Shoulder bumping factory ammo

[milboltnut]

easy to over do it, yes. Kinda defeating the purpose of case life.

 

[CA_Shooter]

Just to follow up,

I installed the .400 Hornady comparator instead of the .375 to get more specific readings.

I have a Clymer No-Go gauge that is supposedly set to 1.547. It measures to 1.5435 with my caliper and Hornady tool. The bolt will not close on the No Go gauge although I can get the bolt to slide forward pretty far. Just can't get that bolt down (as it's supposed to be)

A piece of brass set to 1.5420 chambers and it seems to chamber easily.

I then measure my brass that is very tight in my chamber with 2 pieces of tape on it and it measures: 1.5440

So my brass with tape that gets tight in the chamber is about .0005 longer than the No Go gauge.

The No Go gauge (1.5435)will not allow the bolt to close, but the brass witb tape (1.5440) will with force.

Dumb Question: I am assuming the bolt can close on the brass with tape and cannot close on the No Go gauge because the No Go gauge is made of steel and the brass is made of brass with 2 pieces of tape on the base which is much more pliable than steel.

So does that mean my chamber is basically toward the end of my No Go gauge and I should expect to bump the brass near 1.5420?

Figuring out that exact length seems a bit difficult without a tool to be precise

One thing to add. I measured my Go gauge and got: 1.5380

Yet new Lapua and Hornady brass is 1.5345 which is lower than the Go Gauge! <-- The size of new brass is what confused me the most about this. I was thinking my chamber was off because the brass seemed to have so much to grow

To summarize relative sizes with my Hornady .400 comparator

New brass = 1.5345
Go Gauge = 1.5380
Current Brass = 1.5420
No Go gauge = 1.5435
Brass with tape on the end and tight in chamber = 1.5440

 

[divingin]

Tape is not solid; I'd expect that, given the amount of force the bolt camming action will generate, you may be compressing the tape to some degree. A better test would be to sacrifice a feeler gauge set, and place that between the case head and bolt face.

As an aside, make sure you use the same measurement techniques and tools when you're comparing measurements. The tools don't give you actual measurements, but rather relative measurements so you can compare.

On the new brass measurement, your chamber is a bit longer than SAAMI minimum. It could probably just as easily be a bit below that minimum, hence the slightly short factory ammo (made so it will fit a slightly short rifle.) In general, I think most manufacturers don't look at factory ammunition as a source of reloading components, so they don't care about reusability of brass; as long as the initial stretch doesn't compromise the case on that firing, they figure it's all good.


K22:

When setting up the FL die for zero shoulder bump some cam over may be necessary to avoid extruding (lengthening) the case.

Can you clarify what you're saying here? My take is that if you have the press and die set to cam over, you've got the die as low as it can go, thus bumping the shoulder to the max amount possible, and also sizing the body to the max amount (which will correspondingly lengthen the case.) I'm assuming we have differing definitions of "cam over".

 

[K22]

K22:


Can you clarify what you're saying here? My take is that if you have the press and die set to cam over, you've got the die as low as it can go, thus bumping the shoulder to the max amount possible, and also sizing the body to the max amount (which will correspondingly lengthen the case.) I'm assuming we have differing definitions of "cam over".

Sorry for the confusion. I'll try to clarify.

Cam over means that the ram is firmly contacting the shell holder with some resistance. Depending on the amount the die is turned down on the shell holder, the degree of cam over (resistance) can vary from slight to medium to heavy. The degree of cam over needed to produce the desired sizing can vary from press to press due to variation of play in the press, vary from lot / brand of cases, number of times the case is work hardened, and of course the specific rifle chamber.

You never want to over size cases thus the advent of measuring tools like case gauges and bump gauges because the mfg. instructions for setting up FL dies often resulted in over sizing the cases. Before there were these measuring devices, seasoned reloaders judged the adequacy of optimum case sizing by the way the sized case chambered in the rifle and adjusted the die accordingly. While not ideal, it works but using measuring is more precise.

Ideally, for bolt rifles, you want to size a case to produce a .001 to .002" shoulder set back as measured from a fully fired formed unsized case (primer removed). This may involves some degree of cam over, the amount of which is determined by comparing the fired case to a sized case then adjusting the die to produce the desired amount of sizing, i.e. shoulder set back.

If a FL die is set up so that it does not contact the shoulder the case may lengthen because the case is "squeezed" into the die, i.e. extruded, and the brass is displaced and has to go somewhere. So if one desires to size new cases without setting the shoulder back then the die is adjusted to just contact the shoulder thus preventing the case from lengthening. Because of the play in some presses, some degree of cam over may be needed to make contact with the shoulder to prevent the case from lengthening.

The phrase listed in the above post, "bumping the shoulder the maximum amount possible" does not apply. You only want to bump the shoulder back enough to provide optimum fit in the chamber without over sizing the case.

 

[divingin]

Sorry for the confusion. I'll try to clarify.

Cam over means that the ram is firmly contacting the shell holder with some resistance. Depending on the amount the die is turned down on the shell holder, the degree of cam over (resistance) can vary from slight to medium to heavy. The degree of cam over needed to produce the desired sizing can vary from press to press due to variation of play in the press, vary from lot / brand of cases, number of times the case is work hardened, and of course the specific rifle chamber.

There's the disparity. My definition of "cam-over" is limited to a press whose handle travel will allow the ram to rise to a point, and slightly recede before the stop is hit. When sizing, this can be felt as a lessening of force to move the handle in its last bit of travel. When raising the handle, there will be a "bump" in force required to get it moving again. Cam-over has little to do with the position of the die, but everything to do with the design of the press.

A press that stops the handle before the ram begins to recede will never cam-over, as just before the end of the stroke the ram is still moving upwards.

So if one desires to size new cases without setting the shoulder back then the die is adjusted to just contact the shoulder thus preventing the case from lengthening.

But it doesn't stop it, does it? It moves the growth to somewhere other than the case body. You're squeezing the brass diameter, which is going to try and lengthen it overall. By limiting the shoulder movement to the original location, you'd have to either cause an overall length growth (which is what I'd assume happens) or thicken the brass at some point. As you said, it has to go somewhere.

BTW, I was not advocating blindly sizing with the die in full contact with the shellholder; I was using that as an easily defined and repeatable reference point (and probably confusing the issue.) The full-down position makes it easier to see the amount of stretch in the press (no die/shellholder gap when empty; a gap there when sizing.)

The problem with body dies and standard full length dies is that the body squeeze and shoulder bump are fixed, with no way to adjust the relationship. If you need, for instance, a larger amount of shoulder movement, you're going to have more body squeeze as well. If you need to size the body more, you have no choice but to push the shoulder back more. The only viable alternative is to use a different die.

 

[K22]

The problem with body dies and standard full length dies is that the body squeeze and shoulder bump are fixed, with no way to adjust the relationship. If you need, for instance, a larger amount of shoulder movement, you're going to have more body squeeze as well. If you need to size the body more, you have no choice but to push the shoulder back more. The only viable alternative is to use a different die.

I'm regret to say that were are going in circles here. This is not a complicated process or issue. Please don't take this as a criticism but merely an attempt to offer assistance if you need or want it.

I reload for ten different rifles in the same caliber, i.e. the 223 Rem. I have no problem adjusting the FL die to obtain the desire amount of shoulder set back, i.e. sizing. Some FL die adjustments are sometimes needed depending of the rifle, brand / age of cases I'm loading for. I've been using the same RCBS dies for over 40 years and have loaded thousands of center fire bottle neck rifle cartridges.

I use Skip Shims to make the appropriate adjustments. Some use Redding Competition Shell Holders. German Salazar, in the Rifleman's Journal, explained a method using a no. 17 "O" ring under the die to make sizing adjustments on the FL die. All will work quite well if you have a dedicated set of case for each rifle, set the FL die up properly and measure the shoulder bump.

Remember, all were are trying to accomplish is sizing a case the minimum amount that will produce optimum fit in the rifle chamber and in doing so avoiding over sizing the case.

If you would like, we can continue this discussion. Just PM me and I can elaborate on any questions you may have regarding anything I've offered.

 

[ole-has-been]

Hello Smoke the Clay and everyone else. I've read some good responses to your brass growing issue and most responses give decent answers. If I may, I'd like to chime in and give a little food for thought as to your first post and question.
No ill intentions meant....just trying to state a point.

There is a little bit of lacking and needed info, to truly offer help to a very simple question.

First off, have you ever checked the weapon for proper headspace with a headspace gauge?
IMHO, Never purchase a weapon from a dealer or any seller without checking headspace properly. This goes for any weapon prior to reloading; and this cannot be done with the tools you are using as you stated. Your tools are fine for setting up dies and bumping shoulders; Yes sir, but make sure to check and know the weapons actual headspace per SAMMI specs to start with. If ok, proceed...if not, don't purchase it, have it repaired, or disable it so it cannot be fired and make it a wall hanger.

Second, fire form a few rounds in that rifle.... use your tooling to measure case head to mid shoulder, write the data down, resize that fired brass only enough to get proper neck tension, and be sure to only bump shoulder by .001 only. Check fit in that rifle. If tight to chamber, bump back another .001 and so on, until you feel the casing in chamber and bolt closing is starting to feel right. I think you'll know where this limit is. Once you have found "the limit" bump back .001, reload and fire them again. Maybe repeat this 3 times. 3 firings with most all brass will allow it to fire form to your chamber. Some heavy thick mil spec and some Starline brass is thicker than most and may need 4 firings. Once you see the brass shoulder no longer growing past .002 to .003.....your in there. Now, simply use your tools again, measure brass and set dies to bump shoulder back by .002 or maybe .003. Verify with your "tape test" and/or as the other gentlemen have stated in the post.

This subject is a very deep one, several ways to do it, etc. AND, we haven't even started to discuss it all....As I read the posts, IMO, I felt starting from the very first step may be in order. Hope I have not offended anyone.
Good luck and God speed.