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Discussion Starter · #1 ·
Dry Powder
Posts: 1
(1/12/03 5:21:22 pm)
Reply | Edit | Del All 300 Win Mag Likes new brass?

I have developed a good load for accuracy (Sub 1")
75 grns RL 22 for Nosler Partition. Using Winchester Brass.

When I use the brass for the second time Gun is inaccurate
(3" group), [I reload in other guns, no such problem]. Any ideas or explanations.

The gun seems snappier and maybe more recoil, does this make sense. The gun is awesome with new brass.

Gun is a 300 win Mag from Sako in Stainless synthetic.

*TFF Staff*
Posts: 3091
(1/12/03 6:51:38 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
I'm not very good at rifle reloading, but having recently ran the gammet of trying to load .223 ultra small base loads for a really tighta$$ chamber in an Armalite .308, it might be the casenecks have swelled and lengthened on you. Plus, the shoulder and bottom of the cartridge brass may have swelled a bit more on you.

After all, you launching them buddits with 75 grains has got to do something to the brass.

Got dial calipers? Start measuring everything, necks, shoulders, base etc. Oh, and neck brass thickness too.

I really don't like loading bottle neck brass...but thats just me. Lots of folks do it to perfection.

Hope one of those gents comes along and gives you some better advice.


*TFF Senior Staff*
Posts: 1779
(1/12/03 8:51:13 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
Dry Powder - Welcome to the board! Hope you will join us in all the many forums here and partake of the discussions.

Your .300 Win Mag is a belted case. The cartridge is designed to headspace off the belt. This means upon firing the case will tend to flow from the base of the case to the shoulder and neck, causing excessive length and stretched cases.

You need to carefully neck size your fired cases and trim to below maximum length. If the cases will now chamber without really undue force to close the bolt, you're in good shape. Sometimes you have to neck size and add just a tiny bit of "bump" to the shoulder to have it chamber. A LITTLE required effort to close the bolt is acceptable.

When you do this, the case is fireformed to the chamber and you have the best of all worlds - the case will be supported at the base with the belt and at the shoulder. This will align the bullet with the center of bore (providing the chamber is center reamed!) and you have the best accuracy.

A little thing I do to assure the bullet is centered in the case neck when reloading is to rotate the case in the shell holder 90 deg in stages as the bullet is being seated. This assures the best alignment in case there may be a slight difference in seater die/shell holder. Also, if you're loading a bolt action Sako, you really don't need to crimp the cases, if you don't want to.
"Keep Off The Ridgeline"

Dry Powder
Posts: 2
(1/12/03 9:11:02 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
Thanks Kd, I thought that once firing of the brass would

not stretch the case ... but I have not checked that.

Confidentially, I have had this problem for sometime with

this gun and just keep buying Brass. I have ruled out

powder and primers etc and actually have loaded some cases

with 73 and 74 grains. I have reloaded for 4 years mostly

6mm ppc , 22 ppc, and .308 yet I have never shortened the

cases. The PPC's have been fired 4-5 times (600 rounds)

and the .308 still fires great. I know I have to learn but felt

1 round on a 300 Win Mag would be more forgiving.

Thank you to both of you for your interest in my problem.

*TFF Senior Staff*
Posts: 1785
(1/12/03 10:11:55 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
Glad to be of help, DP -

I've loaded for 7mm Rem Mag and .300 H&H for some years now, both being belted cases. It doesn't take long to find out belted case reloading and non-belted case reloading are two different things. There is a specialty die on the market now especially for reducing the stretch in belted cases. Don't have the name right off the top right now, but it is advertised in the gun rags.

With proper care, you can usually get 7 to 10 reloads in a belted case before the ol' bugaboo incipient crack ring appears just above the belt. Non-belted cases that are neck sized can last upwards of 20 or more reloads before prudent wisdom says to discard. Your 6mm PPC probably has lasted so long due to the very short body and sharp shoulder angle for headspacing, not allowing a lot of stretching.

It is still a must to caliper your fired brass and to not let any go beyond recommended max length. An overly long case may chamber, but the neck will be driven up into the bullet portion of the chamber causing a very tight fit, which in turn will cause excessively high pressure. Cases should be trimmed when any one of the batch reaches max or near max length. Trim back to nominal recommended OAL. Also, turning the outside of the necks after several firings is a great idea, as the necks tend to thicken with brass flow. A thick neck results in the same restricted chamber area and high pressures.
"Keep Off The Ridgeline"

Dry Powder
Posts: 3
(1/12/03 10:42:13 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
Thank again Kd (on both boards)

Not sure how to report this but here goes

overall lenth of case (Spec in Nosler Manual) 2.620

My case "new" cases ready for firing from 2.6180 to 2.620

My once fired cases full body sized 2.6175to 2.6250

not statistical but a good % over 2.6200 but nothing over

2.6250. Is this enough to make a difference? and is this

the right measurement.

Dry Powder
Posts: 5
(1/13/03 11:53:30 am)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
Hey kdub01,

I have been doing a ton of measuring.

My longest case (once or twice fired) 2.650 out of 100
In the random test (picked 20).

My shortest case is 2.6150... Aol of case.

Have tested the shoulder measurement on unfired, fired,

and have seen no variance of note.

I am not that experienced but did note that my
Neck thickness is no different after resizing once fired or
New brass. By the way... after sizing my thickness of the
Neck is .3340 after firing it goes to .340 then resizing
Brings it back to .334, Sami speck is .34 (before or after

I think I am going to back off on the powder, 1 or 2 grains
Just to see if it has an effect.

One more thing, My Wilson (fired case) shell holder shows
Resized cases .150 approx from the belt to the case. Obviously New Brass falls right in and sits on the belt.

Is it possible that the energy required to fire form the New
Brass now goes "out the barrel" and makes the round too hot?

When I worked up this load I always used new brass.

Using 75 grains RL22 on Nosler 180 grain Partition.

*TFF Senior Staff*
Posts: 1788
(1/13/03 2:22:38 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
Your cases should be trimmed back to 2.610 - the 2.620 is maximum length. Anything over this is not acceptable.

There are some variances in the extraction groove of rimless cases - I have some old Sako brass that will not fit into the shell holder unless in turn them down slightly. It may be possible that heavy loads could cause this groove dimension to compress, I don't know for sure.

Your load of 75 gr of RL-22 is 1/2 fr shy of the max recommended by Nosler for the 180 gr Partition.
Lyman shows 73.5 gr as max with 51,500 CUP pressure. That's a little low on the pressure side for full loads. This cartridge normally runs around 55,000.
Speer lists 77.0 gr as max.
Hornady lists 76.0 gr as max.
Hodgdon lists 76.0 gr as max with 54,500 PSI
"Keep Off The Ridgeline"

Dry Powder
Posts: 6
(1/13/03 3:24:04 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?

Sorry for being slow - do you want me to shave back to 2.610?
or alternatively shave back to 2.610 to 2.620?

I think I've figured out how to shave the cases and I have been targeting 2.6150 will make a batch and try it.

I will also try reduced powder loads. I am up in Canada
and Waiting for a nice day this time of Year can be a test of patience. But I will get it done.

If this does not work I will try another brand of brass -
apparently you can get Lampua as of now in 300 Win.


*TFF Senior Staff*
Posts: 1790
(1/13/03 5:51:35 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
You can get a real simple and cheap case trimmer for the .300 WM made by Lee and sold at any reloading supply store.

Yes, you HAVE to trim the cases back to 2.610 (minimum) and not exceed 2.620 in cartridge OAL. You will find even with neck sizing fired cases that after a few firings, the OAL will grow to the 2.620 max length. A lot of gun writers recommend scrapping the entire bunch of brass with the 2nd need to trim any case in the lot. Personally, I'll wait until I spot the incipient ring show up as a light shiny line circling the case just above the belt, then toss.

I'm cheap, tho!
"Keep Off The Ridgeline"

Dry Powder
Posts: 7
(1/13/03 9:30:54 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?

I have a Wilson case trimmer and a Sinclair stand ordered
3 or 4 years a go and left untouched. I read the write ups
in the Sinclair manual. I have called a few guys and have wreaked a few cases but seem to have it working and I
am going to full body size all my clean Brass, case trim
to 2.6150 and sligtly debur the ends.
Thanks and I will report back in a couple of weeks.

V.I.P. Member
Posts: 115
(1/16/03 3:58:55 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?
If I may interject something here, I need to know something. In a post above, you said the following

"One more thing, My Wilson (fired case) shell holder shows
Resized cases .150 approx from the belt to the case. Obviously New Brass falls right in and sits on the belt."

If you are speaking of a case guage, then your problem is over pressure causing the case to head area to expand and this is why it will not go back in after firing. Either that, or your sizing die is not adjusted correctly for sizing the full length case. I would really check to see if the load you are using is max or min. If this is a max load, then you may have a SAAMI spec'd tight chamber and the max load could be over pressure in your gun. With expansion in the area you describe, this is either an adjustment problem or a pressure problem. Please let us know how you came up with this load.

If you are measuring brass for trimming, the brass must first be sized before trimming or your necks will be too small when done. I only say this because I do not believe I saw this discussed above. I may be wrong, been on the road the last week and a half. When measuring case length, it should first be sized then measured.

One more thing, even new cases should be sized before being measured.

Please answer my questions and we can help solve this dilema with you.


Edited by: inplanotx at: 1/16/03 4:05:14 pm

Dry Powder
Posts: 8
(1/16/03 4:35:30 pm)
Reply | Edit | Del Re: 300 Win Mag Likes new brass?

I am using the Wilson/Sinclair case trimming system.

It has its advantages and disadvantages. Onother good

system is the Forrester system.

The Wilson system requires a shell holder to hold a shell

during the trimming process. If you are using new brass

then they recommend you use a different Style Number

of Wilson shell holder, it is tighter. On My shell holders

(Fired) new brass fall trough and fits slopily in the holder,

Once fired but not resized comes to about 3/4 of an inch fron

the belt. Once fired and full body resized it is snug at 1/4

inch from the belt. I called Sinclair about these

measurements and they confirm them as normal. Right now

I have trimmed my cases to where new brass falls at aprox

2.6150 and we Will see what happens. Thanks anyway

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