Case Capacity, Powder Position in the Case & Accuracy

909 Views
Last Post 15 October 2023

Standard Member

Wm Cook posted this 07 October 2023

Since August I've been fighting a problem that has a powder, charge and bullet combination that'll agg in the .8's (my range, hand picked conditions, not implied in any manner that it could be replicated in match competition) some of the time but triple that other times with a production class .308 Savage.

When the load goes south it shoots as a pattern, not as an odd flier or two. And it can go from group to pattern quickly. And within the same range trip I've had it go South and come back North again before the end of the day. Its like every time I go to shoot a group I don't know if it'll be a group or a pattern. Best example I can give is its like the stem on your front rest isn't tight and the POI is wandering around. But bench equipment and bench practices are solid.

Below is an example which is typical of what I've seen many times these past three months. There were two other groups shot between the group on the left and the group on the right in the picture below. Ironically it just so happened that each group was shot with the 8th through 12th shot after barrel cleaning. The group on the left was the 7th group of the day and the group on the right was the 10th group of the day. Both are the same load shot in the same conditions. Side note: I load at the range in increments of 5 to 10 shots at a time as much to keep the barrel cool as it is to tweak the load.

Could it be the burn rate of the powder and the lay of the powder within the case?

All the powders I'm working with (fast to slow IMR4227, 5744, N130, 4198 and H4895) have a fill capacity in the 43% to 47% range with a 220 grain bullet running 1700 to 1780fps. All are extruded powders. I started using 5744 n the early spring after it showed some promise. I went back and bought a jug's worth of the same lot of powder. Far and away, the 5744 out shot all other powders that I've tried by a factor of 2. That said, powder is one of the few things left to tinker with.

If anyone has any thoughts on issues with the % of case capacity being used or the effect the powders position in the case many have on accuracy I would appreciate your thoughts. Thanks, Bill Cook.

A “Measured Response” is as effective as tongue lashing a stuck door.

Attached Files

46 Comments

Order By: Standard | Newest | Votes

Standard Member

Lucky1 posted this 10 October 2023

I'll take the proverbial 'bullet' on this one. I'm very human and prone to error, some larger than others. So there are days I'm really on and days that won't give me a break. Last Nationals case in point. Got a third in the Little Bore with the 233 on Fri. Since it's both group and score, I was really pumped for the rest of the weekend. Saturday and Sunday was the plague of constant flyers etc that just made this match an endurance test. Same rifles, same loads, same shooter. I know better than to blame the rifle or load. The only way I'd be willing to go there would be shooting with a machine rest in a tunnel to reduce operator error. So John talking a 1.5 rule makes a lot more sense to me now and I'd be happy with some days to get it that close. I'm not the only one to go to the range and have a load and rifle do way worse than the week before and then work great the next time. Summary time- this game has so many variables it is hard to pin it down to one particular thing; especially with the human factor. One variable not mentioned so far is temperature changes over a season. With no chronograph readings I wonder about some changes going on there as well.

Scott Ingle

Attached Files

Liked by

CBA Member

pat i. posted this 08 October 2023

I'd lose the 5744 too. I thought it was going to be my savior with this 06 plain base thing I'm playing with but not the case, a lot of unburned powder left behind. I agree with Muley here and would probably start around 25 grains of Varget and work up, its probably cheaper than 135 or used to be and thats a good thing. You could also do yourself a favor and search the national match reports to see what the good PRO class shooters are using. Might require a new mold and change of powder but you'll be one step ahead of the crowd.

Attached Files

Liked by

CBA President

John Alexander posted this 08 October 2023

Bill,

You call them groups and patterns and say your "groups" will age in the 8s but the group you show is .36, if I am reading it correctly, an extreme example of your "groups". The ratio between an .8 and the "pattern" shown is 1.5, a ratio that is very frequent in any string of 4 or five 5-shot groups. For that matter, the ratio of 3.4 of the two groups shown also isn't a rarity in strings of groups. This leads me to suspect that you don't have a (powder, powder position, shooting, case or any other such) problem. But instead are just expecting strings of 5 shot groups to be way more consistent that mother nature allows. This is just a guess andI could be off base because it is based on only the two groups shown.

How about posting the size of consecutive groups in a string of groups using the same load. Then you can judge if you are really seeing groups and patterns or just seeing the usual variation of ALL strings of 5 shot groups -- which none of us like but have to live with because there is no cure.

I tried to debunk the idea that a string of groups should be about the same size with evidence in my second article doubting the "tuning" that jacketed BR shooters think they do in TFS #275.

I would appreciate your, or any other reader's, comment on that article since I received zero feedback of any kind.

John

Attached Files

Liked by

Standard Member

Wm Cook posted this 09 October 2023

Ric

there are two opinionated groups; those that think small variations will make a big difference with consistent size and those of us who know that five shot groups vary greatly in size.

Fully agree. Its the agg that matters, nothing else. Winning a small group award and not finishing near the top is like kissing your sister. What bugs me is that I shot 17 five shot groups in a row that agg'd in the .7's and the next 17 agg'd in the 1.2's. Thats what led me to believe that something was broken.

Bud said

Have you considered the barrel is losing its golden edge of accuracy?

It doesn't look like thats the problem. I've got 1114 cast rounds plus foulers through the barrel now. Zero jacketed. Its bore scoped after every range trip to look for fouling and general barrel condition. It still looks sharp.

Many people report their best group their rifles shoot as the standard.

I wouldn't be concerned a wit if all of 51 recorded groups agg'd in the 1.2's. It was the sudden breakdown after the first week in August when I went from decent group that agg'd in the .7's to the 1.2's.

Does this rifle predictably throw the wide shots? This could be the barrel heating up in an uneven pattern. You can counter this. Either shoot the shots in the berm or hold off when shooting. I had a Trapdoor that reliably shot every eighth shot out at 2 o'clock in the eight ring with smokeless powder.

I thought barrel heat or dirty barrel was my ticket out of jail for a period. I went to tracking the number of shots fired group by group since the last cleaning. Current practice is load and shoot one or two group at a time. So I can rule out barrel overheating and/or a dirty barrel. I had enough data that showed that cleaning every 17 to 23 rounds didn't trash the group size. In other words, groups shot after cleaning did not need a break in period. As is I can go to record after two fouling shots. When shooting groups I can call fliers when they happen. Once a group patterns there could be three or more shots that fling out of the group.

Next trip out I want to try a series of powder charges (still 5744; 19.6, 20.0, 20.4) with one group having the powder shifted toward the bullet and then repeat with the powder pretty much centered and level in the case by rolling them on my bench mat before chambering/loading.

If that doesn't work it back to playing musical chairs with powders and mold selection.

This year Bob Haufschild and Robert Olson both shot sub MOA with a .308 in Producion class. I don't have the experience they have and probably not the bench skills but I have an A+ personality, I'm stubborn and I have a touch of OCD going on. If I live long enough I'll get it sorted out. The one sure thing is that you learn a lot sorting out problems like this. Thanks to all, Bill.

A “Measured Response” is as effective as tongue lashing a stuck door.

Attached Files

Liked by

CBA President

John Alexander posted this 09 October 2023

"but I have an A+ personality, I'm stubborn and I have a touch of OCD going on. If I live long enough I'll get it sorted out. The one sure thing is that you learn a lot sorting out problems like this. Thanks to all, Bill."

Sounds like you have the right personality and attitude.

Some additional thoughts, although I suspect you have already tried them.

I have never had any luck when things went south with diddling with small powder charges or powder changes. I have had real trouble when changing lots of 5744. If I understand correctly it has been made by several plants over the years.

You don't even mention alloy in your table so I assume, like many top shooters it is linotype. I would try something somewhat softer for a few groups. If you do it may be wise to guard against the case sizing or damaging the softer alloy

Cases change as they work harden and more if annealed. I would check a few dummy round to make sure it comes out of the chamber the same length as it went in.

I would seat and pull a few bullets to make sure they weren't being "sized" or otherwise damaged during seating.

I don't think it is likely that a linotype nose would upset to a larger diameter while being seated but you might check to be sure.

Are the land marks or absence of such on the nose the same on an extracted round as they were when shooting the small groups?

Good luck.

John

Attached Files

Liked by

CBA Member

lotech posted this 09 October 2023

As for bullet hardness, as John Alexander touched on, I remember advice from Glenn Latham in THE FOULING SHOT years ago... I don't recall his exact words. but the basic message regarding bullet hardness was to use the softest bullet that would handle the load/ velocity without leading the bore. This would usually provide best accuracy. Generally, I've found this to be excellent advice.

Attached Files

Liked by

CBA Member

RicinYakima posted this 11 October 2023

Shooting cast bullets is an art form, not a science.

Attached Files

Liked by

CBA President

John Alexander posted this 11 October 2023

Geez Bill,

You have about everything covered. It sure looks like something changed 8/21, but what? Try putting a little Kroil on the bullet nose. They say the evil fairies that ride cast bullets and steer them away from the center of the group don't like the smell of Kroil.

When you get it figured out you may be able tell me why my rifle shot as well as it every has on Friday winning the little bore match with room to spare, then not winning a single aggregate when it counted on Saturday and Sunday at the nationals. Same everything except where the holes appeared.

John

Attached Files

Liked by

Standard Member

Wm Cook posted this 08 October 2023

Thanks for the offer Keith. I only shot three groups with the Rel 7 I have and that was just to get a quick impression of its accuracy and to sort out the grains/velocity for future use. To be honest I didn't give it a fair shake. Bill.

A “Measured Response” is as effective as tongue lashing a stuck door.

Attached Files

Liked by

CBA President

John Alexander posted this 09 October 2023

Bill,

Thanks for posting the list of groups. When 17 groups average X and the next 34 average 1.5X that certainly isn't group to group variation as I guessed. I have had the same thing happen sometimes with two weeks of shooting X followed by two weeks averaging 1.5X. Don't know the answer but my best guesses are 1, losing the groove for shooting a light rifle or 2, some sort of semi-permeant bore condition not remedied by routine bore cleaning aka magic. I think I have seen that blasting a dozen full charge JB loads has changed things back to X - but that may also be magical thinking on my part.

But when someone says small group followed two groups (or ten minutes) later by one three times larger we are likely seeing just typical group to group variation for 5-shot groups. Look at the individual group sizes in the 5 groups of an IBS aggregate and you will find that the ratio of largest group to smallest is often 3 or more -- sometimes by the winner. We seem to be able to quickly forget that happened or blame it on a bad shot, but it is just nature's way of telling us it is a probabilistic world whether we like it or not.

John

Attached Files

Liked by

CBA Member

RicinYakima posted this 09 October 2023

You show 50 groups in in 5 months. That is not enough practice, you need to shoot the same load and bullet and settings more.

Last time I shot with Bob Haufschild, he told me he shot 25,000 rounds in less than ten years practicing. When I was getting ready for scoped Military Rifle Nationals, I would shoot 400 - 500 rounds between the middle of April and the first of June when I had to start driving. I tried to make every shot like make or break match winner.

FWIW

Attached Files

Liked by

Standard Member

Wm Cook posted this 11 October 2023

John, thanks:

I have had real trouble when changing lots of 5744. If I understand correctly it has been made by several plants over the years.

I'm still using the same lot of 5744 as I was shooting in the spring but appreciate your heads up about the different manufacturing locations. Maybe I'm the exception but it isn't often that I get two bottles of powders, different lots, that shoot the same way.

I would try something somewhat softer for a few groups. If you do it may be wise to guard against the case sizing or damaging the softer alloy

Both the case and the alloy could be something to work with. As is I've been shooting the same bach of Linotype since early spring. The brass has about 5 to 7 firings by now. I should be keeping track of that but didn't. I haven't had to set the shoulder back yet with the mild loads (~1720fps) I'm shooting. I neck size and don't put much squeeze on the bullet. If I remember right I'm sizing to .335, bullet sized to .308, necks turned to .0145.

I have multiples of the same Accurate Egan style molds. One drops a nose of .3012 and one .3018. The chamber & bore on the Savage is unusual. The freebore is only .3085 and the bore is pretty big at .3019. With the .3019 mold I can feel the nose touching the lands when chambering and I can feel the kiss (about .045" worth) of the Egan tapered front driving band enter the freebore. But it is not sticking or jamming. Extraction of a loaded round comes out easy and gentle with no pulling out or pushing in. There are signs of the lands touching the nose and the freebore but its not heavily engraved. Consider that this is coming from a rookie cast bullet accuracy shooter but seems like a good bullet to bore fit. Understanding bullet fit has been my biggest challenge.

I missed what rifle action you are using,but if any of it’s action screws are blind,check that they are not bottoming out when tightening.

Mike it's a straight up Savage short action with the HS Precision stock Savage sold with it some time back. It's torqued down to the 60lb as recommended and there's no barrel to stock contact.

Try lightly tapping the case head three times on the bench and carefully inserting the case into the chamber to maintain the powder against the primer.

Bud, I'll let you know about the tapping idea. If the heaven permits I'll be at the range in the next couple days. I'll have a backup bullet and a few other powders to try if the powder positioning doesn't effect change. I tried N135 a while back when I was trying to get 1800+ fps but at 1775 it was spraying like a water hose. Varget is the go to powder for jacketed bullet for F class but I honestly never gave it a try. The current plan is to give 4227 and 4895 another try. Maybe bring some 4198 along as well. That should about cover the fast to slow powders.

Its feels as if you took a trigger assembly apart a month ago and today you're trying to put it back together again. You know you'll eventually get it together but you have to keep working at it. Hard to explain all this as fun, but it is. Thanks, Bill.

A “Measured Response” is as effective as tongue lashing a stuck door.

Attached Files

Liked by

CBA Member

RicinYakima posted this 11 October 2023

MP 1886,

I trained, studied and spent the lasts 18 years of my working life as a environmental chemist.

There is no judgment or opinion in science. It deals with facts. Now if you know the facts, you can make better judgements and develop opinions. We use science to make art. Otherwise every picture would look the same.

IMHO, Ric

Attached Files

Liked by

Standard Member

Wm Cook posted this 12 October 2023

Well......this is kind of embarrassing. But here goes.

The problem was self inflicted which (assuming you are a glass half full kind of person) was better to find out at my range than pulling out my hair at a match. The primary objective for the range trip today was to see if the 5744 powder position within the case had an effect on what I've been calling group v patterns. A secondary objective was to try a couple different powders and another bullet.

Conditions were interesting. Wind direction ran from 4:00 to 8:00 and wind velocity ran from a few moment of "A" to strong "C's". I break down wind velocity to alpha characters A, B, C, D. "A" being mild and "D" is with the flag tail held up there right tall and proud. So conditions were tough enough I could only run a couple, three shots then pick the rest. I haven't practiced holding off with shooting cast bullets with wind change because of the iffy "patterns" I was getting.

Now to take ownership for the self inflicted wound. Back in early August I put a cartridge block on my front rest. A cartridge block is elevated off the bench and is in close proximity to the loading port on the action. I've shot in this manner for decades and it helps me when I run (versus pick) a group. When conditions are right I try to put 5 down range as fast as I can. With jacketed PPC that's about 11 seconds. And most competitors were faster than me. We actually practiced how fast we could put 5 shots on record. The theory is that you're trying to shoot a decent aggregate not a tiny group. So when conditions are right you let it fly. I'm too new to know if that's common to cast accuracy.

Now the cartridge block holds the cartridge at about a 45 degree angle so its position so you can pick it as soon as your hand leaves the bolt (RB/RP).

With the angle of the cartridge as held in the block it tilted the case and it had the powder shifting toward the base of the bullet. Today the test groups shot with the cartridge block shot the same "patterns" I've been whining about. I switched back and forth between loading off the cartridge block and loading with the cartridges laying on the bench which had the powder pretty much level in the case.

The two groups on the left were loaded from the cartridge bloc and the powder was in the upset condition. The two on the right were loaded from the bench.

What I found was that 5447 is sensitive to its position in the case. Which opens up a whole new question about powder selection for the .308. None of the powders that I can see will even half fill the case. I would assume that some powders burn more efficiently than others. So when you are shooting honest "groups" and that group includes a flier (which doesn't disqualify it from being a group in my mind) is the flier caused by the powder position? John started a thread some months back with the title something like "What causes fliers". Never though about it since this circus I just waded through but powder combustion could maybe be a great excuse. Good shooters always have to have a couple, three canned excuses when a group is blown. They don't call it the wailing wall for nothing.

So the 5744 is going back on the shelf. The IMR 4227 looked promising and maybe it's shorter extruded power helps ignition. Its only a guess but with more surface area exposed it may burn more consistently? Knowledge about that is above my pay grade. Thanks to everyone, Bill.

A “Measured Response” is as effective as tongue lashing a stuck door.

Attached Files

Liked by

CBA Member

Paul Pollard posted this 12 October 2023

Attached is a target from a previous National. It hangs on the loading room wall and makes me chuckle when I look at it. No two consecutive shots were close on the sighter, and I finally just decided to move up to the record target.

200 yd target

Attached Files

Liked by

CBA Member

muley posted this 08 October 2023

with that bullet weight and the 1-10 twist try 30-33 of varget for a start. or 28-30 of vv135 in 1/2 grain increments

Attached Files

Liked by

Standard Member

OU812 posted this 08 October 2023

I had best accuracy using Reloader 7 in my 308...no vertical stringing from what i recall. Vertical stringing is usually caused by powder positioning inside case.

Attached Files

Liked by

Standard Member

OU812 posted this 08 October 2023

I taper bumped all my test bullets 1.5 degree included, so accuracy was pretty good with alot of powders and bullets (4759, 4198,4895,varget,rel 7,2400 etc).

Rel 7 was most accurate in my rifle. I we lived closer I would give you a pound to try.

Attached Files

Liked by

CBA Member

muley posted this 08 October 2023

you say loading at the bench . years ago Dave Lee used one case and loaded at the bench. he usually had highest score or was near the top. when you shoot the cases sort them as close as possible. reload as a group. I think ,shoulder pressure can also cause verticle. just my thoughts

Attached Files

Liked by

CBA Member

RicinYakima posted this 08 October 2023

John,

I think that you didn't get any feed back is because there are two opinionated groups; those that think small variations will make a big difference with consistent size and those of us who know that five shot groups vary greatly in size. You and JoeB did a lot to convince me of that.

Not meaning to break anyone's rice bowl, but there are a lot of products sold in shooting sports with little or no actual shooting data.

Four ten-shot groups would have less variation than four five-shot ones. And four 25-shot groups would be very close in overall size.

Ric