory, if you have two bullets of equal weight, loaded with an equal weight of the same powder, the bullet with the shorter bearing surface will have the higher velocity if both rounds are fired in the same rifle. When a cartridge is loaded with given weight of powder, the bullet with the longer bearing surface would produce higher pressures - all things being equal.

When we consider the OAL of a cartridge, we are generally thinking about the distance from the bearing surface of the bullet to the lands in the barrel. The farther the bullet can be seated away from the lands the more the pressure is reduced. When barrels are free bored - meaning that they have unusually long throats, the cartridges fired in them can be loaded heavier due to this lower pressure, resulting in higher velocity than otherwise possible, but often at the cost of some loss of accuracy.

If you have a slow twist barrel, and you want to shoot the heaviest bullet possible, chances are you will have better luck with the shorter bullet.
 
Brno used to make their 7x57 bbls with a 1 in 7.66" (as I remember) twist in order to stabilize long, heavy spitzer bullets like 175 grainers.

Here's an answer for you from a custom bullet maker:

QUESTION:
Will you be able to manufacture a 175gr hollow point, boat-tail spitser in 7mm? I have a 7 x 64 and I want the heaviest possible bullet available as I want the velocity to remain below 2700ft/sec.

ANSWER:
We would be happy to make 175gr 7mm monometal bullets as we have been asked for them on numerous occasions. The only snag is we know that they cannot work in standard commercially available 7mm barrels. Any manufacturer who supplies such a bullet is simply responding to an uninformed demand from the market. Here is why: A 7mm 175 gr monometal spitser boat tail bullet will be 18% longer than a similar bullet of conventional construction. That means that it will be about 42mm long and will require a twist of 1 in 7.3" to stabilise. Some rifles may shoot reasonable groups with such a bullet but when it strikes, it will tumble instantly, with the resultant unpredictable penetration and massive meat damage a tumbling bullet brings. A 175 gr round nose flat base bullet can be made to stabilise, but will not expand, and will be too slow for decent momentum and energy levels as are available from the lighter and faster HV bullets

My comment without reading the above would be to go with a lighter quality bullet, and don't take a chance even with 160 gr. spitzers.
 
rodagra said:
Brno used to make their 7x57 bbls with a 1 in 7.66" (as I remember) twist in order to stabilize long, heavy spitzer bullets like 175 grainers.

Here's an answer for you from a custom bullet maker:

QUESTION:
Will you be able to manufacture a 175gr hollow point, boat-tail spitser in 7mm? I have a 7 x 64 and I want the heaviest possible bullet available as I want the velocity to remain below 2700ft/sec.

ANSWER:
We would be happy to make 175gr 7mm monometal bullets as we have been asked for them on numerous occasions. The only snag is we know that they cannot work in standard commercially available 7mm barrels. Any manufacturer who supplies such a bullet is simply responding to an uninformed demand from the market. Here is why: A 7mm 175 gr monometal spitser boat tail bullet will be 18% longer than a similar bullet of conventional construction. That means that it will be about 42mm long and will require a twist of 1 in 7.3" to stabilise. Some rifles may shoot reasonable groups with such a bullet but when it strikes, it will tumble instantly, with the resultant unpredictable penetration and massive meat damage a tumbling bullet brings. A 175 gr round nose flat base bullet can be made to stabilise, but will not expand, and will be too slow for decent momentum and energy levels as are available from the lighter and faster HV bullets

My comment without reading the above would be to go with a lighter quality bullet, and don't take a chance even with 160 gr. spitzers.
Click to expand...

Sounds like that came from GS Custom Bullets. While I agree that a monometal 7mm 175 gr bullet would require a fast twist (particularly one with the HV's style of boat tail) I disagree with the premise that a 175 gr 7mm flat base, lead core, round nose bullet would not perform well. They have since the Bore War, and will reliably open as long as the impact velocity is above 2000 fps.
 
Boomer,
I'm not sure of the source of the info as I pulled it out of a folder in my computer. The reason it was saved was that it backed up a claim by an old friend who started with a Model 70 with a slower twist and was unable to stabilize bullets over 150 grs. He sold the Winchester and bought a Brno 601. Never had any more problems.
Is it not true that several other European 7x57s are barreled with faster twist than 1 in 9 for just this reason?
Of course comparing the 7x57 with the 7mm Rem. mag. is an apples and oranges situation, but at what range can you expect a 175 gr. flat base round nose out of the 7mm mag to be at or over 2000fps? About 300 yds. maximum with a bit less energy than several lighter bullets and more drop I believe. All in all it would make quite a difference in say a plus 4 minus 4 kill zone range with adequate remaining energy.
 
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thanks for the info so far

rodagra i ran some quick numbers and out of my stw 175 's are over 2000 fps out to 500 yrds.

any ways i think i might have to give those mrx a shot as that tungsten core should shorten that bullet up a bit.
 
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