Trim lengths and bullet seating

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Wendyj

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If trim lengths vary by 2-3 thousands will bullet oal do the same? I wouldn't think it should since bullet is in shell holder and tip of bullet is at top but I could be wrong. I'm getting variances using Lee and RCBS seating dies. Did notice that bullets vary some in lengths. All except Hornady Amax. They are all but perfect.
 
OAL is not a function of trim length. It is a function of the distance from the base of the shell holder to the seater plug.
 
The bullet seater does not push on the tip of the bullet, it's more towards the fattest part of the bullet.

Bullet shapes can vary a lot, tips can vary by a few thousandths easily, but the widest part of the bullet rarely varies.

So if you're seating to get the bullet to an optimum position relative to the rifling, then you want the distance between the rifling and the widest part of the bullet (generally called the ogive). This distance could be 0.0000 or maybe up to 0.0400, it's just a matter of what works best for you.

So, the position of the tip of the bullet is really irrelevant, the exception is if you're loading in to a magazine that is on the short side. If the tips are too long the rounds can hang up in the magazine and cause feeding issues.

Hope that makes sense.
 
If trim lengths vary by 2-3 thousands will bullet oal do the same?
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No

The tips of bullets are often very inconsistent . Check this by measuring just the bullet base to tip . You will see that they vary a few thousandths from bullet to bullet . So when checking OAL you should expect that measurement to fluctuate a little . That almost never has an impact unless you are loading to mag length . I made the mistake once of trying to load some 77gr smk very close to AR mag length . Problem was the batch of bullets I had were more inconsistent then normal . Every 4th or 5th round turned out to be to long and hung up in the mag .
 
You are correct Wendy, it does not make a difference. Your variances are due to bullet length and condition of brass. A few thousands difference in COAL means little, the important measurement if CBTO (cartridge base to ogive).
 
I get more consistent readings reading to ogive with Hornady lock and load than tip to tip. I've been loading 2.810 and my magazine is just a few thousands longer. I just don't use the bullet compareter much since I'm loading to fit the magazine. How I'd like to have a Ruger #1 in 308. I wouldn't mind single feeding.
 
Continuing this line of thought - since the overall length is the same but the trim length is different, does that mean that the pressure is going to be slightly different? Even if it is, is it enough to matter?
 
Good question Doyle. I have my own thoughts on the matter. I am interested in what someone with more experience than I has to offer.
 
I trim every time but have been told and or read many times by people I respect on this forum . Case length does not significantly reduce accuracy if at all . Now that's with in reason . I understand that to mean if you trimmed your 308 case to 2.005 and the next time you load that case it"s 2.008 there will not likely be a noticeable difference . I would take that also to mean not having any pressure issue either .

Now I load primarily 308 & 223 and they have relatively short necks . I recently started loading 270 and I'm about to start 30-30 . I've noticed that there necks are pretty long compared to the 308 . It would seem you could trim those cases shorter then minimum and they would still fire . What I'm not to sure about is if you have a much larger case length difference from case to case with those longer necked cartridges . How much that may effect accuracy or pressure . A few thousandths difference in a 308 cases is no big deal but 15 thousandth differences in a 270 or 30-30 may be an issue . I would have to defer to those that load those cartridges more then I to answer that .
 
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Wendyj, I am sure you have listed the L.E. Wilson case gage among the tools you use, most reloaders believe the more a tool cost the better it is when compared with other tools that cost less. The Wilson case gage is one of the most precision tool for measuring case length.

Difficult to wrap the mind around, the Wilson case gage measures from a datum to the case mouth and from the same datum to the case head. AND:eek: case length from the mouth of the case to the case head. I have chambers that are long from the shoulder to the bolt face. When trimming I add the extra length to the length of the case. I have one chamber I add .014" to the length between the shoulder to the case head.

There are case trimmers that set-up on the shoulder of the case when trimming, that system totally disregard the length of the case from the shoulder of the case to the case head.

F. Guffey
 
I use the Wilson case guage on my 7 mm mag. Using Lyman case guage in 308 win. Wish I had bought the Wilson for all my gauges. It's set to adjust with a fired case. The Lyman is a hole to make sure it will fit in the chamber best I can tell.
 
Continuing this line of thought - since the overall length is the same but the trim length is different, does that mean that the pressure is going to be slightly different? Even if it is, is it enough to matter?
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I too would be interested in hearing thoughts on this. Along the same line of thought, I have in the past trimmed to minimum length thinking that would eliminate more frequent trimmings. But of late, I have been wondering if trimming that 223/556 case to minimum length was/is robbing me some of the desired neck tension needed for non-crimped loads. just wondering out loud.......
 
I don't crimp any of my AR loads with out issue . The 223/5.56 has very little recoil and the seated bullet should have plenty of hold . Now that's not to say if you are using custom dies or bushing dies that allow you to adjust your bullet hold you will not have trouble . You must keep in mind the caliber you are shooting , die your using , thickness of the brass and the relative recoil . When using some 308 brass and my .337 bushing . I get a lightly seated bullet that I can push in easily just by pushing the tip of the bullet into the bench by hand . I would not shoot those from a mag fed rifle at least not with out a crimping but then you messed up the bullet hold so why bother . I only shoot rounds with that light of bullet hold from a bolt gun and I single load those .

I just bought a 308 stripped lower and will be building a semi auto 308 soon . I still have not decided how I'll load for it . With crimp , no crimp , small bushing with no expander ball , small bushing with custom expander honed down a few thou to insure good bullet hold or maybe just a standard die , they seem to have quite a bit of bullet hold . I have time to think about it so It's not a pressing mater right now . I'll do some test to see what works for me before cranking them out .
 
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http://www.lymanproducts.com/lyman/case-prep/rifle-headspace-gauges.php

The Lyman is a hole to make sure it will fit in the chamber best I can tell.
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I was not listening. I make gages, I use barrels as gages. It would have helped if Lyman had a reference to 'the chamber' instead of the case. L.E. Wilson makes case gages, their case gage can be used for fired and sized cases. It can also be used with new ammunition and it can be checked with other gages like the head space gage.


I was not listening
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Lyman spends to much time instructing the reloader to size the case to fit their gage. I size cases to fit my chamber. Lyman does call their gage a case gage, then they make a reference to head space on the case to get attention when Google is searched. I have case gages and I have chamber gages.

F. Guffey
 
I was kind of scared when we started loading the magnum. I done a lot of research and the Wilson guage was by far my choice before I sized my first piece of brass.
 
That video was cool . I never thought to use the gages that way , it was kind of a duh moment . I have been using a Hornady comparator to measure my bumps . I was able to confirm that I am bumping my 308 back .002 & my 5.56 back .003 using that method .
 
I noticed Lyman included the instructions for using a straight edge/steel rule. I add a feeler gage. Wilson suggested the straight edge in the early '50s, back then they called it a pocket rule.
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Then there are cryptic ways. A reloader with a straight edge can use a feeler gage. Then there are reloaders that have flat surfaces. A flat surface and the feeler gage can give very precision measurements.

F. Guffey

And there is always that problem when loading and sizing to fit a gage. I want my cases to fit the chamber.
 
Wendyj
I use the Wilson case gauge on my 7 mm mag.
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I have one of those belted magnum adjustable references too. I keep it with my Ouija board and my pocket fisherman.

The SAAAMI range for 7mmRM, 300WM, and 338 WM brass is from 0.212" to 0.220".
The SAAAMI range for 7mmRM, 300WM, and 338 WM chambers is from 0.220" to 0.227".

All the factory rifle chambers are 0.220" or greater.
It is hard to find brass bigger than 0.215".

The shoulders are way back on the new brass so the first firing will be using the belt to counter the firing pin force on the case.

Sure the shoulder will form on the first firing, but look at the damage done to the case on just one firing.

This takes me back to 303 Brit crazy sloppy SAAMI land.

What can I do?
At least these actions are not stretchy.
I got a lifetime supply of brass, it is all 0.215" or smaller.
When I build a rifle, I headspace at 0.215".
I do not take my factory rifles apart and move the barrel back [too lazy].
 
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