How to combine OCW with optimal seating depth.

[jlow]

My question is how best to combine OCW with adjusting the bullet seating depth?

In theory, it appears that both OCW which requires different amounts of powder with fixed seating depth, and adjusting bullet seating depth with fixed amounts of powder would both affect case pressure and thus bullet MV, and thus the sweet spot. What I am interested in is finding an efficient method which uses both of these techniques.

For example, one possibility would be to do OCW development first, find the best sweet spot and then using that powder weight and then vary the bullet seating depth. The question is would this lead me to the most reproducible load?

Another question is if I vary seating depth (<span style="text-decoration: underline">Not to the lands </span>– looking for something mag length) and start at recommended OAL, should I decrease OAL and by how much in each step.

 

[fireguyty]

Re: How to combine OCW with optimal seating depth.

I do OCW for powder weight at maximum mag seating depth. Then once I am happy with one, do OCW with that powder charge starting at mag seating depth and decreasing seating depth by .015 for however many you want (I usually do 5). Of course that .015 varies greatly depending on what caliber I am loading for (204 Ruger vs 338 Lapua for example).

This is what works for me. I am sure others will have different ideas.

As always be aware that in changing things you are always needing to be checking for signs of pressure.

 

[Tripwire]

Re: How to combine OCW with optimal seating depth.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">My question is how best to combine OCW with adjusting the bullet seating depth?

In theory, it appears that both OCW which requires different amounts of powder with fixed seating depth, and adjusting bullet seating depth with fixed amounts of powder would both affect case pressure and thus bullet MV, and thus the sweet spot. What I am interested in is finding an efficient method which uses both of these techniques.

For example, one possibility would be to do OCW development first, find the best sweet spot and then using that powder weight and then vary the bullet seating depth. </div></div>

Correct........

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">
The question is would this lead me to the most reproducible load?
</div></div>

It will lead you to the best load your rifle will shoot with that combination of components, if you are doing it right. The degree of "reproducible" you find is entirely up to you, your load practices, and the gear you use.

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Thanks for the responses and info guys!

So fireguyty, it seems you do a complete OCW with each reduction in seating depth? Do you then compare 5 rounds groups of the best powder weight at each seating depth? Yes, I always go from low to high powder weight and check for pressure signs after each round.

Tripwire, it seems that you do the more abbreviated method as I describe which is one OCW follow by using the optimal powder weight with decreasing seating depth – Has anyone done both methods and compared the two?

 

[doc76251]

Re: How to combine OCW with optimal seating depth.

In general since the powder charge is the largest "volume" variable that is the one you change first to develop the "node" in which the POI is the same over a spread of powder charges.

Once you attain the spread, you pick the one that will allow you the greatest flexibility in temperature that you will be shooting in. If you did your load dev at 70*F but you spend 3/4 of the year in the 20's - 40's you may want to choose a load that is close to the last 1/4 of the spread to cover the "average" temp you are in. Temperature is the biggest non controllable variable you have to contend with.

Once you pick the powder weight inside the "node" you play with the seating depth to "round out" the group. I find that varying the seating depth by more that 0.2" from your zero length creates more problems than it solves and you end up chasing your tail.

Cheers,

Doc

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Doc7651,

Thanks a lot for your input. Removing the larger variable first makes complete sense to me and really makes it easier for me to understand which should go first.

Your comment regarding “greatest flexibility in temperature” also makes sense although I must admit that I had not heard or thought of this at all before today…

So when you say “last 1/4 of the spread”, this would be the greater powder of the node? For example, if the load was clustering together between 41.50, 41.75, 42.00, and 42.25 gr, one might want to choose 42.25 gr if as you say the load was developed at 70F but I spend ¾ of the year in the 20-40’s? My assumption is that as the temps drop, the amount of pressure/MV produced by the powder would drop – is that right?

Thanks for the <0.2” recommendation, that gives me something to work with.

Wonderful info! I thank you very much!

 

[doc76251]

Re: How to combine OCW with optimal seating depth.

Just to add on to complete the thought process which I often neglect as obvious to me is powder selection. I research A LOT to ensure that I am searching for nodes with powders that net me at or near 100% case capacity. This is the part where I go "IMHO, YRMV etc." because this is a thinking man's game and if you don't know what your about you could end up with a problem.

As far as choosing the last charge of a node, I don't as on occasion it get's hot. Analytically I would say that I stay at 20% off the end node even if I'm doing load dev at 90*F.

In my case "IMHO, YRMV etc....." I chose 44.0 of Varget under a 178AMAX/175SMK as the end of the node was at 45. and the beginning was at 42.8 but I did final development at 90*F. What I now have is a POI stable round that covers 20*F (coldest I've shot) to 110*F (hottest). Essentially from 20*F to 110*F I am w/i a 1" pasty at 100 yards at any temp. With that I have dope cards to correct for the velocity changes due to temp.

On Ogive length I started 0.001" off the lands, played with it and ended up going back to it. It fits in my AR-10 mags as well as my bolt gun mag so no issues in either.

Hope that closed the loop some.

Cheers,

Doc

 

[taseal]

Re: How to combine OCW with optimal seating depth.

the hotter it is, the less powder charge you want.

so if you did ur load dev at 70 degrees, but you shoot at 20-40 deg weather, you'd wanna use say 55.8 if your POI was same at 55.4-55.6-55.8-56

me for example, live in S FL. so in my case I'd be doing my load dev right now at 90+ degree weather. so I'd probably pick 55.4 or 55.6 (knowing me, I'd probably pick 55.6)

once you get that done, you can play with the seating. +/- .02. make 5 rounds each at .00, +.01, +.015, +.02 and -.01, -.015, -.02

see what groups the tightest with that.

if you want, you can clean every 5 rounds to start with a clean barrel. wait a little between for the barrel to cool as well. I'd probably just get use my bore snake and do 2 pulls through every 5 rounds. it won't hurt, and bore snake takes a min to do, and is portable compared to a 40" cleaning rod

Hope this helps. I was really confused about OCW, but I think it's better for consistent loads, and also you can work at 100 yards if you have no 200-300 yards for the ladder test (which I don't)

 

[doc76251]

Re: How to combine OCW with optimal seating depth.

If you clean between rounds on an OCW you are wasting your time. Just say'n.

Cheers,

Doc

 

[taseal]

Re: How to combine OCW with optimal seating depth.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: doc76251</div><div class="ubbcode-body">If you clean between rounds on an OCW you are wasting your time. Just say'n.

Cheers,

Doc </div></div>

not during OCW, but during finding optimal seating depth.

yeah, maybe every 5 rounds is overkill, but it's a quick pull of a rope with boresnake.

 

[doc76251]

Re: How to combine OCW with optimal seating depth.

I'm not going to derail this topic with a debate on cleaning but IMHO if your rifle can't handle 100 or more rounds of sustained accurate fire without being cleaned.....your rifle has a problem.

Dragging a bore snake through a tube while doing a round robin will totally skew your results, period.

Cheers,

Doc

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Doc76251 – thanks for the additional info. The choice of powder with nodes near 100% case capacity is a very good thought – will keep that in mind. Wow, 0.001” off the lands and still mag length! I don’t think I would be quite that lucky, but I appreciate hearing that it is possible.

Taseal – thanks for the input and explanation, fit my thoughts exactly. Will try your seating steps and see how it goes. Plan to do mine at 200 yards since that is the one I have best access to.

 

[Tripwire]

Re: How to combine OCW with optimal seating depth.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">

Tripwire, it seems that you do the more abbreviated method as I describe which is one OCW follow by using the optimal powder weight with decreasing seating depth – Has anyone done both methods and compared the two?
</div></div>

I don't think it's a conscious effort at abbreviation for abbreviation's sake. I shoot load development at 200 yards because it puts more dispersion between the good and the bad, and I get to the right decision quicker. Shooting for an OCW I'm looking for at least a full grain worth of powder weights which translates to a range of pressures, that will all fall into the same point of impact with the same point of aim. If your rifle is good enough, and if you are good enough, and with perfect environmental conditions, it can be done with .2 grain incremental increases, and only one round for each. I usually find something to work with by starting at about half way up the load parameter, increase my charges by .2 grains, load three of each, and shoot round robin over a chrono.

In my experience, with just about everything I've developed a load for, I'll find a "node" at about 2/3's the way up a load parameter, and one that's very near a max charge. These two are the most useful to me, and the rest is just noise. I usually go with the faster one, and take the middle of that node's range as my load. This gives me at least half a grain above, and half a grain below, whichs means my load has that much tolerance to pressure variables. Which translates into a better tolerance for variations in ambient temp, altitude, component lot numbers, case capacity, etc.

With that OCW set in stone, the "groups" may or may not be "good". To get my "groups" "gooder" I adjust the seating depth above and below the "zero" that I used to get the OCW. This zero is usually .020" or so shorter than my mag length, whatever seems to feed the best and still give me a little room to increase the COAL if need be. Most changes to seating depth to refine the load are VERY small, and the wrong way is VERY noticable. I don't worship the Gods of the Lands so mag box constraints are a mute point. One of the best loads I ever found for a .270 I once had was with a 90 grain hollow point that jumped .250" to the lands........literally drove tacks.

Get your charge weight nailed down with a seating depth that functions as you need it too. Then refine it with very small changes to COAL one way or the other.

You call it abbreviated, I call it K.I.S.S.........

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Thanks Tripwire. I did not mean anything negative with the word “abbreviated”, in fact I look at it as potentially “efficient” which is what I am looking for i.e. load development that takes the smallest amount of components but at the same time does not sacrifice quality. KISS is in fact the name of the game and the rationale for using OCW development.

I also agree with you regarding the use of at least 200 yards for OCW development. In my own limited used of this technique, I find the groups usually too tight at 100 yards and interpretation difficult. One new thing I have been doing is to set a video camera close (20 yards) from the target, turn it on, return to the line to shoot, and retrieving the camera at the end of the string. This makes figuring which round going to where much easier to determine.

We are pretty much in total agreement in which node to use. Looking forward to doing this with my new precision upper. Thanks again!

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Another question which is an extension of the original.

So assuming that I find the sweet spot using the OCW method and I am going to explore the seating depth. My initial plan was to follow what has been suggested thus far, which is to load five round of each seating depth, shoot them and find the depth that give me the tightest group.

However, to continue with the idea of doing this as efficiently as possible, I am now wondering if it is possible to do an OCW using a single round at each seating depth. I understand that the original OCW method was to test rounds with different amounts of powder, but it would seem that this same method would also potentially be useful for looking at various seating depth. Presumably a sweet/node seating depth would also be there where the rounds would cluster before one gets a dispersion as one leaves this area. If this is the case, it would potentially allow one to get a good map of the seating depth depending node area.

Does this make sense? Has anyone tried this?

 

[doc76251]

Re: How to combine OCW with optimal seating depth.

You "could" achieve and OCW with one round as was opined but when you go to seating depth you are now looking for group size/consistency. One round does not a group make.

Cheers,

Doc

 

[Tripwire]

Re: How to combine OCW with optimal seating depth.

Load development is nothing more than a disciplined system of trial and error based on results found by observing the physics of what's going on.

Pretty simple really......

The rule of any scientific experiment involving changing variables is to change only one thing at a time so that the result can be clearly seen. Trying to incorporate changes in seating depth with changes in charge weight at the same time is counter productive in my opinion concerning the goals we intend to arrive at.

Do one or the other first, then try to refine upon that secondly.......it's only time and money, not the end of the world.

The most efficient way I've found is to quickly rough in my pressure range with changes in powder weight, then see if a seating depth change makes this better or worse.

An OCW work up takes me anywhere from 15 to 20 rounds under pristine conditions, a seating depth refinement takes three rounds of the control that I used to get the OCW, and one or two groups of three above and below that control to see if it helps or hurts. Bad is quick to see with very small changes so once it starts to go bad there's no point going further in that direction. Good must be, and usually is, the other way.

Once that work is done I know I'm either right at an optimal load, or extremely close. I'll then load up 20 or 30 rounds of what I've settled on and shoot for groups at ranges other than what I've tested already. If that meets the criterea then I'll load up another batch of 20 or 30 rounds and shoot this load against a calced dope sheet to confirm or deny that data. What I actually shoot is edited into the dope as real world.

By this time I'm quite confident I'm good to go......

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Doc76251 – is OCW using different powder weights not looking for group size/consistency? One round definitely does not a group make, but in both cases you will have to confirm with at least a 10 round group.

Tripwire - I think you misunderstand my question. I am <span style="text-decoration: underline">not </span>proposing to do both OCW with different powder weights and OCW with different seating depths at the same time. What I am proposing is to do OCW with different powder weight first, confirm the finding with 10 round groups, then come back with an OCW using different seating depths (at that optimal powder weight), and then of course confirming the finding with 10 round groups.

 

[Tripwire]

Re: How to combine OCW with optimal seating depth.

Okay, I probably did misread you, no harm no foul.

I still stand on my methodology as efficient enough to get the job done.........

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Not a problem, it's easy to misunderstand. Just trying to think out of the box here.

 

[doc76251]

Re: How to combine OCW with optimal seating depth.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jlow</div><div class="ubbcode-body">Doc76251 – is OCW using different powder weights not looking for group size/consistency? One round definitely does not a group make, but in both cases you will have to confirm with at least a 10 round group.
</div></div>

In simple terms and in accordance with the OCW process ...... NO. OCW to quote a phrase is about Location, Location, Location...... and did I mention Location. Is it nice and should you expect good groups from well made ammo? Yes! BUT. It is not a requisite to finding the point where the vibrations are furthest from the muzzle resulting in stable POI to POI placement over a range of charge weights.

IMHO, I will find the most accurate group via seating depth AFTER I determine where the "flat spot" in the group location is. This is why I load 10 of each seating depth AFTER I determine the charge weight.

FWIW Tripwire and I (I believe) are singing from the same page, he just does his at 200 - 300 and I prefer to do mine at 100 and confirm out to 1K+ if capable.

With careful loading and precise shot placement (or documentation to the contrary) you should KNOW where the OCW is and how far you can push the envelope in either direction after your first range trip. After that you can futz with the seating depth to your hearts content and it will not vary your OCW load to any great degree until you start pushing into the edges of the OCW either by pressure (seating depth - this takes a lot to get to the edge BTW) or temperature variations.

I opined either on this thread or another that the choice of an OCW load should be predicated on the ambient conditions that you shoot in the most AND based on the conditions when you did the OCW test. For instance, if you do the OCW on a 90*F day but 3/4 of the year is spent shooting at 40 - 70*F you could safely choose a higher charge weight (not the last charge) and be good from say 110*F down to 20*F which is what my pet 308 load does. The closer you get to either end of the range obviously the less stable things will be.

I know that when I set my zero that on a 60 - 70*F day the round will pinwheel the X. On a 90*F day I need to subtract a click (1/4 IPHY) to my dope, conversely on a 30*F day I know I need to add a click to achieve the pinwheel X. I also know that on any given day I am no more or less than 1/4 IPHY from center at 100 yards.

I choose which dope card I use based on temperature. I have a 30*F, a 50*F, a 70*F and a 90*F dope card (2 pages) for my given location. I know that if it's warm I choose the 70* card, if it's cold I choose the 50* card, if its HOT I choose the 90* card and if it's real cold I choose the 30* card. All this is derived from the OCW process and my CBS is rarely off on elevation by more than a 1/2 IPHY out to 1K providing the loose nut behind the trigger is sufficiently tight

You will note that I have said nadda squat about wind

Cheers,

Doc

 

[jlow]

Re: How to combine OCW with optimal seating depth.

Doc76251 – not sure why you think we disagree?

I stated clearly that what I am proposing is to do a regular OCW and confirm with a 10 round group, then follow by another ladder (I used OCW before but this is misleading as I am changing seating depth and not powder weight this second time around) using single rounds with different seating depth.

As for the choice of OCW in the flat spot, I don’t see us disagreeing on this point – that all makes sense to me but I don’t understand how it is pertinent to the current discussion?

 

[vman]

Re: How to combine OCW with optimal seating depth.

I try to keep this simple.

#1 Go with on OAL that is good for you. If thats mag length stick with that, if its hand feeding, then as far out as you can go.

#2 Do load development for powder charges at that OAL

#3 If your satisfied with the end result stop there

#4 If you want you can tweak around with minor adjustments on seating depth

There are a lot of variables, and imo shooter perception is one of the biggest. With so many opinions online, on what works, its hard to come up with a solid answer so I find the best way is to find out for yourself.

To put this into perspective, take a look at VLD projies. Some people think they jump fine, yet if thats the case why is their a solid belief that they need to be kissing the lands?