pushing bullet into powder question 308 imr 4064 plus fx 120i

[rockwind1]

as i mentioned in previous posts, i am loading (my first time reloading btw) once fired federal fgmm 7.62 brass with

178 amax
imr 4064
br2 primers

i full length sized them with a approx .002 shoulder bump.

i have loaded 3 sets of cases with the follow weights

41.5, 41.8, 42.1, 42.4, 42.7, 43.0 43.3, 43.6, 43.9, 44.2

my plan was to go shoot groups and keep track of the mv as well. should i add in the 44.5 and 44.8 or is that going to high, or do i just have to see what my gun shows as far as pressure?

i was going to add 44.5 and 44.8 as well but i was looking down at the powder and it seems very high up into the neck on those. as i was seating bullets, my coal is 2.820, i didn't notice any resistance but i know that bullet is going down into the powder.

question,,, is this a big deal? how do you know when you are pushing against powder.

it did seem as i was seating bullets into the higher weight cases, i had to turn the seater micrometer in a bit to get same coal,,, or actuallly, i started measuring with a bullet comparator to the ogive,

question, is it hard to get an accurate reading on that, it seemed like it was never exact but within a few .oo1's ( thousandths)

i am using an auto trickler set up with the fx 120i, it works great but i have notice that i set up the weight, and it will sometimes be .02 grains short,,,, like if it was supposed to be 41.5 it would read 41.48,,,, then if would lean in with my hand to hand turn the trickler to get that last grain to make it perfect but as soon as i leaned inn it would switch to 41.5,,,so i would lean out and it would go back to 41.48, does any else have this problem. so i got so i would watch it for a bit, then adjust if necessary. anyway, it worked great but it is very sensitive. almost as sensitive as me so please don't make fun of my questions

 

[watercam]

Nothing wrong with compressed loads as long as the bullet stays seated and the load is safe.

 

[Bc'z]

Try isolating your scale, not having on your bench. Srt it up to the side. Be sure to hold your breath when trickling.

 

[divingin]

Those 178 AMAXes are pretty long from ogive to tip. They tend to seat pretty deep for a given COAL.

That said, 4064 is also a pretty granular powder, which means you end up with a lot of air space between the kernels (they don't nestle together too well in the case.) You could try using a longish drop tube or vibrate the filled case a bit in order to settle the powder a bit more before seating.

On the charge weight, .02 grains will not throw you off, IMO. You're dealing with the single step accuracy of the scale, which is iffy at best. A lot of things can affect the scale to that amount: Noise on the power feeding the scale; interference from florescent lights, fans, cell phones, and radios; air movement from breathing or ventilation. Load to a within a couple of steps and you'll be fine. I suspect you'd be hard-pressed to notice any difference in impact point or grouping from a .02 grain variance.

FWIW, I had pretty good luck with those bullets towards the middle of what you are loading (in the low-to-mid 43's, as I recall. I'll correct that if I'm wrong upon verification.) I'm running a factory Remington chamber, though, and single loading, so I loaded with the bullet seated way the hell out to try and get closer to the lands. I gave up on them when Hornady decided to stop marketing them (I saw no point in further refining a load for a bullet that was going away.)

Good luck!

 

[Rsadams]

Some of those may be HOT , watch for pressure closely... Remember faster is not always more accurate... I load 42 grs of imr 4064 behind a 168 gr smk....

The Hornady manual list 41.3 as a Max load for their 178-180 bullets in .308 with imr 4064.. hodgens online goes up way higher with a 180 gr bullet...

If you don't have a Hornady manual I suggest you pick one up...Each bullet is different and I find it's best to use the correct manual per bullet... That's just me though...

I take it you have a crono and ran some of those FGMM over it for a baseline..? I have noticed speed increases with the fgmm brass over Remington brass so I would say it has less volume... Setup your crono and pay close attention to it and your brass... Safety first , if something feels wrong , Stop...

There's alot of loads that are compressed and the book will usually tell you if it is with a C by it... Shoot what you have loaded as planned and if there's a need to go higher then load some up... Each gun is different and likes different things...

 

[rockwind1]

everything went very well, thanks for everyone's advice. i went all the way to 44.80 gr and didn't see any pressure signs and the bolt seemed fairly normal. i believe i found the sweet spot right at 43.90 gr.

it shot a 5/8's group at 205 yds,,, 3 shots.

i think i will load some .1 increments around that 43.90 mark and do 5 shot groups and see what happens.

one thing was odd, as i was shooting 3 at each target, the targets were all in a line, 12 of them. each group dropped about an 1". if i drew a line connecting the groups, it was a very obvious diagonal line going downwards as i went left to right. which is odd because the loads were increasing in powder.

the mirage was terrible, i was using a suppressor, and my barrel was steadilly getting hot, but there was probablk a 6" difference from the first group of 3 at 41.5 grains to 6" lower on the 12th group with 44.8 grains.

 

[Bart B.]

Having seen 308 Win ammo with 1/10ths grain spread of IMR4064 shoot 168 to 180 grain bullets into about half MOA accuracy at 600 yards, I think its a waste of time to have charge weight spreads less than 1/10th grain for that range. 1/10th grain change of IMR4064 causes about 10 fps velocity change for 180 grain bullets. I'd bet 43 grain charges with a 178 grain bullet will be most accurate testing with at least 10 shots per group.

A 3/10ths spread will shoot 1/4th MOA at 200, 2/10ths spread does 1/3 MOA at 300.

Crushed powder burns faster than when intact. There are more surfaces exposed to heat.

Most pressure signs don't appear on 308 cases until loads are over max psi specs.

 

[Dusty Stevens]

longer drop tube

 

[Bart B.]

Sierra's load data for 180's in 308 Win cases shows velocity with IMR4064 changes about 7.2 inches per second for a .01 grain change in charge weight. The 178 AMax will be about the same.

How much does that cause test groups to change?

 

[HomeSlice]

Sierra's load data for 180's in 308 Win cases shows velocity with IMR4064 changes about 7.2 inches per second for a .01 grain change in charge weight. The 178 AMax will be about the same.

How much does that cause test groups to change?

Are you sure you’ve got your units correct, Bart? Inches per second and 1/100th grain increments? You must have a different edition of the Sierra manual than I... ;-)

 

[Bart B.]

Are you sure you’ve got your units correct, Bart?

Yes. The data directly calculated to about 6 fps per 1/10th grain. That's 72 inches per second. One tenth of .1 is .01; of 72 is 7.2.

What does yours calculate to?

 

[HomeSlice]

I must admit that I've not gone to the trouble to do the math.

 

[dmoran]

Yes. The data directly calculated to about 6 fps per 1/10th grain. That's 72 inches per second. One tenth of .1 is .01; of 72 is 7.2.

Sierra's load data for 180's in 308 Win cases shows velocity with IMR4064 changes about 7.2 inches per second for a .01 grain change in charge weight. The 178 AMax will be about the same.

Having seen 308 Win ammo with 1/10ths grain spread of IMR4064 shoot 168 to 180 grain bullets into about half MOA accuracy at 600 yards, I think its a waste of time to have charge weight spreads less than 1/10th grain for that range. 1/10th grain change of IMR4064 causes about 10 fps velocity change for 180 grain bullets. I'd bet 43 grain charges with a 178 grain bullet will be most accurate testing with at least 10 shots per group.

A 3/10ths spread will shoot 1/4th MOA at 200, 2/10ths spread does 1/3 MOA at 300.

None of which is a given, since neither dispersion or velocity are linear to charge increments.
As can be seen in most any incremental load development, from on to off accuracy nodes, the dispersion and velocity of each tenth in charge can increase and decrease in intensity, and are not linear in pattern incrementally.
Where 3-tenths in charge may disperse less then .3-moa when on a node, could easily disperse .6-moa when off the node, that's averages will likely have intensity variation on and off the next nodes.

 

[akajiggs]

None of which is a given, since neither dispersion or velocity are linear to charge increments.
As can be seen in most any incremental load development, from on to off accuracy nodes, the dispersion and velocity of each tenth in charge can increase and decrease in intensity, and are not linear in pattern incrementally.
Where 3-tenths in charge may disperse less then .3-moa when on a node, could easily disperse .6-moa when off the node, that's averages will likely have intensity variation on and off the next nodes.

Ouch,that hurts my head.

 

[Bart B.]

Ouch,that hurts my head.

I'll try to simplify the "fps per tenth" stuff for you in 3 steps.

1. Using any load data, subtract the starting charge weight's velocity from the maximum charge weight's velocity. Example, subtract 50 grains's 2400 fps from 52 grain's 2500 fps. A 100 fps spread.

2. Calculate the number of 1/10th grain increments from starting to maximum charge weight. 50 to 52 grains of powder has a 2 grain spread, 2 grains times 10 tenths each equals 20 tenth grain increments.

3. Divide the fps spread by the number of 1/10th grain imcrements. 100 fps divided by 20 tenths equals a 5 fps change for each 1/10th grain change in powder charge.

There is a 5 fps average velocity change per 1/10th grain charge across that 100 fps velocity spread.

If there's a 6 grain charge weight spread across a 300 fps velocity spread, each 100 fps velocity band will have a different fps change for each tenth grain increment.

It's not linear across a few to several hundred fps velocity bands. Fairly linear across a 50 fps band. Not 100% exact, but reasonable for most applications. It has nothing to do with accuracy. Only approximates small powder charge increments to a bullet's velocity change.

Use it to compare different powder's fps per tenth grain numbers.

 

[dmoran]

I'll try to simplify ....

Doesn't explain how you come up with: "inches per second" like you wrote of in both posts #9, 11, that @HomeSlice questioned you about.

Or how you can state: "3/10ths spread will shoot 1/4th MOA at 200" (post #7).

 

[Bart B.]

Doesn't explain how you come up with: "inches per second" like you wrote of in both posts #9, 11, that @HomeSlice questioned you about.

Read post 11. It's simple grade school math. Or find on line then use a speed unit conversion calculator.

Or how you can state: "3/10ths spread will shoot 1/4th MOA at 200" (post #7).

Recalling Sierra Bullets' accuracy testing results and reloading practises shared with me over the years. At worst, they all gotta shoot inside 1/2 MOA at 200 yards.

 

[dmoran]

Read post 11. It's simple grade school math. Or find on line then use a speed unit conversion calculator.

Recalling Sierra Bullets' accuracy testing results and reloading practises shared with me over the years. At worst, they gotta shoot 1/2 MOA at 200 yards maximum.

Well Bart, your the first guy I've ever read or heard of to talk in "inches per second" for velocity.
And the first guy to claim any random 3-tenths in charge will shoot 1/4-MOA at 200yds.
It's no wonder you and fguffey spend so much time replying to each other.
You to are the only one.... carry on

 

[Bart B.]

Well Bart, your the first guy I've ever read or heard of to talk in "inches per second" for velocity.
And the first guy to claim any random 3-tenths in charge will shoot 1/4-MOA at 200yds.
It's no wonder you and fguffey spend so much time replying to each other.
You to are the only one.... carry on

I cannot fix your ignorance in this accuracy matter. I'm the information messenger, not its originator.

You might want to get mean on Handloader magazine editors for their late 1991 article on Sierra's 155 grain Palma bullet tests. The ammo had a 3/10ths grain spread of IMR4895 that produced the 20-shot about 2.7" group at 600 yards pictured therein. .45 MOA. New cases with up to .003" bullet runout. Impossible for most to believe.

 

[rockwind1]

guys, i've been posting a lot cause this is my first time reloading and I have probably been posting some very newbie questions. there are some very smart and experienced people on here and i would feel pretty bad if one of my stupid questions caused a very unneeded arguement. i'm positive you are both very smart and know the same thing, it's just typing instead of talking,,,i think, can make it seem like each person is looking at something from a slightly different angle even though they both are really on the same page. i'm just saying i think both you guys are right about this and that our typing words is where the breakdown is.

anyway, i am in a hurry to post my ridiculous question thread for the day