Virgin brass VS. once fired brass for load development

[UpNorthAndy]

A while back I read a thread on another site pertaining to doing load development with once fired brass versus virgin brass. The general consensus in that thread was that it is better to use the once fired brass as long as it was fired from the gun the load is being developed for.

What are your thoughts on this? Personally I guess I could maybe see why it would be better to use once fired brass, but I just don't know how much of a difference it would really make. Anyone have any input on the subject?

 

[RegionRat]

Lots of variables in the discussion.

If your work is sensitive to case volume, then expect to see a difference once the case is blown out. Sometimes, there is a significant difference in the internal case volume after firing, sometimes not.

The case volume is the biggest contribution in this context, but depending on your work, you may not see this. Some more depends on your sizing process and the over all accuracy of your system. Some guys never shoot far enough or well enough to notice these kinds of effects.

More unknowns creep into the discussion based on case cleaning and annealing, but for now, lets say the biggest difference between using a case once fired in your own chamber versus a piece of spec virgin brass is the case volume.

How much difference being discussed is a matter of cartridge designs and reamers. For example, some cartridges are notorious for a huge difference once fired and others not so much. Take a .303 Brit as an example. The shoulder can blow out 0.040 or more on the first cycle. For the same virgin case compared to a once fired case, there will be a measureable difference in speed for all other variables being the same in the load recipe.

So, your specific context matters, and even then there are differences between reamers that cause more confusion.

Are you worried about a specific cartridge? Without knowing the specifics, one way to manage this is batch size and lot controls. By loading bigger batches with controls on the brass prep, you can stabilize your dope.

 

[ZiaHunter]

Don't make it complicated. Fire form first then do load development.

 

[Ccollins02]

In an ideal world, I think most would say they would rather do load development on fired brass for your chamber. However, personally I'm not going to spend time fireforming 500 pieces of brass and 500rds of barrel life gone. I will normally mandrel all the necks on my virgin brass for uniformity and consistent neck tension and load develop on virgin. Once its all shot, ill do a quick check just to confirm the loading on fired sized brass. I've never had to adjust much if any to maintain the load. Like a previous reply said, a lot of variables in calibers and chambers to consider...

 

[Milo 2.5]

I put a minimum of 300 pcs in service, most of the time it is 4-500. I do not worry about developing a load on new brass, a quick check once the brass is processed for the first time, make a slight adj if needed.
What I wont do anymore is develop a load before the barrel speeds up, been burned a few times there.
Also, I shot 2- 6.5x47's for years, new virgin brass was always the most accurate for me, think it not being able to ever match the neck tension once it was fired.

 

[ShtrRdy]

It is possible to develop a load with virgin brass but be aware that you will have to adjust the load when it is once fired.

If you have a new barrel that is something else to consider.

 

[Sheldon N]

It is possible to develop a load with virgin brass but be aware that you will have to adjust the load when it is once fired.

I think that's the good practical route. Do some quick load development to find a load that is accurate with virgin brass and shoot it all. Then check the load and adjust or tweak as needed to get the ideal load on once fired brass.

 

[PracticalTactical]

There's a video an F Class shooter posted on YouTube a while ago on this point, that is actually quite misleading.

The YouTuber says to stop using fire formed brass, but does not clarify that he FL resizes with a custom resizing dies that were produced to match his particular chamber. So he is really just doing maybe a 0.002" shoulder bump and probably about the same on the side wall.

So the moral of the story is really to use brass that closely matches your chamber, but not so tight that it results in stiff bolt lift. On this point, stiff bolt lift is normally interpreted as an indication of an over pressure round, but in the case of fire formed brass, may just indicate that it's time for a FL resize.

If you think about how pressure is used between FL and fire formed cases, the FL resized case allocates a certain amount of the energy to blowing the case out to the chamber walls, but a fire formed case already fits so it does not. The difference is transferred to the bullet in terms of higher velocity... maybe not much, but a little.

Additionally we should consider consistency. The fire formed case will result in a statistically more consistent muzzle velocity than a FL resized case for the same reason.

As for the powder charge, since the FL case has a smaller internal volume, you can expect to be able to increase the powder charge slightly on a fire formed case.

As for case to neck concentricity... the fire formed case will likely be more concentric, but that largely depends on your chamber clearance in the neck and the amount of neck sizing that has to occur. A tighter neck will not need to resize as much and therefore will be more concentric.

 

[Milo 2.5]

As for the powder charge, since the FL case has a smaller internal volume, you can expect to be able to increase the powder charge slightly on a fire formed case.

I find the opposite is true, I almost always end up pulling .1-.2gr of powder on once fired brass, just to keep the same velocity.

 

[joel65]

I just shot virgin Lapua brass that has the same POI at 700 yds as my 4x fired brass. Same load. Ran the new brass through my dies just like my fired brass.

 

[PracticalTactical]

I find the opposite is true, I almost always end up pulling .1-.2gr of powder on once fired brass, just to keep the same velocity.

Well, you're correct, but I was referring to the ability to maximize the velocity.

 

[Steel head]

I think that's the good practical route. Do some quick load development to find a load that is accurate with virgin brass and shoot it all. Then check the load and adjust or tweak as needed to get the ideal load on once fired brass.

That is what I like to do.

 

[Milo 2.5]

Well, you're correct, but I was referring to the ability to maximize the velocity.

I gotcha now, lol

 

[UpNorthAndy]

Thanks for the responses guys. I should also add that right now 98% of the shooting I do is when out chasing coyotes or deer. I am hoping to start shooting some border wars matches next summer. I have been reloading for about 8 years now and have learned a lot and have also been able to dial in almost all of the guns I own to shoot under 1/2 moa @100 yards. I know a lot can change between 100 yards and 1000 yards. as far as my hunting guns are concerned I have enough ammo loaded up for those to last me quite a while, but the gun that I'm going to use for the BW matches (a savage 10ba stealth in 6.5creed) I have not even done load development for yet. My current plan is to just order up a couple cases of the Prime 6.5 creed ammo and shoot them and then reload the Peterson (at least I think thats what they use) brass.

 

[Retro-Cow]

There's definitely people out there with a much more intelligent and scientific outlook on this matter than me. But I subscribe to the notion that because most of the rounds fired through my barrels will be loaded from fired cases, I develop loads on fired brass.

Ideal scenario for me is to do my ~100 round barrel break in with factory ammo that uses the brass I'll be loading on, and use those for load development. I will caveat that once I identify a node, I'll typically copy those loads with new brass and note any deviations.