Accuracy Question

Of your close to the end of a accuracy node the ammo getting a little warm could affect poi. Going from bags to the hood maybe to blame some as well. Could be dirty to, I've only used one 204 about 15 years ago and was not running hot but I know not 17s foul quick.

Clasonater, a camera or other use tripod and a crosspiece works well for a 'standing rest' and might be more convenient to carry about than a card table. Not as steady as a full bench rest set up, but does take a lot of wobble away.

As you say it is possible to break out with a load towards the top edge of a powder charge window.
Especially with the ambient temp swings this time of year.
I have better luck staying in the middle on charge windows and the inside or leade side of seating windows.

take a target with you next time (a cardboard box with a piece of paper stapled to the middle should work) and find out.

luck,

murf

Make sure you’ve got something soft under the stock. If you’re shooting off a hard surface the rifle can bounce up and shoot high

I’d suspect it’s from heating the powder. Remember, pressure in smokeless raises in a parabolic curve, not linear. If you’ve got a case with less interior volume running max+ loads and you heat the powder, everything may add up in a very non-linear fashion

Depending upon the powder and conditions, a 10% increase in powder could pressure 30-50% or more. That 10% could be represented by decreased case volume and/or powder temperature

TheClasonater said:

So, I worked up some reloads for a 204 Ruger. Steady at 3/4 at 100yds. Still working on it, but new baby and all, I'd rather be shooting PDs with my available allotment of minutes. Shot for 2 mornings now with the load. On paper, the elevation has never changed. I tested twice off bags at the range. 32 and 40 degrees f. First morning hovered in the forties and today was low 50s. Averaged 35 shots per the last 2 days.

I had three shots at the end of the morning today that baffled me. First standing pd broadside at about 100 yds. Cross hairs dead nuts middle. Second standing at about 150. The first, I saw no dust, herd no thump, sumbitch didn't even blink. So, it either went behind or over top. Behind, ill chalk up to error, but the second I saw dust over top, twice. I think he's probably still standing there.

Here's some more variables. Reloader 10x powder over listed max, but no pressure signs at all. Misc brass. Nosler 40gn BT. The aforementioned shots were around the 80 mark since last thorough clean. I shoot of the hood of my cj with my loads in an mtm box right next to the rifle.

Could the rounds sitting in the sun raise my pressure high enough to fly em over top?? Could it be a hot barrel heating em up? . . . Dirty barrel? Of course I could have yanked them. Just looking for some opinions from guys with more mileage.

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Yes rounds sitting in the sun can cause higher pressure/velocity, especially for "over max" powder charges (which is a problem to begin with, but being in the hot sun with over-max loads is NOT a recommended practice! Load a bit below max when you expect loads to be used in higher temps, especially sitting in the hot sun. If you really want to know what happens with loads used in the field, bring a larger target and backer with you and have someone set it up where the critter was, and shoot a couple of shots, using as close to the same conditions, as possible. To make it even more realistic, have the assistant load both live and dummy rounds without your knowledge about which is which.

Mirage from hot hood and hot barrel?

Just throwin out ideas.

It's not recommended to use a near max load with mixed brass, even the same brand you have to watch out for. Different lots of the same brand could have different internal volume, so drop down a brain or 2 if using mixed brass. You can work the load up with the brand with the least volume, so the others with more powder space will be fine.

taliv said:

I don’t believe velocity based changes will have that much effect at that distance.

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Agreed, but a change in pressure, especially on already a high pressure load could push you into different barrel harmonics.
I've got a 7.62 x 39 bolt gun. Low charge loads were 2" groups, mid <1", high 3" groups all @ 100yds.
Over 2" difference in GROUP SIZE could put you over a PD.

yes, yes, and yes, Outside the safety issue with over-max charges, there is the possibility that one can over rev the bullet spin which can detract from accuracy. Ford8nr has a good point on harmonics. Ya know recoil could also be the culprit and you may not realize it. With shortages what they are, you may want to keep your brass as long as possible. That won't happen when shooting max. Back down your charge maintain the 3/4 grouping You should find a clean barrel, investigating concentricity with bullet seating depth and runout could all improve what you are looking for.

.Why don't you settle on the point where you first found your point of impact at 3/4.
Then take a empty cartridge and smoke a bullet over a candle and insert every so gently at the end of the case. Measure the exact length and slowly insert it fully extended into the chamber and close the bolt. Then remove it. The bullet position and . where the carbon has rubbed off when the bullet was on the end of the case is where the rifling begins. If the bullet comes out you will see where it was from the lack of carbon and measure again. Try this several times and average the distance. Best accuracy occurs somewhere around .02 of an inch less distance from your rifling measurement..

taliv said:

I don’t believe velocity based changes will have that much effect at that distance.

yes barrels speed up in that range. Yes hot sun leads to overpressure Ammo which will be faster. But even if it were suddenly 200 fps faster it would not magically climb several inches

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This, especially at the short range we’re discussing.

ford8nr said:

Agreed, but a change in pressure, especially on already a high pressure load could push you into different barrel harmonics.

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Different harmonics should never promote multiple inches of POI shift at such a short range. If I ever owned a rifle which could fling bullets several inches off course at such a short range, I’d tear it apart to never have a chance of repeating. I shoot a charge weight ladder regularly (a dozen times per year) cycling the gap between 3 nodes - even loads in the antinodes won’t shift my POI by several INCHES at only 150yrds, not even several tenths of inches, frankly. Despite clearly shifting from node to anti node to node to anti node to node, increasing velocity by approximately 100fps throughout, my 100yrd POI only shifts by a couple tenths of an inch at the extremes.

Something else is going on if this rifle is truly shifting several inches at only 150yrds.

Many many variables in this one.First one that comes to mind is shooter error.Those yardages are close enough to look easy,and I'm bad to mess up easy shots because I don't concentrate.Even if there was a huge jump in pressure,all things being equal,the velocity would have to change a lot to move POI very far at 150 Yards.Also,the hood of a vehicle isn't a very good rest for a number of reasons.We tend to lean against the vehicle,which is sitting on a suspension that will move with very little effort.A CJ's hood isn't insulated,and the engine heat can cause terrible mirage,which is second on my list after shooter error.A chronograph is one of the best ways to keep an eye on pressure.More pressure,more velocity.Loading over max isn't a really good practice,especially if you may be shooting in hot weather and you worked your loads up in cold weather.Most of the time a grain or two over max is only going to gain a small amount of velocity,and may cause more trouble than it's worth.I have a cousin who is crazy about running way over max on everything he loads.He sold off a good number of the 100+ rifles at auction last summer,and most of them sold for less that what they were really worth,mainly because the buyers were talking among themselves and some of them knew how he loaded his ammo and treated his guns.He often boasted about how cool it was to watch a 22-250 bullet come to pieces because of the insane velocity that 6 or 8 extra grains of powder gave it.

TheClasonater said:

Since we're on the topic, and this is something I've always wondered from more experienced shooters: I haven't seen any pressure signs, not that I've been taught to look for anyway, ie primer abnormality, brass abnormality, no sticky bolt, no funny sounds, no brass on the bolt....

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Years ago there was an article in Handloader Magazine titled “Pressure Guessing”. They used multiple rifles with advanced pressure measuring equipment to verify pressure, then looked for typical signs that shooters look for. Some of their loads were way, way over anything remotely safe.

Bottom line was that some rifles showed excessive pressure signs via the typical things, but others were WAY over and showed no ordinary signs. Bottom line, trying to use bolt lift or flattened primers is highly unreliable and more often than not a fools errand

Buddy of mine has a 204 I'm not real impressed. Factory ammo after 15 shots, at 300 yards (fired prone off bags with optic) looks like a shotgun pattern.
Let it cool down and scrub the barrel , accuracy returns

TheClasonater said:

I get impatient

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THAT is probably your biggest problem. Remove that before looking at outside mechanical issues.
When you can shoot repeatable 5 and 10 shot groups then look for other issues. Do you shoot other rifles without issue ?