AR Load check [Archive] - Glock Talk

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squirreld
10-01-2011, 15:10
I need a sanity check.
I am working up several different bullets to see which one is the most accurate in my barrel.

I am at least 1.5 gr. over max from several books and I still see NO pressure signs. Do I keep going?

I am looking at the following for pressure signs.
1. Where the brass lands (they all land in the same spot, bout 6 foot away)
2. flattened primers (no signs)
3. How well does the fired round (not resized) fit into a Headspace/Case length gauge ( all fit in just fine. They stick about 6 thousands due to headspace. None of them stick up 1/8" or more which would indicate expanded web and hence overpressure)

attached is the xls file that shows 8 different bullets, and all other load facts.
1 shot test for each powder charge.
http://home.earthlink.net/~squirreld/223.xls

EL_NinO619
10-01-2011, 15:39
Why do you want to push the round so hard. Your brass life is going to be the only thing you'll notice, as in not last as long. As for headspacing a fired round, some will go some will not. I suggest you find a load that is accurate and cycles if using a auto loader and stick with that. Use Ramshot TAC, You will get good accuracy and performance with not having to push the envelope. Velocity and MAX load do not mean best round.

squirreld
10-01-2011, 15:49
The goal here is to find the ceiling on the powder charge for each bullet.
Back off 1 grain, then shoot each for accuracy.
Once I find the most accurate bullet, that will be my load.
1 gr. off of max should offer a good balance between brass life and performance.

Zombie Steve
10-01-2011, 16:08
16" barrel?

squirreld
10-01-2011, 16:19
yeah, a 16" middy with a true mid length gas system.

Boxerglocker
10-01-2011, 16:29
Why do you want to push the round so hard. Your brass life is going to be the only thing you'll notice, as in not last as long. As for headspacing a fired round, some will go some will not. I suggest you find a load that is accurate and cycles if using a auto loader and stick with that. Use Ramshot TAC, You will get good accuracy and performance with not having to push the envelope. Velocity and MAX load do not mean best round.

:agree: I think that your trying to push too many combos at once. Start with one bullet and powder develop 10 rounds each, and test for accuracy / velocity at the same time at the rifle range on a bench.

Zombie Steve
10-01-2011, 16:41
I gotta agree with pick one and go with it. All of them are good bullets. Your combo accuracy / speed load could be hiding in the middle of those half grain jumps. :whistling:

I'm not sure I get the idea of going to max and backing off one arbitrary grain. The most accurate might still suck compared to something elsewhere in the data.

:dunno:

PCJim
10-01-2011, 16:52
Squirrel, look up Audette ladder test on google. If you have a 300yd range, this method WILL find your most accurate load. It doesn't work nearly as well with shorter yardage.

Boxerglocker
10-01-2011, 16:54
I'm not sure I get the idea of going to max and backing off one arbitrary grain. The most accurate might still suck compared to something elsewhere in the data.

:dunno:

Well said, I've actually proven this with a couple different bullets I have tested with my M4. Usually accuracy is close to the top of the published loading range but no need to go beyond.

Jumper
10-01-2011, 17:01
I need a sanity check.
I am working up several different bullets to see which one is the most accurate in my barrel.

I am at least 1.5 gr. over max from several books and I still see NO pressure signs. Do I keep going?

I am looking at the following for pressure signs.
1. Where the brass lands (they all land in the same spot, bout 6 foot away)
2. flattened primers (no signs)
3. How well does the fired round (not resized) fit into a Headspace/Case length gauge ( all fit in just fine. They stick about 6 thousands due to headspace. None of them stick up 1/8" or more which would indicate expanded web and hence overpressure)

attached is the xls file that shows 8 different bullets, and all other load facts.
1 shot test for each powder charge.
http://home.earthlink.net/~squirreld/223.xls

Work up your load however you want. I don't see a problem with finding your max then backing off a comfortable margin.

High pressure signs in a semi-auto are going to be mainly flattened primers. You can also tell by how vigorous the action cycles.

Since your using mixed brass I'll add this: case pressure varies greatly between different brands of brass because of the difference in internal volume. As you work up with mixed cases you'll see a lot of extreme spread in your velocity strings. And some cases will have flattened primers some won't. The method of load development your using would work more safely if you used one brand of case.

steve4102
10-02-2011, 01:05
The goal here is to find the ceiling on the powder charge for each bullet.
Back off 1 grain, then shoot each for accuracy.
Once I find the most accurate bullet, that will be my load.
1 gr. off of max should offer a good balance between brass life and performance.

It is my understanding that the pressure signs you seek don't rear their ugly head until pressure are well above 65K psi, more like 70-75K. Finding this "ceiling" and backing off 1 grain will still have your AR running way above safe operating pressures.
I have done what you are trying to do in a few wildcats and Ackley Improved bolt actions, but never in a semi-auto, especially in an AR.

Good Luck!

squirreld
10-02-2011, 18:00
Thanks everyone.
I guess I should re-evaluate how I am doing this.
I have never heard of the Audette ladder test. It makes sense.
I'll give it a try.
I'll start at .4 gr. over published max and come down .3 grains to 2 gr. below the published max.
That will be 8 shots per bullet.
I do have access to a 300 yard range.

How does that sound?

Boxerglocker
10-02-2011, 18:04
Thanks everyone.
I guess I should re-evaluate how I am doing this.
I have never heard of the Audette ladder test. It makes sense.
I'll give it a try.
I'll start at .4 gr. over published max and come down .3 grains to 2 gr. below the published max.
That will be 8 shots per bullet.
I do have access to a 300 yard range.

How does that sound?

Honestly, your taking a real risk starting at above published max and working down.

robinsok
10-02-2011, 21:05
Honestly, your taking a real risk starting at above published max and working down.

Honestly i am kind of wondering the same thing. Although they may be ABLE to be exceeded, the max is there for a reason. It seems you are taking the exact opposite approach from all advice i have ever read, which is to start low and work your way up. To me it doesn't make sense to start about what is listed as being safe, but it's your eyes and fingers I guess.

squirreld
10-03-2011, 19:30
Caution noted,
I'll start from the bottom and work my way up stopping at the max.
Is .3 gr a small enough step?

PCJim
10-03-2011, 20:32
.3gr steps should be enough for a rough estimate of where your barrel's sweet spot(s) is/are. Once those are determined, revisit them with .1gr variances on either side of the sweet spot to find the most accurate load.

And, yes, the test should always be worked up, NOT down.

Zombie Steve
10-03-2011, 20:48
.3 is roughly 1% jumps - it's not a hard and fast rule, but on a high pressure round that doesn't have a lot of case volume I try to stick to 1%. Seems like a pain when you're burning up components during testing, but it's nice to look back at your data and see / know exactly what was going on.

squirreld
10-04-2011, 17:37
Sweet.
Thanks everyone.