Does Bullet Seating Depth Change as your brass stretches?

[Taxman1]

Theoretical ? - assume you know that with a new piece of Lapua brass the perfect seating depth to have a specific bullet just kiss the lands is 1.000 (you have used every tool and method known to man to make this determination). Therfore if you want the bullet to jam .002 you set your seating die accordingly so the loaded round using a expensive caliper and comparator measures exactly 1.002. You also leave the seating die in the press make no adjustment to it and use it to reload the specific piece of brass you used to determine the 1.000 length. Assume that the new Lapua brass you used to make the determination measured exactly the SAAMI minimum chamber specification (Lapua brass in 6mmBR does in fact measure almost exactly to the SAAMI minimum or a few 1/10,000 less). You then fire that specific piece of brass three times in your gun neck sizing only. You then measure the brass and determine that the distance between the base of the brass and the datum line on the shoulder of the now fire formed brass is .004 over the SAAMI mininum because your guns headspace (distance from the bolt face to the datum line in the chamber) is .004 over the SAMMI minimum (well within the tolerance that SAAMI allows). As you are using the seating die/press that has not been adjusted since the first loading have you now gone from jam .002 to jumping .002 because of the brass stretching between the base and shoulder by .004 ?

 

[CatShooter]

Nice first post (Not)

First off, my set of SAAMI (presumably the latest) does NOT have the 6mmBBR - neither the Remington or the Norma/Lapua version, so I don't "think" you have done your homework, but I might be wrong, since SAAMI might have approved the 6mmBR drawings last week...

But that is really a moot point, since the question could apply to any cartridge, including the .218 Bee

The answer is... the jam (+0.002") would stay the same, no matter how much the case grew, because the OAL is determined by the distance between the bottom of the shell holder (the part that contacts the case head), and the bullet seating cup - if that distance stays the same the jam stays the same.

Come up with something better next time, this was a looser

Meow

 

[Fat Albert]

The point where the bullet contacts the stem in the seater die can easely be +OR - 0.005". If I want to get nit-picky and sort my bullets before they are seated I check the bullet with my Hor/stoneypoint unit with just the caliber gage on a set of calipers and sort them into groups. The worst bullets for contact point variations are the VLDs with their long slopeing noses.

 

[Erik Cortina]

No.

 

[Shynloco]

Taxman1,
I agree with Erik's response which is "NO" to your question. One other thing I might suggest is that you loose the word "assume," as it is not a good idea for anything having to do with reloading. But hang in there and keep at it. Do some reading on basic reloading principles contained in such books as "The ABC's of Reloading" that addresses issues such as what you ask. There are several other books available as well, including more advanced discussions having to do with "Extreme Accuracy" issues in reloading and bullet seating..

 

[necchi]

No,
,Your brass changed, the seating depth may have changed but the COL is the same.

And your theory is flawed, you state the brass stretched,
,but then later say it went from a .002 jam to a .002 jump,,that means the brass would have to get shorter.

Keep tryin, it's always good to excersize the brain

 

[bozo699]

Taxman1,
I would like to welcome you to the forum, it really is a great site and a lot of great guys willing to help, with all that said you had a very unusual first post, you may not feel it was a very warm welcome but if you had posted that on snipershide it would have been much worse. Do some reading, there are a lot of good books available and just cruz this site on subjects your interested in. when you do have a question, ask it in a manner the can be understood by using proper terminology and as much info as needed so you get a quality answer. I am not ordering you around just trying to give you a little helpful info for future posts so you get quality answers. good luck to you and enjoy
Wayne.

 

[necchi]

Ya, I'm another one that doesn't want Taxman turned off just cause he got ripped, I wasn't tryin to be mean but the question does ramble a bit.

I learned along time ago not to assume anything, it leaves the children to giggling about the old as dirt analogy ass-u-me. It's much safer to presume.

Anyways, Taxman kinda put two different thing together in the question, chamber fit of the brass, and where the bullet is seated too in relation to the rifling.
You hafta add trim length of the brass into the equation too. Even if that changes, the seating die (being unchanged) would still place the bullet in the same position, but the grip of the neck would be a little different.

 

[CatShooter]

You hafta add trim length of the brass into the equation too. Even if that changes, the seating die (being unchanged) would still place the bullet in the same position, but the grip of the neck would be a little different.

If the bullet is seated into the neck, ~0.250", and you trim the cases 0.003" or 0.004", then the change on grip is a non-issue. There are much larger variables that override this infinitesimal amount.

Meow

 

[necchi]

I know, but it's the only change I could think of too try an help taxman grasp the concept.

 

[Taxman1]

First I apolizes if I offended anyone or everyone. The informtion I have on the SAAMI min/max came with the instructions included with the Redding Headspace and bullet comparator gage which lists SAAMI min/max for numerous cartridge including the 6mm B.R. Remington. The comparator I purchased was labeled 6mm BR Rem. With the comparator they provide a gage to zero the dial to the minimum length. I use this tool to determine that new 6mm BR Lapua brass is basically right at the minimum. Using the same tool I determined that my fire formed brass was .004 over the minimum. Recently on this forum there was a post regarding the Horandy/Stoney point bullet seating gage which comes with a new piece of brass. Some responders to that post indicated you should use fire formed brass to determine length to the lands. My Sinclair bullet seating depth gage instructions indicate you should use fire formed brass. The only reason I could think of for this difference in opinons/instructions would be that you would get a different measurement as to OAL depending on what method you used. I don't own a Stoney Point gage to test if my thinking is correct. Your responses indicate that as long as I do not change the OAL (using the same bullet) whether I am firing new brass or brass that has been fired five times without being full sized or having the shoulder bumped the relationship of the bullet to the lands will remain the same. I appreciate your responses and I again apolize but I will tell you I am a slow learner.

 

[mikecr]

Taxman, as mentioned seating is taken from the casehead to your seater stem datum on the bullet nose. What happens in between shouldn't affect distance to/into lands.
But that doesn't mean you shouldn't check every one. I do, and occasionally need to 2nd seat with a fine adjustment to get my OgvOAL(that's just what I call it) exact.

What can happen with so much negative HS(4thou is a good bit), is the shoulders can make contact/early contact within a seating die(depending on the die type and die setup).
With this, the ram will need to overcome some resistance caused by the shoulders, to reach proper 'casehead to seater stem datum'. If the bottom of your seater die isn't set to contact the shell holder, then varying shoulder-resistance can apply to the dynamics and tolerances of your press. It wouldn't likely be a one-to-one relationship though, where 4thou -HS causes -4thou OgvOAL. But it could cause a couple thou of reduced seating depth. So it may be a factor for you(I don't know).

I run into it using primarily Wilson seater dies, after minimally bumping my cases(~1thou). If the bump didn't stick because the case has hardened some, then the shoulder can cause ram resistance that I have to be sure to overcome. Otherwise, I'll see that further adjustment will be needed.

 

[Erik Cortina]

First I apolizes if I offended anyone or everyone. The informtion I have on the SAAMI min/max came with the instructions included with the Redding Headspace and bullet comparator gage which lists SAAMI min/max for numerous cartridge including the 6mm B.R. Remington. The comparator I purchased was labeled 6mm BR Rem. With the comparator they provide a gage to zero the dial to the minimum length. I use this tool to determine that new 6mm BR Lapua brass is basically right at the minimum. Using the same tool I determined that my fire formed brass was .004 over the minimum. Recently on this forum there was a post regarding the Horandy/Stoney point bullet seating gage which comes with a new piece of brass. Some responders to that post indicated you should use fire formed brass to determine length to the lands. My Sinclair bullet seating depth gage instructions indicate you should use fire formed brass. The only reason I could think of for this difference in opinons/instructions would be that you would get a different measurement as to OAL depending on what method you used. I don't own a Stoney Point gage to test if my thinking is correct. Your responses indicate that as long as I do not change the OAL (using the same bullet) whether I am firing new brass or brass that has been fired five times without being full sized or having the shoulder bumped the relationship of the bullet to the lands will remain the same. I appreciate your responses and I again apolize but I will tell you I am a slow learner.

Taxman, the reason they suggest using a fireformed case is because of the position of the shoulder, not the lenght of the case.

For instance, if the shoulder of the case being used is 0.005" shorter than the fireformed brass, then when you insert it to check OAL of bullet, the case will be inserted 0.005" further into the chamber, therefore giving you an error of 0.005" when you go to fireformed brass because the fireformed brass will hit the shoulder 0.005" sooner, therefore the OAL will be 0.005" shorter than the measurement obtained with a non fireformed piece of brass.

I hope that makes sense.

 

[necchi]

Recently on this forum there was a post regarding the Horandy/Stoney point bullet seating gage which comes with a new piece of brass. Some responders to that post indicated you should use fire formed brass to determine length to the lands.

and,,
My Sinclair bullet seating depth gage instructions indicate you should use fire formed brass.

OH!,,There in lies the rub,
The Hornady and the Sinclair tools measure in completetly different manners

The Hornady measures with a modified case that threads on too the tool and is inserted from the breech,, the bullet is then pushed into the lands.
,The Sinclair measures from the bore/muzzle and you WILL see a differance in the length of the case,

A fireformed case to a custom chamber has to be sent to Hornady to have the threads cut in the head for the tool.

Comparing the two tools and their measurements to each other won't work.

 

[dtucker]

CatShooter, as far as a looser question i think not. If you don't ask you don't learn. We all started somewhere and sometimes things just don't sit well in the mind. Ask all the questions you want, none of them are ever stupid

Nice first post (Not)

First off, my set of SAAMI (presumably the latest) does NOT have the 6mmBBR - neither the Remington or the Norma/Lapua version, so I don't "think" you have done your homework, but I might be wrong, since SAAMI might have approved the 6mmBR drawings last week...

But that is really a moot point, since the question could apply to any cartridge, including the .218 Bee

The answer is... the jam (+0.002") would stay the same, no matter how much the case grew, because the OAL is determined by the distance between the bottom of the shell holder (the part that contacts the case head), and the bullet seating cup - if that distance stays the same the jam stays the same.

Come up with something better next time, this was a looser

Meow

 

[bozo699]

First I apolizes if I offended anyone or everyone. The informtion I have on the SAAMI min/max came with the instructions included with the Redding Headspace and bullet comparator gage which lists SAAMI min/max for numerous cartridge including the 6mm B.R. Remington. The comparator I purchased was labeled 6mm BR Rem. With the comparator they provide a gage to zero the dial to the minimum length. I use this tool to determine that new 6mm BR Lapua brass is basically right at the minimum. Using the same tool I determined that my fire formed brass was .004 over the minimum. Recently on this forum there was a post regarding the Horandy/Stoney point bullet seating gage which comes with a new piece of brass. Some responders to that post indicated you should use fire formed brass to determine length to the lands. My Sinclair bullet seating depth gage instructions indicate you should use fire formed brass. The only reason I could think of for this difference in opinons/instructions would be that you would get a different measurement as to OAL depending on what method you used. I don't own a Stoney Point gage to test if my thinking is correct. Your responses indicate that as long as I do not change the OAL (using the same bullet) whether I am firing new brass or brass that has been fired five times without being full sized or having the shoulder bumped the relationship of the bullet to the lands will remain the same. I appreciate your responses and I again apolize but I will tell you I am a slow learner.

Taxman1,
No need to apologize, think of it as a learning curve. You see you slowed down thought before you typed, reread your post and probably changed a thing or two then hit post, now look at all the helpful posts that have replied to your second post. It's no big deal my friend, your going to fit right in. Go back through and read some of my posts, I have had to edit them a couple of times, I sometimes write before I think as well and as Dan just said no question is stupid, were all learning daily, the really stupid questions were the ones that were never asked because someone thought they were stupid or non important and then someone gets hurt or worse, ask away
Wayne.

 

[mikecr]

Oh,, there are completely stupid questions.
We see them all the time in forums.
But Taxman's question was not, because he sought information leading to better understanding. He had also put some efforts into his notions beforehand.

Many times that is not the case, and we shouldn't deny the underlying truths in it...

 

[bozo699]

Oh,, there are completely stupid questions.
We see them all the time in forums.
But Taxman's question was not, because he sought information leading to better understanding. He had also put some efforts into his notions beforehand.

Many times that is not the case, and we shouldn't deny the underlying truths in it...

I Stand corrected
Wayne.

 

[Taxman1]

Thanks everyone. Erik C., necchi and mikecr your responses today were very helpful and make sense to me. I really could not afford this latest gun (but I bought it anyway) and now that I have it don't want waste anymore of it barrel life then I have to finding the seating depth it prefers. mikcr you seemed to suggest in your post that .004 headspace is quite a bit - is there a standard or general rule as to what the headspace should be?

 

[mikecr]

Well with new brass, you've pretty much got what ya got.
With fully fireformed brass, that has sprungback as typical, there would be ~1thou to zero headSPACE as chambered with the case shoulder against the chamber shoulder. This is what you'd have with the firing pin pushing the shell forward. With this, and the firing pin cocked back, the bolt should close and turn easy enough.
Most people try to keep shoulders bumped to this ideal condition(a little more with semiautos).

If headspace goes negative(no chambered clearance and an actual interference fit), bolt closure get's really difficult, there is 'wiping' of the caseheads, and pressure on the boltface.
When you say 4thou of grown headspace in context with stretching brass, I take it as this condition(negative HS).
And 4thou shoulder interference as I've measured, causes pretty tuff bolt turning.

Excess positive HS(clearance) creates a dangerous condition where the brass stretches/slams back violently against the boltface. It's best to keep the caseheads close as possible to the boltface and keep oil out of chambers, to prevent this. Alot of people fireform brass with bullets jammed, or using a false shoulder to HS off, to prevent this with new brass on 1st firing.