What's the real world difference

[marshall]

Hey guys,

I've been sorting brass by manufacture. I'm not a bench rest shooter, just a guy that works real hard at getting the best out of my loads.

The question is,

I have Winchester, Federal and Nosler .204 Ruger brass and it is all sized, prepped and trimmed to the same length. I measured wall thickness and weight on three of each and listed the average below.

Nosler case thickness .0100 and weight 98.3gr
Federal case thickness .0125 and weight 95.4gr
Winchester case thickness .0105 and weight 95.5gr

Nosler the thinnest wall however it is the heaviest, it must have a thicker head. Federal is the thickest but it is the lightest. How do these small variations affect accuracy?

Can it be as easy as adjusting the charge for each case type to achieve best case results?

Is this really necessary?

I'm guessing you would have higher pressure in one case so how much would that affect velocity?

Is any of this really an issue at all?


Thanks in advance for your response. Real data would be appreciated.

[marshall]

I guess what I'm getting at here is:

I have developed a really good load for a REM 700 in .204 Ruger using Sierra Blitz King 32gr bullets and 10x with Federal brass. If I load that recipe in other brass and case prep is the same what kind of difference might I expect to see?

[Float Pilot]

I have experimented with mixed case groups and even played around with only changing the primers. Both can change the group size, velocity and even where the group impacts.

Stay with a consistant load. Try loading all of one type of brass per box or loading session. It really can make a difference.

[Murphy]

Many gun writers talk of sorting brass by weight and within the same brand that may have some merit but once we cross brands or even lots it has less to do with internal capacity. This should be determined by weighing fired cases filled with water then subtract the empty weight. An average of ten cases so measured will provide useful information about which case has the greatest capacity. Cases with less capacity will need to have the loads reduced or will giver higher pressure and likely, higher velocity. Large variations with maximum loads can cause trouble.

I haven't used the new Nosler brass but would suspect it to be of the highest quality. I have used a train load of Winchester rifle brass and find it more than adequate for even the most demanding of applications. I'll always take Winchester brass when I can't find or afford Lapua. Lately I've found good brass from Hornady in many calibers and can recommend that brand.

There is more to brass than just wall thickness or capacity. One of the most important attributes of good brass is correct anneal gradient. Brass should be softer at the mouth and harder at the base area. This gradient will be a general transition from correct softness to **** tough at the base. I have usually found this vital aspect lacking with Federal brand of brass. We can improve this to some extent. If it is too hard and is brittle at the mouth, by torching it to about 650 degrees F at the neck and dropping into cold water. We can do very little to strengthen it at the bottom half and this seems to be where Federal Cartridge and I disagree.

Many folks think that this torching process every other firing is all that's needed to make brass last for many firings but fail to heat the brass to anneal temperature and consequently waste time and butane heating the case to about 300 degrees and often make the case worse. Good brass doesn't need to be annealled, it is already at the correct anneal gradient. We can also damage good brass by heating it to anneal temperature too far down on the body and soften it where it needs to be hard and tough. It's true that after many firings brass will get harder at the neck and loose elasticity and this will effect neck tension. Correct annealling will then breath new life into tired brass but it must be done correctly.

Brass neck thickness is suspect in the cause of inaccuracy in many calibers, especially the 22's and smaller stuff. Neck thickness, just as anneal and elasticity or the springiness (is that a word) of the case neck, can be the culprit. When we size the case we squeeze it down to some diameter smaller than the bullet, then pull the expander back through and it springs back to a slightly smaller neck diameter. This smaller than bullet diameter that the brass springs back to is the finished product that the bullet sees. This is neck tension.

If the brass was thicker than expected or inconsistant in this dimension from case to case, we would have inconsistant neck tension. The springiness of the case mouth will yield inconsistant neck tension if the anneal isn't correct for each case. Neck tension must be consistant from shot to shot for the best accuracy. This has a far greater effect on accuracy than a couple of tenths of a grain of capacity.

Generally brass is of close dimensions of neck thickness. This is a SAAMI dimension. The brass neck diameter must fit inside the chamber without binding when a bullet is seated in the case. Sometimes when we form wildcats from one case by necking down or up or pushing the shoulder back, we get a case neck that is non standard in thickness. If it is too thin as when necking up several calibers, we loose neck tension and accuracy due to weak bullet pull.

When necking down and especially when pushing the shoulder back and using what was thicker case body for the new neck we get a neck that is too thick and may be dangerous due to binding of the case neck in the chamber when a bullet is seated. Then neck reaming (not turning) is needed to make correct neck thickness from top to bottom of the neck. Neck turning should only be needed when a non standard tight necked chamber is use for a standard caliber. Many custom guns are made this way but should be stamped with any special notation about the non-SAAMI neck dimensions.

For standard calibers in standard rifles brass dimensions are rarely ever a problem. Minor variations in capacity are only of a signifcant issue when loading maximum loads or shooting standard brass in non standard chambers. All batches of ammo of the same powder/charge/primer/bullet should be in the same brand of brass. Adjusting powder charge for cases with less or more capacity can be done with a chronograph if it is significant to gather readings of velocity with variations greater than standard deviation numbers. Generally we will be unable to determine any difference. One exception might be when using thicker mil-spec brass compared to commercial brass. This show itself most often with the smaller capacity 5.56 brass compared to commercial 223 brass. The limited capacity of the 223 case yields a greater percentage of difference between the two.

Good loading practice dictates we work up all loads on the same brass case by brand and lot. This will avoid any trouble spots and give better performance at the target.

[marshall]

Murphy,

I was hoping to get this type of response from you. Your experience is unquestionable, thanks. I read most of your responses to most posters and learn.

My mind is in the sponge stage at this time. My results have improved over the past year and I feel it is do to data collection and careful assembly and testing rather than loading a random sample and shooting it.

I have been helping a few good friends with their rifles and quite honestly enjoy the challenge. I have recently developed a great load for Rem 700 VS SF-II chambered in .204 Ruger. This rifle is a good platform, the accuracy has really come in with careful testing.

Charges have been tested from 24.2gr - 26.9gr in .3gr increments. Velocities have ranged from 3582fps - 4019fps. COL from 2.355,(.020 off) to as deep as 2.240, (factory Federal length).

The final numbers are:

Federal Brass trim 1.843
RL-10X @ 25.6gr, (25.4gr and 25.7 grouped well so I picked 25.6gr in between to allow for scale error on future loads)
Primer Fed 205M
Sierra 32gr Blitz King
COL 2.280
Velocity 3802 (5 shot average)

Five shot groups are an honest .216 center to center @ 100 yards off an adjustable front rest and rear bag.

My questions about the brass came up because all testing was done using the original 40 pieces of once fired Federal brass. My friend has ordered brass from everyone and it was of course back ordered early on. Recently all of this stuff has come in and I have 100 of each type of case that he wants loaded.

I'm reluctant to load without testing each brand and I'm a little short on time. I guess I will load 5 of each and hit the range some time in the next two weeks. Most likely +/-.2gr each side of the final recipe with each case type. The final load is no where near max tested so I should be fine. If I get this done in the next couple of weeks I'll post the results.

Cheers,

[marshall]

Here is a picture of the 100 yard 5 shot group from the .204 referenced below.

These rounds were progressively loaded in a Dillon 550B. The RL-10X extruded powder has very small granules and meters virtually perfect.

I weighed twenty samples for reference before I decided to load progressively. Generally I only load ball or flake powders progressively and weigh each round loaded with extruded separately.

Federal Brass 1.843"
RL-10X @ 25.6gr,
Primer Fed 205M
Sierra 32gr Blitz King
COL 2.280"
Velocity 3802 (5 shot average)