Brass Question

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Emietenkorte
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Brass Question

Post by Emietenkorte »

Hello! This might seem like a newbie question but here goes….
When loading for high power silhouette does it matter if you use brass that is made by the same manufacturer? I know there could be slight metallurgical differences but does it make a difference in your accuracy? Any information will be greatly appreciated!
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Bob259
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Re: Brass Question

Post by Bob259 »

I always have keep my brass lots separated by manufacture and did not shoot mixed lots unless I had to, just the way I was taught. I know others that don't and shoot well too.
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Jerry G
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Re: Brass Question

Post by Jerry G »

If you are shooting bench rest it matters. The case volume difference won't show up in a silhouette rifle. Don't complicate your life with things that don't make a difference.
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Re: Brass Question

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Some folks here do treat their silhouette rifles like BR guns while working up accurate ammo. Mixing head stamps / brands would not be recommended while testing for accuracy. Every component should be uniform to produce the most accurate ammo.

There are volumetric differences between brands. Just this week I received 400 PRVI brand 7-08 cases. I usually shoot WW and RP but needed to replace some tired brass. Try and find some domestic brass now. I took 20 out of the bag at random and measured them. Very repeatable dimensions and tight primer pockets. I also rolled them across a flat, level plate. No heavy side wobble...nice. Can not say the same of the RP brass. This seems to be very good quality brass from Serbia. Time will tell how many firings I can expect from them.

Your post made me go back and weigh them against WW, Hornady and RP. I took 20 new samples of all four brands. Empty new WW 7-08 brass weigh 156-158 grains. The RP brass weighed 159-163 grains.The Hornady brass was 159-161 grains. The Serb made PRVI came in at a whopping 176- 178 grains each. Assuming all outside dimensions are similar, this brass has considerable less case volume. I also weighed 10 LC 90 .308 military cases reformed to 7-08. These were in the 170-171 grain weight.

A simple test was an eye opener for me. I seated a dead primer in backwards in a new WW case and a new PRVI case. I filled the WW case with H335 fine ball powder to top. I then poured the H335 from the WW case into the PRVI case. All but FIVE grains would fit proving reduced case volume with the PRVI brand. Using my standard loads in this brass will increase pressures resulting in slightly flatter trajectory. If these cases were mixed in with other brands with same charge the group size will increase....how much??

I will have to reduce my standard loads when I start using the PRVI brass. Due to it's rather robust weight they may last for many firings.
Last edited by Bob Mc Alice on Fri Apr 24, 2015 2:20 pm, edited 1 time in total.
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BCloninger
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Re: Brass Question

Post by BCloninger »

Have you checked length on the PRVI? In particular for any variance between pieces?
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Re: Brass Question

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Here ya go, Bob. Just got home from the range. :mrgreen:

The five in the picture measure in spec at 2.026-2.028, about the same length as the other brands. You can get away with mixing brass that is similar in weight and volume. Afterall, this is an offhand game. Heck, I do it all the time with just my practice and plinking ammo. For the match ammo I stick with all the same brass. This batch of Serb brass will be used in my factory barreled practice guns after I dial in the right charges for them. My supply of domestic stuff will replace tired match brass.

Did I mention they were only $42.78 per 100 at Powder Valley? 8)

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redmist25
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Re: Brass Question

Post by redmist25 »

All but FIVE grains would fit proving reduced case volume with the PRVI brand.
Hi Bob:
I'm curious now, When you say all but five grains are you refering to a measured five grains of weight or five individual pieces of powder ?

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Re: Brass Question

Post by Bob Mc Alice »

A measured full five grains (weight). Not much, but when your average charge is 38-40 grains this is a big deal. I slowly poured the H335 into the PRVI case to the top using a powder funnel. I then pan weighed the extra that would not fit.

We have some Ca. friends that had a problem with brass at the AZ state two weeks ago. They shoot the 6XC round with 115 gr. DTACS and RL-17. They recently went with PRVI .22-250 brass to form the XC round. They were getting extremely flattened primers and even had a few head separations during the match. Makes one wonder if they, too, were cases with less capacity than what they were previously using.
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Re: Brass Question

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I just went and repeated this little test, this time using a short drop tube. I pulled three cases each of WW and PRVI. I plugged the pockets as previously described and carefully trickled H335 to fill the cases to the top. I then weighed each charge using my trusty old Lyman-Ohaus beam scale.

The WW brass each holds 60.0 grs filled to the top. The PRVI each held 57.0 grs. to the top. So I stand corrected.....THREE grains difference, not FIVE. Using the drop tube made a difference. No doubt the PRVI brass holds about 5% less propellant than WW. Someday I will repeat this test with both brands fire formed in the same chamber. Don't think it will be any different, though.

The one photo shows the 57.0 gr. charge dumped directly into a WW case on the right.


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Three grains of H335

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Varn
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Re: Brass Question

Post by Varn »

Excellent work Bob! And I'm glad that you used powder for this test. I've seen case capacity given in units of water and it makes me wonder what the hell does water have anything to do with my purposes? Other than it's readily available I can't see why anyone would use water. FYI I did this same test with Lapua 6.5x55 brass vs Lapua 243 brass reformed to 260. And found that the 6.5x55 had a 3 grain greater capacity when filled with H4895. Therefore proving that the rounds are basically identical for our intents and purpose when both are chambered in a modern bolt action. My chronograph shows this as well.
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Re: Brass Question

Post by Jim T. »

Varn wrote:Excellent work Bob! And I'm glad that you used powder for this test. I've seen case capacity given in units of water and it makes me wonder what the hell does water have anything to do with my purposes? Other than it's readily available I can't see why anyone would use water. FYI I did this same test with Lapua 6.5x55 brass vs Lapua 243 brass reformed to 260. And found that the 6.5x55 had a 3 grain greater capacity when filled with H4895. Therefore proving that the rounds are basically identical for our intents and purpose when both are chambered in a modern bolt action. My chronograph shows this as well.
It seems to me that if you are trying to measure the volume/capacity of a cartridge case the best measurement medium would be a liquid versus a medium of varying shaped and sized particles such as gunpowder. I guess the best illustration of this is the picture Bob posted above of the two cartridges where you can observe voids between the "grains" of powder and different sized "grains" that are far from identical from one case to the other. Of course the difference from case to case will not be large, but there will be more variation than if water or Kool-Aid was used.
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Re: Brass Question

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OK, Jim. You made me do it. Not Kool-aid but light gun oil instead. I weighed and recorded one each WW and PRVI with inverted primer cup plug in place. Then I slow and carefully added light oil a drop at a time to exact level fill. I then carefully set the filled cases on the pan to weigh again. I don't have a digital scale ( like no cellphone either :D ) but was able to get them done. My calculator shows exactly 2.8 grains difference with WW holding more oil. Pretty close to using the H335.

Fun stuff to do on a cold rainy day, eh Jim? :)

Hey...HP next Sunday, see you there?

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Bob Mc Alice
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Re: Brass Question

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HA. here is a timely article on the case volume measuring subject. These guys go off the deep end. :)

http://forum.accurateshooter.com/index. ... =3872078.0
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Re: Brass Question

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Wonder what the weight of that WW brass would actually be if it was clean, looks like at least a grain of crud on it as compared to the new brass. If you want to do something and not have to worry about brass or anything else, hook up with one of those Philipino gals at the bottom of the page. They will leave you in the corner starched dried and without brass, copper, paper or plastic.
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Re: Brass Question

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JB...Sara says you are getting those girly porn pop up ads on your page because you frequent those type of websites. [-x I see stuff like Cabelas , Allstate Insurance and hunting ads.
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