Proper amount of FL shoulder bump 308

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Kryogen

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I had adjusted my lee die "by feel" to just close my bolt without resistance.

Today, I got my hdy headspace measurement kit, with my mitutoyo calipers.

I made some measurements, and the headspace appears to be 1.6220 fired, and my sized cases are 1.6165. That gives 5.5 mils of shoulder bump, which is excessive vs the suggested 2 mils.

Adjust die for 2 mils of bump and deal with a little bolt resistance?

Thanks
 
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Ganderite said:
With a bolt rifle I like the bolt to hit resistance about half way through the swing closed.

make sure the bolt locking lugs are greased.
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This /l\

When I reload cartridges for bolt rifles, I don't reload for the cases to be used in another rifle which may have a slightly different chamber. That's why they recommend the 2mil set back. I never set back the shoulders on my cases and neck resize only unless I start getting some issues, which are checked out before a hunt by cycling all of the rounds I will be taking. When I do set back the shoulders, I re anneal the necks and shoulder to slightly below where the case wall and shoulder come together.

When brass has over a dozen reloads, I will reanneal the whole case by heating in an oven and dumping into cold water. I have some 30-06 with over 60 reloads through them and they ae still going strong.

Bench Rest shooters have rifles with very tight chambers. Usually they have to turn down the diameter of their necks to get them to fit into the chambers when loaded with a bullet. I won't go into the process because that would just take up space and it obviously doesn't apply to you. Most commercial rifle chambers are cut with generic reamers that are made up to maximum specs and sharpened as they wear to very close to minimum spec. If you should be lucky enough to have a minimum spec chamber then you might need to bump back the shoulder after the first firing. After that, the brass, if loaded under maximum pressures shouldn't flow enough to cause you any issues. Anyway, bench rest shooters seldom if ever bump back the shoulders. The cases will never be chambered into any other rifle other than their specific match rifle. They never full length resize. We are talking about chambers cut to minimum specs and the cases only sized with special order Wilson dies on an arbor press. These dies have special carbide inserts that are sized so that there is only .002in of compression on the bullet and about the same clearance in the neck area of the chamber. Bullets are usually seated out far enough to be set back by the leade. This usually gives the best accuracy.

Because of the generous proportions of commercial chambers this practice isn't always encouraged. By neck sizing only, not only does your brass last longer but you customize the brass to fit your rifle's particular chamber and they may not work in other chambers.
 
bearhunter said:
This /l\

When I reload cartridges for bolt rifles, I don't reload for the cases to be used in another rifle which may have a slightly different chamber. That's why they recommend the 2mil set back. I never set back the shoulders on my cases and neck resize only unless I start getting some issues, which are checked out before a hunt by cycling all of the rounds I will be taking. When I do set back the shoulders, I re anneal the necks and shoulder to slightly below where the case wall and shoulder come together.

When brass has over a dozen reloads, I will reanneal the whole case by heating in an oven and dumping into cold water. I have some 30-06 with over 60 reloads through them and they ae still going strong.

Bench Rest shooters have rifles with very tight chambers. Usually they have to turn down the diameter of their necks to get them to fit into the chambers when loaded with a bullet. I won't go into the process because that would just take up space and it obviously doesn't apply to you. Most commercial rifle chambers are cut with generic reamers that are made up to maximum specs and sharpened as they wear to very close to minimum spec. If you should be lucky enough to have a minimum spec chamber then you might need to bump back the shoulder after the first firing. After that, the brass, if loaded under maximum pressures shouldn't flow enough to cause you any issues. Anyway, bench rest shooters seldom if ever bump back the shoulders. The cases will never be chambered into any other rifle other than their specific match rifle. They never full length resize. We are talking about chambers cut to minimum specs and the cases only sized with special order Wilson dies on an arbor press. These dies have special carbide inserts that are sized so that there is only .002in of compression on the bullet and about the same clearance in the neck area of the chamber. Bullets are usually seated out far enough to be set back by the leade. This usually gives the best accuracy.

Because of the generous proportions of commercial chambers this practice isn't always encouraged. By neck sizing only, not only does your brass last longer but you customize the brass to fit your rifle's particular chamber and they may not work in other chambers.
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If you anneal the whole case, it's ruined. Your oven won't even get hot enough anyways. It also doesn't matter if you quench brass in water, or let it air cool
 
Tenguns said:
If you anneal the whole case, it's ruined. Your oven won't even get hot enough anyways. It also doesn't matter if you quench brass in water, or let it air cool
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You should explain that to the people that reload military ammo in Brazil. You also don't know my oven's capabilities. I have been doing this since watching a commercial reloading company in Brazil in 1976. They get millions of cartridge cases from all over South America to reload for the surrounding nations militaries to use for target practice. They do it in two stages. One they take the brass back to the same condition it was in when first made by heating up the whole case then after prepping the case they reheat the necks to anneal them by allowing them to air cool so they can increase neck tension enough to hold the bullets during full auto fire. Ask H4831 about what he learned when only annealing the necks.
 
A headspace guage reads to a arbitrary data point. That's better than nothing but no guarantee that this is the point where your shoulder hits in your chamber. You gonna believe your gauge or your gun?
 
bearhunter said:
You should explain that to the people that reload military ammo in Brazil. You also don't know my oven's capabilities. I have been doing this since watching a commercial reloading company in Brazil in 1976. They get millions of cartridge cases from all over South America to reload for the surrounding nations militaries to use for target practice. They do it in two stages. One they take the brass back to the same condition it was in when first made by heating up the whole case then after prepping the case they reheat the necks to anneal them by allowing them to air cool so they can increase neck tension enough to hold the bullets during full auto fire. Ask H4831 about what he learned when only annealing the necks.
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So does your oven get over 700 degrees F?
 
I go zero to .002" bump, but do it with Redding competition shell-holders. Nothing to measure, just run through the series until I get the resistance or lack of resistance I want.
 
Dogleg said:
A headspace guage reads to a arbitrary data point. That's better than nothing but no guarantee that this is the point where your shoulder hits in your chamber. You gonna believe your gauge or your gun?
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Below a Colt Field gauge for a AR15 at 1.4736

headspacegauge006_zps3cdabdf4.jpg


Below my "calibrated" Hornady gauge reading the Field gauge.

headspacegauge_zps14d3b71f.jpg


And now a fired case from my AR15 rifle and even with brass spring back will not be .001 longer than this measurement.

headspacegauge005_zps20685e73.jpg


And now to my main point, any case that does not have uniform case wall thickness can warp when fired. And when this happens the base of the case will no longer be 90 degrees to the axis of the bore. Meaning if you do have resistance closing the bolt the case will be tilted and the bullet will not be in perfect alignment with the bore. With these type cases they recommend doing a runout test on the base and placing a index mark at the highest point. Then the cases will be placed in the chamber with the index mark at the 12:00 position.

Now if you bump the case shoulder back .002 from its fired headspace length the base of the case will not be touching the bolt face. And a warped tilted case has very little effect with bullet alignment.

Below a full length resized case with .002 shoulder bump is supported by the bolt face and the ejector is pushing the case away from the bolt face. (.002 to .003 head clearance with brass spring back)

boltface2_zpsdf1f12bc.jpg


Below the front of the full length resized case is supported and centered in the throat of the rifle.

chamber-neck-diagram-with-cartridge2x_zps7395df40.jpg


The above full length resized case with .002 shoulder bump is only touching at the shoulder in the chamber. The base of the case is not touching the bolt face, the body of the case is not touching the chamber walls. This means by full length resizing with approximately .002 shoulder bump you "greatly" reduce the chance of miss-alignment caused by errors of warped cases or chamber errors.

Below is by Kevin Thomas who worked in the Sierra ballistics test lab and now shoots for "Team Lapua USA".
Mr. Thomas full length resizes all his cases with .001 to .002 shoulder bump in his custom made rifles.

And I'm a firm believer in the "rat turd in the violin case theory". ;)

KTLapua-b_zps8d1abc2c.jpg
 
With belted mags like 300 win mag, because it headspaces on the belt, how do we deal with headspace? not bother and just adjust shoulder bump .002 ?
 
Kryogen said:
With belted mags like 300 win mag, because it headspaces on the belt, how do we deal with headspace? not bother and just adjust shoulder bump .002 ?
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I usually ignore the belt and size the cases like anything else. Where the belt is given some thought is on chambering the barrel in the first place. We shorten it up until the bolt won't even close on a go gauge but will swallow any brass case we ever tried. Spec on a headspace gauge is huge compared to brass, and shortening it up gets the case head back where it belongs from the first shot on new cases.
 
bearhunter said:
You should explain that to the people that reload military ammo in Brazil. You also don't know my oven's capabilities. I have been doing this since watching a commercial reloading company in Brazil in 1976. They get millions of cartridge cases from all over South America to reload for the surrounding nations militaries to use for target practice. They do it in two stages. One they take the brass back to the same condition it was in when first made by heating up the whole case then after prepping the case they reheat the necks to anneal them by allowing them to air cool so they can increase neck tension enough to hold the bullets during full auto fire. Ask H4831 about what he learned when only annealing the necks.
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You're confusing me. Brass is non ferrous. It doesn't matter how you cool it, the results are the same. Brass is annealed during case manufacturing steps to prevent it from splitting. Once fired a few times, you only anneal the neck/shoulder area to soften the brass that's been work hardened to prevent neck splits. ( and again it doesn't matter if you air, or water cool it )What happens when you only anneal necks? Nothing. Anneal the whole case? Junk. Show me an annealing machine company that recommends doing the whole case. Show me a component manufacturer that recommends annealing the whole case. Show me a source recommending annealing the whole case.
 
I'll not only agree with Tenguns, but add that there are sources that say that annealing the case body is a horrible and dangerous idea. The body and base of the case should be hardened to resist the pressures of firing, whereas the shoulder and neck should be ductile/annealed for plasticity/crack prevention and release of the bullet.
 
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