Case/Neck Trimming for 6.5mm Creedmore

[GunnyUSMC]

I reload 6.5 creedmore and have used small primer brass from Lapua, Peterson, and Alpha Munitions. When reloading, I always check my brass length with the appropriate gauge. So far, I have not intuitively seen a situation where my brass actually needs to be trimmed.

In conversations with others, they were surprised i do not trim and said they trim every time they reload.

I guess I may be a little confused because if my case length gauge indicates I am good, why would i trim case length and what would I trim it to if i am already within SAAMI Specs?

Thoughts and advice welcome.

 

[Carlos Danger]

Creedmoor

 

[GunnyUSMC]

Creedmoor

... ooops bad habbits are hard to break

thanks

 

[KnowNothing256]

Two camps, I think:

1) Trim when necessary only, to minimize time/effort/risk of damaging or ruining brass.
2) Trim every time so that every case is as perfectly uniform as possible.

I am very, very firmly in Camp 1. So much so that another Hide member recently suggested using a borescope on a chambered empty case to see if trimming is necessary at max book length and my mind went "Hell yes, that's brilliant." And sure enough, I was like 0.009" over book max length on my 4x fired Creedmoor brass and still not hitting the transition into the freebore, although it was very close. I'll trim that whole batch before I load up the 5x fired brass.

I'm not currently worried about an extra 0.009" of neck brass holding the bullets slightly differently. YMMV

 

[hafejd30]

The amount needed to be trimmed will depend on several things.

First when you fire virgin brass it’s not uncommon for the length to actually get shorter the first firing as the brass conforms to your chamber.

If you run mild loads it could be several firing before trimming is actually needed.

I’ve also noticed the more you size such as full length vs neck or neck/bump with body die will effect how much brass flows and needs to be trimmed

Running Lee collet dies on 308/260 etc I’ve needed to trim very little in the course of reloading

Lapua 308 casings will typically come around 2.005 in overall length. First firing may reduce the length a couple thousandths. But trim length is 2.015. So you’ll have a while running mild loads before trimming is needed

I usually shoot for 2.006” OAL on Lapua 308. I trim any casings over 2.008. Which usually means trimming a small amount in each reloading session.

 

[Baron23]

I have a Giraurd and trim every time to insure I have a nice inside chamfer (and it does a bit of exterior also). I do NOT adjust my trim length setting on the Giraurd...its set and I leave it there. I set for middle of SAAMI spec for 6.5 CM...1.91.

So often its the very least of trimming but it still seems to put the chamfer on the neck.

Oh, and I wouldn't listen to a thing I say as I'm very inexpert! haha...well, funny but true! LOL

 

[GunnyUSMC]

I am very, very firmly in Camp 1. So much so that another Hide member recently suggested using a borescope on a chambered empty case to see if trimming is necessary at max book length and my mind went "Hell yes, that's brilliant." And sure enough, I was like 0.009" over book max length on my 4x fired Creedmoor brass and still not hitting the transition into the freebore, although it was very close. I'll trim that whole batch before I load up the 5x fired brass.

Great idea... I have a borescope

However, how were you able to get that 0.009" measurement?

 

[GunnyUSMC]

I have a Giraurd and trim every time to insure I have a nice inside chamfer (and it does a bit of exterior also). I do NOT adjust my trim length setting on the Giraurd...its set and I leave it there. I set for middle of SAAMI spec for 6.5 CM...1.91.

Just to make sure I am following... SAAMI says COAL is 1.92-.020. You are trimming to 1.91, which is shorter than SAAMI.

Did I understand correctly?

If so, are you doing that to reduce neck tension on the bullet?

 

[KnowNothing256]

Great idea... I have a borescope

However, how were you able to get that 0.009" measurement?

Calipers, from the case head to the case mouth (basically, stick the whole case in a set of calipers). It didn't have to be super precise; I just went through 10 or 15 cases, found the few that were the longest, and chambered them with the borescope inserted through the muzzle to see where the end of the case sat in the chamber. None of the cases were getting pinched by the chamber at the case mouth, but they were getting pretty darn close. So I loaded that batch (have since fired a fair number of them and had no pressure spikes or accuracy problems), and will trim them all before the next loading.

 

[CK1.0]

Two camps, I think:

1) Trim when necessary only, to minimize time/effort/risk of damaging or ruining brass.
2) Trim every time so that every case is as perfectly uniform as possible.

I am very, very firmly in Camp 1. So much so that another Hide member recently suggested using a borescope on a chambered empty case to see if trimming is necessary at max book length and my mind went "Hell yes, that's brilliant." And sure enough, I was like 0.009" over book max length on my 4x fired Creedmoor brass and still not hitting the transition into the freebore, although it was very close. I'll trim that whole batch before I load up the 5x fired brass.

I'm not currently worried about an extra 0.009" of neck brass holding the bullets slightly differently. YMMV

This is nearly the same way I view it too, except that I feel like keeping the cases shorter and not worrying about it for a long time is better maybe than letting them get too long.

 

[Baron23]

Just to make sure I am following... SAAMI says COAL is 1.92-.020. You are trimming to 1.91, which is shorter than SAAMI.

Ah....no. haha 1.92 minus .02 = 1.90 and I trim to 1.91. Right in the middle of the range.

Its ok...I'm a senior and I think you may be also! LOL

Now, I have recently come across the startling concept of actually looking down my damn barrel with a bore scope with a trimmed case in the chamber to check the gap I'm leaving for carbon between the end of my neck and the small step up to the throat. So, depending on what I see, I may lengthen my cases a bit to reduce this if it seems excessive. There needs to be some clearance to ensure smooth cycling (and for what reasons??...as said, I'm no expert).

If so, are you doing that to reduce neck tension on the bullet?

No, I set neck tension either with the expander ball in my FL die or recently I've taken that ball out and have used mandrels and pin gauges to more accurately set the degree of neck tension. I actually just started with the mandrels with this batch of once fired Lapua brass that I prep'd but I haven't shot any of it yet (minor lumbar fusion surgery in early Mar...won't be shooting again until July). So, while I'm assuming that this will reduce my ES/SD, I really don't know. But I'm retired and reloading is more a hobby than a requirement so if I waste some time on unproductive processing its not a big loss.

I hope this is helpful, Gunny.

 

[AllenOne1]

I never have to trim my 6.5C cases and they have 12-14 firings on them. I do anneal every time and I do chamfer inside and out every time.

 

[GunnyUSMC]

Ah....no. haha 1.92 minus .02 = 1.90 and I trim to 1.91. Right in the middle of the range.

Its ok...I'm a senior and I think you may be also! LOL

ahhhh.... i did not interpret SAAMI correctly, got it now

yea, i am a senior. I got addicted to this precision ELR stuff and just making up for lost time.

 

[GunnyUSMC]

No, I set neck tension either with the expander ball in my FL die or recently I've taken that ball out and have used mandrels and pin gauges to more accurately set the degree of neck tension. I actually just started with the mandrels with this batch of once fired Lapua brass that I prep'd but I haven't shot any of it yet (minor lumbar fusion surgery in early Mar...won't be shooting again until July). So, while I'm assuming that this will reduce my ES/SD, I really don't know. But I'm retired and reloading is more a hobby than a requirement so if I waste some time on unproductive processing its not a big loss.

I hope this is helpful, Gunny.

Very helpful... thanks

Sorry to hear about the surgery. I suffer from degenerative disks in the L4 L5. I considered the same surgery until a Dr recommended trying the Rhizotomy procedure, which is simply a 30minute outpatient procedure to burn the nerve endings so they cannot transmit pain signals. It works and greatly reduces pain though i do have to get the procedure done twice each year because the nerves will grow back. I am still able to get into the prone and the pain is minimal. One day, i may need the fusion.

I have heard of guys not seating their bullets to the full length of the neck using the rationale that the more contact the bullet has with the neck the more pressure needed to push it out of the neck, hence neck tension question. I personally do not subscribe to this approach. However, I also do not allow my bullet to be seated deep into the case beyond the neck either and for multiple reasons.

I switched over to the Redding 3-die set allowing me to full-length resize separate from neck sizing. At that time, i stopped using the expander ball and instead follow the process you mention above... size the neck followed by the mandrel. This process has improved my SDs.

I also turn/trim my necks after first firing to achieve equal tension on the full diameter of the bullet. Only gotta do this once and it did help with SDs as well.

 

[Baron23]

Very helpful... thanks

Sorry to hear about the surgery. I suffer from degenerative disks in the L4 L5. I considered the same surgery until a Dr recommended trying the Rhizotomy procedure, which is simply a 30minute outpatient procedure to burn the nerve endings so they cannot transmit pain signals. It works and greatly reduces pain though i do have to get the procedure done twice each year because the nerves will grow back. I am still able to get into the prone and the pain is minimal. One day, i may need the fusion.

I have heard of guys not seating their bullets to the full length of the neck using the rationale that the more contact the bullet has with the neck the more pressure needed to push it out of the neck, hence neck tension question. I personally do not subscribe to this approach. However, I also do not allow my bullet to be seated deep into the case beyond the neck either and for multiple reasons.

I switched over to the Redding 3-die set allowing me to full-length resize separate from neck sizing. At that time, i stopped using the expander ball and instead follow the process you mention above... size the neck followed by the mandrel. This process has improved my SDs.

I also turn/trim my necks after first firing to achieve equal tension on the full diameter of the bullet. Only gotta do this once and it did help with SDs as well.

not to turn this into another “oh my painful back” thread…haha…but nerve ablation was not applicable to my situation. L3/4 disk was gone and L4/5 was in its way. Doing pretty good already and I don’t expect any issues w prone once healed.

I have SAAMI chambers in my barrels with a fair degree of free bore so I seat to mag length minus 10 thousands. Base of the boat tail Berger hybrids is right at the neck-shoulder junction and the powder is not compressed with this seating depth.

You neck turn? That’s a rabbit hole I have not yet dove into.

Cheers.

 

[GunnyUSMC]

You neck turn? That’s a rabbit hole I have not yet dove into.

I do. There are different solutions out there. K&M, Hornady to name a few. I went with K&M but I think Hornady is easier to use. Only do it once. I was inspired by others then i started measuring case thickness at the neck and found many where not the same for the full diameter of a given neck and not consistent from case to case. Trimming necks helped to resolve that and improve consistency of my loads.

 

[Baron23]

I do. There are different solutions out there. K&M, Hornady to name a few. I went with K&M but I think Hornady is easier to use. Only do it once. I was inspired by others then i started measuring case thickness at the neck and found many where not the same for the full diameter of a given neck and not consistent from case to case. Trimming necks helped to resolve that and improve consistency of my loads.

Do you have a micrometer to measure wall thickness?