Measured new WW and RP brass for 300 win mag with an RCBS case mic,most shows .012-.015 under "0" setting. Did full basic prep on brass(no neck turn),trimmed to min. spec. (2.610) For first firings of rem 700 5-r milspec,decided to use a generic rem. 165 SP, 150 SP and a jug of IMR 4895,grouped 1.5".Tried also RL 22 and a speer 165 spbt and smk 168,not impressive.Measured brass after first firing,still .002 under "0".Brass shortened up .005 also during fireforming! Was wondering if this first firing should have much effect on accuracy,haven't had problems with 308 700's in past. Measured chamber length as 2.668,so won't trim future brass. The bench is starting to run low on $15/100 SMK's,bought 175 smk's, don't want to waste, any info welcome,going to go fishing now,thanks.
New brass fire forming effecting accuracy much?
- Thread starter leadbury
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I finally printed a cloverleaf with 3 shots,fourth slightly out,with 175 smk and NEW brass,first time trying load/bullett, barrell warm after 12 shots with other loads.Tried to repeat after barrell cool down,same load opened up to 1.75+. Rifle only has 100 rounds thru it, best groups so far are 1"+, (4 shots).!68 smk did 2".Maybe barrel needs time to settle in? Also did not clean for next outing,have read here some barrells don't shoot well after cleaning for awhile. I'm trying to find a load for gun with new brass instead of wasting $ and wear fire forming cases if possible.Barrel might just want a heavier bullet,twist is 1/10+ I believe. One other thing bothers me-Tried to find length to rifling with new to me 175 smk,seemed excessive compared to 168 smk's and other bullet profiles measured.Went back and re-measured other bullet types again,everything is now .060-.090 + longer to rifling! Testing done by chambering round to push back bullett.Sorry for rambling,getting frustated,gun should be tack driver. Tanks for any input,new to this site, noticed several categories of topics,should I post in the one related to my questions?
alsaqr
Member
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IMR 4895 is too fast, especially for 168 and 175 grain bullets. My favorite powder for the .300 Win Mag is IMR 4831. When i do my job; My .300 Win Mag guns make .75" three shot groups at 100 yards.
i have never tried IMR 4895 in mine either. i have used IMR 4831 for 20 years. last year i bought a pound of IMR7828 to try in it. depending on the bullet, i get very good results with either one or the other of these two. the best groups are 220g Hornady round nose with IMR7828. 5 shots all touching each other @ 100 yards. my 180g hunting loads (old winchester silvertips) are not quite as good, but just over 1" @ 100 yards with those using 71 g of IMR4831. the strangest thing i have run into so far is i have to run 30-06 velocities with Hornady 180g btsp interlocks to get any accuracy out of those. when these are gone, i am going to try the 190 grain btsp's and see if they group better.
gamestalker
member
You said your chamber measures 2.668" so your not going to trim future brass. Keeping bottle neck brass within SAAMI spec. regarding trim too length. It is monumental in avoiding unpredictably high pressure spikes resulting from the mouth getting pinched. This is in fact the entire reasoning for maintaining SAAMI trim too length on bottle neck brass. Just because your chamber measures 2.668" doesn't mean you have additional space to accomodate necks that are longer than the maximum case length as determined by SAAMI, I think that is 2.620".
And yes, it is pretty normal for brass to do some shrinking during the fire forming. And as long as the brass does not exceed maximum case length there are no issues. But once again, if it is longer than SAAMI max. it must be trimmed back to some where between min. and max. case length. And this is an interesting area concerning the 300 WM to begin with, because it has the shortest neck of the 30 mag. cartridges. With some long olgive bullets, it can be difficult to get enough neck tension with that cartridge. Trying to get long bullets seated deep enough to fit magazines can also cause problems with the powder charge of some slow burning types to fit in the case.
As to when brass seems to reach it's best for accuracy, is when it is fitting the chamber like a glove. With new brass this can be accomplished with the first loading, especially if you get pressures up to average operating range.
And yes, it is pretty normal for brass to do some shrinking during the fire forming. And as long as the brass does not exceed maximum case length there are no issues. But once again, if it is longer than SAAMI max. it must be trimmed back to some where between min. and max. case length. And this is an interesting area concerning the 300 WM to begin with, because it has the shortest neck of the 30 mag. cartridges. With some long olgive bullets, it can be difficult to get enough neck tension with that cartridge. Trying to get long bullets seated deep enough to fit magazines can also cause problems with the powder charge of some slow burning types to fit in the case.
As to when brass seems to reach it's best for accuracy, is when it is fitting the chamber like a glove. With new brass this can be accomplished with the first loading, especially if you get pressures up to average operating range.
Right you are on the 4895,used it to "break in" barrell with some 150 psp.It did not do to well in tests with 165 psp and some 168smk for hell of it.( 1.75"),just wanted to know. All other test were with RL-22.I did do 7 shots into under 1" hole with one out with 75g rl-22 and a speer 180 spbt seated 3.375 so I'm getting there. Just put Imr 4831 in powder hopper to try next which I believe is slightly faster than Rl-22. I'm a reformed powder junky,here we go again! Was considering RL-25 and H1000 for 180 and up loads.Goal is to get a 600 yd. load for target use only,met someone who is shooting 8" groups at 1000 yds. with berger 175 vld's in norma brass and low end scope,3.5" @ 500,same 5-r milspec rifle,going to try and get his loads. Will keep and eye on case length for sure,just don't want to end up with 100 shorties again. Also just ran down and case mic'd some NEW LC '75 unfired 30.06 match brass and new 308 ,both only .001 under "0". Thanks guys
ArchAngelCD
Member.
I agree, buy some quality ammo and run a baseline.
That right there can be a problem. With only 100 rounds through a barrel you really can't know how accurate it will be. Also, you may already have some copper fouling since you're not cleaning your barrel regularly. Copper fouling will ruin accuracy.leadbury said:
You already know the powder you're using is too fast.
Now for my question, why are you worrying about group size during barrel break-in and while using a powder that's too fast? Stop buying brand new brass, do whatever barrel break-in you think is necessary, make sure the barrel is Copper fouling free and then start load development for accuracy. (IMHO of course)
Reminds me of time shooting with a Bud who bought a supposedly tack driving Hbar match AR, not doing good at all with Fact. match ammo,I was shooting my everyday mini 14 loads. Even though he despised and was afraid of reloads his groups went in half when he shot my ammo!:banghead: I think the last ammo I bought was Black Talon before the ban.
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