Seating depth accuracy (tip to ogive)?

[CZ550]

Ok if I am seating bullets into the lands shouldn't tip to ogive be more important than base to ogive? I am struggling with consistent seating depth it will vary and I think it relates to the contact of seating stem. I was thinking if I sorted bullets by tip to ogive I might get more consistent seating depth.

If I am trying to achieve a certain amount of contact with the rifling it would appear to me that tip to ogive would be more important for accuracy.

Anyone got the same idea?

 

[CZ550]

Well let me put it another way.

Seater stem to ogive measurement.

Not sure how to measure but I am gonna try.

 

[woolenmammoth]

are you seating with hand dies or threaded dies? I went crazy with inconsistent seating depth, measured everything under the sun and then when I switched to hand dies and an arbor press the problem became instantly apparent: inconsistent neck tension. You can easily feel some cases seat easier or harder with hand dies, makes culling those much easier to do. Never could feel that on a press with threaded dies. Doesnt directly address your question, but might be the answer...

 

[CZ550]

I use redding and forester seating dies.

How does neck tension effect how far my seater seats a bullet?

The last batch of Bergers I was working with were horrible as far as consistency goes.

 

[lmorrison17]

Looky here!
http://greensrifles.com/New_Products.html

 

[CZ550]

Looky here!
http://greensrifles.com/New_Products.html

Now that's what I am thinking. Doesn't look like he offers .284.
I was also thinking I could use redding comp seater and back it off .005 every time and fine tune each bullet? I know it would be slow but that's okay.

 

[sailhertoo]

Well let me put it another way.

Seater stem to ogive measurement.

Not sure how to measure but I am gonna try.

I know exactly what your talking about and I've thought about this alot too. That seems to me would be an important measurement to sort bullets by.

On sorting by over all length, I don't do that. I sort by the measurement taken from the ogive on the point of the bullet to the ogive on the boat tail of the bullet. This gives the same friction area for sorted bullets to travel down the barrel which seems would be more important than the over all length. In other words you measure the bullet surface that rides the bore.

Does that make sense?

 

[CZ550]

Makes perfect sense but I want my bullets engaged in the rifling excactly the same every time which seems important to me. Iam not happy with curent variations I am getting.

If one bullet is 7thou in and the next is 3 and then you have one that is 11 thou that has to affect accuracy. And I can easily get 3 to 4 thou variations here and there.

 

[BoydAllen]

I believe that arbor press seaters may have an edge in the area that you are looking at, and I have been told that opening up the seater stems so that they make contact much closer to where the rifling contacts the bullet can be helpful. As far as measuring the variations in the distance between seater stem contact to rifling contact from bullet to bullet goes, I believe that you can use a pair of inserts for a Hornady/ Stoney Point ogive length attachment, and make up a spreadsheet , that subtracts one measurement from the other. Obviously, this would be slow, but it can be done. One insert should hit the ogive where the rifling does, and the other where the seater stem does. I have looked into this and the big problem is that with larger ogive numbers that are the rule in high BC bullets the point where the rifling makes contact is so near to parallel, that measuring technique becomes unacceptably critical. If you remeasure the same bullet several times, it will show considerable variation. I have not found a way around this problem....yet.

 

[JaxCatm]

I have taken to measuring each bullet and sorting by the .001 into batches then seating by the batch very consistent OAL. Another problem may be your seater stem. Buy a seater die from Forster and send the stem to them with 3 bullets of the type you would like to shoot. They will machine the stem to the particular bullet ogive and if you sort them into batches then your problem should go away.

 

[Erik Cortina]

I don't understand how you guys can get so much variance. I have used Redding and Wilson dies and my base to ogive measurements is always dead on on all my loaded rounds, and I load quite a few!

What I do is when I get a new die, I take a bullet that I'm planning to use and chuck it up in a drill. I then apply IOSSO on the bullet and inside the seating stem and spin the bullet inside the stem applying pressure. This provides a perfect fit between bullet and seating stem.

 

[lynn]

Erik Cortina
If you are loading mass produced bullets like Berger VLD's you will get batches with 0.013 variation.
There is no way on planet earth you can open up a seater stem that will correct for that much variation.
A typical seaing stem runs 0.219 or less at it widest point and that is only because they are bellmouthed.If your rifling is 0.242- 0.243 your seating depth will be all over the place when checking with a comparator.
A very easy check is to seat 50 rounds then measure them with a 22 caliper comparator then a 6mm comparator.One represents your seating stem while the other represents your bore if your shooting a 6mm chambering.
If all of your rounds are coming out great whebn measured with a comparator you can buy all of my future bullets as you are one lucky guy.

CZ550
Seat each bulet 0.015 long and adjust as necessary.You can then and only then achieve the kind of accuracy your after with the vld type bullets.
Lynn

 

[JaxCatm]

I agree with Lynn that bullets will vary by lot. Prime example ran out of Sierra 168 Match Kings last night at my bench. So I walked over to my supply shelf and grabbed a new box to finish off the last four rounds of the ammo I was loading. As is my norm I measured each round to sort them. Each and every one of those bullets was .009-.011 shorter than the batch I had just finished off. Does that mean my remaining four rounds of ammo came out a shorter length? No I just measured for the same length and adjusted the die for .009 compensation. Part of what makes redding seating dies so accurate is they are cut for very common bullet profiles. For example the Redding 30 match seating die stems are cut to match the Sierra 168 SMK bullet which also shares the same profile as the 175 SMK. BTW Redding will make custom seating stems for you and the cost is very low. This in my opinion is much more precise then trying to hone/machine items at home by hand.

 

[CZ550]

Lynn I think I am gonna start seating my bullets like you said. It might be completely unnecessary in some eyes but every variable I can control is one less thing for me to wonder about.

Corey

 

[lpreddick]

the thickness of the brass in the neck does vary. the tip is the thinest and thickens as one goes to the neck /shoulder junction,. i use neck bushing dies and have noticed that during bullet seating that the pressure i have to exert to seat the bullet increases as the bullet goes down the neck. if the pressure ring of the bullet goes past the neck shoulder juncture i feel a definite change in resistance. if i keep the bullet base in the neck and adjust the seating depth, there is varing neck tension depending on how far into the neck the bullet base goes. to correct this i have resorted to neck turning. i neck size with the appropriate bushing, expand the neck with the expander and turn the neck taking off the thinnest amount of brass to "clean" the neck. i like to see no brass coming off the neck for the first 1 millimeter or so, followed by a thin strip on brass and noticing this strip getting thicker as i approach the neck/shoulder juncture. i envision the thickness of the neck brass to be very consistent from tip to shoulder. now when i seat bullets i can feel a consistent resistence all the way down the neck, noticing a very slight change if i go into the case. i think all this bother makes a difference in accuracy. i also believe my runout is less since neck tension is more uniform. my 2 cents.[/quote] if i can see you, i can touch you. BANG!

 

[sailhertoo]

I'm all with what you're saying.

 

[fordwrench]

reading the above post i have to wonder about neck tension remaining consistent as the brass starts to harden? some will say anneal other may say neck turn. i understand that.. but if you have "your best " load and neck tension increases the more you fire the cases as felt on the Wilson die, is it best to seat long and sneak up on your oal measurement to match all cases to your depth? change to a looser bushing? or work on cleaning the necks and use some sort of dry neck lube or moly to ease seating for more consistency? also Ive heard guys having good luck sorting by ojive, but i can still see the chance for rounds having variance? lastly, if you were to seat with a threaded die on a co ax press, you would have even more variance because of the loose fitting slot the die settles in ? who's got the answer? for now i have been letting the target do the talking. a fellow member alf said it best... dont argue with your gun... any thoughts?

 

[BoydAllen]

With the relatively thin turned necks for my 6PPC I find the after sizing neck spring back increases as the brass work hardens(increasing OD). This tends to compensate for the work hardening because the expansion of the neck when the bullet is seated is decreased. IMO the thinner the necks, the less the absolute value of the differences in bullet pull caused by differences in brass hardness.

 

[lpreddick]

fordwrench: once i get my necks uniform in thickness after turning, i shoot that case 3-5 times then pay attention to the resistence to seating the bullet. i frequently lubricate the moving parts of my press so i can feel precisely the resistence. if it is increasing i anneal all the cases in that group. the reduced resistence to seating is gone. i'v tried dry lubes to bullets but i can't get uniformity. measuring bullet bbase to ogive doesen't actually measure the point on the bullet that actually contacts the lands. the inserts for my hornady device clamped to my comperator have openings slightly smaller than the lands diameter in the barrel. thought about drilling the openings of the insert to match the diameter in my barrel since we have noticed varing base to ogive on bullets in the same box, sometimes 5-10 thous and this has to make a difference. 2000 variables and we have some control over about a dozen...now i understand why i shoot two thru the same hole and the third goes off to the side! [/quote] if i can see you, i can touch you. BANG!

 

[fordwrench]

i did a little research on this last night and what Ive found out is suprising. boyd, your experience with the thin necks of the ppc cases help the problem but really mask whats really happening. first, all the snake oil in the world isn't the answer. no lubes.. loaded neck round diameter vs. chamber diameter is the main problem in needing to anneal the brass. the more work to the brass within reason is where it starts. from there reamer design is the answer to the problem. modified reamers done by people who know way more than me along with the right neck clearance from the get go is where its at. lastly some folks with new calibers{newer reamer designs} may correct the problems from the start without the end user running into problem that other users do. all cartridges are not created equal...