Hi,
I’m stuck on what’s happening here and need some help. I’m not an inexperienced reloader but I do have a lot still to learn.
I’m reloading 6.5CM using Lapua brass, CCI 450 small rifle primers and Berger 140gr Target Hybrids loaded to 2.85” COAL to fit in a magazine, mainly for PRS. The lands are at 2.90” using a Hornady headspace tool so I have a considerable jump but accuracy is excellent so no issues there.
I’m using a 26” Bartlein 1:7 and have 800 rounds down the barrel.
My brass prep is pretty basic. I knock the shoulders back 2 thou measured with the Hornady comparator tool and using a Foster Bushing Bump Die with a 290 insert to give 2 thou neck tension. I use a steel pin tumbler to clean and I don’t anneal. The brass OAL is 1.910 so hasn’t grown materially since new.
The brass is 4x fired and everything has worked well. I load 40.0gr and get 2840 FPS so on the warm side but no obvious pressure signs.
So here’s the issue - I loaded 200 rounds and found half won’t chamber. Hmm. I checked and found they had the same shoulder bump as the ones that chambered without an issue - i suspected case spring-back but that wasn’t a problem. I checked base, body diameter and they are also pretty consistent between the ones which chambered and those that didn’t.
The other important point to note is the cases chambered without a bullet loaded so the clue would seem to be somewhere in the neck area perhaps ? The Bergers are consistent and I measured a few of the pulled bullets and found them all to be 0.264 diameter.
In need of ammo for a match I loaded up some brand new Lapua brass to exactly the same dimensions as the previous batch (half of which chambered but half didn’t). Where it gets confusing is I loaded the same amount of powder from the same lot and seated the bullet to the same depth (both my Forster Bushing Bump Die and Forster Micro Seater Die have the lock rings tightened so never move) but when I chrono’d the load my velocity fell to 2700 FPS vs 2840 FPS for exactly the same components / load aside from new brass vs 4x fired that was bumped 2 thou with the 290 insert.
So what am I missing ? One thing I’ve noticed is new Lapua 6.5CM brass has neck case thickness of 0.14 but my 4x fired is 0.16. Would that be enough to stop the rounds from chambering and cause the velocity difference ? The ones which chambered are between 0.15 and 0.155. Can a chamber be that tight ? I do notice my fired case mouth is still around 2.92/93 so it doesn’t seem to be expanding that much. Is it possible for 2 thou extra neck thickness to build up when using a bushing bump die and could that be the issue ?
Also, why is my velocity so different between the new brass and the 4x fired brass ? Again, could neck wall diameter cause such a dramatic velocity change (temp / weather conditions were identical). I chrono’d them on the same day using a Magnetospeed and double checked by using a friends to confirm the velocities.
I have another multi caliber rifle and have fired thousands of rounds of .260 Rem and .308 Win just bumping the shoulder with a bushing die and some of my brass is 8-10x fired and I’ve never had an issue chambering, nor seen a velocity change.
Before I go out and learn about neck turning is there anything else i should check or be aware of ? Is it possible to tell if I have a particularly tight chamber, especially in the neck area ?
All help and advice is greatly appreciated. Thanks
I’m stuck on what’s happening here and need some help. I’m not an inexperienced reloader but I do have a lot still to learn.
I’m reloading 6.5CM using Lapua brass, CCI 450 small rifle primers and Berger 140gr Target Hybrids loaded to 2.85” COAL to fit in a magazine, mainly for PRS. The lands are at 2.90” using a Hornady headspace tool so I have a considerable jump but accuracy is excellent so no issues there.
I’m using a 26” Bartlein 1:7 and have 800 rounds down the barrel.
My brass prep is pretty basic. I knock the shoulders back 2 thou measured with the Hornady comparator tool and using a Foster Bushing Bump Die with a 290 insert to give 2 thou neck tension. I use a steel pin tumbler to clean and I don’t anneal. The brass OAL is 1.910 so hasn’t grown materially since new.
The brass is 4x fired and everything has worked well. I load 40.0gr and get 2840 FPS so on the warm side but no obvious pressure signs.
So here’s the issue - I loaded 200 rounds and found half won’t chamber. Hmm. I checked and found they had the same shoulder bump as the ones that chambered without an issue - i suspected case spring-back but that wasn’t a problem. I checked base, body diameter and they are also pretty consistent between the ones which chambered and those that didn’t.
The other important point to note is the cases chambered without a bullet loaded so the clue would seem to be somewhere in the neck area perhaps ? The Bergers are consistent and I measured a few of the pulled bullets and found them all to be 0.264 diameter.
In need of ammo for a match I loaded up some brand new Lapua brass to exactly the same dimensions as the previous batch (half of which chambered but half didn’t). Where it gets confusing is I loaded the same amount of powder from the same lot and seated the bullet to the same depth (both my Forster Bushing Bump Die and Forster Micro Seater Die have the lock rings tightened so never move) but when I chrono’d the load my velocity fell to 2700 FPS vs 2840 FPS for exactly the same components / load aside from new brass vs 4x fired that was bumped 2 thou with the 290 insert.
So what am I missing ? One thing I’ve noticed is new Lapua 6.5CM brass has neck case thickness of 0.14 but my 4x fired is 0.16. Would that be enough to stop the rounds from chambering and cause the velocity difference ? The ones which chambered are between 0.15 and 0.155. Can a chamber be that tight ? I do notice my fired case mouth is still around 2.92/93 so it doesn’t seem to be expanding that much. Is it possible for 2 thou extra neck thickness to build up when using a bushing bump die and could that be the issue ?
Also, why is my velocity so different between the new brass and the 4x fired brass ? Again, could neck wall diameter cause such a dramatic velocity change (temp / weather conditions were identical). I chrono’d them on the same day using a Magnetospeed and double checked by using a friends to confirm the velocities.
I have another multi caliber rifle and have fired thousands of rounds of .260 Rem and .308 Win just bumping the shoulder with a bushing die and some of my brass is 8-10x fired and I’ve never had an issue chambering, nor seen a velocity change.
Before I go out and learn about neck turning is there anything else i should check or be aware of ? Is it possible to tell if I have a particularly tight chamber, especially in the neck area ?
All help and advice is greatly appreciated. Thanks
