6.5CM Lapua case: FL resize 1x COAL & trimming question

[Zatoichi66]

The more I think I know, the less i think I understand.....

rifle: Tikka T3X TAC1 6.5CM
optic: Vortex Razor Gen 2 HD 56mm 4.5-27x

dies: Redding Precision Full length & micrometer “Premium”

i recently attended a course on precision shooting and am processing the spent brass.
My load, for the interested:
virgin small rifle cap Lapua brass (i didn’t measure or no anything other than prime & load, as per Lapua email)
CCI400 cap
H4350 41.0gr (measured individually on PACT non-automated scale)
Hornady 140gr OTM
OAL 2.800”

my best group in the 2 day course was just under 0.750” 5 shot @ 100 yards, prone. Since i have seen 0.30” groups reported with similar Tikka T3x & match ammo, my skills are the issue. I have previously posted about my eyesight/optic issue & was able to replicate the errors this weekend—i keep the power under 20X and am doing ok.

i have dry tumble-cleaned (walnut husk), lubed (Hornady One-Shot) & full length resized the brass. BUT, now i am confused at the next step, because some of the FL-resized brass is the same exact 1.9115” COAL virgin brass. Virgin, unprimed brass = 1X FL-resized brass!?! I would have lost that bet!

8 fired, cleaned, FL-resized cases are 1.9115” same as virgin brass
2 fired, cleaned, FL-resized cases are 1.9130” which was what i expected from firing & resizing— brass stretches with obturation, right? Guiraud to the rescue!
2 fired, cleaned FL-resized cases are 1.9095” which is shorter than virgin brass (brass gremlins?!?)
yes, the cases & calipers are wiped, so this isn’t dirt/dust error. I haven’t measured every case prior to loading, so some may be shorter, but ok per specs. As noted above, i know i’m the rate-limiting reagent with the gun, optic & load.

I wash the case lube (Hornady One Shot) off in my wet tumbler after resizing cases, then trim with my Guiraud trimmer with 5.56 Lake City; 6.5CM and precision reloading is new to me. Since precision is the goal, i don’t mind the work.

Is “trim“ vs “no trim” typical, or is Lapua brass atypical?

yes, I realize this can be as involved as i want—i’m just confused at the resized brass being identical to virgin. No, I don’t weigh brass, based on available data/my own research. My only prior rifle reloading experience is 5.56 NATO, Lake City specifically, & i haven’t been this OCD with reloading—i shot, processed brass which included trimming, then hand-pick cases i deemed “A+“ and 1.750” COAL were to be used for handloads, which were individually weighed & carefully seated for OAL. I trimmed 100% of Lake City cases and based on the Guiraud trimmer noise, 99%+ cases required trimming, but i never measured.

Bottom line question: do you guys measure cases and decide in trim/no trim? The mouth needs a chamfer, regardless, but this is new to me. Or, am i over-thinking? Or, is this expected of Lapua brass? Or, is it the Tikka chamber? Or, did i ask if i’m over-thinking?

thank you for your help.

 

[Krob95]

Are you measuring actual COAL from one end to the other or are you using a head space comparator? It sounds like you’re measuring the entire case and not the Base to Datum as you would do when checking for proper shoulder set back.

 

[Krob95]

I set everything back 2 thou and then trim every few firings to even it all back out. Some brass grows differently than others when fired as noted when I trim my brass with varying amounts of shavings from it.

 

[Zatoichi66]

Are you measuring actual COAL from one end to the other or are you using a head space comparator? It sounds like you’re measuring the entire case and not the Base to Datum as you would do when checking for proper shoulder set back.

Actual COAL. I put the case in the caliper. I may have bought the fancy shoulder gauge measurer, but was so flabberghasted by the result, i didn’t think of that. Stay tuned!

 

[Zatoichi66]

I set everything back 2 thou and then trim every few firings to even it all back out. Some brass grows differently than others when fired as noted when I trim my brass with varying amounts of shavings from it.

Ok—i set this up like a typical Lee die—FL die impacts the shell holder. Yes, i said Redding, but there aren’t instructions about set up. The micrometer piece is only for seating bullets. But it good to know you trim in several firings. Thank you. I was under the belief trimming with a high power rifle is expected.

 

[Krob95]

IIRC correctly with the Redding dies, they say to screw it all the way down to the shell holder and then give it another 1/8th of a turn for a slight cam over in the press. This is how I set my dies up.

I will run one through and measure pre and post sizing and see where I’m at. If nothing changes I’ll screw down the die a little further and try again and make small adjustments. If it sizes too much, I will back the die off a little bit until the desired headspace is achieved. I check this with the hornady headspace comparator. Once achieved I’ll size several pieces and make sure it’s good to go and then that’s it for setting up the die.

Ill clean the brass after sizing and then trim it to length and debur and chamfer.

If you know you’re bumping back shoulders to where you want them (between 2 and 4thou) then you can measure a sample of say ten cases., find the shortest one, and trim all of them to that length. Then in a few firings, trim them again. This has worked great for me shooting 6BR, 6BRA, 6CM, 6.5CM, 308, and a 22GT.

The max length of a 6.5cm case should be published somewhere (I want to say it’s 1.920”). keep it under that and you should be good to go. Min trim length should be 1.910”. I usually go 5 thou under recommended since I don’t like trimming cases. Won’t hurt anything.

 

[Zatoichi66]

I only have the caliper insert to measure base to ogive, not shoulder.

sounds like an order with Sinclair is in my future.

ETA—i thought i want to be as close to leade for accuracy?

 

[Krob95]

i think you mean lands. And different bullets like different jumps (distance to the lands). ELDM’s and Berger hybrids are pretty insensitive to jump. VLD’s are very sensitive to jump. But judging by the group above you’re fine where you’re at especially if that’s a consistent group size.

 

[Zatoichi66]

i think you mean lands. And different bullets like different jumps (distance to the lands). ELDM’s and Berger hybrids are pretty insensitive to jump. VLD’s are very sensitive to jump. But judging by the group above you’re fine where you’re at especially if that’s a consistent group size.

yes. Lands. I planned Berger Hybrid, but didn’t have enough 140s, so Hornady was “Plan B.” I impressed myself with that group. The instructor had me look at the plastic board behind to show all 5 exits—i was convinced I totally missed.

so, the “datum” shoulder measure is more accurate?

i feel like the Hollywood “mad scientist” trying to get this right.

 

[spife7980]

Ditch the low pressure cci400 primers before they start piecing and ruining your bolt. Use the 450s or 205s or anything thicker if you can find it that wont let a jet of plasma ruin the insides of your action.

Where the bullet is seated in relation to the lands has zero bearing on where the case shoulder is in relation to the chamber. They are independent of one another.

Case overall length doesnt mean shit so long as its not tooooo long to pinch the bullet when the chamber neck ends, youve probably got .020 of free space at least. So stop bothering worrying about it. Its the least of your concerns.



(I had a good video but it seems youtube/google is hiding wheeler accuracy videos? I cant link it but you can view it on embedded his site still so its not like its gone entirely. Its the sizing brass video when you scroll down, do the same for the finding your lands video https://www.wheeleraccuracy.com/videos )



Use a comparator so that you can measure the same spot on the shoulder each time you measure. Bump a fired case shoulder back .001-.002 and youll be good.

 

[Winny94]

To throw another wrench into your process. Consider not bumping the shoulder on once or twice fired brass. Brass grows over several firings, and if you're constantly bumping it back before it hits it's max, you may be always chasing consistency.

Also, if you're placing an order, consider picking this up: https://www.brownells.com/reloading...s/sinclair-chamber-length-gage-prod32925.aspx

It shocking to see how much longer many chambers are over spec.

 

[Zatoichi66]

I planned to switch tp CCI450s. I wasn’t savvy on caps & couldn’t get CCI Bench Rest, so i used what i thought was ok, then learned i should have used my 450s after loading about 300. Will switch to 450s now, but i still have just under 200 of the 400s loaded.

 

[Krob95]

so, the “datum” shoulder measure is more accurate?

in relation to bumping shoulders back, it’s the only accurate way to measure it. There’s three measurements that matter. How far you bump back shoulders, how much powder you have in the case, and how close or far your bullet is from the lands. I sample my sized brass and then my seating depths across 10 random rounds. I don’t measure each case as it comes off the press. Too time consuming for my purposes but you’re welcome to check all of your cases after they’re sized and then after seating your bullet.

Case length should be measured every couple firings to see where you’re at. Measure a sample of your choosing, if you have any that are getting close to max trim length, trim them all back down and make a mental note of how many firings It took before it reached that length.

 

[Zatoichi66]

Midsouth reloading had the 6.5CM in stock, so i ordered one.

thank you for thr help.

 

[Zatoichi66]

Is the CCI400 primer such an issue i should break-down the remaining almost 200 rounds? I figured i would just shoot them. All loads will otherwise be CCI450s, since i used to use them for AR loading.

 

[Krob95]

I’d just shoot em man. It’s a pretty reasonable load and I wouldn’t think you’d encounter any issue with pierced primers.

 

[Zatoichi66]

Thank you. Will await comparator and assess accurate measurements before proceeding.

as always—thanks to those who helped—i appreciate the guidance & patience.

 

[spife7980]

Yeah, if you’ve loaded em, use em.
Just keep an eye out, once they start popping they will erode the firing pin hole and tip with each puncture which only serves to further exacerbate the problem and increase the likelihood that it happens.

 

[Zatoichi66]

I’ve fired almost 400 of the 500 i made & checked each case: no pressure signs, smears or primer cratering. No flat caps or anything that looks like my M193 or M855 cases.

as noted, am planning on CCI450s from now on.

 

[Zatoichi66]

And….Part Deux!

I finally received my Hornady Lock n Load 0.375” Comparator to give datum data on measurements. I measured each piece several times, with the Mitutoyo digital (0.0000) calipers zeroed & rezeroed to be sure i’m consistent. And, within a few 0.0005” i was reproducible.

Ten pieces of Lapua virgin unprimed brass ranged 1.5570“ to 1.5585”. These are the same lot.

Ten pieces of my resized brass 1x that led to my question/concern ranged 1.5520” to 1.5535”. As noted above, their OAL was a major surprise to me. As an aside, these represented a mix of 4 different lots that were fired, tumbled with walnut, lubed and resized. These are ready for a wet tumble with stainless pins & Frankfort cleaner.

For curiosity, i checked a different lot of primed Lapua virgin brass (i hand primed with CCI400 caps) and they were 1.5585” for 10 cases.

My original question stands—seems i “over-resized” by roughly 0.005“ plus or minus a few thou, depending on which high/low are compared—but my resized brass doesn’t appear to need to be trimmed! Just a chamfer after cleaning.

i would have lost this bet, as i said above.