120-130 gr. bullets in 6.5x55?

[lilabner]

I'm having some problems getting consistently tight groups with the lighter bullet weights in my T-3. Have tried the 125 gr. partitions and 129 gr. spire points but can't consistently get MOA with either of them. Maybe I'm seating the bullets too deep. If you have a good loading for 120-130 gr. bullets, what bullet are you using and what cartridge overall length? Thanks.

[wareagleguy]

Now this is a guess but if my mind is right the T3 has a 8" twist.  If that is the case then you may be shooting a bullet that is a little too light.  I think 130gr would be on the bottom.  You may want to try something in the 140gr range.  Sierra 140s would be my first try.

[doctordisaster]

I have used Nosler BT 120s with great results.Seating depth is something I was fooling around with but with the Tikka I don't think it matters all that much.With the BTs I used the given COL right out of the Lyman book.Perhaps your pushing them too fast.My loads always start right around the bottom,starting load.I got good enough accuracy and never saw the need to increase the charge any where close to the max charge.I may be able to find my load charge but I haven't used the 120s for quite some time.If I find it in my notes I'll post it.I have a T3 Hunter 6.5X55.

[lilabner]

My understanding is that barrel twist rates are affected by bullet length and diameter, not bullet weight. Anybody using the Barnes bullets? They are long for their weight.

[Old English]

I enclose a pic of my load development for T3 in 223. I believe that it shows that bullet seating depth is extremely critical. All 3 loads were the same, seating depth was .01" difference with each load. Check it out!!

[wareagleguy]

Sorry lilabner but I think you are wrong.  According to Shilen on selecting the correct twist..

"The information below will help you select the best barrel twist for your specific needs, providing of course there are multiple choices. If you'll be shooting one bullet weight, choose a twist from the chart just fast enough to stabilize it. Too fast a twist simply overspins the bullet and may result in reduced accuracy. On the other hand, a twist too slow for any bullet will likely produce instability, keyholing and rotten accuracy. So if you're going to be using several bullet weights, be sure to select a twist that will stabilize the heaviest one, since lighter bullets will also be stabilized.

By way of explanation, the numbers in the "Twist" column indicate how far the bullet must travel through the bore to make one full revolution. This is determined by the rate of rotation of the rifling. For example, a 9"-twist barrel spins the bullet one full turn when it passes 9 inches through the bore. In a 16"-twist barrel, the bullet makes one revolution in 16 inches. So at the same bullet velocity, the 9" twist is faster (spins the bullet faster) than the 16" twist. Consequently, as the chart reflects in the .224 CF section, the 9" twist is necessary for stabilizing heavier bullet weights.

Again looking at the .224 CF section, if you're planning to shoot 55-grain bullets, the 14" twist is ideal. This twist is also the best choice for 52- and 53-grain match bullets driven at moderate velocities. But if you're also contemplating shooting a 60-grainer, go with the 12" twist, since it will stabilize all the bullets you'll be using. As you can see from the 15" and 16" twists, higher velocities also spin the bullet faster and may enable a slower-than-recommended twist to stabilize a marginally overweight bullet. However, this is tricky stuff best left to those who are highly experienced in operating at the ragged edge of stability and sanity.

The basic principles just outlined apply to all the calibers .

[Brithunter]

I'm having some problems getting consistently tight groups with the lighter bullet weights in my T-3. Have tried the 125 gr. partitions and 129 gr. spire points but can't consistently get MOA with either of them. Maybe I'm seating the bullets too deep. If you have a good loading for 120-130 gr. bullets, what bullet are you using and what cartridge overall length? Thanks.

Actually I found that in a 7x57 rifle I have that seating the bullets (139 Grain Hornady) deeper improved accuracy, seating them out gave poorer groups which is contrary to just about all I read. I have also got good accuracy in 6.5x55 with 120 Grain Speer Spitzers. One rifle likes them the other prefers 140 grain bullets. Funny thing is that I have not discovered a good load using the 129 grain Hornady's as yet. With the 120 grain bullet I used IMR 4350 powder and WLR primers.

[Big Blue]

lilabner,
To determine your seating depth you might want to seat a bullet in a fired case with no powder or primer and slowly try to chamber the round. You can seat it deeper a little at a time until you get it to chamber. Sometimes just the act of closing the bolt is enough to push the bullet into the case or you can just take it out if it doesn't chamber and use your press to seat it deeper a little at a time. Once you determine the chamber depth just back it off about .020" and try that length. Some bullets like to be seated right up to the rifling, Berger bullets suggests that for their bullets. Most will do better when they are backed off a bit. Loading them right to the rifling may also create dangerous chamber pressures. With the Tikka you will also be limited by the length that will fit in your magazine, so take that into consideration.

One of the first persons to try to develop a formula for calculating the correct rate of twist for firearms, was George Greenhill, a mathematics lecturer at Emanuel College in Cambridge, England. His formula is based on the rule that the twist required in calibers equals 150 divided by the length of the bullet in calibers. This can be simplified to:

    Twist = 150 X D2/L

    Where:
    D = bullet diameter in inches
    L= bullet length in inches
    150 = a constant

This formula had limitations, but worked well up to and in the vicinity of about 1,800 f.p.s. For higher velocities most ballistic experts suggest substituting 180 for 150 in the formula. The twist formulas used in the Load From a Disk program, featured at this web site, uses a modified Greenhill formula in which the "150" constant is replaced by a series of equations that allow corrections for muzzle velocity from 1,100 to 4,000 fps.

The Greenhill formula is simple and easy to apply and gives a useful approximation to the desired twist. The Greenhill formula was based on a bullet with a specific gravity of 10.9, which is about right for the jacketed lead core bullet. Notice that bullet weight does not directly enter into the equation. For a given caliber, the heavier the bullet the longer the bullet will be. So bullet weight affects bullet length and bullet length is used in the formula.
Don

[Brithunter]

Hi All,

     Ahhhhh I see another myth is being spouted. This is the one which states that the best accuracy is obtained by having the bullet nearly touching the lead of the rifling however if you load enough and experiment with different rifles you will actually find that like Free floating barrels it's not always the way to go for best accuracy.

   This was brought home to me back in 2003 whilst preparing for a hunting trip to the US with a 7x57 rifle. For bullets I chose the Hornady 139 Grain Bullets both Spire Points and the Flat point of the same weight. The Flat Point bullet shot superbly however it would not feed from one side of the magazine because the flat point collided witht he edge of the chamber and hung up, so I used the same load just switched the bullet the bullet to the Spire point and loaded them so the base of the bullet was level with the shoulder of the case, the result on the target was surprising as the Spire Points groups over double the size of the Flat Points.

    Using the old myth of seating the bullet close to the leade I seated the bullets out and tried again yet nother tried at this point improved the grouping which was hovering around 1-1/"-2" not good enough for confidence in my mind. I would have switched rifles but this was the one on the Temp Form 6 so I was stuck with it. By this time I was running low on the Spire Points so a trip to the gun shop for further supply was called for. To my horror I found that they didn't have any in stock only yhe 139 BTSP so I brought a couple of boxes of them and started over again. Seating the bullets out close to the leade again produced large groups to in desperation I seated the bullet to the cannlure and tried them again. Shockingly on examining the target the groups was quite a bit tighter so I loaded further batches just varying the seating depth out by 0.010" each time. A load was finally found that shot 3/4"-1" that had the cannulure showing out of the case mouth and it was this load that was used on the US trip.

    Thinking about it later I should have realised sooner as the Sporterised Swedish Mauser I have shoots 100 & 120 Grain bullets shoot very well and they are nowhere near the leade as the barrel is throated for the 156 grain Round Nose bullet and it's impossible to get the ogive near the leade using the spitzer or spire point bullets.

    The only way to find the best load for your particular rifle is to experiment and try a variety of bullets and seating depth. Of course powder choice can also make a difference to accuracy. The wonderful thing about ballistics and handloading is that there are no hard and fast rules to getting the best out fo different guns. As each barrel is different the recipe each barrel likes will also be different.

[lilabner]

All very interesting! See my new posting. I found that my rifle shoots better with a slower burning powder - RL-22. Also, I found that the Hornady cannelure is located at a very good spot for my rifle and the 129 gr.bullet. I just seat to the cannelure. I am shooting full power loads at a velocity of 2880 fps. As stated, some bullets in some rifles shoot better seated rather deeply. The barrel makers recommend a slower twist than the 1 in 8 for the 6.5 Swede, but the disadvantage would be that bullets in the 155-160 gr. weights would not stabilize well with the slower twist. One barrel maker recommends a twist fast enough to stabilize the heaviest bullets that might be used and states that accuracy loss is generally not a big problem if light bullets are used.