so i went back to the range to try and improve this load but it was a lot worst.
the first 2 targets are the ones from the other day.
i shot a 0.658 group with 94 gr.retumbo and a coal of 3.600
i also tried a coal of 3.650 as this shot the best with the TTSX 168.
that group was worst at 1.50"
so this morning i tried again.
i kept 94 gr. of retumbo for a charge and played with OAL.
the first group i made i still used 3.600 but with WLRM primers.
group was .937"
second group i kept 3.600 and CCI250 that gave me .658" the other day and used the 1st circle on my BDC reticle just to see how it would group compared to a crosshair. group was 1.19"
then i tried a group at 3.615" that was 1.82"
and finally a last group at 3.630" that was 2.25" .

now is it possible that such small changes in COAL make that much difference in group size?
you can see in the pics that group keep the same pattern but enlarging when i lenghten COAL.
can i go shorter than 3.600" with a 200 accubond in 300 rum? like 3.585"
the last 2 groups were shot 22 to 27 since i cleaned the barrel. is it possible that it's already fouled? i don't see groups beginning to open before 45 shots with the barnes TTSX.
velocity for the 12 shots were between 3052 and 3079. ave.3060 fps.

what would you do next?
should i try cleaning the barrel and a shorter coal (if possible to go below 3.600")
try a 10 shot group at 3.600?

that load is already not bad with 1 group at .658 and 1 at .937.
it's just that i was spoiled with the 168 ttsx shooting something like 15 - 3 shot groups between 0.37 and 0.82.
and 1-10 shot group where 7 of those were in .532" and the other 3 enlarged it to 1.36"
i'm hoping to be able to do the same with the accubonds

thanks in advance for the hints

You're not the first to find small seating depth changes can affect group size. It changes pressure and barrel time can move you on and off barrel time sweet spots. Because they change pressure it is also usually not a good idea to alter them a lot with a near maximum load. It is better to be at a starting load 10% below maximum. When you find the best depth for that reduced load, then tune the powder charge.

Take a look at Dan Newberry's site for a good systematic way to find a best accuracy load. You can adapt his round robin method to seating depths as well as to powder charge.

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Nick

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"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley

I shoot the 300 RUM, I prefer Rx22 for my loads, I have used the 200 Accubond, but I prefer the 200 garin Barnes TSX. You have to really pay attention to the length and the load, I agree with unclenick about starting off with a reduced load and measuring the over all length accurately.

My groups are very tight because I spent the time and the money to figure out what works with my rifle and my skills. Over the years I have found that what works for me doesn't always for some one else, but your really close to have a good load.

Jerry

300Bacardi,

I think your range results pretty much answer your question, that you should stick to a shorter COL, possibly going even shorter. Measure your COL, minus bullet length, to see how far into the case you're currently loading the 200gr ABs. Also, are you crimping at all? Sometimes a deeper seating depth means more neck tension is indicated and a crimp might be in order.

My biggest question concerns your lack of cleaning while attempting to work up a load for your rifle: Why would you put that much time and money into reloading and not take the extra few minutes to keep your barrel clean? The goal while working up a load for accuracy is to eliminate as many variables as possible. Among other things, that means allowing the barrel to cool between shots in a string, and cleaning the barrel thoroughly, between strings. To answer your question...YES! A barrel can see enough copper fouling from 20 shots to affect the accuracy you're getting. Probably not the amount you're seeing, though.

After all of that, I have to wonder about something. You've got a load that shoots under .700" with a 200gr bullet and 3050fps...and you're not satisfied? If it was a hot .22 and you were shooting at prairie dogs 300 yards away, I could see needing to tighten them up, but for the kind of hunts you'll use that 300RUM on, why would you need it any better? You're already shooting well enough for a 400 yard shot. Did you have something a lot further than that in mind?

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Ask me about QDMA.

I would increase the powder charge and leave the COAL at 3.6" I also use Retumbo but with a heavier powder charge than you are useing with the 168 and I use the 180 grain TSX and 180 AccuBond bullets for 3375 FPS from my 300 RUM with a 26" barrel


Hodgdon list a starting load of 97 grains of Retumbo with a 165 grain bullet. They also list a starting load of 94 grains of Retumbo with a 180 grain bullet


http://www.hodgdon.com/

thanks guys
i thought it was actually the other way around, first finding the powder charge then playing with oal.
i'll change my way of doing it then.
i'll also clean between string. it didn't seem to change much with the ttsx so i got lazy ...LOL

for jwp475 this load of 94gr retumbo is for the 200 accubond.
for the 168 ttsx i have a load with rl25 that 1 gr below max.

Hodgdon list 95.5 grains of Retumbo for the 200 grain AccuBond with a load of 95 grains of Retumbo and a 200 grain AccuBond my rifle gives 3250 FPS chronographed

IMHO increase the charge wieght a bit

Jwp475 i tried 95 and 95.5 gr. But velocity was only
3100 av. And groups started to open a bit, that's why i kept
94 gr. But i didn't try 94.5 gr.
I'll try this next time with 3.600 coal

Try the Federal 215 primer Match or other wise. I have always had good luck with them

I've been trying to grab some for a year LOL!!!
I WILL try them when i find some...
Thank a lot for taking Time to help.

Don't know if you have tried them, but I've had better luck with RL25 and IMR7828 than any other powder in my 300RUM SenderoSFII.

I miss Tang. Even with his "youthful exuberance", he was a good egg.

RJ

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Keep your powder dry and when you go afield take the kids and please..........wear your seat belts.
I am the ORIGINAL recoil junky, often imitated, but never equalled.
Proud Father of a SoldierMedic in The 82nd Airborne 325thAIR White Falcons
IUOE Local #9

Is tang banned for good? or will his ban be lifted in the future? He definitly brought a lot of entertainment to the forum. Never did have the heart to post the groups i get outa my .338 using factory corelokts

I kinda miss Tang, as well...it's good to have someone "stir the pot", once in a while!

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Ask me about QDMA.

It was 30 days. I don't know if he'll come back or not, that's up to him.

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MikeG

I do too...I liked poking him with a sharp stick now and then (and I believe he liked doing so in return) .

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I emailed him. He said as far as he knew it was permanant.

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Recoil is God's way of letting you know the power in which you hold

I forget who put it on, but it was supposed to be temporary. I just looked it up and the system still hasn't unbanned him according to his user profile but, I see, he hasn't posted since February 25 so this is wrong. He is also not on the system's separate list of banned users. This is some kind of system screw up. I am going to attempt to lift the ban manually. Cross your fingers.

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Nick

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"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley

O.K. It looks like he's unbanned. Weirdness.

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Nick

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Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Instructor
NRA Patron Member

"First contemplation of the problems of Interior Ballistics gives the impression that they should yield rather easily to relatively simple methods of analysis. Further study shows the subject to be of almost unbelievable complexity." Homer Powley

Thanks Nick, I hadnt even been back to check it since the 25th of March.

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Volatile & Unstable

For the 300 RUM, I use Magnum Rifle Primers, with these types of powder and the quantity, you need a really good fire to get it started.

Jerry