OK,..let me lay this out for you. I found out about an IBS factory class 100yd shoot 2 days ago. I had some MILD loads worked in a ladder with RL15 and a 50gr v-max that had yet to be tested in my rem700 VSSF 220 swift. I run to the range after work last night and shoot my ladders round robin style from 35.8-37.1gr in .3gr increments. So the 36.1gr load shoots in the high .2's. This is virgin match prepped brass while this is taking place. I end up with a remaining 20 cases unfired yet,..and 30 cases fire-formed.

I go home and load the 20 virgin and 15 more fireformed cases for todays match (finished at 12:00 AM). I measure the expansion at the body/shoulder junction between virgin and unfired and find the fired case to be .005" larger in dia. I measure the datum line on the shoulder from the case-head and find it has grown .004-.005" as well after firing. So,.I load the virgin brass at 36.1gr and the fired brass at 36.2gr and leave everything else the same. My first 5 targets with the virgin brass yield a 49 with 2x's (one went right to the 9 ring) Now I don't feel like I have enough virgin loads left after the warmup target sighters and the record target sighters and record shots,..so I go to the fireformed brass with 36.2gr. I fire 2 into one hole just high and right at the top of the 10ring. I click to center and go for the 5 record shots. My first is X' for a 10. My second is low and a 9 My 3rd is a low 9 I hold high on the 10ring for #4 and it's an X'. I get barrel mirage and run #5 low for a just barely missed the 10 ring, 9 Second round is a 48 with 2 X's. The match was called for heat (102* in the shade plus the east coast humidity). It was enough for 3rd overall in the factory class

My question is this,...is there a formula or program someone has that can tell me how much the powder needed to be increased by to give me the same velocity and POI so I didn't drop the second set of record shots. I could only guess with no time to test anything.

The formula is....



Trial and Error

Nobody???? come-on,..doesn't quickload or some other program have a calculation I can use?

Ask the number 1 and number 2 shooter how many clicks on your culver for that particular range as they are obviously better dialed in for that particular range. If you find a computer that has all the answers versus the old try and buy method then let me know.

one-holer,..noone else was using the 220swift,..they were using 223's and PPC's. I know it was me going from the first record target with virgin brass (lesser volume) to 1x fired NK sized brass (larger volume) on the second record target. I should have bumped the charge by .3gr to acheive that same pressures as it is obvious .1gr did not produce enough. I was hoping someone had "been there,.done that".

The problem is every case will vary. The chamber geometery, case wall thickness, case expansion on fireing, and the amount of shrinkage when cooling will all change the interior capasity.
As the others state it`s all trial and error

JustC--Now I'm playing with you. There is a lot to be said for shooting what everyone else is and not being the odd man out.
I just don't see any other way but the old fashion way of shoot it and see what happens.

quote:

Originally posted by JustC:


My question is this,...is there a formula or program someone has that can tell me how much the powder needed to be increased by to give me the same velocity and POI .

Who gave you the notion that the (temporary) internal volume of the brass has anything to do with velocity? The ultimate pressure (and resultant velocity) are largely determined by the volume of the pressure vessel, which in this case is the chamber (and to a lesser extent, any freebore). The brass is only a "sealer" lining the walls of the chamber and shapes itself to the chamber (matches the chambe's volume, less the mass of the case) with very little (relatively) pressure.

Now. What you do to the brass in reloading it CAN have an effect on where your shots go, but this is related to concentricity of the case/neck, relative position of the case in the chamber, and other variables. It has practically nothing to do with the temporary volume of the chamber lining, ie. the unfired case capacity.

Adjusting the volume of powder to the volume of an unfired case is just about like adjusting the amount of trash you intend to stuff in a trash bag to the internal volume of a flat-folded plastic trash bag (zero). What you're filling up is the can that the trash bag lines, not the unsupported bag itself.

The only thing I could imagine is to take the brass you use and neck size only when you get home from the shoot. Load it up with minor variations and shoot it over a chronograph to see what it takes to give you the velocity you want. There may be a better way, but I'm not aware of it. Best wishes.

Cal - Montreal

quote:

Originally posted by Stonecreek:

quote:

Originally posted by JustC:


My question is this,...is there a formula or program someone has that can tell me how much the powder needed to be increased by to give me the same velocity and POI .

Who gave you the notion that the (temporary) internal volume of the brass has anything to do with velocity? The ultimate pressure (and resultant velocity) are largely determined by the volume of the pressure vessel, which in this case is the chamber (and to a lesser extent, any freebore). The brass is only a "sealer" lining the walls of the chamber and shapes itself to the chamber (matches the chambe's volume, less the mass of the case) with very little (relatively) pressure.

Now. What you do to the brass in reloading it CAN have an effect on where your shots go, but this is related to concentricity of the case/neck, relative position of the case in the chamber, and other variables. It has practically nothing to do with the temporary volume of the chamber lining, ie. the unfired case capacity.

Adjusting the volume of powder to the volume of an unfired case is just about like adjusting the amount of trash you intend to stuff in a trash bag to the internal volume of a flat-folded plastic trash bag (zero). What you're filling up is the can that the trash bag lines, not the unsupported bag itself.

Nice explanation,well done. roger

bartsche, My thinking was that as all the cases had been sized prior to firing the first time and all measured the same external dimensions at the case-head, shoulder, and neck/body junction as well as all having been neck turned and primer pockets uniformed and flash holes deburred, they were as close to the same as possible. Now once the others were fireformed 1x, they would also be relatively close to one another in dimensions (external dimensions within .0003" or so)

That being said,..I ASSUMED the fired dimensions would be close to equal (given body thickness variations) and that the powder charge would obvioulsy need to be increased as both the body/shoulder dia and datum line were both increased by .005" each to meet the chamber with a suspected springback of .001'-.002". Therefore, I figured that slight increase in internal volume would necessitate an increase in powder to make for a similar pressure. Keep in mind,..these were IBS 100yd targets with a very small x-ring. My bullets only dropped to the 9ring or cut both the 10 and 9. That shows a very slight drop in pressure, which I would have thought .1-.3gr should have taken care of,...

am I off base with my thinking here?

Nice explanation,well done. roger[/QUOTE]

Thanks for the note, Roger. But as you say, talk is cheap, and I'd rather have the whiskey!

quote:

My bullets only dropped to the 9ring or cut both the 10 and 9. That shows a very slight drop in pressure

am I off base with my thinking here?

A bullet striking the target lower than another bullet from the same gun/load is not necessarily the result of less pressure or velocity.

Your assumption appears to be that less pressure equals less velocity equals more bullet drop. In actuality, a variation in pressure/velocity may manifest itself in the bullet exiting the muzzle at a slightly different point of amplitude in the oscillations of the muzzle, therefore a load producing lower velocity might well exit the barrel as the muzzle is "pointing" slightly more upward, resulting in a lower velocity bullet striking higher on the target. Taming barrel oscillations is the theory behind the Browning AccuBrake system and other similar barrel "tuning" devices.

Another manifestation of lower velocities, especially noticable in handguns, is for the bullet to strike HIGHER on the target due to increased barrel time and the gun having tilted upward slightly due to the effects of recoil by the time the slower bullet exits the muzzle. This phenomenon is hardly ever noticable in rifles, but if you'll shoot a heavy-bulleted revolver with both a fast, light-bullet load and a slow, heavy-bullet load, you'll find the effect to be pronounced, ie., it is impossible for me to adjust the sights on my 4 5/8" Ruger .45 Colt low enough to use a 300 grain Hornady at 800 FPS, whereas a 200 grain Speer stepping out at 1100 fps strikes more than a foot lower with the same hold.

Just a thought here if I may interject. What Stonecreek said was true and, you are shooting a .220 swift where the others are shooting .223 and 6mm ppcs. You're going to have to make a few modifications to compete with them and really truely win. There rounds are more compact and have greater repeatability than that 220 swift however, you have probably been loading it very near the edge, which is 500fps nearly faster than they are running. This is doing two things to you. 1) It is increasing your std in velocity due to the cases, bullets, powder charge and temp, etc... and any variation of the above and 2) Has increased your temperature since you are burning nearly 10 more grains of powder with each squeeze of the trigger over your competition. The barrel is getting hot and the chamber and the volume is increasing. The rounds will naturally pattern in a counterclockwise circle and will go downhill slightly due to the increased volume in the barrel and chamber caused by Expansion due to heat. Lower your charge to the low end of your charge, re-zero and go after them. Your Std will decrease and your temp will as well. The lowering problem will not be as marked either. Neck size only as is suggested by Cal and only use the fire formed brass next time, that will keep the volume increase to a minimum. Try this and let us know what happens. You should give them a good run for their 1st and 2nd this time.

SHOOT WELL.
LOAD BETTER.

Thanks gents.

stonecreek,..I would have again ASSumed that by my pills running from the 1x rifed brass instead of the virgin brass there would be a variation in the "node" or barrel frequency. That was my reasoning for bumping the charge a tad,..so as to maybe "force" the 1x fired (greater volume) cases to approach the same frequency as the virgin brass. Now,..as I have done quite a bit of load testing with the "ladder" method,..I have seen the groups that exit the muzzle at varying points in the cycle, they tend to run up and down, left and right. My 10ring misses were all in the 9 ring just under the 10 ring,..none to the left, right, or high. I figured I may be on to something since they all impacted similarly. Maybe that was just coincidence. I was hoping it was as simple as a pressure issue related to internal volume differences,..but then this stuff wouldn't be frustrating enough if it were that simple

osoksniper,..if I plan to regularly run in these factory class shoots, I may well grab a 223 chambered rifle to reduce barrel heat. But since my swift is wayyyyyyy under 1/2moa with even a few factory loads,..I knew I had a good chance to place well, so that was what I used (most everything else will not make the factory class regulations). I did plan well enough to use the lower end harmonic load of 36.1gr of RL15 with the 50gr V-max which is well under the max load in the book. I knew my bore heat would be an issue, especially in 102* heat,..so I was at least forward thinking enough to use the slower load that was in the .3's during testing the day before. Not bad for the supposed barrel burner that the swift was always said to be,..I know a bunch of those boys with their sako's in 6ppc and no doubt costing at least 50% more than my VSSF stood back and got worried I liked that best of all. When I catch them again with a little less heat and a little more time to test the ladder and use brass that is on the same firings,..they will need bring their "A" game for sure Thanks for the encouragement.

JustC,

Sorry if I misunderstood, in the 32 years of reloading I'm sure I've done that more than once. Have you tried another bullet with a softer shell or is this one the one you have pretty much dialed in? One other item I would do right away is change the primers. The 220 swift is very aimiable to the BR2 primers if you haven't already gone to them, due to the larger powder capacity, uniformity will be greatly exagerated at those temps. Am sure you have already flash holed the cases and probably even washed the cases in the dishwasher right? Weighed them out and seperated by the nearest 3 grain weight? I'm giving you more help than I usually do a competitor, hope you don't shoot 1000yd open class high power against me!!! Just kidding dude, I always like to see a good shooter...my 40X is ready usually long before I am. That's about all that is left to check on your end, after that the only thing that can beat you is the gun, sounds like it is as good as gold, give em what for dude...later.

No misunderstanding osoksniper,..I followed ya I found about this match on a thursday afternoon and shot it saturday morning. I had loaded the v-max load ladder as the very first loads for the gun. I had never even run the ladder until friday eve at 5:30-7:00PM in 95* temps. But you know how it is when you want to shoot a match,..you do what you have to do. So I found that 36.1gr went high .2's and I went home and loaded up to shoot this factory class match the next morning. I had the remaining 20 virgin and 30 1x fired cases (not my best effort) to go with. They were nk turned, primer pocket uniformed, flash hole deburred, trimmed, weighed to a <2% variance etc. I knew I had my dookey together except for the variance in internal volume but I figured 100yds,..what the heck,...whoops. I feel like I shot her respectfully enough though,..so next time if the temps are down in sept/oct, I'll be back with a more tested load and maybe a different pill just for the matches