reloading tolerances for precision shooting?

M

mbessey

CGN Regular
Rating - 100%
6   0   0
Location
Toronto area
how must of a velocity spread is acceptable? i made up some +/- .2 grain loads (on 96 grain charges) and was getting a high and low velocity 35fps apart, and got noticably different points of impact on these . I shot 8 rounds through a chrony at a target and maped out each shot and gave the velocity reading for each, i found that velocities that were with in 10 fps of 2900 fps were closest to where i wanted them and would be shooting less than .4" but higher than 2935 would open the groups up to .8" (mind you the barrel was getting hot by then and im not that good of a shooter yet to say its not just me)
so my question is, what else other than weighing each charge (this question is giving me dejavou for somereason!) can I do to make velocities consistant?? can seating depth off the lands make for more consistant velocities? any input would be great on this! , list of components and equipment i am using are,

lapua brass, lapua lockbase bullets and sierra game king bullets, H1000 powder, fed 215 match primers, forster f/l sizer and benchrest seater.
I want to do more work with these components before i write them off ! the velocity thing is the first thing i want to look at.
thanks!
m
 
To answer your question, it depends...really.

What are you trying to accomplish? Sounds like you are working with a RUM or similar sized case.

In precision shooting, small groups is what we are after. The rest is info that can help us diagnose a problem. Shooting sub MOA (.4") with a factory rifle is wonderful. However, if this is a LR rig, best to start doing your testing further out. Will show you what really makes a difference in group size which is what matters.

Not trying to be mean but if you are not confident in you shooting abilities yet, why waste a whole bunch of time and money where the weakest link is not the rifle...yet. Become a precision shooter and your rifles will improve in accuracy.

Without info on the rifle and intended goals, you may have exactly what you want or need to start clean slate.

There is enormous info in the precision forum, on BR central.com, accuratereloading, and other sites.

Determine what you are trying to do, get your skill level to where you are not the problem, then worry about the small stuff.

Jerry
 
Velocity isn't as important in precision target shooting as it is for hunting. Consistent accuracy is. Telling us what calibre would help too.
10fps is extremely consistent. Mind you, you need to post what your definition of precision shooting is. Benchrest? DCRA?
"...game king bullets..." Are for hunting. Try the same weight bullet and load in a Match King bullet.
 
Velocity isn't as important in precision target shooting as it is for hunting. Consistent accuracy is. Telling us what calibre would help too.
10fps is extremely consistent. Mind you, you need to post what your definition of precision shooting is. Benchrest? DCRA?
"...game king bullets..." Are for hunting. Try the same weight bullet and load in a Match King bullet.
Click to expand...

the game king vs match king seem to have some arguments, I have been told by a few to get them a try and that they have given exelent results, IVO on this board I think can contest to that,:)
as for the rest of the equipment sorry! i was trying to post last night with the girlfriend looking over my shoulder and whining that im on the computer haha!

a) im basicly looking to try competing in anything that allows a muzzel brake, so sniper shoots and the likes,
b) its a sako TRG in 338 lapua, so i am hoping its still just me not being a competative shooter yet. this rifle has shot 3 holes touching at 300 yards consitantly with match black hills factory ammo, I cant shoot hundreds of rounds of factory so im working up something for it from scratch. I have to get out to a decent range then, maybe i will practice some more shooting with my 22 before wasting more 338s? or should i just work on the 338s? rifle has sako's tac scope mount and rings, sako's muzzel brake and what seems to be a half decent but not a pernament scope- springfield armory government model 6-20 X 56 mm with illuminated reticle.
thanks
m
 
For long range shooting, the Game King is not as accurate a bullet as the Match king.

The Match king will get to the 1,000 mark with a little more stability than the Game king, and that is what we are after in precision shooting, consistancy =accuracy....
Cat
 
With .4" inch groups, and a 10 fps spread you do not have a lot to worry about, both you and the rifle have demonstrated capability. For further improvement potential I would recommend Matchkings as others have; bullet core to jacket concentricity is a prime accuracy parameter. Another prime factor is ignition consistency (more so than charge weight varience), so the use of match primers versus standard primers is paramount.
 
+/- .2 grain loads (on 96 grain charges)
Click to expand...
So you are talking .4 grains difference from highest to lowest powder charge? :shock: I would have to say this would make the biggest difference, other than the bullets used.
Forget the +/-.2 grains, take the time to load the exact weight.
 
Actually, a variation of plus or minus .2 grain in a 96 gr charge is meaningless.

As well, weighing charges instead of throwing them with a good powder measure, is a lot of extra work that really won't make any difference on the target, especially in a case the size you are using.

If you speak with a dozen or so bench rest shooters, you will find that most of them use a good powder measure rather than a scale to charge the case, and they are concerned with shooting groups much smaller than 0.4 inch. :)

Ted
 
If you speak with a dozen or so bench rest shooters, you will find that most of them use a good powder measure rather than a scale to charge the case, and they are concerned with shooting groups much smaller than 0.4 inch.
Click to expand...
Short range bench rest shooters, maybe, but they go to alot of work preparing brass and shoot tight chambers.
What are the 1000 yard bench rest shooters using? I will bet that most of them weigh every charge.
I shoot TR, about 1200-1500 a year, I weigh everything, even the brass.
Load some up at -.2 grains and then some at +.2 grains, shoot it at 300 yards and see what your group looks like.
Then load some up right on the money, see if the group is smaller.
 
Like maynard, I weigh all my charges. There is already an error of +/- 1 tenth in the scale and I don't want to add to it.

I have several rifles that will show a difference on paper with as little as 2 tenths change in load. These are in bigger cases like the 7RM and RUM. Some rifles are very tolerant of even 1/2 grain variations but that seems to be the exception in my rifles.

When I work up a load, I go in 1/2 gr increments and find where the best 1/2gr load is. Then I rework up in 2 tenths going from 4 tenths below to above. That has reduced my groups sizes tremendously at LR. I sometimes don't see a change in velocity, just a change in pressures signs on the brass/primer.

From there, I will watch to see if ambient temp affects the loads. If so, I will adjust again for the seasons.

Watch when shooting a brand new barrel. I have found that the first 200 to 400rds go along just fine then suddenly accuracy goes for a dump (nothing severe but obvious). That usually requires a REDUCTION of powder to brings things back in line.

My guess is that the throat is starting to roughen up enough to elevate pressures the same as an increase in powder. Dropping the charge brings things back to the sweet spot.

This has repeated with every single NEW barrel, factory or match, that I have shot. Once this 'wear' occurs, things settle down until major throat erosion occurs but that is just the expected barrel wear.

Bizarre thing is that the used barrels I have set back do not show this behaviour. maybe they are already happily cooked...

Jerry
 
mysticplayer said:
My guess is that the throat is starting to roughen up enough to elevate pressures the same as an increase in powder. Dropping the charge brings things back to the sweet spot.

Jerry
Click to expand...

You can minimize this with proper use of Iosso or GB's on the offending throat. At first its a build up of baked on carbon...eventually the steel gets cooked and the jig's up.

NormB
 
NormB, that was my initial thought that fouling was building up but cleaning with JB didn't resolve the issue. I don't have a bore scope so can't confirm but will assume that its the throat getting a bit rough.

No big deal, normal wear and tear, but something to look for or at least something to help reduce the head scratching when a great load goes south.

Jerry
 
mysticplayer said:
NormB, that was my initial thought that fouling was building up but cleaning with JB didn't resolve the issue. I don't have a bore scope so can't confirm but will assume that its the throat getting a bit rough.

Jerry
Click to expand...

After firing a day's course of fire, pushing a good fitting wet patch through your bore with a guided 1 piece rod, you may find it tight and chatchy to about 6 inches ahead of the chamber then smoother to the muzzle. I think this is baked on carbon and most solvents and bronze brushes won't get it out. The patch will still be tighter here after thorough cleaning.

Bill Gammon likes TM solution for this. I don't know, but after a treatment with IoSSo on a softer nylon brush the problem goes away. A bore scope shows a polished surface, nice finish and cracks and all.

NormB
 
Hey Norm,
Do you throw your charges or weigh them. What about the other 1000 yard bench rest shooter?
Welcome to Gunnutz.
 
I am no bench rest shooter....off the bi-pod but feel I take precision just as seriously. I personaly weigh each load i do. Whats the point of reloading for precision and taking the time it takes just to toss a powder charge.....might as well just buy a factory load. Just an Opinion here.
 
maynard said:
Hey Norm,
Do you throw your charges or weigh them. What about the other 1000 yard bench rest shooter?
Welcome to Gunnutz.
Click to expand...

Tom... I weigh them.... I throw them into a pan within few tenths under then pinch in the rest on the balance beam... an old Lyman 505 from 1967.

But for large vol. cases its just a head game, IMO. I can do it quick, so I do.

A missed wind call, or vertical turbulence off of a berm makes more difference than a 1/10.

The random act of ignition of a column of powder, likely makes for 10-20 FPS variation in MV.

I think most 1000 yd BR shooters weigh charges... They have the time as they go preloaded to a match...short range BR shooters throw them. They don't have the time at a match and they like to adjust for conditions... which you can't do if you are preloaded.

NormB
 
And there lies the irony. Short range BR shooters adjust their loads on site to account for different conditions. They adjust their loads only a tenth or two. So precision in load amounts DO matter, yet they say they don't. That's a head scratcher.

I don't know of any long length extruded powders used in PPC's so a good quality powder measure can hold to 1 tenth variance. This makes adjustments worthwhile or else the error in the measure would exceed the amount of change desired.

I wonder if this practise is reducing since the use of temp stable powders????

Most of the LR shooters I know use temp stable powders so they don't need to fiddle during a match. Why loading before works.

if the pressure was due to a build up of fouling, you would always get different performance with a clean bore until the bore built up the fouling enough to stabilize pressures.

That actually isn't so far fetch as we know most barrels do not shoot their 'best' until a few fouling shots have been fired. Maybe this is simply a bore pressure meeting a load. A barrel looses accuracy because the pressure increases enough to push a load out of tune.

if this were true, a clean barrel load might be higher for the first few shots, then going to a standard load, then going to a lower load as fouling builds up.

Ah, we may never have to clean again.....

Jerry
 
maynard said:
Hey Norm,
Do you throw your charges or weigh them. What about the other 1000 yard bench rest shooter?
Welcome to Gunnutz.
Click to expand...

A weighed load at 1K is the only way to go!
I throw 'em for 500 meters, however, becuase the difference when shooting at sillhouettes is not too great and i can let that go .

My form and wind calling is far more important.
But at 1K I don't want that variable in there......

Cat
 
You must log in or register to reply here.
Back
Top Bottom