COAL

[TTE]

Case over all length (the actual brass case length, not the loaded OAL)

When trimming cases, how much variation is too much variation for good accuracy ?
.001 - .002 - .0005 ?

Yes, we would like them all to be exactly the same, however sometimes it does not work out that way.

Variations for -
Big Game -
Varminting -
Bench Rest -

Thanks for your replies

 

[Bill Norris]

Case over all length.

How much variation is too much variation for good accuracy ?
.001 - .002 - .0005 ?

Yes, we would like them all to be exactly the same, however sometimes it does not work out that way.

Variations for -
Big Game -
Varminting -
Bench Rest -

Thanks for your replies

Considering some of the S R Bench Rest shooters say that .001 in seat depth on the ogive will make a difference in group size it appears that even .001 variances would show up on the target in that bracket. Hard to say how much variations would affect the Varminting bracket and maybe not so much in Big Game.

 

[TTE]

Considering some of the S R Bench Rest shooters say that .001 in seat depth on the ogive will make a difference in group size it appears that even .001 variances would show up on the target in that bracket. Hard to say how much variations would affect the Varminting bracket and maybe not so much in Big Game.

Thanks Bill.

Was asking more about the actual brass case length, not the loaded OAL
I guess I should have worded it differently. Just changed my OP some.

 

[Bill Norris]

Thanks Bill.

Was asking more about the actual brass case length, not the loaded OAL
I guess I should have worded it differently. Just changed my OP some.

Got it. Several of the B R shooters claim that trimming the case to maintain a uniform length will enhance group sizes. Would think it would affect the other mentioned areas to some degree.

 

[JLT]

I hunt and shoot F Open. I don't sweat plus or minus a thousandth or two. With many trimmers indexing on neck length, we have a classic case of tolerance stacking showing up in case length variation, albeit slight, after trimming.

I wish I were good enough to shoot the difference, plus or minus a thousandth or two.

 

[Clancy]

It’s so easy to get .001 that I’d make that my standard. I’m not sure .002 would hurt anything, but .001 is just too easy to achieve so why not?

 

[Coyotefurharvester]

I don't trim my 223 range brass until they are more than max recommended. So I'm guessing that there could be 0.015 range, some under "minimum" some just over "maximum" length. These hunting/varmint loads are still minute of prairie dog out to 300 yards with bolt and gas guns. Don't believe you will see a difference accuracy wise with a hunting rifle with 0.005 range in the brass, now if you are crimping with a standard seating die, I would have all the brass +,- 0.001.

 

[Straightshooter1]

Case over all length (the actual brass case length, not the loaded OAL)

When trimming cases, how much variation is too much variation for good accuracy ?
.001 - .002 - .0005 ?

Yes, we would like them all to be exactly the same, however sometimes it does not work out that way.

Variations for -
Big Game -
Varminting -
Bench Rest -

Thanks for your replies

Just like seating depth can, the case length can effect the timing of the blowby as the bearing surface exits the case mouth. How much of an effect it has will vary on various cartridges and rifle chambers.

For Bench Rest, you really want as little variation as possible for all aspect of the cartridge if your after winning matches. On the other side of the spectrum, Hunting cartridges don't have to have that kind precision, especially when taking game down at less than 200 yds or so and can easily deal with .002 or .003" of variation. I would think any trimming tool can do .002, maybe less consistently and that shouldn't be an issue for the vast majority of applications. IMHO

With my process and using a Giraud trimmer, I easily get .001 or less where those at .001 tends to be very few. And I can't really see any affect of those on target or in my chrono data (probably too much noise involved). Just be aware, I'm not a bench rest competitor.

 

[K22]

I can't comment on the Benchrest category but will offer my experience with big game and varmint reloads.

I use a Wilson trimmer with a carbide cutter. It's not difficult to trim well within + or - .001" of a target dimension.

A few years ago, I purchased a Sinclair Chamber Length Gauge and measured the chambers of all my rifles. In doing so, I reduced the amount of trimming needed* even using the safety factor Sinclair recommends to over 50%. What I discovered is the most, but not all, chambers, depending on rifle brand, have chambers much longer than SAMMI specs published in reloading manual.

Therefore, my cases may vary a few thousands of an inch over time since they are allowed to lengthen until they reach the target trim value, however I have not noticed any effect on precision or accuracy shooting at this level.

* Maximum chamber length - .010" = targeted trim value.

Maximum chamber length = measured length - Sinclair's recommended safety factor.

 

[KMW 1954]

Shooting 223 and 6ARC Bolt at .5moa targets from 100 - 300yds. for the past 4 years. I load brass that has been fired a few times in the same rifle and my set point is .005" short of max and do not trim until I reach .003 short of max. Most of my brass now does not need to be trimmed again until shot 3 to 4 times. It's just not stretching.

 

[Chubbs]

I don't think you can really say .001" makes a difference if your not making sure all your case capacities are exactly the same. Probably more psychological than actual real benefit.

 

[JEFFPPC]

Cubbs hit them nail on the head. As long as it's safe for YOUR chamber I have not been able to see it's critical. Today we obsess about many things to cover up our deficiencies in other areas that are MUCH more important but not considered sexy.

 

[Rat Rifle]

It’s so easy to get .001 that I’d make that my standard. I’m not sure .002 would hurt anything, but .001 is just too easy to achieve so why not?

^ THIS ^ It’s totally easy. Speaking for Benchrest Accuracy. So why not do it.

 

[Shooter13]

We stress over neck tension so adding .001 or .002 won't make a difference? I'm asking (for a friend of course), as I see it, it would, you'd have more bullet in the case if you are .002-.005 longer so........................

 

[D-4297]

When I first began reloading for F-TR , I was learning about chamber neck length , the dreaded "Carbon Ring" , and all the other things that affect accuracy . Somewhere along the line ; there was discussion on this issue , and it was stated that a variation of case lengths could also cause a variation on the Target . Since I had Brass that was from 2.00" to 2.015 long , I decided to test the thought that any odd variation would show up on target .
What I discovered was kind of "Eye Opening" ! If shot in a group , of Matching case Lengths , shot placement can be "ADJUSTED" to get on , and stay on Target but shooting a string of Case Lengths that varied more than .003 in length caused both Points and X-Count variations in scores .
I ran these types of simple tests for a entire Summer at Ben Avery at 600 yards , and it proved to me , without a doubt , that it didn't matter what the over-all Case length was , within the standard limits of your chamber neck distance , as long as they were less than .002" in overall length variation , you were good to go , but .001" was even slightly more consistent .
This "Testing" was done with over 1,000 rounds being fired in varying conditions of wind and Temperatures , usually over 105-F degrees . But it showed the information I was seeking .
If you think it doesn't matter , then don't be precise with your trimming . My standard is .001 !

 

[JMayo]

Competition - As close as possible to the same for my 200.
But I'll say i really don't keep up with it after initial case prep.....

 

[Clancy]

My real life friends and acquaintances look at my groups and just ask “how?” They never like my answer.

I tell them and anyone that I take on as a reloading grasshopper that assuming your rifle is sound, case prep is half the battle. Seating depth is 40% of it and the remaining 10% is wind and combustion.

Case prep is more important than flags, more important than seating albeit barely, more important than bench manners- more important than anything. BUT, it’s a hell of a lot of work and most people are too lazy to do it and that’s why they’ll never consistently shoot small. Well, that and poor choices in optics, but we covered that back under “assuming the rifle is sound.”

Not to get off on a tangent, but another thing that gets a ton of guys is chasing that dragon. They’re always changing presses, dies, tools, etc. That’s simply not the path to success. I’ll die with the same press, arbor, dies and God willing the same reamers.

These are just my opinions. I know what works and frankly don’t care if anyone disagrees.

 

[DShortt]

I hunt and shoot F Open. I don't sweat plus or minus a thousandth or two. With many trimmers indexing on neck length, we have a classic case of tolerance stacking showing up in case length variation, albeit slight, after trimming.

I wish I were good enough to shoot the difference, plus or minus a thousandth or two.

Agree with this. Try it. If you see the difference over a few outings then stick with it. If not, then move on to something else because right now, that doesn't matter in your situation.

 

[mikecr]

Why not just call it case length, or trim length?
My ideal trim length puts me within 5thou clearance to chamber end. Factory acceptable is inside 10thou.
A reasonable variance(2thou) inside this doesn't matter.

Lower chamber end clearance provides less gass blowby around the neck, so faster neck sealing.
I believe this allows more consistent firing dimensions and combustion.
Lower blowby also mitigates formation of a carbon ring.

 

[Dave M.]

Considering some of the S R Bench Rest shooters say that .001 in seat depth on the ogive will make a difference in group size it appears that even .001 variances would show up on the target in that bracket. Hard to say how much variations would affect the Varminting bracket and maybe not so much in Big Game.

He is talking about the overall brass length, not loaded round overall length.