velocity and group thoughts

[jhalcott]

A buddy of mine made the comment"just load to the same velocity with another powder" when I said I was running low on a certain powder.It had given me excellent groups in several guns and I was half way thru my last can.! I never really tested his theory,BUT I have several good loads with different powders. They DO NOT shoot to the same velocity or point of aim! They do give sub inch groups but at lower/higher velocity and groups are not in the same area on the target. Am I alone on this or has any one else discovered it?

[Ricochet]

I don't think there could be any validity to his theory. Certainly with jacketed bullets, most of us have found that loading the same bullet to the same velocity with different powders doesn't always result in equally good shooting loads. And there are more variables with cast boolits. The biggest difference is in pressure curve profiles. I might load an 8mm cast boolit to similar velocity with a case full of slow burning IMR 7383, or a smaller charge of fast burning 2400. The peak pressure is likely to be a good bit higher with the 2400, and the peak arrives a lot quicker and lasts a shorter time. They'll affect the boolit differently so far as obturation under pressure. The barrel harmonics will be energized differently with a faster or slower pressure rise, and the bullet transit time down the barrel will be different with different rates of acceleration, even though the exit velocity is the same. Whether the bullet is leaving while the muzzle is relatively still near a node in its harmonic vibration pattern, or swinging wildly at an antinode, will make a huge difference in both how it groups and where the point of impact is relative to the point of aim. Trajectory is NOT a fixed path based on the bullet's velocity, the boreline and sightline, because the barrel is not a fixed, rigid object during firing. It whips around in rather lively fashion, on a small scale that's hard to see in pictures but is quite magnified at usual rifle shooting ranges.

[1Shirt]

Well, many years ago I tried that theory cause it sounded good. Like a lot of other things it doesn't pan out. It is like substituting one mfg. blt. of the same weight for another. That don't work either. In my opinion, rifles are all female and particular about consistancy. Mess with a consistant load with powder, or blt, or primer, and you screw up the constant. Just stay with what works, or as the old Yankee saying goes, "If it ain't broke, don't fix it!![smilie=1:
1Shirt!:coffee:

[jhalcott]

Richochet, that's what I told him in a lot less words , some thing like "bull (crap)" ! He said it for years till we moved apart because of work. He had 1 pistol,2 rifles and a shotgun,and spent more on reloading than I did. Nosler's, pact scale ,Redding dies and Forster? press and top $$ dies. I asked him to adopt me so I could inherit HIS good stuff.That way I'd have an excuse for shooting better groups

[Bullshop]

This has nothing to do with velocity but it does for accuracy. I learned this from old Harv Donoldson. It works with the IMR powders and some others.
Harvey said that there is an optimum volume charge for best accuracy.
If you work up a load with a certain powder then switch to the next faster or next slower powder the accuracy load will work out to be the same setting on the measurer. The weight of the charge will be different but the volume the same. Harv said once he set his measurer while loading for a certan cartridge he would not change the setting just the powder.
I have prooven it true many times Try it this way, work up a load with a certan powder and bullet till you cant get it to do better or to the best you know the gun will do. Then switch powders in the measurer. Before you change the setting throw a charge and weigh it. Then rework the load with the new powder from suggested starting loads. When you have worked up to the best load you can find throw a charge and weigh it. If its not right on I bet its awfully close. Of cource this cant work with the full range of IMR powders for each cal but it sure works for powders near the same burn rate that would be considerd normal for the cartridge while keeping all else the same. Try it again with a powder just on the other side in burn rate this time and I think you will find the same thing. Old Harvy lived a long time and shot right to the end. In that strech of time he burned alot of powder. He spaned the BP to smokless time frame and saw the comming and going of many new propellants and in that time developed a feel for burning powder.
I like to think I have a feel for it too but I have a long ways to go to get to where ol harv left the ship.
BIC/BS

[NVcurmudgeon]

Bullshop, I wish I had kept better records about 40 years ago. I loaded a number of medium burning rate powders, (3031, H4895, 4064, 748) in a .308 with 165 gr. J bullets. Naturally I had no chronograph in those days, but loaded up to book maximum and found accuracy and point of impact to be close enough to the same with all those powders for hunting purposes. It never occured to me to compare volume, but I imagine it was close. There must be something special about the .308 to cause it to deliver about the same results with a number of powders. Now that I am more experimentally minded, and know about HD's volume theory, and have a chronograph, I would like to revisit the .308 again. but, alas, I don't have a .308 now!

[NickSS]

The 308 is one of the easiest cartridges I ever loaded as far as finding accurate loads. Almost any medium burning speed powder will give good results with any 30 caliber bullet. I have shoot in excess of 20,000 hand loads through a 308 and tried most available powders looking for an advantage. The only thing I found was not more accuracy just higher velocities with some powders.

[montana_charlie]

It was during the late sixties when I came to believe the articles in the gun magazines which said hand loading was the path to 'consistent ammunition', and that it included the additional reward of being cheaper than factory loads.

Being in the military and single, I could not reload 'at home' because home was a barracks room shared with three other guys, and rules did not allow materials of that sort in the building.

So, I picked a table in a back corner of the Rod & Gun Club, where I would spread out my five reloading tools. I had a Lyman D7 scale, a teaspoon for dipping powder into the pan, a trickler, funnel, and a 310 tool with dies.

According to the books, a guy could choose to load for 'knockdown' (quickest kill)...'velocity' (flattest trajectory)...or 'group' (best accuracy), and I considered the things required to test those three goals.
Without a large supply of killable animals and no chronograph, I settled on a stack of paper targets as my 'testing facility' and chose the last of the three goals.
I have never changed...even though my equipment has evolved quite a bit.

So, when I see the title of this thread, I am reminded of the dozens of discussions I have heard, read, or taken part in, which argued the merits of one goal over the other...but always recognized them as separate and (basically) unrelated. The only attribute shared between them is 'consistency'.

By the time a guy sits down at his reloading bench, a number of 'experts' have been involved in creating the tools and materials he has available, and one of those is the expertise involved in producing the propellant he is using. Keeping in mind that 'consistency' is the one shared factor, I will let the experts tell me which powders are suitable for my purpose and I will choose one which will consistently be available for as long as I plan to shoot that gun.
That means choosing one which is...and will continue to be...manufactured (essentially forever).

Just as I won't build up my cowherd based on the number of leased acres I might have access to (which can 'disappear' at the whim of the owner), I won't search for my pet load by using a type of powder that can be expected to become unavailable over time.

Therefore (to me), 'running low' on a particular type of powder just means a trip to the store...not a need to find a different propellant which acheives the goal (knockdown, or velocity, or group) without changing my loading procedure.
If my powder did become unavailable, I would expect to have to start from scratch and hope to work back up to the previous performance level.

Realizing that reloaders often become 'experts' in their own right, I read with interest these threads where guys share their findings on component comparisons and substitution. But, I studiously avoid a situation where 'running low' would require a substitution...and I still have trouble considering 'velocity' and 'group' as related goals.
CM

[jhalcott]

Well yes,MC BUT at the time I was working 12 hr /6 days a week and did NOT want to waste time going to the GUN store! I'd usually walk out with a new toy to figure out. My REAL goal was to get HIM to pick the powder up for me. I had several types of powder on hand that were not tried in that gun. From what Bullshop said I COULD just have loaded them ,Or at least SOME of them in that gun. I still use the old loading og 4350 powder in that gun

[Bullshop]

If you were to make a connection to accuracy with different powders from a certain rifle I would think it would be more related to pressure than to velocity. You can see velocity variations of 200 to 300 fps at equal pressure from different powder types with the same bullet. Pressure/time has much to do with it also, getting the whip to crack at the same time for each shot.
BIC/BS

[Ricochet]

I know Harvey Donaldson was a smart fellow with a heck of a lot of experience, but I think that volume/accuracy relationship had to be a chance thing, not a general rule.

[Bullshop]

If you have access to the book Yours Truely by Harve Donaldson put out by Wolf publishing you should read what he had to say about it. For him at least the way I read it it seemed to be a rule rather than happenstance.
In my experiance not a rule but I see enough of a connection to pay close attention.
BIC/BS