The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Rifles Wildcats And Their Development Ok..what the hell does bump the shoulder back mean...Go | New | Find | Notify | Tools | Reply | |
| Ok..what the hell does bump the shoulder back mean... | Login/Join |
One of Us |
I am assuming it means push the shoulder down closer to the case head... but assumption is the mother of all f**K ups... Mike Legistine actu quod scripsi? Never under estimate the internet community's ability to reply to your post with their personal rant about their tangentially related, single occurrence issue.  What I have learned on AR, since 2001: 1. The proper answer to: Where is the best place in town to get a steak dinner? is…You should go to Mel's Diner and get the fried chicken. 2. Big game animals can tell the difference between .015 of an inch in diameter, 15 grains of bullet weight, and 150 fps. 3. There is a difference in the performance of two identical projectiles launched at the same velocity if they came from different cartridges. 4. While a double rifle is the perfect DGR, every 375HH bolt gun needs to be modified to carry at least 5 down. 5. While a floor plate and detachable box magazine both use a mechanical latch, only the floor plate latch is reliable. Disregard the fact that every modern military rifle uses a detachable box magazine. 6. The Remington 700 is unreliable regardless of the fact it is the basis of the USMC M40 sniper rifle for 40+ years with no changes to the receiver or extractor and is the choice of more military and law enforcement sniper units than any other rifle. 7. PF actions are not suitable for a DGR and it is irrelevant that the M1, M14, M16, & AK47 which were designed for hunting men that can shoot back are all PF actions. 8. 95 deg F in Africa is different than 95 deg F in TX or CA and that is why you must worry about ammunition temperature in Africa (even though most safaris take place in winter) but not in TX or in CA. 9. The size of a ding in a gun's finish doesn't matter, what matters is whether it’s a safe ding or not. 10. 1 in a row is a trend, 2 in a row is statistically significant, and 3 in a row is an irrefutable fact. 11. Never buy a WSM or RCM cartridge for a safari rifle or your go to rifle in the USA because if they lose your ammo you can't find replacement ammo but don't worry 280 Rem, 338-06, 35 Whelen, and all Weatherby cartridges abound in Africa and back country stores. 12. A well hit animal can run 75 yds. in the open and suddenly drop with no initial blood trail, but the one I shot from 200 yds. away that ran 10 yds. and disappeared into a thicket and was not found was lost because the bullet penciled thru. I am 100% certain of this even though I have no physical evidence. 13. A 300 Win Mag is a 500 yard elk cartridge but a 308 Win is not a 300 yard elk cartridge even though the same bullet is travelling at the same velocity at those respective distances. | ||
|
| one of us |
Zakly. In a rimless, unbelted case is means more headspace. Problem. | |||
|
| one of us |
Instead of full-length resizing the case you set the dies to just barely "kiss" the shoulder moving it back about 1/1000" or so. This allows you to have a more perfect fit in the chamber the round was shot in....may or may not chamber in a different rifle of the same caliber. DB Bill aka Bill George | |||
|
| One of Us |
DB is right. You don't want to resize/push the shoulder back any more than needed, only enough the close the bolt easily. Any more than that and you are over working brass and it won't last as long. The best way to set upi the die is take the firing pin out, so all you have is the empty bolt. Then back the sizing die up, run a case in and try it. Keep sneeking the die down until the bolt just falls on closing. Lock it down. And, again as DB said, it may not be enough for another gun | |||
|
| One of Us |
OKay so it does mean push the shoulder down towasrds the case head...but why not just neck size? Or is the technique use when trying to do minimum sizing on caes not fired in a particular gun? Mike Legistine actu quod scripsi? Never under estimate the internet community's ability to reply to your post with their personal rant about their tangentially related, single occurrence issue. What I have learned on AR, since 2001: 1. The proper answer to: Where is the best place in town to get a steak dinner? is…You should go to Mel's Diner and get the fried chicken. 2. Big game animals can tell the difference between .015 of an inch in diameter, 15 grains of bullet weight, and 150 fps. 3. There is a difference in the performance of two identical projectiles launched at the same velocity if they came from different cartridges. 4. While a double rifle is the perfect DGR, every 375HH bolt gun needs to be modified to carry at least 5 down. 5. While a floor plate and detachable box magazine both use a mechanical latch, only the floor plate latch is reliable. Disregard the fact that every modern military rifle uses a detachable box magazine. 6. The Remington 700 is unreliable regardless of the fact it is the basis of the USMC M40 sniper rifle for 40+ years with no changes to the receiver or extractor and is the choice of more military and law enforcement sniper units than any other rifle. 7. PF actions are not suitable for a DGR and it is irrelevant that the M1, M14, M16, & AK47 which were designed for hunting men that can shoot back are all PF actions. 8. 95 deg F in Africa is different than 95 deg F in TX or CA and that is why you must worry about ammunition temperature in Africa (even though most safaris take place in winter) but not in TX or in CA. 9. The size of a ding in a gun's finish doesn't matter, what matters is whether it’s a safe ding or not. 10. 1 in a row is a trend, 2 in a row is statistically significant, and 3 in a row is an irrefutable fact. 11. Never buy a WSM or RCM cartridge for a safari rifle or your go to rifle in the USA because if they lose your ammo you can't find replacement ammo but don't worry 280 Rem, 338-06, 35 Whelen, and all Weatherby cartridges abound in Africa and back country stores. 12. A well hit animal can run 75 yds. in the open and suddenly drop with no initial blood trail, but the one I shot from 200 yds. away that ran 10 yds. and disappeared into a thicket and was not found was lost because the bullet penciled thru. I am 100% certain of this even though I have no physical evidence. 13. A 300 Win Mag is a 500 yard elk cartridge but a 308 Win is not a 300 yard elk cartridge even though the same bullet is travelling at the same velocity at those respective distances. | |||
|
Moderator |
I think what it really means is properly sizing the case for your chamber. There should be a few thousandths clearance for a new case in the chamber. The problem is when you fl size in a generic die, and then feed the round in a chamber that wasn't cut to minimum specs, you get more then a few thousanths of clearance, ie excessive headspace. Brass does grow, and neck sizing only doesn't provide the needed clearance. Chambering brass that has grown is difficult, not good in hunting situations, and the added stress on the locking mechanism of the action isn't a good thing. __________________________________________________ The AR series of rounds, ridding the world of 7mm rem mags, one gun at a time. | |||
|
| One of Us |
In a word, yes. You are pushing the shoulder back towards the case head. Now, the statement of growing brass came up. Why do you suppose this happens? If a chamber/bolt lock-up is tight, in theory there should be no growing. But this rarely happens. Most factory guns have some amount of non-contact in the locking lugs. So when the round fires, the bolt sets back a small degree, the brass expands to this set-back distance, hence the growing brass. And this is when you will have a sticky bolt opening. The better the lock-up, the less brass problems you will have. A friend has a 10" BAT action, massive is a better word for this. It is so tight, locks up so tight, you can expand the primer pockets to where the primers won't stay in, in one firing. Never had a sticky bolt, no signs of pressure, except the pockets. | |||
|
| one of us |
In my experience, brass "grows" by flowing forward, resulting in a longer "neck". That's why cases periodically have to be trimmed. It has nothing to do with bolt setback IMO. "There are only three kinds of people; those who can count, and those who can't." | |||
|
| one of us |
One of the easiest ways to adjust your sizing die is to "paint" the neck and shoulder of the case with red magic marker. Turn your die back from it's precious position and run a case thru it. You can see how far you need to go by how much of the red ink is removed. Do this in increments until it just starts to smduge the shoulder...another 1/4 turn and you should be there. P.S. Use one of the nifty Stoney-Point tools to measure the shoulder before and after you start to confirm how much you moved the shoulder. 2nd PS I don't like to just neck-size for ammo that is going to be used in a repeater. In a rifle that will be used as a single-shot it's fine. DB Bill aka Bill George | |||
|
one of us |
This can be especially vexing whem working with Ackley mproved cases. When "ironing out" the mouths or perhaps necking up, one must be particularly cautious as a little (actually a lot) "bumping back" can occur. When the standard (say 27*) shoulder is "bumped back" to the (set back) 40* A.I. shoulder, there is absolutly no headspace control for fireforming whatsoever. GOOGLE HOTLINK FIX FOR BLOCKED PHOTOBUCKET IMAGES https://chrome.google.com/webs...inkfix=1516144253810 | |||
|
| One of Us |
Glen, You are right that brass does flow to a degree. But, the brass comes from somewhere, and that is from the body of the case. At some point it time, a ring will form in front of the web, and a separation is imminent. However, what I was addessing, was why this need for bumping the shoulder occurs. Granted, there is always clearance between the case and chamber. In a true match chamber and a properly sized case, this clearance is minimal. Yet, it is still possible to get a sticky bolt lift from hot loads. Now, if there was ZERO locking lug deflection, how would the brass be allowed to expand and create the need for bumping back the shoulder? The small amount of clearance in the tight chamber scenario, the brass "spring-back" would not create the strectching brass. It happens when the chamber is extended from the set-back. Dan Lilja studied and wrote about this when evaluating certain actions. | |||
|
| Powered by Social Strata |
 | Please Wait. Your request is being processed... |
|
The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Rifles Wildcats And Their Development Ok..what the hell does bump the shoulder back mean...
Visit our on-line store for AR Memorabilia