Help! Newbie chasing C.O.L.!

[79camaro]

Hello everyone,

I'm new to this forum, and have a question:

I just started reloading 300 Blackout, and this is my very first attempt at reloading.

I am using prepped brass from Carolina Brass, CCI #41 primers, and Sierra 125gr Matchking bullets, it's going to be fired from an AR pistol with a Noveske 10.3" barrel, and a BCM BCG, NOT suppressed.

When I finished the pistol, I ran some factory loads, 155gr HP, and it ran GREAT! I decided to go with the 125 gr Sierras, and after loading a few, I found myself "chasing" the COL. According to Hogdon, using this bullet and H110, I should have a COL of 2.060. I set my Redding bullet seating die, and after a while, was able to nail it to the recommended COL. Well, after a few rounds, it started "jumping" around...being new to this, I was LOST! The shortest round is probably 2.054 or 2.055, the longest 2.062. After cussing for hours, I decided to measure the bullets, and found (as stated in other posts elsewhere) they varied quite a bit.

I read about measuring from the "Ogive", and I think I understand the concept. Although I see the significance of getting the right "chamber" length, how does that help with the COL? My concern (keep in mind I am a rookie) is that I don't know what LENGTH bullet the load data is using, and as I found out, 125gr can mean a LOT of different lengths! So, even if I measure from the "Ogive", how do I determine the proper seating depth in order to not create excessive pressure?

I believe the starting load is 16.7gr, and the max is 17.8, I loaded all of them right at the starting load, so I assume I have some "BUFFER", but it does not feel comfortable. If I measure from the Ogive, what is my "standard" for making sure the seated depth is correct? the load data only gives COL, which I think we can all agree is very much dependent on the length of the bullet, which VARIES quite a bit!

Is the variance between 2.060 and 2.054 enough to worry about?


I hope someone out there can read this and understand my rookie confusion and give me some guidance!

thank you in advance!

 

[NCsmitty]

Welcome to THR, 79camaro.

It's not uncommon to see variations in bullet dimensions and ogive position of around .010" in mass produced bullets. Don't get caught up in the COAL anomalies as it will take the fun out of shooting for you. You're not making match ammunition if you use an AR pistol, and work with what the components give you.

Your completed rounds will function fine and it's likely you'll never see any difference on target that isn't caused by human sighting error. Start low, but realize that H110 functions best towards it's maximum loads with crimped bullets. H110 can be a bit finicky in that regard.


Ncsmitty

 

[spitballer]

In my experience, varying OAL has almost always been caused by hardened brass with varying neck wall thicknesses. When brass is new and soft, bullets seat consistently. But when the brass starts to get hard, the brass is extremely unforgiving and the varying neck wall thickness of cheaper brass starts to cause varying OAL.

As a stopgap measure I've segregated each 50-round box into three or more groups of cases necked down to various sizes, but the problem wasn't really solved until I started buying the premium brass with consistent wall thickness. This was as an alternative to buying equipment to turn necks with.

If I went through a lot of ammo like some of these guys, I'd definitely be investing in the neck-turning equipment. Good luck to you.

 

[79camaro]

At this point, I am not even that concerned with accuracy. My main concern was understanding the concept of how not to seat the bullets too deep and creating a situation of too much case pressure. Not being experienced, I mostly would like to know if the difference between 2.060 and 2.054 was very critical.

Looking back, since NOW I realize that bullet length varies that much, I should have found the longest bullet in the batch and set it to the proper COL so that subsequent (shorter) bullets would not go in any deeper into the case. But, I am starting to understand the concept that the die is setting the bullet "depth" from the Ogive, so the extra thousands from the varying tips should not be an issue.

My fear is that I may have set up my die and COL initially with a shorter bullet, and when I end up pressing in longer bullets, they will go too far into the case. I know that the COL is good as far as the magazine, so not too concerned about that, it was the "evil" pressure in the case (and blowing up my gun!) that concerns me.

 

[spitballer]

It wasn't until I started seating bullets into fairly loose necks that I got a true picture of what my OAL length was supposed be. Afterwards I pulled the bullets (didn't even need primer or powder), resized the necks, and tried again. This was when I realized that the bullets were more consistent than I thought they were.

 

[greyling22]

if you are running starting loads shouldn't be an issue. 300 loads run at lower pressure loads than the 5.56 rounds the gun and bolt were designed to handle.

I've said it before and I"ll say it again, loading starting loads covers a multitude of sins. (in this case "sins" being minor oops' in case volumes, powder lot variations, primer substitutions, atmospheric conditions, sunspots, bullet variations, etc etc)

 

[NCsmitty]

To answer your question, minute seating depth differences in bottle neck rifle cases have far less influence on pressure than short straight pistol cases.
A .010" variance on seating depth in a rifle case will have virtually no affect on pressure.


NCsmitty

 

[R.W.Dale]

Beyond fitting in the mag COL is irrelevant.

What matters is ogive to rifling distance and ogive to base (internal volume). This tends to vary from bullet to bullet very little.

A simple nut style bullet comparator is an invaluable tool for determining this and repeating this between loadings.


The variance you're seeing is almost always between the bullet tips. Since your seater does not seat off the bullet tip this variation you note is not passed downward into the case as variation of actual seating depth as it relates to internal case volume

 

[R.W.Dale]

http://www.sinclairintl.com/reloadi...r-hex-style-bullet-comparators-prod34262.aspx

Everyone should have one of these

 

[spitballer]

Hex-shaped bullet comparators are valuable tools but are difficult to try to hold with a caliper. Someone should invent a jig to hold the thing straight so a more accurate reading can be obtained. This might involve a stepped block with a cradle for the case...

 

[R.W.Dale]

Hex-shaped bullet comparators are valuable tools but are difficult to try to hold with a caliper. Someone should invent a jig to hold the thing straight so a more accurate reading can be obtained. This might involve a stepped block with a cradle for the case...

I don't have any problem using mine

 

[Muddydogs]

COL is not telling you much at all, you are worried about seating to much bullet into the case but you don't really know if you are or not by measuring COL. The bullet seater die seats the bullet by pushing on the Ogive of the bullet or close to it so until you measure your bullets from ogive to base you will not know if the variation in length is from ogive to base or ogive to tip. Chances are the length variation in a bullet comes from the tip of the bullet so you probably have about the same amount of bullet in each case.

 

[rg1]

Hollow point bullets even Match hollowpoints have slightly different tip shapes due to the folded copper tips. Even lead tipped bullets vary in the tip. Match hollowpoints Sierra's and Nosler's I've loaded vary as much as .005", sometimes a little more, when measuring the loaded overall length. Like mentioned the ogive should be closer if you measure that instead of oal. Even plastic tipped bullets vary sometimes in the plastic tip shape. Not as much as lead tipped or hollowpoints though. Some long-range match shooters uniform the tips of match hollowpoints with a meplat uniformer tool but it'd take a precision shooter at very long ranges to even notice the difference.

 

[spitballer]

I don't have any problem using mine

I've gotten pretty good at using mine, too, but it's still awkward holding the cartridge perpendicular to the tool while adjusting the caliper.

 

[kcofohio]

It's not so much as to how much length you have outside the casing, but the seating depth of the bullet inside the casing.
If you're worried about the small variance, try this. With a trial run of ten bullets, measure and write down each bullet's length. Seat the bullets and compare the COAL's to what you recorded with the bullet's length. Are the seating depths consistent?

 

[Coldfinger]

An option would be to measure each round after seating and adjust accordingly. Time consuming. Load up 10 and get an average COL if it is within .010 you should be ok esspecially loading light. I will say however that as a new reloader being concerned with this issue is good. It means that you are careful and are considering things that most dont until KABOOM and then argue that the load was within safe limits.

 

[R.W.Dale]

An option would be to measure each round after seating and adjust accordingly. Time consuming. Load up 10 and get an average COL if it is within .010 you should be ok esspecially loading light. I will say however that as a new reloader being concerned with this issue is good. It means that you are careful and are considering things that most dont until KABOOM and then argue that the load was within safe limits.

By forcing even col through manipulation of each round you're actually making a things worse by taking what was a minor difference in bullet tips and passing that into the case where it changes internal volume and therefore pressure.

 

[Walkalong]

A .010 variance is nothing to worry about. Those factory rounds you shot may have varied more.

Load them up at a reasonable OAL and shoot them. Go from there.

The Sinclair nut works just fine, but there are other options as well. I bet you can find a nice accurate load without something like that without ever knowing how much "jump" you have. I would wouldn't worry with it unless you just want to.

You were happy with the factory loads and were blissfully ignorant as to the jump on them.

 

[larry syverson]

Relax, you're doing fine

Like other said don't sweat a few mils on overall length. If you tried to get them all nuts on, you'd never get any reloading done. Using MY Lee reloader it is very sensitive to how hard you stroke the handle when reloading. Just try to be consistent and you'll eventually get the feel for it. Do-Check-Adjust is my mantra... I check them after seating and sort of calibrate the stroke. Then I can get maybe within 3-4 mils of the same COAL pretty consistently.

 

[jell-dog]

don't sweat a few mils on overall length

I know this thread is about rifle brass/cartridges, and am not trying to hijack it, but wanted to share my thoughts on the subject of COL and a new reloaders concerns with achieving consistent COL on their finished cartridges.
I'm new to 380 & 9mm reloading and have found a whopping +/- 0.003" to 0.005" variance in Cartridge Overall Length (COL) after seating/crimping my bullets. BUT after plunk testing the +0.005" COL found they passed!
After finding MAXIMUM COL and adjusting for magazine/feed/eject functions, I reduced by 0.015" and have had no failures (yet). Now I don't worry about measurements less than a human hair and enjoy reloading and shooting my reloads much more.
I use FRONTIER CMJ bullets and after measuring length (100 random bullets in a 1000 round box) found they are almost all within 0.007" of each other.
So, I concluded that the difference in COL was due to seating against the ogive, and the variations of +/- 0.003" to 0.005" COL was nothing to worry about.
I do work up my loads with accurate PUBLISHED data, and find good accurate loads.
Sorry to be long winded!