The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Minimizing muzzle fps variationGo | New | Find | Notify | Tools | Reply | |
| Minimizing muzzle fps variation | Login/Join |
| one of us |
Gents, I am seeking advice that would shorten my learning curve  Task: 300 RUM long range rifle, bullet: 180 gr Powder RL 22 , RL 25 so far All powder charges are weighed, all bullets seated with an arbor press/die Problem: variation of muzzle spead I get typically a string between 3230 and 3290 fps Because I thought I couldn't do much about this, I always accepted the fps variation . This year though I need a better pattern,so fps variation matters.I read a decent one would not be greater than 10 fps. If anyone went thru this before, I would appreciate learning how one gets down to that kind of variation. thnx in advance | ||
|
one of us |
Forget all the magic numbers...select the load that gives you the tightest 5-shot group at 200-yards. | |||
|
| one of us |
Consistent velocity is conducive to accuracy, but is not the most important factor. Sixty fps from slowest to fastest at 3200-3300 fps is not bad. Ten fps maximum variation is highly unusual, as well as something you are unlikely to achieve. I haven't used much of the RL line, so I can't say what it's velocity variation potential is. About the most consistent in large cases for me has always been original surplus 4831. I would try IMR 7828SC if my only goal were to reduce velocity variations, but factors such as bullet seating depth, cartridge concentricity, case uniformity, and other factors are much more important to accuracy. However, none of it is going to help you hit a sheep at 800 yards  . | |||
|
| one of us |
sheephunter: What ricciardelli said! Listen to him. Really 60 fps extream spread isn't too bad. The 10 fps numbers you have see are I think the standard deviation. muck | |||
|
One of Us |
Well, you might try to change the primer type, and vary the load a few tenths of a grain. Then there is also the seating depth and bullet pull. The latter is controled by neck tension and the amount of bullet in the case, the type of jacket material, and the bullets exact diameter as well as it's construction... basically friction. Good luck...  Member NRA, SCI- Life #358 28+ years now! DRSS, double owner-shooter since 1983, O/U .30-06 Browning Continental set. | |||
|
one of us |
Consistent velocity is about consistent ignition. You have to: Have reasonably high and consistent neck tension (i.e. trimmed; cleaned and polished the insides; new, near new or annealed brass), OR load into the lands with little or no tension, Have good primers suitable for the task (consistent and powerful) Run you powder into the correct pressure range, Uniform flash holes, and seat primers consistently. The Rum is not that easy to tame, but try lots of neck tension and Fed 210M primers, and a powder on the faster side of things (i.e. something a little faster than the maximum velocity powder listed), but run at least 75 to 80% of the case full. JMO, Dutch. Life's too short to hunt with an ugly dog. | |||
|
| one of us |
Single-based powder tends to exhibit less velocity variation than double-based RL-types, so you might try changing that. Another possiblity is the primer as 308Sako indicates. In my experience people use magnum-type primers more than they should for best results. Again, though, 60 fps max to min isn't bad. Jaywalker | |||
|
| one of us |
Thank s to all for their respective comments. I am alrady using necksized brass in a tight custom chamber, Using Fed 210M primers done all the usual brass cleaning , although I read that most really doesnt matter. Concentricity is a vexing issue that I really dont have a handle on yet,although I load with an arbor press ( Wilson) Just for kicks, I run the numbers in my ballistic table If zeroed in at 300y muzzle speed 3200 fps I have a drop of 6.75 MOAs at 600y, muzzle spped 3280 I show a drop of 6.25 MOAs SO the diff would be a 3". We all would be happy to shoot 3 " groups at 600y but these 3" come on top of all personal and circumstantial variations. At 800y it would be 4". I am just trying to control what is controllable. | |||
|
one of us |
Steve's right. Do the best you can in the reloading room and pick the best load. Otherwise all the numbers and data will drive you mad. ZM | |||
|
| One of Us |
Stoney, I'd normally agree with that... But in testing a 6mm Remington with 75 grain Hornady HPs... with 15 different powders.... The load that was the most accurate... one hole consistency at 100 yds ( the best ANY of my rifles have ever shot, and I can't take the credit.. it is pure dumb luck if I did!).... Was a load of 47.5 grains of H 414, with a CCI LR primer, Winchester Brass.... But believe it or not.. the H 414 load had the biggest velocity spread out of all 15 powder loads... like 140 fps deviation.... go figure... The only thing it proved was Murphy's Law and "each rifle is an entity unto itself"..... It is a fluke, but flukes seem to happen when you just think you learned everything....  cheers seafire  | |||
|
| one of us |
| |||
|
| one of us |
When you happen onto a load that is really in the sweet spot of the barrel vibration, a change in velocity won't throw it out of the group. I have a .220 AI that will shoot half inch groups when working up a load with H414 with a 2 grain variation in powder charge. With almost no variation in charge it shoots .3's however. A shot not taken is always a miss | |||
|
one of us |
Check for consistent neck tension while your at it. Make sure all the case necks are the same thickness by outside turning all of them. Mic all your loaded rounds and make sure they measure the same diameter. Frank "I don't know what there is about buffalo that frightens me so.....He looks like he hates you personally. He looks like you owe him money." - Robert Ruark, Horn of the Hunter, 1953 NRA Life, SAF Life, CRPA Life, DRSS lite | |||
|
One of Us |
Logically, group size would seem to be related to velocity variation. Indeed, it sometimes is. But in actual practice, this is often NOT the case, some loads with greater variation giving better grouping than ones with a lot less. As Ricciardelli says, test for target accuracy, not velocity variation... "Bitte, trinks du nicht das Wasser. Dahin haben die Kuhen gesheissen." | |||
|
| Powered by Social Strata |
 | Please Wait. Your request is being processed... |
|
The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Reloading Minimizing muzzle fps variation
Visit our on-line store for AR Memorabilia