I have never known to have seen the donut inside a case neck. Never had issues with inaccuracies from my loads. So what do I look for and/or what are the signs one is forming? Have loaded 6.5 cm custom rifles for years with no issues.
Donuts
- Thread starter bbowles
- Start date
One of the classic tests is to take a fired case, a new bullet, and drop it in the case neck. If it hits/stops at the case neck/shoulder junction, you have a donut (and a bad one). Lesser versions could probably be found using pin gauges of the appropriate size i.e. just slightly smaller than the fired case neck ID.
In my mind... donuts used to be a lot bigger deal than they maybe are nowadays. Different bullet and cartridge designs now, that seat the bullet out to where the bullet body/boat-tail junction is just ahead of that case neck/body junction, so that even if you *do* have donuts start forming, they don't really affect anything. Older bullet and cartridge designs tended towards a lot longer bullet bearing surfaces, longer/skinnier cases and/or shorter OAL, all of which conspired to push the body diameter of the bullet down past that case neck/body junction, right where donuts can form. Also, older cartridge case designs tended to have more body taper, and shallower shoulder angles - both of which tend to accentuate brass 'flow' towards the case mouth during the reloading cycle, meaning more of the thicker shoulder brass ended up flowing into the thinner neck area, i.e. donuts.
In my mind... donuts used to be a lot bigger deal than they maybe are nowadays. Different bullet and cartridge designs now, that seat the bullet out to where the bullet body/boat-tail junction is just ahead of that case neck/body junction, so that even if you *do* have donuts start forming, they don't really affect anything. Older bullet and cartridge designs tended towards a lot longer bullet bearing surfaces, longer/skinnier cases and/or shorter OAL, all of which conspired to push the body diameter of the bullet down past that case neck/body junction, right where donuts can form. Also, older cartridge case designs tended to have more body taper, and shallower shoulder angles - both of which tend to accentuate brass 'flow' towards the case mouth during the reloading cycle, meaning more of the thicker shoulder brass ended up flowing into the thinner neck area, i.e. donuts.
Appreciate the help! I shoot mostly 6.5 cm with berger 140 hybrids or hornady 143 eld-x. Never noticed seating harder as the press neared the bottom of the stroke. Also, I seat it about 0.020 off lands in custom rifle. So don't get too close to the neck/shoulder junction. Thanks again for the help!
To check for doughnuts you need to use a PIN gage of the correct size for your RESIZED case neck.
For example a 6.5mm will typically need a pin gage of between .261 to .263. The pin gage should just fit
and slide into the case neck. If the pin gage stops at the neck shoulder junction you have a doughnut.
Now if the bullet you use does not go past the doughnut then it is a non issue but if your bullet gets pushed
into the doughnut then it will cause issues.
Hard seating at the bottom of the stroke, inconsistent bullet seating depth, lousy ES/SD numbers and
dents (rings) caused by the bullet seating stem to name a few.
For example a 6.5mm will typically need a pin gage of between .261 to .263. The pin gage should just fit
and slide into the case neck. If the pin gage stops at the neck shoulder junction you have a doughnut.
Now if the bullet you use does not go past the doughnut then it is a non issue but if your bullet gets pushed
into the doughnut then it will cause issues.
Hard seating at the bottom of the stroke, inconsistent bullet seating depth, lousy ES/SD numbers and
dents (rings) caused by the bullet seating stem to name a few.
The 6.5CM was specifically designed to address some of the... shortcomings... of the .260 Rem.
Before the .260 Rem was the 6.5-08 (my first XTC match rifle, and no, I'm not a Boomer) which really was meant (in my mind) for pre '64 Mod 70s i.e. long action. In a R700SA, it still worked, but for the short yard lines you were 'stuck' with 107-120gn bullets seated short to mag length (2.800") and fed from a stripper clip. For 600+ you could use S142MKs seated long, and take more (not full) advantage of the extra boiler room. Forming that brass was a PITA - you could either take Lapua .243 Win, neck it up, and be turning off donuts on the regular, or neck down Winchester .308 brass, but have to sort/cull the everlovin' shit out of that crap brass.
The .260 Rem was an attempt to get the ballistics of that 6.5-08, in a factory mag-fed round. They took basically the exact same case - a .308 Win necked down to 6.5mm, and then loaded it up with 140gn bullets that were stuffed *way* back in the case. Fortunately (for Remington, not so much in terms of general good design) the 6.5-08 / .260 had a *lot* of excess case capacity that largely went un-used. You could pick up a max load and shake it like a maraca. Lots of downsides - neck donuts, because you still had the body taper and shoulder angle of the parent cartridge (.308 Win), and some inconsistent MV due to how the powder sometimes lay as the gun was handled prior to pulling the trigger and igniting the powder - the powder 'column' wasn't always right up against the flash hole. No bueno.
The 6.5 CM basically took the same general bullet design at the same OAL, and trimmed away all the 'extra' in between there and the case head. The case body lost most of the taper, the shoulder angle sharpened up a bit (still a little bit shallow to allow for easy feeding), and the case body got a lot shorter to lose that extra 'air' space inside the case, and get the case neck down where it needed to be on that 140+ gn bullet.
So yeah, if most of your reloading has been with the 6.5CM and later... congrats, you got to skip over a lot of painful B.S. that came before
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Truth 100% but I loved and still have a few 260 that I'll never get rid ofThe 6.5CM was specifically designed to address some of the... shortcomings... of the .260 Rem.
Before the .260 Rem was the 6.5-08 (my first XTC match rifle, and no, I'm not a Boomer) which really was meant (in my mind) for pre '64 Mod 70s i.e. long action. In a R700SA, it still worked, but for the short yard lines you were 'stuck' with 107-120gn bullets seated short to mag length (2.800") and fed from a stripper clip. For 600+ you could use S142MKs seated long, and take more (not full) advantage of the extra boiler room. Forming that brass was a PITA - you could either take Lapua .243 Win, neck it up, and be turning off donuts on the regular, or neck down Winchester .308 brass, but have to sort/cull the everlovin' shit out of that crap brass.
The .260 Rem was an attempt to get the ballistics of that 6.5-08, in a factory mag-fed round. They took basically the exact same case - a .308 Win necked down to 6.5mm, and then loaded it up with 140gn bullets that were stuffed *way* back in the case. Fortunately (for Remington, not so much in terms of general good design) the 6.5-08 / .260 had a *lot* of excess case capacity that largely went un-used. You could pick up a max load and shake it like a maraca. Lots of downsides - neck donuts, because you still had the body taper and shoulder angle of the parent cartridge (.308 Win), and some inconsistent MV due to how the powder sometimes lay as the gun was handled prior to pulling the trigger and igniting the powder - the powder 'column' wasn't always right up against the flash hole. No bueno.
The 6.5 CM basically took the same general bullet design at the same OAL, and trimmed away all the 'extra' in between there and the case head. The case body lost most of the taper, the shoulder angle sharpened up a bit (still a little bit shallow to allow for easy feeding), and the case body got a lot shorter to lose that extra 'air' space inside the case, and get the case neck down where it needed to be on that 140+ gn bullet.
So yeah, if most of your reloading has been with the 6.5CM... congrats, you got to skip over a lot of painful B.S. that came before
