Question on loss of accuracy

[wmitty]

Given: An accurate load has been worked up with a particular gas checked boolet. The boolet is constructed of ww which has been heat treated to allow increasing the velocity beyond the point where the most accurate groups were obtained. As velocity is increased, accuracy begins to fall off to the point of being unacceptable.

Assuming the lubricant used is adequate for the higher velocity, has the alloy's compressive strength been exceeded, which allows the base of the bullet to be distorted? If this is the case and the alloy has been heat treated to the maximum hardness allowable, then the velocity limit will have been reached for that boolet design (I am asking; not stating this).

By using a bullet with as large a cross- sectional area as possible, maximum velocity potential should be obtained. It would seem that Loverin's designs would allow this. Why are there not more boolets with multiple shallow lube grooves and relatively large, flat meplats being designed for use as hunting projectiles?

[ANeat]

Ive found certain bullets like a certain velocity. Get above of below that certain spot and the accuracy falls off. This has proven out in cast and jacketed bullets both.

Lack of accuracy doesent necessarily indicate a failure of the bullet or alloy. You might try to capture a fired bullet in a water trap or some other way and see how its holding up to the extra velocity.

[HORNET]

Multiple shallow lube grooves and large flat meplats??? Ever look at Ranchdog's mold designs??:holysheep

[randyrat]

Lee makes that kind of bullet also, it's call a "mirco groove" I'm waiting for one in the 40 cal.

[VTDW]

Lee makes that kind of bullet also, it's call a "mirco groove" I'm waiting for one in the 40 cal.

The Marlin microgroove barrels like speed with EDIT: hardcast boolits for sure. I develop loads using a ladder test by only increasing each successive charge by .2 gr. I find that there are usually two sweet spots with each boolit or bullet. One on the lower end and one toward the upper end. I have never found accuracy with max loads.

Dave

[44man]

Every boolit or bullet reaches maximum accuracy with one load, one velocity. Go up or down and groups open. Nature of the game and you can't beat it. You might get acceptable accuracy somewhere along the line but there will be a very small window for the best and it is anywhere from 1/2 gr to 1 gr up or down from the most accurate load.

[mag_01]

wmitty----You will find pressure not velocity dictates Boolit strength (BHN)---As pressure goes up Boolit strength must also increase to produce acceptable accuracy. It is possible to have the same velocity with two different powders but pressure may vary---Hope this helps you with what you are trying to do----Mag

[buck1]

wmitty----You will find pressure not velocity dictates Boolit strength (BHN)---As pressure goes up Boolit strength must also increase to produce acceptable accuracy. It is possible to have the same velocity with two different powders but pressure may vary---Hope this helps you with what you are trying to do----Mag

True story! A slower powder may be in order.

[44man]

Yep, each powder has it's own window. Even a primer change can alter it.

[Cloudpeak]

Every boolit or bullet reaches maximum accuracy with one load, one velocity. Go up or down and groups open. Nature of the game and you can't beat it. You might get acceptable accuracy somewhere along the line but there will be a very small window for the best and it is anywhere from 1/2 gr to 1 gr up or down from the most accurate load.

Bingo. And the above is also true for jacketed pistol and rifle bullets as I'm sure most everyone knows. I've reloaded for .243, .270, .357, 44 mag, 40 S&W and 45 ACP and none of my best grouping loads have been max. Change one thing about your most accurate load, i.e. bullet design, seating depth, amount of crimp, etc. and it can change everything.

I just loaded up 60, .270 loads for the friend that I sold my Ruger .270 M77 to. 130 gr Hornady, 55.5 grains of 4350. This gun would group under 1 inch at 100 yards. It has the first scope I ever bought on it. A 3x9 Redfield I bought in 1963.

The new box of 130 gr Hornady's Kevin bought had a crimp groove that was different by around 1/8" from the 20 year old Hornadys I'd worked up the load with. I told him he'd better check the grouping because of the different seating depth, accuracy could have gone down hill. I don't think he shoots the rifle much. He's shot 5 times at deer/antelope and bagged 4 animals. He said he had no idea how that happened. It should have been 4 for 4:-D

Cloudpeak

[Char-Gar]

Others on this board are far better qualified than I am to tangle with your questions but as some general principals, there are a number of factors involved. I am going to take as a given your lube has not rolled snake eyes.

1) The burning rate of the power controls how fast the pressure is applied to the bullets. Fast powders will start to distort the bullets past their accuracy potential at a lower speed than slower powders even though the pressure might be the same or similiar.

2) At the velocity increases (due to pressure increase) a harder alloy is required

3) Often the bullets at higher velocity must be sized smaller to recover the accuracy it has at a lower velocity.

4) Let's not forget the rate of twist and the rpm limits an alloy can take before it starts to degrade.

Until we add all of these factors into your question, we are just sorta feeling around in the dark.

Loverine designed bullets were a moderization of the old multi-band Schutzen bullets of the Days of Yore. There were and are very fine bullets, but IMHO their sucess is more due to their fit in the barrels than any other factor. The design tends to introduce them straight into the rifling.

[Char-Gar]

VTDW.. I have no problem getting top notch accuracy out of Marlin MG barrels at top end velocity. I am talking 30-30 here. MG barrels tend to run larger in groove and land diameters than conventional barrels making bullet fit more problematic. Given a bullet that fits an MG barrel well, the MG is not any sorta of handicap.

I run a SAECO 180 GCFN bullets out of my Marlins at 2.s -2.3 fps (24" bbl.) with top notch accuracy. I think the bullet is SAECO 305 (it is their .303 Brit. offering) and the powder charge is 31 grains of 3031. I size the bullets .310 and cast from No. 2 alloy.

O also have an older 311291 that runs .303 on the nose that also does will in these MG barrels.

I have one Marlin 30-30 (1960 vintage Texan) that runs a full .305 accross the lands. I had to have Mountain Molds make up a version of the Fat 30 to get that once to shoot well and shoot well it does.

I firmly hold to the notion that finding a bullet that fits properly is the only downside to Marlin MG barrels.

[Lloyd Smale]

alot of verals lbt molds use multiple small lube groves too. I never liked them there to much of a pain in the but to lube in my lubesizer and ive never seen where they outshoot a convetional bullet in a handgun

[cbrick]

wmitty, there is a lot your post doesn't say, like what caliber? At what velocity? With what powder? What boolit weight? What grove diameter? What sized diameter? Heat treated to what BHN?


Given: An accurate load has been worked up with a particular gas checked boolet. The boolet is constructed of ww which has been heat treated to allow increasing the velocity beyond the point where the most accurate groups were obtained. As velocity is increased, accuracy begins to fall off to the point of being unacceptable.

An article in HandLoader # 73, May/June 1978 by Ken Mollohan addressed this same topic. Ken's conclusion for 30 Cal was a lower sectional density.


Assuming the lubricant used is adequate for the higher velocity, has the alloy's compressive strength been exceeded, which allows the base of the bullet to be distorted? If this is the case and the alloy has been heat treated to the maximum hardness allowable, then the velocity limit will have been reached for that boolet design (I am asking; not stating this).

Without knowing many more of the details one of many possibilities is that your bullet is now too hard, not too soft.


By using a bullet with as large a cross- sectional area as possible, maximum velocity potential should be obtained. It would seem that Loverin's designs would allow this. Why are there not more boolets with multiple shallow lube grooves and relatively large, flat meplats being designed for use as hunting projectiles?

Many of the posts already mention many of the possiblities, closer to groove diameter as velocity goes up is one. Slower powders another. Bullet design can play a role here if pressures get high enough to cause the bullet nose to slump to one side.

In my humble oppinion the single most important thing is bullet fit. Then comes chamber and bore condition (more and more important as velocity increases), the slowest powder that will give acceptable velocity, lubrication and then BHN. You might want to read this article on how to get a specific BHN.

Heat Treating (http://www.lasc.us/HeatTreat.htm)

Additionally, as velocity and distance increases bullet quality becomes more and more important. I am in the school of thought that says the bullet base steers the bullet, not the nose. I did extensive 150 meter revolver group testing and found that even very minor defects on the bullet base (such as even a minor rounding of the base as seen when first opening the sprue) was unacceptable.

Hope this helps. Good luck.

Rick

[wmitty]

CBRICK - I plead guilty to not being specific in my original post. I'm shooting a Sav.99 chambered for .308 with the 31141 group buy six cavity boolets; 34 gr surplus 4895, WLR primers, commercial brass, boolets sized .311" and seated touching lands. I realize this still doesn't cover all the varibles, but it should give some idea of what I'm looking at. Group was 1.4 moa at 100 yds and from past experience I know the groups will start opening up as charge is increased. I am trying to determine if the reason is because of inadequate alloy hardness or change in moon's phase or what.

[Char-Gar]

Mr. Mitty... Do this... try sizing you bullets .310 and .309 as you add the powder, then get back to us. I predict you will see improvment in high velocity accuracy.

[wmitty]

CHARGAR - I just bought a lubrisizer, and haven't come up with the .309" and .310" dies yet. As soon as I obtain them, I'll follow your recommendation!

[Bass Ackward]

CBRICK - I plead guilty to not being specific in my original post. I'm shooting a Sav.99 chambered for .308 with the 31141 group buy six cavity boolets; 34 gr surplus 4895, WLR primers, commercial brass, boolets sized .311" and seated touching lands. I realize this still doesn't cover all the varibles, but it should give some idea of what I'm looking at. Group was 1.4 moa at 100 yds and from past experience I know the groups will start opening up as charge is increased. I am trying to determine if the reason is because of inadequate alloy hardness or change in moon's phase or what.


Yep. The secret to launching cast is to use as slow a powder as possible to have the bullet moving the farthest down the bore when pressure peaks. If you want to do better, try slower. If you use anything from the IMR line, it should be about 2 grains more with every slower change. So about 38 grains with 4320 / RL15, etc. Change to a pistol primer and you can get more velocity yet.

[44man]

Every change made to the boolit, whether hardness, lube, annealed checks or not, seating depth or whatever will open a different accuracy window and can change even if you are using the same powder. When you change the powder burn rate, the window moves up and down the velocity range depending on the speed of the powder until you either reach the limits of the alloy or the twist rate for that boolit or you just can't get the velocity wanted.
Shooting a short boolit fast from a fast twist doesn't work, neither does shooting a long boolit from a slow twist. Most forget that the boolit must be matched to the twist and velocity range of that twist.
What it boils down to is there is only one window for each change you make and you have to find it.
I have not mentioned boolit fit because we all know that and the wrong fit has almost no accuracy point with bad leading, stripping, tipping and all the other problems.
It sounds like wmitty has a good fit because he has an accurate load but he is trying to move the window for that alloy, boolit style and his twist without changing anything but the powder charge.
If he follows all of your suggestions on alloy and powder changes, he just might be able to up the velocity and maintain good groups. However, if he has exceeded the ability of the rifle to stabilize that boolit, he might need a boolit change.
This was not an easily answered question so I can't give one and say it will work.
Guess who has to do the work?

[VTDW]

VTDW.. I have no problem getting top notch accuracy out of Marlin MG barrels at top end velocity. I am talking 30-30 here. MG barrels tend to run larger in groove and land diameters than conventional barrels making bullet fit more problematic. Given a bullet that fits an MG barrel well, the MG is not any sorta of handicap.

I run a SAECO 180 GCFN bullets out of my Marlins at 2.s -2.3 fps (24" bbl.) with top notch accuracy. I think the bullet is SAECO 305 (it is their .303 Brit. offering) and the powder charge is 31 grains of 3031. I size the bullets .310 and cast from No. 2 alloy.

O also have an older 311291 that runs .303 on the nose that also does will in these MG barrels.

I have one Marlin 30-30 (1960 vintage Texan) that runs a full .305 accross the lands. I had to have Mountain Molds make up a version of the Fat 30 to get that once to shoot well and shoot well it does.

I firmly hold to the notion that finding a bullet that fits properly is the only downside to Marlin MG barrels.

Chargar,

I am talking MAX loads sir, are you. I wish I could be so fortunate. I run my cast .002 larger than my slugged barrels. I am at least slightly anal as I do not accept anything less than sub MOA at 100 yds. I have the problem of finding that my Ballard .444 doesn't shoot hardcast as well as my two Microgroove .444's...yet! :mrgreen:

I think you and I are on the same page. My circa 71' and 78' slug at .429 and my circa 2002 slugs at .431. Go figure eh?

Dave