What's a few tenths do?


PDA






mm1ut1
June 1, 2010, 09:05 AM
My powder dispenser isn't the most consistant, it will vary a couple tenths either way when throwing for 223 or 308. I use Varget for these loads, 23.8 gr with a 75 gr bullet and 39.5 gr with a 168gr bullet. I do not own a chrono and only shoot at paper, 100 yards for 223 and 200 in my 308 Garand. How much would my velocity change for both loads if the charge was +/- a tenth of a grain ? Would accuracy improve noticeably if I weighed each charge to the tenth of a grain at the ranges I shoot? Some of the club "Experts" say Varget weight is not that critical. TIA !

If you enjoyed reading about "What's a few tenths do?" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
kestak
June 1, 2010, 09:49 AM
Greetings,

If you are not at the low or max of the loading charge, under 100 yards you will not see any difference. At longer distance, you will see some vertical discrepancies.

If you are at the min or max, you may have a squib or signs (or no sign but experience overpressure) of overpressure.

Thank you

DickM
June 1, 2010, 09:55 AM
Even at the lower charge weight (for the .223), one tenth of a grain is less than a half of one percent of the total charge. You will never see any difference, regardless of range or how close you are to maximum load.

ranger335v
June 1, 2010, 10:24 AM
At normal ranges there will be no significant trajectory effects from small differences but grouping effects may exist.

Fact is, the best shooting powder charge is NOT a specific point, +/- nothing; there will always be a range in which small varations mean little. How wide that good range is will vary but it's typically as much as .5 gr, somewhat dependant on the size of the cartridge, powder, rifle, etc. Small variations in the middle of the good charge range mean nothing, that's why BR people rarely bother to weigh their charges. BUT, if your chosen load is on a ragged edge of the good shooting range, any that go the wrong way WILL enlarge groups.

GaryL
June 1, 2010, 09:47 PM
It shouldn't matter, if you can find the sweet spot in the load range. What I mean by that, is if you carefully weigh out a number of different loads of 5-10 rounds each, you can figure out what load can tolerate that greatest variance and still shoot to the same point of aim and accuracy. If you go in .3-.5gr increments, you should be able to find 2 or 3 together that are close, and fine tune from there. Then you just have to figure out what to set the dispenser at to stay within the best range.

Lorenzo Rojo
June 2, 2010, 01:02 AM
I agree with everyone else. One tenth or so won't really make a difference. Now, if, like the thread title says, "a few tenths", say three or more, will start to make a difference. I try to do all of my loads +/- 0.1 grains. I get pretty good results with that, particularly with .308. I do see a difference at distances 200 yards or over if I vary the loads by as little as .3 grains. Bottom line, +/- 0.1 from the nominal load poses no problem.

kestak
June 2, 2010, 07:47 AM
Greetings,

I still stick to my "gun".

At the extreme ranges of the load, a few thenth WILL make a difference. In fact, the closer you are from the extreme range, the more effect the variation will have.

In the middle of the range, at the longest the distance, the more effect it will have.

Of course, a difference of .1 grain is like 6-8 pieces of powder 2250 or TAC. It is really little. it won't matter much.

.3 or .4 grain in a 223 will have more impact than in a 7MM magnum. The size of the case matters too.

Moreover, I read many times and was told by many old timers here, when you load military brass, you need to remove .5 grains of powder because of the case volume being smaller than commercial in .223. That same 3. or .4 or .5 in the same type of case will then make a difference....

Personally: I always load around the middle. When it is for "plinking" or under 100 yards, I don't care too much about a variation. If it is for precision, I weight to the exact thenth AND I prepare VERY carefully my case.

Thank you

qajaq59
June 2, 2010, 01:37 PM
IMO 1 tenth wont do much. But if it is 3, plus or minus, then you could possibly get a difference of 6 tenths between any 2 rounds. That will likely be noticable.

docsleepy
June 3, 2010, 12:12 AM
I did some calculations of the change in vertical due to 0.1 grain of H322 in .223 and 6PPC. I think it was on the order of 0.03 inches for each. This will differ depending on where you are on the typical "sinewaves" of powder/velocity/vertical response (read about that other places).

However, on the UPPER end, with my 6PPC, I found a definite point at which I would get flattened primers and then a pierced primer. A couple tenths there migght make a difference. I pulled back 0.5 grains or more, because temperature also can play a role.

On the LOWER end, I have used charges several grains below what is listed, and I assure you, in a rifle, the bullet will still come out. When you're talking Mach3 for a high end load, unless you crimp the **** out of it, that bullet is going to move along smartly. 3.0 grains of Win231 reliably moves my 148 grain 38special lead bullet out of the barrrel at 500 fps. Moving a 60 grain .223 with many many more grains than this is definitely going to ignite.

I've toyed with my cheapie Lee powder thrower and found it was pretty good. The ones on my turret, which are also Lee, are also pretty good. I think they are generally +/- 0.1 but that is just "generally". I know that benchrest competitiors have far more expensive ones, but a lot of them just use their thrower and don't weigh (others seem to be switching to the automated dispensers for rifle, which is what I did -- and love it)

If you enjoyed reading about "What's a few tenths do?" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!