Shoulder Bump Tolerance

[Alex Wheeler]

Hmmm. That's counter to the actual physics involved and perhaps the results are supporting it.

The small amount I have dabbled with short range shooting with forgiving cartridge's and bullets shares no resemblance to my 1k experiance. Im not saying you cant see small changes at short range, but they are small. At 1k they are big. In my 30 BRA or my 308 with forgiving bullets I can cover a range of seating and maybe see .1-.2 moa change. Thats a lot at 100. But that same range of seating at 1k would produce close to 1 moa of change with the bullets we use in that game. My 30 BRA or 308 wont compete at 1k. Theres a very small window at 1k, I have been saying this for a long time. No .5 grain windows of powder or .005 windows of seating. I have never seen it. Not to shoot at the winning level. Now the flip side of that is, pull it back to 100yds and load a light bullet and it starts to act more like a ppc. Im not sure if its a bullet length issue or a distance issue.

 

[tom]

That was the first BRA barrel Alex. 2017 heavy, because I wasn't going to experiment with some stupid new cartridge in light class, which I "cared about". It wasn't awful off that seating, but yes very small window for the "stupid small". It had quite a wide window jumping, but wouldn't shoot small "enough" to be a topic here tonight!

Tom

 

[gunsandgunsmithing]

The small amount I have dabbled with short range shooting with forgiving cartridge's and bullets shares no resemblance to my 1k experiance. Im not saying you cant see small changes at short range, but they are small. At 1k they are big. In my 30 BRA or my 308 with forgiving bullets I can cover a range of seating and maybe see .1-.2 moa change. Thats a lot at 100. But that same range of seating at 1k would produce close to 1 moa of change with the bullets we use in that game. My 30 BRA or 308 wont compete at 1k. Theres a very small window at 1k, I have been saying this for a long time. No .5 grain windows of powder or .005 windows of seating. I have never seen it. Not to shoot at the winning level. Now the flip side of that is, pull it back to 100yds and load a light bullet and it starts to act more like a ppc. Im not sure if its a bullet length issue or a distance issue.

Well, only one of those two options is a definite. That being distance.

 

[jackieschmidt]

On my 6PPC and 30BR Competition Rifles, I use no less than .003 bump.

 

[sqrlgtr]

I dont know if .001 difference in shoulder bump would make any difference on paper are not, because I have not tested for it. I have been very satisfied with my results. but still strive to do better....If I had it my way each cartridge that I was reloading would be exactly the same. Good luck with that right.

Someone mentioned that your bullet would be in different spot because of variation of shoulder but in my mind that would depend on if you were into the lands or jumping the bullet into the lands.

 

[INTJ]

I haven't tested enough to narrow it down to tight cycling or other causes, but most all of us have seen a tight round go both into and out of a group. One logical way to do away with a tight round is to bump the shoulder a tad more.

Well, we know that shooting slow at 1000 yds more often than not opens up our groups, because the longer we take to shoot the more the conditions change. Sticky cases upset the rifle's tracking, and that slows us down.

 

[sqrlgtr]

Just an update here, since starting this thread I have went to using a lyman lube pad with rcbs lube. My shoulder bump is much more consistent with this method compared to the imperial wax on thumb and finger method....

 

[rwj]

Just an update here, since starting this thread I have went to using a lyman lube pad with rcbs lube. My shoulder bump is much more consistent with this method compared to the imperial wax on thumb and finger method....

Interesting… do you think it is more a function of lube quality/consistency or how it’s applied?

 

[sqrlgtr]

Interesting… do you think it is more a function of lube quality/consistency or how it’s applied?

I think its the consistency of how you apply it to your brass. Hope that makes sense....

 

[Scott-ak]

I'd be interested in knowing the model number of calipers folks are using to measure exactly to the thousandth. I have some very expensive mitutoyo and the specs says +/- .001 accuracy. The ten thou 'measurement' on those digital models is not real.

 

[INTJ]

Just an update here, since starting this thread I have went to using a lyman lube pad with rcbs lube. My shoulder bump is much more consistent with this method compared to the imperial wax on thumb and finger method....

Same for me. I get a more consistent application of lube with the pad vs my fingers.....

 

[sqrlgtr]

I was actually surprised how much more consistent my results are by using the lube pad...

 

[338 dude]

Don't lube the neck or shoulder? What is the negative from lubing the neck and shoulder?

Dented brass

 

[sqrlgtr]

"Don't lube the neck or shoulder? What is the negative from lubing the neck and shoulder?"​

dented brass and inconsistent shoulder bump...