Bullet seating depth and accuracy

YosemiteSam357 · August 27, 2004, 12:09 PM

I've been working up loads for a .243, recently started using an OAL gauge and comparator, and made my latest batch of loads to all be .010" off the lands. Upon shooting I was surprised to see much larger groups than I'd been getting previously. I then shot some leftovers from older loads, which were seated as far back as .10" off the lands, and got much better results with the same bullet weights and powder charges. In fact, some of the most accurate loads I've developed have been using 55gr bullets which have absolutely no chance of getting anywhere near the lands due to the short bullet length. This surprised the heck out of me. It seems to fly in the face of conventional wisdom, or at least everything I've read about the subject, which indicates that having the bullets as close to the lands as possible will provide the best accuracy.

Yes, I know "every rifle is different", but this really surprises me. I mean, .10" off the lands? Is it possible that something else is going on here, or is it really not that uncommon?

Any advice or commiseration will be appreciated.

-- Sam

P.S. Why is it that it seems very few people shoot the .243? It has a great trajectory, weight, accuracy potential, etc, but it seems no one talks about it much online. Is it just that it's not the latest whiz-bang trendy round to be foisted on us by the manufacturers, and not a military round?

.45 Vet · August 27, 2004, 01:27 PM

I've had just the opposite results with my .243 Bull BBL., but I"m shooting 80gr. SHP"s. Years ago an older gentleman advised me that when loading for rifles to always try to seat the bullet "AT LEAST" one caliber deep.

Don't know if it's to provide better ignition or what. But sure seems to hold true in my guns with light bullets. Good Luck......

YosemiteSam357 · August 27, 2004, 01:54 PM

Quote:

I've had just the opposite results with my .243 Bull BBL.

Meaning, "just the opposite" of what I'm calling conventional wisdom, or just opposite of what I'm seeing? That is, do you have more luck with more deeply seated bullets or those closer to the lands? It sounds like you're saying "deeper is better".

It should help with concentricity/runout, if nothing else. But I keep hearing people harp on "closer to the lands for accuracy".

-- Sam

P.S. I'm using 95gr Nosler b-tips for these tests. As mentioned, the 55 grainers can't be made to seat near the lands.

Arc Angel · August 28, 2004, 02:09 AM

OK Sam, Are you ready?

Oh, boy, is this a, ‘loaded question’! First I share your fondness for the 243 – It’s one of my all time favorite rounds. For most serious long range work it’s a little light, though; consequently, it’ll never catch up with either the 308, the 30-06, or the 300mag. If you want to get really nit picking and fastidious about precision riflery you’ll need to take everything into consideration – not just; ‘I took some old loads and did much better with them.’ That truly doesn’t cut it with precision riflery.

So, here we go: Get yourself some Sweet’s Australian and do a thorough cleaning job on that barrel. (Be careful with this stuff. Read the label and don’t over use it or let it sit in the barrel too long.) My suggestion would be to take the easy way out and start with new brass. Choose a powder that pretty well fills the case and measure it out by hand with a precision drop measure. You may have to load your rounds in batches of a dozen until you find the best match between bullet weight and velocity for the rifle you’re using. Make sure you use the proper bullet seater to avoid skewering the bullet, too. Before final assembly lamp blacken a round until it, just, engages the lands. Record the OAL and use it for all subsequent rounds. Keep accurate written records, too; or you’ll end up really confused about which round is which and for what rifle.

(If you insist on using fired cartridge cases to make your ammo, then, turn the necks. Although it's not a crucial factor, don’t forget you’ve, still, got the cartridge head base dimensions to worry about; in this regard, you may, also, want to use, ‘half-length’ sizing dies that reform only the neck and shoulder area of the case.)

If you use optics check your scope; make sure it’s properly mounted and tight. Try to get a hold of a rifle rest – sand bags and all. Now you’re ready to check for precision rifle accuracy. Limit your shots to groups of three each and let the barrel cool down between sets. While you’re waiting you can remove the bolt and quickly brush the barrel out. (There will be variation between the first and last shot fired in each set.) At some point before 5 or 6 ammo batches or 60 to 75 fired rounds you should know what your rifle likes to digest. This is a lot of work; but, if you like to consistently hit small targets between 200 and 300 yards out with that 243, it’s worth the effort.

Seating the bullet deeper in order to improve ignition doesn’t make sense! If the charge is light and you want to keep it together, either, raise the muzzle prior to firing or use a filler on top of the powder. (There’s all different sorts of fillers from oatmeal to kapok; but most rifle rounds, and especially those intended for either competition or long range shooting, don’t require it.) About the only thing you’ll get with deeper seated bullets is increased pressure. It’s that little bullet jump to engage the lands that’ll affect accuracy more than any other single parameter – including neck concentricity. (Which if you want really accurate, consistent rifle rounds is worth the time to lathe out.)

Sorry, but, that informal field test you’ve related means absolutely nothing with regard to serious precision rifle shooting. It isn’t going to tell you anything you want to know!

By the way, what is, ‘One caliber deeper’? I’ve never heard that one before.

YosemiteSam357 · August 29, 2004, 05:38 PM

Thanks Arc Angel.

It wasn't as informal as I made it sound; All the previous loads have been cataloged, and I knew exactly what I was shooting. I've been using benchrest techniques even though I don't plan on competing in IBS events.

All the brass has been segregated by manufacturer and again by weight. All primer pockets have been uniformed, flash holes and necks deburred. I must admit I haven't started segregating bullets by weight yet. Gun is cleaned thoroughly, regularly. I've been doing all my testing with one powder, IMR3031, which gives me about a 70% load density at the charge I'm using. I'm loading three charges of the same powder; I used the "Optimum Charge Weight" method to find a consistent load, and in doing so found two others which were very accurate in my gun. I've got a Stoney Point OAL gauge and bullet comparator. The biggest variable is me.

My "old" rounds had an OAL of 2.652" @ the bullet tip, and 3.015" @ the comparator. The last rounds I made and tested had an OAL of 2.746" @ the tip, and 3.190" @ the comparator. Full chamber depth (contacting the rifling) according to my OAL gauge is 2.756" @ tip and 3.200" @ the comparator for this bullet (Nosler 95gr ballistic tip).

The "old" rounds were, in general, more accurate than the last rounds, despite the last ones being within .010" of the rifling and the old ones being almost .10" away. I don't understand it either.

It may be just me, maybe it was an off day. I only did a few separate groups with each loading. I'm going to reload more at the longer length and see if I can do better with them.

Quote:

By the way, what is, ‘One caliber deeper’? I’ve never heard that one before.

Neither have I. Don't know where you saw it, but it wasn't in this topic... The only reference I can think of is somewhere I read to start pressure testing a load with the bullet seated one caliber's depth into the case.

-- Sam

.45 Vet · August 29, 2004, 06:56 PM

Sorry for the confusion, was running late for work and didn't read what I wrote. What I meant was, if you're loading .30 cal. bullets, then to have at least .30" of bullet seated into the brass.

I also find my rifle prefers the heavier(80-105gr), bullets seated .010/.015" from the lands. All well and good if your magazine will allow for the O.A.L.

Your initial post only mentioned 55gr bullets, and they're probably seated .240" or so into the case neck. And as a result, are way off of the rifling. (this is the part that flies in the face of conventioal wisdom)

The .243 is a great cartridge. The fellows I know will shoot right with the .22-250 crowd out to about 250yds. with the 55/60 gr.bullets. And then walk all over them at 300/450 yds with heavier bullets to better fight the wind drift.

Arc has some very good points for long range shooting. Trouble is, with my(50+yr) old eyes, 250yds "IS" long range shooting.

.30 calibers have ruled true long range work for quite a while, and now we have the .50's. But on the other hand, our militery shooting teams still compete regularly out to 600/700 METERS with lightly reworked M-16's in .223"

Arc Angel · August 29, 2004, 08:48 PM

Hi, Sam!

That quote about, 'seat the bullet "AT LEAST" one caliber deep' comes from the second reply in this thread. I think 45 Vet has, already straightened it out.

What a great problem! I'll try to follow this thread until it's figured out. Obviously you really know what you're doing - How refreshing! Look, if it isn't a cruddy barrel, it isn’t a skewered bullet, and I’m positive it isn’t uneven case lengths and a correspondingly uneven crimp, (Because you wouldn’t make a mistake like that.) then, ‘What is it’? Not the powder, of course, because 3031 is an ideal powder for the 243; and you’re taking greater pains weighting it than, quite frankly, I ever have! As a matter of fact your reloading regimen almost duplicates that followed by the Army Marksmanship Team. Weight the bullets and you’ll be there - too!

So far we’ve got: 55, 80, and 95 grain bullets in play. What I don’t know is the difference, if any, between your, ‘old’, and, ‘new’ rounds? So, Sam, what’s your rifling? 1 turn in how many inches; and were you using identical weight bullets and bullet configurations in both your, ‘old’ and ‘new’ rounds? This is all I can think of; when you figure it out, please let me know.

YosemiteSam357 · August 30, 2004, 04:09 PM

Hey, I've got some 70gr Sierra Match Kings and some 87gr Hornady BTHPs to throw in the mix, too!

I'm going to double check case lengths; All test rounds were in once fired brass. No crimp. Barrel is 1 in 9.250" (Savage 12BVSS). There really should be no difference between the "old" and "new" rounds other than OAL, as they were both made on the same equipment. We're using a PACT digital scale and powder thrower combo, weighing every cartridge. (We're both engineers; it comes with the territory...)

FWIW, I'm using a lot of techniques out of Glenn Newick's "The Ultimate in Rifle Accuracy", AccurateReloading, and another looseleaf book on benchrest methodology that my reloading partner has.

More loading on Wednesday, shooting on Thursday. I'll post more results. I'm specifically going to load exactly the same load at the two different lengths, and see what I get for results. At least shooting them on the same day I'll be shooting under the same conditions.

-- Sam

P.S. Another thought I had: perhaps any runout/eccentricity of the bullet is exaggerated when it's seated less deeply into the cartridge, thereby imparting some weird spin/wobble on the bullet in flight. The only problem is, those 95gr bullets are seated pretty deep even when .010" from the lands.

YosemiteSam357 · September 3, 2004, 12:47 PM

Well, this week I got exactly the opposite results as compared to last week; The deeper-seated rounds peformed less well than the longer rounds, which is what one would expect. I'm sure it's not my record keeping, either. So I must conclude it's "me" and my technique.

I do believe heat is playing some role, too. My barrel gets pretty hot, and I need to start allowing it more time to cool between shots to get more consistent results. When I start getting mirage off the barrel, I know it's time to let it rest awhile.

Practice, practice, practice. Darn.

-- Sam

Arc Angel · September 5, 2004, 12:30 AM

Of course, Sam, the obvious - always the obvious! Now I get to say; 'Why didn't I think of that?'

mete · September 5, 2004, 07:18 AM

While 'touching the lands' and the length of throat has become the mantra for accuracy, no mention is made of the diameter of the throat !The larger the diameter of the throat the more the bullet can wobble.

August 27, 2004, 12:09 PM	#1
YosemiteSam357 Senior Member Join Date: April 8, 2002 Location: Oregon, USA Posts: 231	Bullet seating depth and accuracy I've been working up loads for a .243, recently started using an OAL gauge and comparator, and made my latest batch of loads to all be .010" off the lands. Upon shooting I was surprised to see much larger groups than I'd been getting previously. I then shot some leftovers from older loads, which were seated as far back as .10" off the lands, and got much better results with the same bullet weights and powder charges. In fact, some of the most accurate loads I've developed have been using 55gr bullets which have absolutely no chance of getting anywhere near the lands due to the short bullet length. This surprised the heck out of me. It seems to fly in the face of conventional wisdom, or at least everything I've read about the subject, which indicates that having the bullets as close to the lands as possible will provide the best accuracy. Yes, I know "every rifle is different", but this really surprises me. I mean, .10" off the lands? Is it possible that something else is going on here, or is it really not that uncommon? Any advice or commiseration will be appreciated. -- Sam P.S. Why is it that it seems very few people shoot the .243? It has a great trajectory, weight, accuracy potential, etc, but it seems no one talks about it much online. Is it just that it's not the latest whiz-bang trendy round to be foisted on us by the manufacturers, and not a military round?

August 27, 2004, 01:27 PM	#2
.45 Vet Senior Member Join Date: May 21, 2004 Location: Western Penn. Posts: 387	I've had just the opposite results with my .243 Bull BBL., but I"m shooting 80gr. SHP"s. Years ago an older gentleman advised me that when loading for rifles to always try to seat the bullet "AT LEAST" one caliber deep. Don't know if it's to provide better ignition or what. But sure seems to hold true in my guns with light bullets. Good Luck...... __________________ For those who've never fought for it, the price of freedom shall never be known...

August 28, 2004, 02:09 AM	#4
Arc Angel Senior Member Join Date: May 17, 2004 Posts: 284	OK Sam, Are you ready? Oh, boy, is this a, ‘loaded question’! First I share your fondness for the 243 – It’s one of my all time favorite rounds. For most serious long range work it’s a little light, though; consequently, it’ll never catch up with either the 308, the 30-06, or the 300mag. If you want to get really nit picking and fastidious about precision riflery you’ll need to take everything into consideration – not just; ‘I took some old loads and did much better with them.’ That truly doesn’t cut it with precision riflery. So, here we go: Get yourself some Sweet’s Australian and do a thorough cleaning job on that barrel. (Be careful with this stuff. Read the label and don’t over use it or let it sit in the barrel too long.) My suggestion would be to take the easy way out and start with new brass. Choose a powder that pretty well fills the case and measure it out by hand with a precision drop measure. You may have to load your rounds in batches of a dozen until you find the best match between bullet weight and velocity for the rifle you’re using. Make sure you use the proper bullet seater to avoid skewering the bullet, too. Before final assembly lamp blacken a round until it, just, engages the lands. Record the OAL and use it for all subsequent rounds. Keep accurate written records, too; or you’ll end up really confused about which round is which and for what rifle. (If you insist on using fired cartridge cases to make your ammo, then, turn the necks. Although it's not a crucial factor, don’t forget you’ve, still, got the cartridge head base dimensions to worry about; in this regard, you may, also, want to use, ‘half-length’ sizing dies that reform only the neck and shoulder area of the case.) If you use optics check your scope; make sure it’s properly mounted and tight. Try to get a hold of a rifle rest – sand bags and all. Now you’re ready to check for precision rifle accuracy. Limit your shots to groups of three each and let the barrel cool down between sets. While you’re waiting you can remove the bolt and quickly brush the barrel out. (There will be variation between the first and last shot fired in each set.) At some point before 5 or 6 ammo batches or 60 to 75 fired rounds you should know what your rifle likes to digest. This is a lot of work; but, if you like to consistently hit small targets between 200 and 300 yards out with that 243, it’s worth the effort. Seating the bullet deeper in order to improve ignition doesn’t make sense! If the charge is light and you want to keep it together, either, raise the muzzle prior to firing or use a filler on top of the powder. (There’s all different sorts of fillers from oatmeal to kapok; but most rifle rounds, and especially those intended for either competition or long range shooting, don’t require it.) About the only thing you’ll get with deeper seated bullets is increased pressure. It’s that little bullet jump to engage the lands that’ll affect accuracy more than any other single parameter – including neck concentricity. (Which if you want really accurate, consistent rifle rounds is worth the time to lathe out.) Sorry, but, that informal field test you’ve related means absolutely nothing with regard to serious precision rifle shooting. It isn’t going to tell you anything you want to know! By the way, what is, ‘One caliber deeper’? I’ve never heard that one before. __________________ ‘There are, only, two kinds of warriors in this world: Those who dream of war, and those who have nightmares about it. As for me? I dream of a better world. I dream of war!’

August 29, 2004, 06:56 PM	#6
.45 Vet Senior Member Join Date: May 21, 2004 Location: Western Penn. Posts: 387	Sorry for the confusion, was running late for work and didn't read what I wrote. What I meant was, if you're loading .30 cal. bullets, then to have at least .30" of bullet seated into the brass. I also find my rifle prefers the heavier(80-105gr), bullets seated .010/.015" from the lands. All well and good if your magazine will allow for the O.A.L. Your initial post only mentioned 55gr bullets, and they're probably seated .240" or so into the case neck. And as a result, are way off of the rifling. (this is the part that flies in the face of conventioal wisdom) The .243 is a great cartridge. The fellows I know will shoot right with the .22-250 crowd out to about 250yds. with the 55/60 gr.bullets. And then walk all over them at 300/450 yds with heavier bullets to better fight the wind drift. Arc has some very good points for long range shooting. Trouble is, with my(50+yr) old eyes, 250yds "IS" long range shooting. .30 calibers have ruled true long range work for quite a while, and now we have the .50's. But on the other hand, our militery shooting teams still compete regularly out to 600/700 METERS with lightly reworked M-16's in .223" __________________ For those who've never fought for it, the price of freedom shall never be known...

August 29, 2004, 08:48 PM	#7
Arc Angel Senior Member Join Date: May 17, 2004 Posts: 284	Hi, Sam! That quote about, 'seat the bullet "AT LEAST" one caliber deep' comes from the second reply in this thread. I think 45 Vet has, already straightened it out. What a great problem! I'll try to follow this thread until it's figured out. Obviously you really know what you're doing - How refreshing! Look, if it isn't a cruddy barrel, it isn’t a skewered bullet, and I’m positive it isn’t uneven case lengths and a correspondingly uneven crimp, (Because you wouldn’t make a mistake like that.) then, ‘What is it’? Not the powder, of course, because 3031 is an ideal powder for the 243; and you’re taking greater pains weighting it than, quite frankly, I ever have! As a matter of fact your reloading regimen almost duplicates that followed by the Army Marksmanship Team. Weight the bullets and you’ll be there - too! So far we’ve got: 55, 80, and 95 grain bullets in play. What I don’t know is the difference, if any, between your, ‘old’, and, ‘new’ rounds? So, Sam, what’s your rifling? 1 turn in how many inches; and were you using identical weight bullets and bullet configurations in both your, ‘old’ and ‘new’ rounds? This is all I can think of; when you figure it out, please let me know. __________________ ‘There are, only, two kinds of warriors in this world: Those who dream of war, and those who have nightmares about it. As for me? I dream of a better world. I dream of war!’

August 30, 2004, 04:09 PM	#8
YosemiteSam357 Senior Member Join Date: April 8, 2002 Location: Oregon, USA Posts: 231	Hey, I've got some 70gr Sierra Match Kings and some 87gr Hornady BTHPs to throw in the mix, too! I'm going to double check case lengths; All test rounds were in once fired brass. No crimp. Barrel is 1 in 9.250" (Savage 12BVSS). There really should be no difference between the "old" and "new" rounds other than OAL, as they were both made on the same equipment. We're using a PACT digital scale and powder thrower combo, weighing every cartridge. (We're both engineers; it comes with the territory...) FWIW, I'm using a lot of techniques out of Glenn Newick's "The Ultimate in Rifle Accuracy", AccurateReloading, and another looseleaf book on benchrest methodology that my reloading partner has. More loading on Wednesday, shooting on Thursday. I'll post more results. I'm specifically going to load exactly the same load at the two different lengths, and see what I get for results. At least shooting them on the same day I'll be shooting under the same conditions. -- Sam P.S. Another thought I had: perhaps any runout/eccentricity of the bullet is exaggerated when it's seated less deeply into the cartridge, thereby imparting some weird spin/wobble on the bullet in flight. The only problem is, those 95gr bullets are seated pretty deep even when .010" from the lands.

September 3, 2004, 12:47 PM	#9
YosemiteSam357 Senior Member Join Date: April 8, 2002 Location: Oregon, USA Posts: 231	Conclusion: It's me Well, this week I got exactly the opposite results as compared to last week; The deeper-seated rounds peformed less well than the longer rounds, which is what one would expect. I'm sure it's not my record keeping, either. So I must conclude it's "me" and my technique. I do believe heat is playing some role, too. My barrel gets pretty hot, and I need to start allowing it more time to cool between shots to get more consistent results. When I start getting mirage off the barrel, I know it's time to let it rest awhile. Practice, practice, practice. Darn. -- Sam

September 5, 2004, 12:30 AM	#10
Arc Angel Senior Member Join Date: May 17, 2004 Posts: 284	Of course, Sam, the obvious - always the obvious! Now I get to say; 'Why didn't I think of that?' __________________ ‘There are, only, two kinds of warriors in this world: Those who dream of war, and those who have nightmares about it. As for me? I dream of a better world. I dream of war!’

September 5, 2004, 07:18 AM	#11
mete Senior Member Join Date: June 14, 2004 Location: NY State Posts: 6,575	While 'touching the lands' and the length of throat has become the mantra for accuracy, no mention is made of the diameter of the throat !The larger the diameter of the throat the more the bullet can wobble.