May not be excessive pressure but probably an increase in pressure because the pressure will have to build higher to push the bullet into the rifling than it will it is can move freely for a short distance first. Yet again, seating the bullet longer with the same powder charge increases case capacity and should decrease the pressure. Using an AR-15 (16" NATO barrel) and LeHigh 55g bullets with CFE223, loaded to 2.260" 28.4g averaged 3,045 fps. The same round with a COL of 2.300" dropped the average velocity to 3,014. It took an additional 4/10 grains of powder to get back the velocity, 28.8g averaged 3,050 fps.
Bullet Seating Depth and Pressure
- Thread starter South Pender
- Start date
Northridge
Gold $$ Contributor
accurate seating depth measurement? All this talk about how precise one method is compared to another really does not matter at the end of the day. all methods of finding" zero "are flawed even if they where not other aspects of your reloading are constantly different or changing every time you start a new cycle be it brass, powder, primers time of day that your shooting etc. every outing is a variation of some base line and likely will benefit from a slight tweak to draw the best out of it, sometimes slight and some times drastic. seating zero is only a changing reference that needs verified through some "ladder test "or another every series and not assumed. not to say this is all way achievable because of range restraints, time etc. but its the most efficient way to keep a rifle tuned at its ragged edge. its human nature as a whole to try and find the quickest way from A to Z with out personal effort out, but the beauty of it is not one aspect or another is a line item on a "check list" to success. we all are dealing with a sliding scale that really is never constant but changing & our personal willingness to verify or not is up to each of us. once you find your initial "zero" touch you really do not have to regress back once loaded round money spot has been found. just continue to do refined ladders as your season & throat advances. A few thousands on either side of changing money depth each ladder should suffice if monitoring zero tweaks you out....
pressure with in reason is your friend,use it to find the most officiant tune you can, not all way lowest single digit ES or highest velocity. view powder as a means to get the show going & seating as the fine control when exterior ballistics begin.
In finding the best tune on a given day I recommend leaving Science at the gate, let the rifle make decisions not your buddies.
Shawn Williams
pressure with in reason is your friend,use it to find the most officiant tune you can, not all way lowest single digit ES or highest velocity. view powder as a means to get the show going & seating as the fine control when exterior ballistics begin.
In finding the best tune on a given day I recommend leaving Science at the gate, let the rifle make decisions not your buddies.
Shawn Williams
dmoran
Donovan Moran
Yes... that is what I am saying. Example:
Say I measure one of my rifles for touch/zero, and I get 1.830" comparator measurement.
Now say I want to seat 15-rounds at that touch/zero number.
When I get done all 15 rounds will measure 1.830" ( +/-.0005-thousandths)
As can and do many of my fellow competitors !.!.!
Donovan
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It's not really hard to get all loaded rounds to have the same BTO measurement, it just takes time. Seat long, measure BTO, adjust the micrometer dial, re-seat, re-measure, repeat as necessary. They'll be +/-0.0005" of target if your tools and measurement technique are capable of that kind of accuracy.
But isn't this sort of a trick question? There isn't really any tolerance allowed if the goal is strictly "touch". Given a +/- 5 ten-thousandths range some will not touch and some will more than touch. Is that 0.001" range more important when the target is "touch" vs when the target is 0.010" OTL? or 0.005" ITL?
dmoran
Donovan Moran
From segregated bullets, a good seater die, and the right neck preparation, have no problem getting spot on consistent seating depths in one stroke (no readjustments needed). Inline dies work best - IME.
Donovan
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Sounds to me like ego-speak. I don't doubt you can get a consistent BTO, I do that all the time, that was never the question. The question is how absolutely sure you are that it is actually touch length.
Even if one could, since we are consistently getting throat wear, it is still a fool's errand to use a load that "just kiss the rifling".
I can shoot 3 seasons, (about 900 rounds) in a 300 WSM and i only get .004 to .005 throat wear. Not all guns move much. Another reason to shoot .010 or more in the lands. It wont matter if it moved one or two since the last shoot.
If you keep your throat clean it is not hard to tell where touch is. MATT
dmoran
Donovan Moran
It is relatively easy, since I check for touch/zero every time before seating bullets.
To maintain precise seating depth to the lands/rifling, it is necessary and part of the ritual of staying "in tune", regardless of the elected position we seat them at.
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Well if you can't set your die up for a certain base to ogive measurement and hold that measurement within a .001 for a loading session something is wrong with your setup.
I use sorted berger bullets, 21st century shooting hydro press and wilson micro in line dies and can easily keep a loading session dead on seating depth. I also can easily vary that seating depth either way by a thousandth.
This seems to be a stupid/ludicrous discussion. With the weight of a loaded round which also has significant contact with the chamber, who the hell can tell if the ogive is just touching the lands vs. being slide into it say a thousands or being a thousand off?
Given the whole idea of loading to touch is just plain stupid to begin with for obvious reasons already mentioned. I am done wasting my time trading who has a longer dick discussion. Please get a life people…
Given the whole idea of loading to touch is just plain stupid to begin with for obvious reasons already mentioned. I am done wasting my time trading who has a longer dick discussion. Please get a life people…
Northridge
Gold $$ Contributor
jlow I would agree things do get long in the tooth at times. I think there is a miss conception on why we or at least why I keep track of a touch location, my intent is never to shoot or load at" zero" touch but it gives a loose reference to your target seating be it into the throat a given distance or a jump location. I think the lion share who have shot or tested at zero will get poor results at best, if your not sure perform a ladder test of some kind and I think most will come to a similar conclusion. happy tuning guys.
Shawn Williams
100% agreed.
Stupid /Ludicrous for you or simple for me.The question of how this is done would be of more value to others.
For me I use a wooden dowel inserted into the muzzle.I just barely seat the bullet into a case(way too long) .Then with one hand insert the round into the chamberand use my finger to push the round until I feel resistance.With my other hand I can push on the wood dowel.I can push back and forth to get just touching. Mark the dowel ,push the cartridge out close the bolt ,push the dowel in to a closed bolt face ,mark dowel again.
Try it it's not too hard.
John
BoydAllen
Gold $$ Contributor
There is a longstanding flawed procedure that is commonly used. We see it in primer tests and seating depth as well. When you change something that can effect pressure and timing to the muzzle you really need to play with the other variables with that change held constant. For example, we have some evidence that tuning nodes are related to velocity, but when we try different primers we may get different velocities, some of which may be out of the node velocity range. The only way that we can do a good test is to play with charge a little with each primer so that we establish the best tune with that primer. Similarly, if we make a substantial change in seating depth with regard to position relative to "touch" I believe that backing off and retuning is the appropriate method. If you are really touching, or more likely slightly into the lands based on Hornady tool measurement then you will not see a large increase in pressure going a little farther into the lands, but that does not mean that you will be in your best tune with the same powder charge. On the soft seating thing, some powders like more neck tension, more than is feasible to soft seat with, so you may want to do some testing to see what your powder likes. Again this would involve some tuning at each neck tension to see what the best available result would be for each.
Opinions vary. I say what works for you.
I find it very easy to hold OAL to less than .001.
Now the moving target of throat erosion gives validity to your argument.
This may be a little off topic but i am including it because it very well could impact those to the lands measurements
Just recently i became aware of another possible issue. The dreaded carbon ring. Looking at the pics below in the first one you can see carbon is begining to bury the begining of the lands. Now this is a new barrel with no more than 200 rounds through it. I clean after every range session and really thought this barrel was clean. I could imagine what the throat would look like after 5 or 6 hundred rounds without this special attention
The next picture is after a little special attention on the throat.
Just curious, since the bullet engages the rifling for the first time right there, what would be the impact for allowing carbon to continue to build up here?
Would the fact that you aren't engaging the rifling until further down the barrel impact those measurements to the lands?
I already know my rifle shoots about a tenth better since i started cleaning this area
Good point raised by you both. Seating to what I have measured as "just touching" with the Hornady (Stoney Point) tool will probably mean that some are just a hair (maybe .002 ) off the lands, and some just a hair into the lands. So maybe best to seat some to be, maybe, .005 off the lands, and the others various distances into the lands.
Perhaps a good plan of action would be to set up four depths: (1) .01" OTL; (2) .005 OTL; (3) .005 ITL; and (4) .01 ITL. Or should the differences be greater, such as .02" and .01" OTL and .01" and .02" ITL? I would have all the loads with the same powder charge to test solely for seating depth effects in this rifle.
Well i would start with a .010 jam then .005 off and.continue .005 increments till you find your seating depth.
Then with your new found seating depth do an OCW TEST
then with your new found charge weight fine tune seating depth.
I always run an OCW test jammed .010 to start. But then i am just.going to run them jammed anyway.
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