Shoulder bump

[danj]

What will too much shoulder bump (.009 vrs .002) do to velocity (ES) and accuracy. I know it's hard on the brass but what else does it affect?

 

[Dmagna]

The reason why hand loaded ammo is more accurate is because of less brass movement. Makes things more consistent. I am not saying that it will make it less accurate but it could. When it comes to bump you really want to use the minimum amount to keep the brass from stretching every shot. Most hunters bump .002 because it seems that's the minimum amount to deal with dirty situations. Some people don't bump at all but I wouldn't recommend it in a hunting rifle.

 

[jimbires]

virgin brass will usually have a lower velocity , compared to brass that is properly resized . energy is used for expanding the brass causing loss of velocity . I assume that would hold true for brass that has been oversized .

in my one rifle virgin Norma brass is 50 FPS slower than properly sized brass .

 

[MagnumManiac]

I aim for a bump that ends up being .001"-.0015", which is AFTER any spring back.
If you have sized .009", then you have created an excessive headspace issue and your load, and brass, will be different to a properly sized case…so, yes, it can affect accuracy. It will also change ES/SD, no way around that.
Do not be surprised if your cases show incipient head separations in one or two more sizings if you shoot them with .009" headspace.

Cheers.

 

[Finsta]

.002 reduces the chance of case head separation and much shortened brass life; while leaving some play for functionality. The feel method works best for me. Annealing helps too. Take firing spring/pin out of bolt(unless you have a 3 way safety), turn die out and then turn the die back in while feeling for the point where the bolt cams without any tension. Wash lube off brass before chambering brass. It's the transition from feeling resistance as you cam the bolt, to no resistance. But it's a very fine line between no resistance and too much head space, so go in small increments. You will then have good headspace(likely about .002 or less) , and you can use a full length die. Also you can just raise the shell holder to die and use different sized shell holders.Broz does an excellent video on this with a Redding shell holder set ranging from .004 to 010. .009 is not even recommended for lever actions and semi autos. That sounds like way too much ! And likely to affect accuracy and ES for the worse. For those you do .003 to .005. Of course you should always measure anyway to determine what your brsss is doing.Comparators are used by many as well. They'll give you a reference point for measuring. Hornady work, Sinclair are likely better. Neck sizing will ultimately lead to using a full length sizing die anyway. So just shoulder bumping while using a full length die is fine. Your next concern should be bushing dies or honing a die without a mandrel to prevent run out. Concentricity gauge will be needed for that. Precision shooters get into that more seriously, for hunting it's not as critical. Although, this is a Long Range hunting forum, so that should be steps you will want to learn about. CBTO (cartridge base to ogive) measurements as well for bullet seating. The heavy for caliber bullets(with quick twist rate barrels), are common for long range shooters, as they seek the jump measurement to the lands (if any) in the free bore. Consistent charges give consistent pressures that help accuracy and velocity. Please excuse the lengthy post, but once you mentioned.009 I figured you for a newbie in need of some suggestions. Hopefully it was a typo and you know all this. Then ignore my post.

 

[Reelamin]

Interesting info.

 

[Doom2]

What will too much shoulder bump (.009 vrs .002) do to velocity (ES) and accuracy. I know it's hard on the brass but what else does it affect?

It should not be a lot, if any but I doubt that anyone has run a test. And by that I don't mean 3 or 5 rounds.

 

[Doom2]

Interesting info.

I'm not a Eric fan but this is a pretty good video. He did not mention an important fact about the SAAMI specifications. The cartridge drawing gives maximum dimensions. The chamber drawing give minimum dimensions. He tended to confuse references but his information is correct.