COAL not consistent - why?


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AussieInUtah
February 2, 2012, 11:33 PM
I don't understand what is going on: I've full-length sized and trimmed my cases, and set the seating die on my press. When I mic the loaded cases, the COAL varies by a few 1000th's of an inch. How can that be? I thought that the seating die was supposed to give you a consistent COAL.

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A-FIXER
February 2, 2012, 11:37 PM
It is because of deformed projectiles you will need to get the Hornady compartator this along with the Hornady COL gauge with metered brass will give you " depend how exact you want to be'' The true measurement from the rifling/off the lands, because you will measure the o-give instead of bullet tip.

AussieInUtah
February 2, 2012, 11:55 PM
So are you saying that my Sierra Matchking projectiles aren't consistent length? I don't understand why people even bother to record COAL if you can't load to a consistent length...

oldandslow
February 3, 2012, 04:15 AM
AIU, 2/3/12

When first working up my loads for my Rem 700 .270 Winchester I was very careful but still had significant differences in COAL with my cartridges. I finally measured a number of bullets and found the following differences in bullet length.

1. Speer 130 grain Spitzer Point BT- 1.085" plus or minus 0.003"
2. Nosler 130 grain Partition- 1.127" plus or minus 0.003"
3. Sierra 130 grain Spitzer Point BT- 1.104- 1.141", or a 0.027" spread in lengths.

Thus there was a diffenence in COAL's, especially with the Sierra's. I finally bought a device from Sinclair International so I could measure the distance from the case base to the bullet ogive and then could adjust the distance the ogive sits off the lands of the barrel. I'm sure others will chime in with additional info. I guess this is what makes reloading lots of fun.

best wishes- oldandslow

helotaxi
February 3, 2012, 05:07 AM
It will at least get you in the ballpark. The meplat of pretty much every bullet made is slightly different. If getting them to all measure exactly the same matters to you, buy a meplat trimmer, but realize that in some cases, the BC of the bullet suffers.

For the most part, as long as your seater isn't drifting, the difference in the meplat isn't going to matter. The distance from the ogive to the lands is what matters and that is going to be consistent since the ogive is what the seater references on.

USSR
February 3, 2012, 07:11 AM
So are you saying that my Sierra Matchking projectiles aren't consistent length?

Yes, even Sierra MatchKing's ogives will vary by as much as 0.010". The bullet seating die seats by bearing against the bullet ogive, not the meplat.

I don't understand why people even bother to record COAL if you can't load to a consistent length...

Probably because they don't have a bullet comparator tool. Also, it is useful to ensure that the OAL is not too long for the magazine.

Don

Walkalong
February 3, 2012, 07:38 AM
it is useful to ensure that the OAL is not too long for the magazine.
Yep...

Jasper1573
February 3, 2012, 05:54 PM
Another issue can be neck tension. If one brass case has greater tension than another, the bullet may not seat as easily or as deeply, and give you significant variations (> a few thousandths). I find this to be more likely if using a collet neck sizing die due to my inconsistency in the pressure I place on the press handle.

+1 for what everyone else said above

James2
February 3, 2012, 08:17 PM
What everyone said, just let me add, nothing to worry about!

twofifty
February 4, 2012, 12:03 AM
If your ammo COAL is within .003" you are doing better than most of us.
None of the components are identical even within the same batch #, so everything ends up with a + or -.

After awhile reloading you will learn what aspects to keep to close tolerances, and where is does not really matter. Hunting ammo need not be made with the same exacting meticulous attention to small details that goes into benchrest ammo.

gamestalker
February 4, 2012, 02:46 AM
It's either one of two elements of the bullets, or someting with the press of die.
The most common cause of inconsistent OAL's is because we A. Measure from tip of the bullet to the head, should be the same every time right? Wrong, first of all the tip of a bullet, even the ballistic poly carbon tips will vary by .001" on a good day, they get flatten or deformed slightly during shipping and dayto day handling. And then if it's a lead tipped bullet, the number's your going to get are going vary by quite a bit, lead obviously gets very easily flatten or deformed just while getting made and packaged, not to mention shipping, handling, and while in the hands of the retail store you now have clerks and customers handling them.

And another for sure element that effects OAL is, inconsistencies of olgive location. your seating does not seat off of the tip but off of the tappered area of the bullet. So with that onconsistency being nearly impossiible to avoid, it becomes extremely frustrating. A bullet comparator will eliminate much of the problem, but the unavoidable issue of deformed bullets is just something we are forced to accept.

This is one of the reasons I prefer to seat my bullets to where they chamber nicely, but most or all of the bullets are seated right up to contact with the lands. As a matter of fact I just finished seating 20 Speer 110 gr. TNT's and the OALs varied by as much as .015" on the extreme end, from the tip. And average was probably .007"-.008" variance from the tip. Fortunately for me though I wasn't realizing any of this variance at the olgive. The variance at the olgive was only about .003" and I seriously doubt that a variance .015" OAL from the tip is going to effect my accuracy enough, to degrade my recent worst 5 shot group with these TNT's of .620".

RVenick
February 4, 2012, 09:08 PM
Measure some factory rounds and you will see much worse variance.

NeuseRvrRat
February 4, 2012, 09:14 PM
a handloader might drive himself crazy without a good understanding of tolerances

AussieInUtah
February 4, 2012, 10:19 PM
Guys,

Thanks for all of those comments. I'm handloading for a Savage Model 10LE .308 (i.e. bull-barrel). Going to go out tomorrow and put a few rounds through it with different charges of Varget behind a SMK 175 gr HPBT. I guess the question I have now is whether this rifle can be made appreciably more accurate by messing around with the Hornady COL gauge and bullet comparator. Is this piece of kit the sort of thing you go out and buy when you have a benchrest rifle? Also, I note that RCBS makes a gauge for measuring the chamber, so which product is going to do a better job for the kind of rifle I'm shooting?

Thanks again

Dave

NeuseRvrRat
February 4, 2012, 10:47 PM
some rifles are particular about seating depth. some rifles don't seem to care. you don't have to be a benchrest competitor or have a high dollar benchrest rifle to play around with seating depth and possibly see benefits from experimenting with it.

you can use the candle soot on the bullet method if you don't want to spend the money for the tools. i did that for a while, but the hornady COAL gauge makes it so much easier and quicker. i think bullet comparators are kind of a must-have if you're serious about accuracy. you'll go crazy chasing meplats around. neither of these tools will break the bank.

5thSFGroup
February 5, 2012, 12:29 AM
Another factor is "consistantly doing the same thing each time." If you catch your load being shorter from time to time, you may notice that you pulled your press a bit harder on that set.

A-FIXER
February 5, 2012, 01:09 AM
a handloader might drive himself crazy without a good understanding of tolerances
i think bullet comparators are kind of a must-have if you're serious about accuracy. you'll go crazy chasing meplats around. neither of these tools will break the bank


After awhile reloading you will learn what aspects to keep to close tolerances,


some rifles are particular about seating depth. some rifles don't seem to care. you don't have to be a benchrest competitor or have a high dollar benchrest rifle to play around with seating depth and possibly see benefits from experimenting with it.


As my fellow reloaders we all have been where you are at and now we all choose to get the best out of or firearms and our money spent, time and experience will drive you to levels beyond of novice starters and as other may not agree with EVERYTHING entailed to reloading we each do more than maybe required with repeatabilty knowing when we go to the range and have an off day it more than likely us but when we go to the range and have those oooooh and aaaah TARGETS makes it all worth it.....

918v
February 5, 2012, 02:02 PM
OAL variance does not matter.

If you want low variance, get some hand made benchrest bullets and some sorted cases with identical neck tension. This will involve sorting through a hundred cases and firing them several times just to be sure.

NeuseRvrRat
February 5, 2012, 04:16 PM
OAL variance does not matter.

that's a very bold statement.

Walkalong
February 5, 2012, 05:09 PM
Well, it doesn't. That is not what is important. :)

NeuseRvrRat
February 5, 2012, 05:22 PM
it matters to me

well, i measure off the ogive, so OAL doesn't really matter to me, but seating depth certainly does matter to me.

Walkalong
February 5, 2012, 06:31 PM
Which will be consistent with a seater plug that fits the bullet well.

You can mangle bullet tips and still shoot great groups.

918v
February 5, 2012, 06:39 PM
that's a very bold statement.

I am 918v

R.W.Dale
February 5, 2012, 06:45 PM
Beyond fitting in a magazine COL is completely irrelevant to me.

I use a Forster nut style comparator that measures from the full bore ogive terminus on the bullet. I base all my records off this measurement which is far far more consistent AND can carry over to different projectiles.

I use the simple magic marker dented case mouth technique to determine where the rifle's "comparator to casehead" point is.

posted via tapatalk using android.

One78Shovel
February 5, 2012, 09:20 PM
Yes, even Sierra MatchKing's ogives will vary by as much as 0.010". The bullet seating die seats by bearing against the bullet ogive, not the meplat.



Probably because they don't have a bullet comparator tool. Also, it is useful to ensure that the OAL is not too long for the magazine.

Don
+.010 is right. I'm loading some 30-06 Sierra MK 175 grain FMJ-BT to OAL 3.340 for my Garand. The majority of them come in at 3.340 but others will vary +.005 or +.010. Even at these variations the ebloc loads and rounds chamber fine.

I don't notice such variations with my pistol loads however.

-178S

dickttx
February 6, 2012, 11:07 AM
Beyond fitting in a magazine COL is completely irrelevant to me.

I use a Forster nut style comparator that measures from the full bore ogive terminus on the bullet. I base all my records off this measurement which is far far more consistent AND can carry over to different projectiles.

I use the simple magic marker dented case mouth technique to determine where the rifle's "comparator to casehead" point is.

posted via tapatalk using android.
Explain.

blarby
February 6, 2012, 01:11 PM
Quote:
OAL variance does not matter.

:evil:

Well, that truth is in the eye of the beholder, with some certainty.

With that said, even nutzo gents like me realize there are tolerances in any machining/ assembly process.

To me, just helps to separate "perfect" from "good enough"

In reality, the difference is unlikely to effect you significantly assuming that your seater die is engaging the ogive, not the point.

gamestalker
February 6, 2012, 05:11 PM
The most consistent olgive I've seen was with .277" Speer Hot Core PSP BT back in the early 1980's. It was a long time ago, but I remember how amazed I was that they were within .003" of being the same to the lands from the olgive.
In an attempt to hang on to my last thread of sanity, I just seat up as close to the lands as possible, provided they chamber without problems.

A-FIXER
February 6, 2012, 05:25 PM
I just seat up as close to the lands as possible, provided they chamber without problems. gamestalker states it correctly but do be aware of pressure on the shot if you extend into the lands and may want to move down a 1 grain or 2 to avoid overpressure and yes you will lose some fsp but should give you greater accuracy.

USSR
February 6, 2012, 08:05 PM
The problem is, a bullet seated so it's a couple thou into the lands will normally chamber just fine. For competitive shooting, I was seating mine so that they were .020" into the lands, and they chambered without any resistance. Of course, I had to reduce the charge weight by about 1 grain to match the velocity with the bullet seated off the lands.

Don

AussieInUtah
February 7, 2012, 12:00 AM
OK, guys. You've convinced me. I ordered a Hornady OAL gauge and bullet comparator today.

I'm still going through the process of finding the best powder charge. (Firing rounds loaded at 0.5 gr increments with Varget from 42 gr to 45 gr behind a 175 gr HPBT, I got my best groups around 42.5 gr to 43.5 gr.) I'll go back to the range with 0.1 gr incremental loads soon...

Question: Once I've measured the chamber, etc how do I go about finding the best distance off the lands to load my bullet? I'm asking here about the actual process of experimentation - i.e. do I load 5 rounds with my favorite powder charge and seat to 0.01" off the lands, then 5 rounds 0.015" off the lands, then 0.02" etc?

BTW, all indications so far are that this Savage 10LE .308 is a very accurate rifle, before I've even finished tweaking the handloads. Can't believe I bought it used for $650 with a Leupold VX-II scope on it! Thanks for your helpful advice.

Regards

Dave

A-FIXER
February 7, 2012, 12:40 AM
Aussie,
Now you will just have to make that find yourself and the rifle in question for example you have 3 different powder load and you shoot them and if your grouping is good and then you take the 1 best group and try different COL measurement and find which of the distances your rifle works well then you are doing the process of designing a load for that rifle and that particular round (bullet) to make things repeatable you should trim your cases every time so all the bullets are exactly the same each and everytime, don't mix different type of cases what you strive for is REPEATABILITY......
once again you will have to do this ALL OVER AGAIN for each different type of powder/bullet/case it is called reloading and again how technical you want to be is just to get the best out of you and your rifle.

twofifty
February 7, 2012, 12:48 AM
Since your best groups were with the 42.5 and 43.5 loadings, I'd cut to the chase and load up a bunch at 43 grains, but with different seating depths.

Reason for splitting the difference is that a 43 grain load should in theory still perform well and safely if your over or under charge a round. It should also still perform well and safely if hunting/match air temps are above/below your development temperatures. Why? Because that your rifle did well at 42.5 and 43.5.

For seating, I'd start .040" off the lands, then move in closer to .030", .020", .010", then almost touching. Say .020" gives you the best and most consistent groups, then you could fuss over it more by loading some to .025", .020" and .015". Taking it that far is splitting hairs, esp. if you'll end up shooting these SMKs at 200yds or less. Joey won't be able to tell the difference. ;)

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