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Old September 12, 2012, 08:18 PM   #1
davery25
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Load increments & number of rounds

Hi guys,

I've just received everything I need to reload for my 7.5x55 (k31 swiss). I'm using AR2209 (aka H4350) and 2 manuals have the range going from 44.0 to 48.0 grains.

When I was working up a load for my 223, i loaded 5 rounds in 0.1 grain increments which was fine because there was a 2 grain range. For my 6.5x55 there was a 4 grain range but extensive reading showed that with H4350 i'd get the best accuracy from 42 - 43 grains so there was only a 2 to 3 grain spread that i needed to test for.

How would you guys determine a load safely? I need to test from 44 to 48 to check for pressure tolerances and accuracy so i cant load any less then 3 rounds in each increment and i cant jump too high incrementally either.

I've read Dan Newberry's OCW method and while that has merit to it, he recommends increasing the increments by 0.7 to 1% which is a 0.4 grain jump from each increment. That sounds and is dangerous. I blew a primer on a 22-250with a tight chamber 0.8 below the listed maximum charge so jumping 0.4 grains at a time isn't something I want to do.

How would you guys tackle this?
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Old September 12, 2012, 09:47 PM   #2
frumious
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Davery,

I think that most of the time as you increase towards the load that blows up the rifle, you first hit a zone where there are pressure signs but no real damage, and after that is the real danger zone (cue Kenny Loggins). Also, I think that warning zone is at least a few tenths of a grain wide. So as long as you are increasing slowly (1% at a time?) you will easily see the warnings and know to back off before you blow up the rifle.

On that 22-250 where you blew the primer, were you increasing a little at a time?

FWIW personally for loads in the 30-40 grain range I like to increase by .3 grains at a time.

-cls
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Old September 12, 2012, 10:20 PM   #3
Brian Pfleuger
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.1gr is barely within the resolution of your scale. You can't really be sure you're even increasing on every load.
Newberry's recommendation of 0.7-1% is perfectly safe. I increase 0.3gr with max loads of 28.0gr.
If max is 48.0, 0.7% would be .336, so use .3 or .4. Either would be fine. No danger.
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Old September 13, 2012, 01:16 AM   #4
davery25
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When that primer blew i was firing the 3rd of 5 rounds of a certain charge of BM2powder. The 1st and 2nd rounds were cratering slightly but i wasn't sure i wasn't imagining it because i was so far below the listed max and i wanted to fire all 5 to see whether i was imagining the cratering or not.

The 3rd round fired and there was a ton of smoke pouring from the action and thats the round that the primer blew on.

Do you guys stop increasing by 0.3 at some point, ie. if you were at 47.6 grains on a charge with a listed max of 48 would you jump up to 47.9 for the next increment or play it safe and go 0.1 from then on? or just stop altogether?
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Old September 13, 2012, 01:34 AM   #5
UncleGrumpy
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In a 4 grain 44 -48gn suggested range I would normally start increasing in .5 grain increments until 47 then play around with smaller increments to find the spot.

I would suggest that if you blew primers at no where near the top something needs to be checked out pronto. It doesn't sound right
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Old September 13, 2012, 01:46 AM   #6
1stmar
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You should see other pressure signs early, specifically stiff bolt lift and flattened primers
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Old September 13, 2012, 07:53 AM   #7
Brian Pfleuger
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As I said before, 0.1gr increments are not helpful. You can't even really be sure that you're increasing from one to the other. The scales margin of error is at least 0.1gr.

I use the same increment from start to finish. if max is 48.0, I'd use 0.4gr starting at 43.2 and I'd go one increment ABOVE 48.0, which would be 43.2, 43.6, 44.0, 44.4, 44.8, 45.2, 45.6, 46.0, 46.4, 46.8, 47.2, 47.6, 48.0, 48.4

Each succesive increment, including 48.4, will be safe if the previous increment didn't show pressure signs. I say "safe", as in it won't blow up your gun. It might show pressure signs, that's why we do increments, but it's not going to go from nothing to disater.

Why don't you give us the specifics of your laod so we can help you figure out the problem. The more information, the better.
Bullet weight and type, bullet length
Unsized case capacity in gr H2O
Case length
Cartidge OAL
Distance you seat from rifling
Powder charge
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Old September 18, 2012, 07:02 PM   #8
davery25
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Hi Brian,

No problem now as such - was just checking to see how to tackle the load increments. I've now done it exactly the way suggested - in 0.4 grain increments.

One more issue - I ran out of Win LR primers and subbed in with Federal LR primers. The ones with the federal at at the top of the load range - 47.6 grains and 48 grains flat. Could this be a problem?

As load data doesn't indicate primer choice I'm assuming it should be fine. I've loaded some 'pressure workup' loads with the Federal primers as well in 0.5 grain increments just to make sure.
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Old September 19, 2012, 07:51 PM   #9
Edward429451
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I always start with a start load and use .5 increments and switch to .2 later in development. I load ten rounds at a time for testing. Loads that show promise and no pressure signs get a batch of 20 or 50 (rifle/pistol) for further testing and another 10 rounds of the next increment. Sometimes I'll get a reduction in measured velocity without any visible pressure signs, but I can take a hint and back off that one to the last good recipe in the ladder and try some fine tuning there.
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