How to adjust published load data?

[slackersean]

I'm loading some Lee c309-180-2r boolits with HiTek coating, sized to .309 for a 300 blackout AR. I have a Lyman load book that shows a Lyman 180gr with load data using 12-15g Reloader 7 and a COL of 2.110. The problem i have is that using the Lee boolits, I can't get anything longer than 1.990 to chamber with this boolit. If I test load 12-14 in half grain increments at my required COL, would this be reasonable or would the pressures be to high? Should I back down to below the suggested starting grains to begin testing? Having a COL needed that is below the Min listed made me a little nervous. The listed loads are about 5gr below a jacketed load of the equivalent bullet. These are just for plinking, and I'm just trying to get a good starting load since it's 40 miles to the range for testing.

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[GhostHawk]

So that is .2 thousandths total distance change? In a round 2 inches long, and at the neck?
What is that less than 10% of total?

I would start low and see what it does. And I would probably start with single loads. And examine brass carefully.

You also might want to look for a powder that is a little more commonly accepted as being good in the .300BO. REL 7 was on the list but no comments on the list I saw.

And Alliant does not list the .300BO under Rel 7. So you may be pushing your luck.

When you go off the road you have to accept a couple of things.

A This is not the normal path most take, almost always there is a good reason for this.

B If you do this it is strictly at your own risk. So be careful. Make one change at a time, write it down, test it carefully.

Good luck.

[Bzcraig]

Please heed Ghosthawk's warnings............I think there are much better choices.

Having said that I looked on Load Data and found one (1) receipe using RL7...... 17.6gr for 1726 fps using Win 190gr jacketed.

[clearcut]

slackersean I have been having the same deal with the Lee 160 but I'm using IMR4227 I reduced the load to below the boolit then came back to the load I started with 15.8 grn. in small increments and my groups came back together. It is different powder so my info may not help. Welcome to Castboolits, there many more here with more knowledge than I have, hang in there some one will have the answer. Good luck !

CC

[slackersean]

I can try loading with H110, or other commonly used powders. I just figured RL7 was going to be OK since it was a published load for a cast bullet in my Lyman manual. But with any powder, if you have to adjust your COL to shorter than the min, what's a safe way to adjust the load. I'm going 2 hundredths shorter, so yes just about 10% of the original COL. Is there a mathematical calculation? Something like a 12gr load then reduced 10%, so then 10.8gr starting load?

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[Bzcraig]

You can by allmeans use published data with confidence! Since you're just shortening OAL by .002 you should be fine if you start at the starting load and work up watching for signs of pressure.

[slackersean]

The COL is .12 shorter though. Going from the listed 2.110 to 1.990. I made an error saying 2 hundredths. It's almost an eighth of an inch. I'm not sure why this AR-Stoner barrel needs such a short COL to chamber. Should I reduce the starting load? This is my dilemma. Hell, maybe i just need a new barrel that doesn't have this issue.

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[Bzcraig]

Naw, don't replace the barrel, that's half the fun of reloading/casting......finding the best possible load for each firearm and also why it's a marathon and not a sprint. I personally would have no problem starting with 11gr and working from there. The first hurdle is getting function, then start looking for the pressure signs. Don't make too many until you make sure it will work, don't ask how I know! I would also make a few dummies to to try manually out of your mag.

[Yodogsandman]

If the nose profiles of both boolits are different, say a pointed one and a round nose, where does the boolits bottom land? You need to figure out the volume of the powder space available with that listed load, at that C.O.A.L. and then put the questionable boolits base at the same level if possible. That (the case volume) would be closer for figuring out the charge.

[slackersean]

If the nose profiles of both boolits are different, say a pointed one and a round nose, where does the boolits bottom land? You need to figure out the volume of the powder space available with that listed load, at that C.O.A.L. and then put the questionable boolits base at the same level if possible. That (the case volume) would be closer for figuring out the charge.
Great idea. Did some research and the listed Lyman 311332 comes in around 1.13 inches. My bullet comes in around 1.00 inches. The difference is .13 inches. This should mean my bullet @ my COL and the listed bullet @ listed COL bottoms should land at the same spot (Technically mine would allow .01 more space). The internal case space should be identical, meaning I can use the listed loads at my COL without issues. If my logic is correct.

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[SSGOldfart]

slackersean I have been having the same deal with the Lee 160 but I'm using IMR4227 I reduced the load to below the boolit then came back to the load I started with 15.8 grn. in small increments and my groups came back together. It is different powder so my info may not help. Welcome to Castboolits, there many more here with more knowledge than I have, hang in there some one will have the answer. Good luck !


CCI've tried 14grs of IMR 4227 with a 180 grain PC bullet
But using a single shot I don't have your OAL problem.

[clearcut]

That is in an AR 300BK that load will cycle for me.And print well, as for OP I don't know the math formula you are looking for.

CC

[runfiverun]

yodog gave the answer I would work with.
case volume, boolit weight, and the boolit not jammed into the lands.
should give you a similar result between the two compared rounds.

[Boolseye]

RL 7 has been my main powder for 300 BLK. I use 16 grains under the Lee TL312-160-2R. 12.5 gr. under the Lee 309-230-5R. No issues. I only extrapolate when I am very familiar with the powder and the cartridge/bullet, and even then very cautiously.

[DougGuy]

You could always have that barrel throated so you can use safe, tested, published load data without having to get off into "Hey y'all watch this" land...

.200" is a LOT and yes runfive has seconded the safe way to do it is by figuring where the base of the boolit is, and then extrapolating load data for a listed load that has the base of the boolit in the same location.

[Tackleberry41]

Book data is often little more than a guide. Unless you use the exact same everything they did in testing, if they even say. Lee data book gives no info on test weapons and even bullets are generic like '150gr jacketed'. Theres alot of variable in a 150gr jacketed bullet. Spitzer are shorter than boat tail, HP are shorter than pointed, etc. Brand specific books will say this bullet made by us etc. But may use unrealistic barrel lengths in testing, like hornady 308 data was all thru a 24in barrel, which is not very common. Or some 357 data I was looking at was for a 10in barrel, when 4-6 is way more common.

I was messing with some 357 the other day, its an NOE HP mold. Using the crimp groove OAL length was way more than the load in the book, and the velocity showed it. Only way to get the OAL length from the book was sink it way deeper and cant be crimped anymore. Stuff like this I end up with various bullets side by side to compare OAL and seating depths.

If you start at the min data, it gives alot of room for variations in seating depth. Shorter they should speed up, longer slow down. Run em over a chrony and compare to what the book says. Without a chrony, its near impossible to try and figure out.