Bullet weight variations; good data/lower accuracy v. bad data, very good groups?

[huntinlever]

There is a thread on cast bullet weight consistency and rather than hijack that thread, as the question is slightly different (though related in terms of acceptable variations in bullet weights), wonder if I could get your opinions.

Two different loads for the 46-405VG from Accurate with a 1% variation or up to 4 gr variation in the cast bullets. Both at 100 yards.

First is 39.5g I 4198, second is with 33.8 gr AA 5744.

39.5 gr I 4198. My notes show the chrony numbers terrible. ES = 183, SD = 80. On the other hand, groups, confirmed on a few trips, were really good:

313502

33.8 gr AA 5744 yielded great data. I don't have it in my notes whether the high shot was a flyer or not, but in general groups are good across trips, just not quite as good as the 39.5 gr 4198 load. But on the other hand data is very good. Avg = 1520, ES = 12, SD = 5.

313501

So couple of questions. Let's presume 100 yards hunting distances. If you had to choose, would you choose the first or second load - great groups but lousy data, or good data but for some reason groupings aren't quite as good?

And given I'm accepting up to 4 gr variations in bullets as cast or 1%, is there some kind of thought on whether the casting needs to be better sorted - how much does weight variance affect accuracy at, say, longer than 100 yards (45-70, so let's say no longer than 150 yards)?
-

[M-Tecs]

When everything is said and done the only method of measurement that has any importance is grouping. When was the last time a shooting match was won by the SD numbers? The longer the range the more aligned the two become but the groups are still king.

[TD1886]

When everything is said and done only method of measurement has any importance. That is grouping.

I believe you are right. I look at lots of data that gives velocity, energy, SD, ES and groups. They tell us the better loads have the lowest SD and ES, but more then often the best groups don't come from that.

[Bigslug]

Open the distance to 150-200 yards for both loads and see if the wide 4198 numbers spread shows their lack of mettle. Assuming you aren't routinely throwing flyers, it seems to me that 5744 is a better fuel for that rifle, but you may not have found the exact accuracy node for it yet. A few tenths up or down may be what it needs.

That said, I'd happily pack up with either load and go brush hunting.

[Larry Gibson]

A five shot group is not enough of a sample to make any decision on. Neither is a 5 shot test of ES/SD numbers. Since you appear to be interested in the intrinsic accuracy ["precision" is the correct term] I suggest you increase the sample size and test the loads to 10 shots per group/chronograph test.

[huntinlever]

A five shot group is not enough of a sample to make any decision on. Neither is a 5 shot test of ES/SD numbers. Since you appear to be interested in the intrinsic accuracy ["precision" is the correct term] I suggest you increase the sample size and test the loads to 10 shots per group/chronograph test.

Thanks all. And thanks Larry. So I've done repeat trips with 5-shot strings.

I'd thought to take a look again at the I 4198 loads, in case there was just something haywire going on with my chrony setup. So, 39.3, 39.5, and 39.7 gr I 4198. 10 shots each - this is what you are saying? (I'll be doing the same with AA 5744 per bigslug's thoughts, 33.5, 33.8, 34.0).

Precision v. accuracy. Thanks.

[Larry Gibson]

Yes, 10 shot strings. That sample size can eliminate the effect of "random dispersion" within the group size. Unless you can actually call any shot a flyer then don't discount any shot outside a tight group.....it is telling you something.

[Bigslug]

Considering the ultimate objective of having a stupidly accurate hunting gun, a few suggestions:

1. Load a couple of your reject bullets on top of each of your powders to use as foulers before beginning the actual string. Not a bad thing to do pre-season either.

2. Don't shoot more than 3 before allowing the barrel to return to "room temperature". Bring a .22 to keep yourself entertained during cool downs.

3. As I recall, this is for a Marlin 1895? There may be some benefit to simulating field conditions with the front of the magazine full of dummys, factory cartridges, etc..., and loading and feeding your test rounds singly. It's the first shot from the cold bore we're most concerned with, and barrel harmonics with a full or minus-one tubular magazine are likely the most relevant.

[huntinlever]

Considering the ultimate objective of having a stupidly accurate hunting gun, a few suggestions:

1. Load a couple of your reject bullets on top of each of your powders to use as foulers before beginning the actual string. Not a bad thing to do pre-season either.

2. Don't shoot more than 3 before allowing the barrel to return to "room temperature". Bring a .22 to keep yourself entertained during cool downs.

3. As I recall, this is for a Marlin 1895? There may be some benefit to simulating field conditions with the front of the magazine full of dummys, factory cartridges, etc..., and loading and feeding your test rounds singly. It's the first shot from the cold bore we're most concerned with, and barrel harmonics with a full or minus-one tubular magazine are likely the most relevant.

If I'm hearing you, point taken. The other thread's last comment might be saying it well. "Don't let perfect become the enemy of good enough".

I do make sure I shoot a few foulers on a clean barrel. I've actually decided to change up on a lifetime's habit, and only clean the action/receiver, etc., between range sessions, leaving the bore fouled. Only when the groups start looking peculiar after a certain time will I again clean the bore. But on a clean bore I shoot a few "sacrificial" rounds.

Your point 3 is excellent. Many thanks, never would have thought of that.

I'm probably chasing my tail, when I should be chasing whitetail.

[charlie b]

One of the other things I recall from my lever action days was the front rest. I was taught to always put my hand on the rest and hold the forearm of the rifle with the hand.

I agree with everything said. I do most of my load development at 200yd and when I hunted I would always shoot a group at a range longer than I expected to see during the hunt.

IMR4198, when I use it in my .308, is very position sensitive. And using a dacron filler has not resulted in better groups for me.

For hunting, I'd use whichever load I like. If I like it and am confident with it, I will hit the target where I want.

[Bigslug]

I'm probably chasing my tail, when I should be chasing whitetail.

You gain wisdom, Grasshopper.:mrgreen:

A lot of what Dad and I learned about load development with jacketed in Highpower gets applied to the hunting and plinking ammo process simply because we've found those shortcuts to making better ammo.

But once you've developed that whizzbang tight-grouping ammo and get off the sandbags to practice offhand, kneeling, etc..., you realize your ammo's better than you are. Yes, that's how it should be, but if you're a 5-MOA shooter in the real world, bashing your head against a wall to tighten up a 1.5-MOA load may not be as good a use of your energy as burning up a bunch of it practicing to become a 3-MOA shooter.

As my Pop says, good lab technique is good lab technique, but when you're ammo is below MODH (Minute Of Deer Heart), it's time to consider sticking in a fork and calling it done.

[M-Tecs]

The OP stated he fired multiple groups. If all the groupings are reflective of the ones pictured is a choice between a 1 MOA groups and 2 plus MOA groups at 100 yards with the longest being 150.

Larry is 100% correct for statical analysis 10 shot groups are a better sampling size.

The real question is what are you trying to achieve? Is it reflective of your actual usage?

For hunting the most important shot is the first shot from a cold bore in the bore condition you will be hunting with. Most barrels need a couple of shots to settle in. Some don't. Only way to know is to test.

Next is what happens with quick follow up shots? Does the barrel start to walk when is heats up?

Same of a full magazine to empty? Does POI change as the mag is being emptied?

Different shooting application require different test methods. One example is for NRA Highpower you need to know what happens when you fire two 10 shot groups in under 60 seconds per 10 shot group and what happens when you fire 22 shots in under 10 minutes. At 600 yards you have 2 sighter shots and 20 minutes for 20 shots for record. With a good target puller and steady conditions ten minutes for 20 shots is very doable.

On the other hand, shooting a single shot for hunting rarely require more than a second shot unless you are shooting something like prairie dogs. That being said I test every center fire rifle I own with a rapid fire 10 shot group to check for barrel walking from heat. I have one Savage 99 that starts to walk badly after 3 shots. Luckly, it walks straight up. It's a hunting rifle so more than three shots realistically will never be needed but it still nice to know what it does as it heats up.

My single shot F-Class, Palma and match rifles can be subjected to as many as 30 shots in less than 30 minutes. For 1,000 yard NRA LR you have 30 minutes for 20 shots for record with unlimited sighters. They need to be tested accordingly.

[TD1886]

The OP stated he fired multiple groups. If all the groupings are reflective of the ones pictured is a choice between a 1 MOA groups and 2 plus MOA groups at 100 yards with the longest being 150.

Larry is 100% correct for statical analysis 10 shot groups are a better sampling size.

The real question is what are you trying to achieve? Is it reflective of your actual usage?

For hunting the most import shot is the first shot from a cold bore in the bore condition you will be hunting with. Most barrels need a couple of shots to settle in. Some don't. Only way to know is to test.

Next is what happens with quick follow up shots? Does the barrel start to walk when is heats up?

Same of a full magazine to empty? Does POI change as the mag is being emptied?

Different shooting application require different test methods. One example is for NRA Highpower you need to know what happens when you fire two 10 shot groups in under 60 seconds per 10 shot group and what happens when you fire 22 shots in under 10 minutes. At 600 yards you have 2 sighter shots and 20 minutes for 20 shots for record. With a good target puller and steady conditions ten minutes for 20 shots is very doable.

On the other hand, shooting a single shot for hunting rarely request more than a second shot unless you are shooting something like prairie dogs. That being said I test every center fire rifle I own with a rapid fire 10 shot group to check for barrel walking from heat. I have one Savage 99 that starts to walk badly after 3 shots. Luckly, it walks straight up. It's a hunting rifle so more than three shots realistically will never be needed but it still nice to know what it does as it heats up.

I like what Ross Seyfred said about sighting your hunting rifle and load. He said put up your target at the distance you want and shot one shot at it. Take the target down and go back to the house and waist a period of time in as days. Then take the same target out and shoot one shot again. Repeat as many times you feel you need to and you will definitely find where your first cold barrel shot is going to on hunting day. Like mentions some barrels are walkers.

[huntinlever]

The OP stated he fired multiple groups. If all the groupings are reflective of the ones pictured is a choice between a 1 MOA groups and 2 plus MOA groups at 100 yards with the longest being 150.

Larry is 100% correct for statical analysis 10 shot groups are a better sampling size.

The real question is what are you trying to achieve? Is it reflective of your actual usage?

For hunting the most import shot is the first shot from a cold bore in the bore condition you will be hunting with. Most barrels need a couple of shots to settle in. Some don't. Only way to know is to test.

Next is what happens with quick follow up shots? Does the barrel start to walk when is heats up?

Same of a full magazine to empty? Does POI change as the mag is being emptied?

Different shooting application require different test methods. One example is for NRA Highpower you need to know what happens when you fire two 10 shot groups in under 60 seconds per 10 shot group and what happens when you fire 22 shots in under 10 minutes. At 600 yards you have 2 sighter shots and 20 minutes for 20 shots for record. With a good target puller and steady conditions ten minutes for 20 shots is very doable.

On the other hand, shooting a single shot for hunting rarely request more than a second shot unless you are shooting something like prairie dogs. That being said I test every center fire rifle I own with a rapid fire 10 shot group to check for barrel walking from heat. I have one Savage 99 that starts to walk badly after 3 shots. Luckly, it walks straight up. It's a hunting rifle so more than three shots realistically will never be needed but it still nice to know what it does as it heats up.

My single shot F-Class, Palma and match rifles can be subjected to as many as 30 shoots in less than 30 minutes. For 1,000 yard NRA LR you have 30 minutes for 20 shots for record with unlimited sighters. They need to be tested accordingly.

Excellent. Many thanks. Yep, honestly, I only care about killing well on a hunt in what may be brutally cold conditions. That's it. Like all of us I love shooting and have been having fun with my .338 WM (as well as a new Skinner on my son's 336, and his new Savage '06), but at the end of the day, at least for the next couple of years, it will be myself, my 45-70, my son and his 336 in northern big woods, tracking (then we hope to start a tradition together out west). I have to admit a decent number of years with the I 4198 and a 425 gr WFNGC from Accurate that was a stiff shot, but the groups were hard to beat. I'm finding the same now - needs it hot, but I find getting 1 MOA on the lever pretty nice.

Anyway, loaded up tweaks with 5744 and 4198 for what should probably be my last load development trip. Then heading to another range for offhand practice, and longer distances.

Appreciate all the views and expertise here, guys. I learned some new things and it was good to be reminded on what I was actually after.

[gwpercle]

Great groups beat everything seven ways to Sunday .

Only accurate loads count ... the rest of the numbers don't mean Doodly-Squat!
... don't let the data confuse you .... Accuracy Matters Most .
Gary

[M-Tecs]

I like what Ross Seyfred said about sighting your hunting rifle and load. He said put up your target at the distance you want and shot one shot at it. Take the target down and go back to the house and waist a period of time in as days. Then take the same target out and shoot one shot again. Repeat as many times you feel you need to and you will definitely find where your first cold barrel shot is going to on hunting day. Like mentions some barrels are walkers.

For the long-range hunter that is OK advice. Same for wood stocks with barrel pressure points. I've owned a couple of rifles that would change POI from week to week due to stock warpage from temp and humidity. They grouped about the same, yet POI moved as much as 2 MOA due to the different pressure point pressures.

The problem with the one-shot method (if used exclusively) is it will not detect issues like barrel walking or POI shift from reduction of cartridges in the magazine. Using the same target or recording the POI for your 3, 5, or 10 shot groups over weeks or months will give you more information than the one-shot method. The only downside to shooting groups is you are using more ammunition. Other than that, I don't see any upsides to the one-shot group method.

[TD1886]

For the long-range hunter that is OK advice. Same for wood stocks with barrel pressure points. I've owned a couple of rifles that would change POI from week to week due to stock warpage from temp and humidity. They grouped about the same, yet POI moved as much as 2 MOA due to the different pressure point pressures.

The problem with the one-shot method (if used exclusively) is it will not detect issues like barrel walking or POI shift from reduction of cartridges in the magazine. Using the same target or recording the POI for your 3, 5, or 10 shot groups over weeks or months will give you more information than the one-shot method. The only downside to shooting groups is you are using more ammunition. Other than that, I don't see any upsides to the one-shot group method.

Well when hunting we're hoping that one shot is all you will need. This is big game hunting, not shooting praire dogs.

I've only owned one wood stock rifle that walked the shots and really bad too.

Basically I was talking about the hunter that takes his rifle out of the closet and goes out on first day of whitetail deer season. I have two SAKO Foresters in 243 factory wood stock and they don't walk one iota in five shots. With 100 grain bullets they both are an honest 1/4 inch group for five shots. I don't believe SAKO done anything special to the walnut stock. At that time they used no bedding compound, they didn't even use the steel tube pillars on the action screws, yet they shoot that well.

The one rifle that was a walker was a 260 Remington I built on a Jap Type 38 action and stocked with a Boyds walnut stock. Glass bedded action too. Five shots and it walked to the right, perfectly level, 1/2 inch or there abouts with five shots and ended up like almost 3 inches from the bullseyes. Let it cool and it repeated it consistently. I bedded the forend with a pillar of Devcon Steel putty and the rest was history. Nice round groups, but it's not a very accurate rifle. I suspect the el cheapo E.R. Shaw barrel on it. I was on a buget then and that was all I could afford. It's good for about 3/4 inches.

[M-Tecs]

Particularly with deer lots of states/areas offer more than one tag. For 20 plus years I would have one buck tag and two doe tags for the rifles season, one for archery and one more for muzzleloading for a total of 5 with 3 being bucks.

Twice I dropped three deer in less than a minute. Once was one buck and two does. The other time I only had one buck and one doe license; however, my dad's buck license was open. He was too sick to sit in his tree stand so he sat in the truck overlooking a ravine about 400 yards from me. He wanted to tag the first buck we took so he could go home. Two bucks were chasing a doe. We all went home at the same time.

Another time while deer hunting I spotted 6 coyotes trying to take down a nice 4x4 buck. I had already filled my buck tag. The snow was fresh and deep which slowed the coyotes down some. My Browning Sako 243 held 6 rounds. Only one coyote got away. I did miss once and fired two additional finishing shots.

I haven't firearm hunted Antelope in 20 plus years but when I did normally had two tags. Only one could be a buck. Never had a good opportunity to shoot a doe immediately after dropping a buck.

Barrel walking as they warm up is generally from uneven stress in the barrel. POI shift is generally from stock warpage and a sperate issue. That can be a problem with some of the cheap plastic stocks also.

[TD1886]

Particularly with deer lots of states/areas offer more than one tag. For 20 plus years I would have one buck tag and two doe tags for the rifles season, one for archery and one more for muzzleloading for a total of 5 with 3 being bucks.

Twice I dropped three deer in less than a minute. Once was one buck and two does. The other time I only had one buck and one doe license; however, my dad's buck license was open. He was too sick to sit in his tree stand so he sat in the truck overlooking a ravine about 400 yards from me. He wanted to tag the first buck we took so he could go home. Two bucks were chasing a doe. We all went home at the same time.

Another time while deer hunting I spotted 6 coyotes trying to take down a nice 4x4 buck. I had already filled my buck tag. The snow was fresh and deep which slowed the coyotes down some. My Browning Sako 243 held 6 rounds. Only one coyote got away. I did miss once and fired two additional finishing shots.

I haven't firearm hunted Antelope in 20 plus years but when I did normally had two tags. Only one could be a buck. Never had a good opportunity to shoot a doe immediately after dropping a buck.

Barrel walking as they warm up is generally from uneven stress in the barrel. POI shift is generally from stock warpage and a sperate issue. That can be a problem with some of the cheap plastic stocks also.

Even as bad as my 260 Rem walks it's shoots as the barrel warms up it is still plenty minute of deer accurate enough to get the job done.

[huntinlever]

Well, frustrating day at the range. 10 shot strings over 5744. Again, great stats - about 12 SD (ranged 13, 10, 11, 13 SD across 4 load levels), good velocities. And absolutely lousy groups. Many flyers, but even with those taken out (they shouldn't be - with those in, let's say 4-5 moa), with groups without these flyers maybe 3.5 moa (I do not recall any specifically called pulls, so really have to go with the 4-5 moa, not acceptable). I just don't think my gg likes the 5744. Ran out of patience, too bad, because it's a great day to soldier on into my I 4198 levels, but after several hours and taking it slow over 40 bullets 5744, thought best to come back fresh.

Whether pushing 46-425 grain Accurate bullets over 39.7 grain I 4198, or at least so far, 39.5-39.7 I 4198 for this 46-405 VG bullet, I'm getting 1 moa or thereabouts across many trips. Yet the data so far is way out of line compared to the 5744. I can't figure it out, but my gut has always told me 4198 is the powder for this gg, and I'm almost certain now it's where I'm staying. 8 lbs, here we come.

On the other hand, got my load for my son's 336 30-30, over Lever Revolution. Even with these tired old eyes and a Skinner peep, I was getting right around 1.5" at 50 yards, which I'll call good. He'll probably do better. Couldn't get chrony to work on this lever, but load estimates give about 2500 fps.

[Bigslug]

Well. . .it's an 1895 Marlin Guide Gun. The chrono numbers spread probably WOULD matter if you were plugging this 4198 load into a 30" Winchester High Wall for a BPCR match at serious distances. You're regularly getting fat MOA groups out of a brush gun not terribly well suited to work much beyond 100 yards. Trying to go farther with load development at this point may be akin to crafting a championship-level .45ACP Bullseye load. . .to use exclusively in an open-bolt Thompson submachinegun. Your 150 yard meat-stick is ready.

[huntinlever]

Well. . .it's an 1895 Marlin Guide Gun. The chrono numbers spread probably WOULD matter if you were plugging this 4198 load into a 30" Winchester High Wall for a BPCR match at serious distances. You're regularly getting fat MOA groups out of a brush gun not terribly well suited to work much beyond 100 yards. Trying to go farther with load development at this point may be akin to crafting a championship-level .45ACP Bullseye load. . .to use exclusively in an open-bolt Thompson submachinegun. Your 150 yard meat-stick is ready.

You're right and well said, poetically even, lol. I think that old load with the 425 gr is sticking in my craw. Getting close to 1 moa AND good data, if memory serves. But I hate the groups on this 5744, good data or not. That 39.5 I 4198 is 1 moa. I'm doing one more trip at 39.3-39.5-39.7, but I should probably pull all bullets, load up a ton of 39.5 and call it.

[huntinlever]

Boy, I have to be more organized. Just to correct the record, that first photo of the "1 moa" 39.5 grain IMR 4198 is completely in error. That is 39.5 grains IMR 4198, but it's a photo of a 2015 range trip, it's 50 yards, and it's a 425 grain 46-425Q Accurate Mold 50:50 COWW:Pb + solder to bring tin and antimony up to 2 % each. Ben's Red, not MML. So completely messed up the current data with a past photo on a completely different setup. I have to get my act together.

Now, completely perplexed.

Yesterday's range trip showed similarly unspectacular data as the 4198 has all along with this year's load development (see below), and I'm not very happy with my groups - likely, my shooting. Anyway, 5-6-23 range trip 39.7 grain IMR 4198 over the 405 grain bullet.

313794

It has consistently given the best groups among all the loads of 5744 and 4198, though I have no clue on the flyers. Other outings have been tighter overall on this charge. Weirdly, this load level is identical to the one that worked best with the above-photo's 425 grain bullet (see comparable stats and photo, again, below).

Repeat of that first post's 39.5 grain I 4198, and 425 gr pill. This is 2015:

313793

Another range trip from 2015 - corrected elevation mid-string, so only 5 shots at the corrected elevation at 50 yards, you can see similarly good groupings with the load and 425 grain pill. Note this is my final load at the time, though - just like now but with the heavier pill, 39.7 gr IMR 4198:

313792

Also weird is that my data shows the same 39.7 grain drove the 425 grain pill significantly faster than it does this lighter (405 grain) pill. Different chrony. Totally perplexed.

2015, 425 grain 46-425Q
Chrony: Competition (shoot through):

Bullet: 46-425 425 grain WFNGC
Grain 39.7 gr I 4198
Shot No. FPS
1 1702
2 1709
3 1707
4 1724
5 1709

Summary
AVG 1710
ES 22
SD 8

5-6-23, 405 grain
Chrony: Magnetospeed Sporter (Bayonet):

Bullet: 46-405VG 405 grain WFNGC
Grain 39.7 gr I 4198
Shot No. FPS
1 1614
2 1567
3 1619
4 1613
5 1625
6 1631
7 1544
8 1621
9 1613
10 1615

Summary
AVG 1606
ES 27
SD 87

I can't explain this - a lighter pill travelling 100 fps slower than the heavier pill, with the same charge on both? Am I missing something? The only thing I can think is that I'm not confident of this Magnetospeed data. Load books would predict this bullet travelling close to 1700 fps, just like the actual data on the 425 shows from 2015. 1600 fps seems way off to me.

I'm thinking of just going back to what worked well before, which is the 425 grain Accurate over 39.7 grain 4198. And going back to the Comp Electronic chrony.

[huntinlever]

Well, not to resurrect a more less completed thread, but I think I've learned (or relearned) a lesson. I weighed out my stock of cast, gas-checked and lubed bullets, and saw way too much variation. I realize now that "previously," all those years ago, when I was very pleased with the loads, I not only visually inspected but weighed-sorted a bullets as cast to much tighter tolerances. Even with a nominal grain bullet of 405 grains and allowing 1% or 4 grain variations, I had some pretty wild swings - from 405 (again, note this is lubed and gas checked, so the cast bullets weighed out 392 or so - avg. weight of gas checks 10 grains) all the way up to 414 (i.e., 404 as cast).

So I ended up dumping a ton of rejects back into the pot. This time, I accepted only bullets weighing out 408.8-409.9, with one bin sorted 408.0-408.9, the other 409.0-409.9. Loaded up for a redo on load development only bullets weighing 409.0-409.9. With a later look at the 408's.

That might be overdoing the culling - looking for opinions on weight tolerance for a 400ish cast bullet. But clearly I need to find a way to cast much more consistently, and that wild as-cast weight swing might, I think, explain some of the wild flyers.

[Bigslug]

Do some serious visual scrutiny on the light ones before you re-melt them, checking the bases and bands and compare them with those in the optimal range. If you're getting a 20 grain weight swing, my guess is that you might need to spend some time developing your culling eye. If they are truly visually indistinguishable from the "good ones" with a weight spread that large, my thoughts then run to crud in the pot and internal voids in the bullets.

I will admit that my Dad and I "cheat". His hands don't let him cast in quantity, and I don't have the room at my place to reload, so our answer is for me to cast the bullets and for him to visually cull them right out of the mold, so the rejects get tossed back in the pot without a chance to cool. This probably makes it easier for us to determine if something is "not right" and get the minutiae sorted out on the fly than it is for others. Even when we hit "the zone", we're probably still culling 25% on average. What manages to pass that visual cull is usually within 1% variation for weight.

As to the small number you get that fall well above the nominal weight, check their diameter to ensure they aren't large due to a mold closure problem, and that your sprues are cut off square. One solution to the former is locking mold handles that adjust to operate similar to a pair vise-grip pliers - I would not consider casting without them. My solution to the latter is to pinch down on the sprue plate with a gloved hand while I make the cut.

Protruding dimples on the base of your bullet will affect your accuracy, even under a gas check. I tested this after I had developed a good load for .303 British; for the sake of "SCIENCE!", I deliberately loaded up a batch of "outy-based" 314299's with no other changes to the ammo, and it blew what was otherwise a 1.5-2MOA round out to about 4-5 MOA.

Now on the other hand, if your heavy bullets are passing inspection for visual flaws AND diameter, it's possible your "optimal" weights are the flawed ones and you are only managing complete fill-out on a very few. As with what you currently think are the too-light bullets, visually compare the too-heavy to what you currently think is ideal.

I'd guess Dad and I have been at the casting game for a bit over 15 years now, and while we've gotten a lot more picky about what survives to get loaded, we're still doing our culling almost entirely on visual cues. If you're going to play the long range or high velocity smallbore game, you'll likely have to break out the scale and cull further, but for rupturing milk jugs within 200 yards at 2000 fps or less, I can't really call that necessary. That said, if you don't have "the eye", the scale is probably your best bet.

[huntinlever]

Do some serious visual scrutiny on the light ones before you re-melt them, checking the bases and bands and compare them with those in the optimal range. If you're getting a 20 grain weight swing, my guess is that you might need to spend some time developing your culling eye. If they are truly visually indistinguishable from the "good ones" with a weight spread that large, my thoughts then run to crud in the pot and internal voids in the bullets.

I will admit that my Dad and I "cheat". His hands don't let him cast in quantity, and I don't have the room at my place to reload, so our answer is for me to cast the bullets and for him to visually cull them right out of the mold, so the rejects get tossed back in the pot without a chance to cool. This probably makes it easier for us to determine if something is "not right" and get the minutiae sorted out on the fly than it is for others. Even when we hit "the zone", we're probably still culling 25% on average. What manages to pass that visual cull is usually within 1% variation for weight.

As to the small number you get that fall well above the nominal weight, check their diameter to ensure they aren't large due to a mold closure problem, and that your sprues are cut off square. One solution to the former is locking mold handles that adjust to operate similar to a pair vise-grip pliers - I would not consider casting without them. My solution to the latter is to pinch down on the sprue plate with a gloved hand while I make the cut.

Protruding dimples on the base of your bullet will affect your accuracy, even under a gas check. I tested this after I had developed a good load for .303 British; for the sake of "SCIENCE!", I deliberately loaded up a batch of "outy-based" 314299's with no other changes to the ammo, and it blew what was otherwise a 1.5-2MOA round out to about 4-5 MOA.

Now on the other hand, if your heavy bullets are passing inspection for visual flaws AND diameter, it's possible your "optimal" weights are the flawed ones and you are only managing complete fill-out on a very few. As with what you currently think are the too-light bullets, visually compare the too-heavy to what you currently think is ideal.

I'd guess Dad and I have been at the casting game for a bit over 15 years now, and while we've gotten a lot more picky about what survives to get loaded, we're still doing our culling almost entirely on visual cues. If you're going to play the long range or high velocity smallbore game, you'll likely have to break out the scale and cull further, but for rupturing milk jugs within 200 yards at 2000 fps or less, I can't really call that necessary. That said, if you don't have "the eye", the scale is probably your best bet.

Wow, ton of great info, thanks. This is one I'm going to have to sit with. Much appreciated.