the + and -'s of shoulder angles
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I know with straighter cases there is less need for trimming, so I assume that means less case stretch. I haven't experimented in any kind of way, I just know my straighter bodied cases need less than the more tapered stuff.
+ Less case stretch
+ Less frequent trimming. I trim my AI cases about every 7-8 firings vs every 3 for non-AI cases.
+ Less split necks.
+ Extends case life
- Often require fire forming brass.
+ Less frequent trimming. I trim my AI cases about every 7-8 firings vs every 3 for non-AI cases.
+ Less split necks.
+ Extends case life
- Often require fire forming brass.
nothing like the 22-250rem case the way it's tapered, but a moderately tapered case (say, .001-.003 per inch). going off modern cartridges that have less case taper that either use an AI type shoulder (give or take 5*) and possibly a longer neck.
given it's formed for that particular firearm, correct.
22-250 is the worst that I've ever had. Most everything I have now is "modern" and it's a big reason I don't own some cartridges that are considered staples.
MagnumManiac
Well-Known Member
To answer this simply as someone that designs my own cases, YES, shoulder angle and case taper matter, not just for the brass, but for the chamber throat too.
Minimum case taper to stop ANY chance of sticky extraction, has been tested to be .005" per inch. Ackley is .010" per inch.
Shoulder angle does 2 things, the steeper it is, the less case growth you get and it holds the flame front longer inside the case and protects the throat/leade for longer. Even straight walled cases have a minimum case taper parameter.
Neck length is also a consideration in conjunction with shoulder angle.
30° is useless for throat protection, 35° does provide SOME throat protection, 40° definitely protects throats with neck length minimums and 45° provides maximum protection to the throat with neck length optimums and cases hardly ever stretch.
The ONLY difficulty with these shoulder angles is the fact that sizing them becomes difficult as the brass resists and springs back to memory, so annealing is necessary every firing.
If you understand these difficulties first, then have your dies made, there should be no clickers and other such issues.
Cheers.
Minimum case taper to stop ANY chance of sticky extraction, has been tested to be .005" per inch. Ackley is .010" per inch.
Shoulder angle does 2 things, the steeper it is, the less case growth you get and it holds the flame front longer inside the case and protects the throat/leade for longer. Even straight walled cases have a minimum case taper parameter.
Neck length is also a consideration in conjunction with shoulder angle.
30° is useless for throat protection, 35° does provide SOME throat protection, 40° definitely protects throats with neck length minimums and 45° provides maximum protection to the throat with neck length optimums and cases hardly ever stretch.
The ONLY difficulty with these shoulder angles is the fact that sizing them becomes difficult as the brass resists and springs back to memory, so annealing is necessary every firing.
If you understand these difficulties first, then have your dies made, there should be no clickers and other such issues.
Cheers.
so, throat angle centerer in neck before mouth would be best compared to center in front of mouth opening? this keeps flame more contained in the case itself? does this harden the brass so it's springback is more difficult?
i see where some newer designs don't have this, but with steeper angle only gives greater powder capacity and w/o single feeding it defeats some purpose as to seat bullet further out to give that room needed. this of course can be a mag restriction problem? by keeping the boat-tail in the shoulder you might defeat the purpose of an improved shoulder if it can only be seated to the same coal/oal.
MagnumManiac
Well-Known Member
Throat angle is irrelevant.
Shoulder angle is what protects the throat because the angle is harder for the gasses and powder plug to force through after the bullet has left the case. The bullet, being seated so the boattail is only below the neck/shoulder juncture, is covering the throat as it leaves the case, less gas is therefore eroding the throat. Think of it like a delayed ignition.
Unlike what QL says, optimum burn, 90-100% powder burn, happens within a few inches of the chamber, this heat and, any minimising of said heat, is what makes throats last longer.
Longer throats also erode slower, but it depends on powder type used. Large kernels are abrasive. The coolest burning powders are Ball powders, even though double base, they aren't classified as progressive, but Digressive in burn. This makes them cooler although gas volume is higher.
Anyway, shoulder angle, neck length, case taper all play a role in protecting throats, especially in large 100+ grains of powder volume cases.
The worst shoulder angle and tapered case is the 375H&H, it grows .010" after sizing EVERY time, sometimes more.
This is why I went to 375 Weatherby, still have my 375H&H Kimber Talkeetna, but I don't shoot it often and definitely not hunting with it.
The other 2 I have are 22-250 and 257 Roberts, these stretch much too, so I chambered in Ackley, brass has never been trimmed in either.
Cheers.
Shoulder angle is what protects the throat because the angle is harder for the gasses and powder plug to force through after the bullet has left the case. The bullet, being seated so the boattail is only below the neck/shoulder juncture, is covering the throat as it leaves the case, less gas is therefore eroding the throat. Think of it like a delayed ignition.
Unlike what QL says, optimum burn, 90-100% powder burn, happens within a few inches of the chamber, this heat and, any minimising of said heat, is what makes throats last longer.
Longer throats also erode slower, but it depends on powder type used. Large kernels are abrasive. The coolest burning powders are Ball powders, even though double base, they aren't classified as progressive, but Digressive in burn. This makes them cooler although gas volume is higher.
Anyway, shoulder angle, neck length, case taper all play a role in protecting throats, especially in large 100+ grains of powder volume cases.
The worst shoulder angle and tapered case is the 375H&H, it grows .010" after sizing EVERY time, sometimes more.
This is why I went to 375 Weatherby, still have my 375H&H Kimber Talkeetna, but I don't shoot it often and definitely not hunting with it.
The other 2 I have are 22-250 and 257 Roberts, these stretch much too, so I chambered in Ackley, brass has never been trimmed in either.
Cheers.
Are you using a full length die with expander or a neck bushing die?
Full length sizing for Me these days basically consists of bumping the 40 degree shoulder .0015 to .002
Just enough to make them chamber without too much engagement of the lugs.
AND: get that expander ball/button out of the sizing die. Use a bushing die and separate expander mandrel.
Just enough to make them chamber without too much engagement of the lugs.
AND: get that expander ball/button out of the sizing die. Use a bushing die and separate expander mandrel.
MagnumManiac
Well-Known Member
Polished, correctly sized expanders used with powdered graphite do not pull brass causing longer cases. This is a fallacy, the extra length comes from the body being squeezed and brass is forced into the shoulder. Have seen this fallacy re-written so often it's ridiculous.
Agree with using mandrels.
Cheers.
I use non-bushing full size dies with expander ball removed. I use an expander mandrel to establish neck tension.
