Increased powder and decreased velocity working up a new load...

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AH64ID

AH64ID

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This is a new one for me.

I am working on a new hunting load for my R700 300H&H with a 26" Lilja bbl.

180gr Barnes TTSX, H4831SC, and Federal 215M primers

I was doing 1 shot tests the other day and got the following (42°). I cleaned the rifle and shot it 5 times before starting this.

71gr: 3044fps
72gr: 3063fps
73gr: 3069fps
75gr: 3155fps
75gr: 3162fps

So I loaded up 3ea at 74.7, 75, and 75.3. All loaded the same day, individually weighed, same scale calibration, same once fired brass from the same rifle, and seated to the same depth.

I went out shooting today and got the following (63°)

74.7gr: 3139,3149, 3136 (3141 avg, 13 fps spread, 5.5 std dev)
75.0gr: 3186, 3074, 3153 (3137 avg, 112 fps spread, 48 std dev)
If I throw out the 3074 as probable chrony error and add the 2 from last weekend
75.0gr: 3155, 3162, 3186, 3153 (3164 avg, 33 fps spread, 13 std dev)
75.3gr: 3136, 3130, 3130 (3132 avg, 6 fps spread, 2.8 std dev)

So as you can see the 75.3 gr has the best consistency, other than it's slower than 74.7 and 75... why?

Also, while I wasn't shooting for extreme accuracy and had a nasty sidewind at 60ish yard all 3 of the 75.3's were touching, none of the other test rounds were even remotely close....not putting a lot of stock in this thou as I was more concerned with velocity.

No pressure signs on the bolt opening or the brass, in fact the "plinker" Hornady 180gr BTSP's with 215Ms and 68gr of H4831SC show flatter primers but they also have more resistance in the bore than the TTSX's do, so they should run more pressure. They are all around 2850fps.
 
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Curious AH64ID, where did you get the load data for H4831SC powder? A couple of my manuals list data for regular ol' H4831 (in fact I burn a lot of it in my 308 Norma Mag), but neither list H4831SC.
At any rate, there are quite a few sources that you can find with a Google search that claim when you get close to a maximum charge of powder for a particular cartridge, you might actually see a decrease in velocity as you increase your powder charge even more. I'm not saying for sure that's what's happening, but it looks like it could be according to what I read.:)
 
You may have found a node to work in. I always look for zones where the velocity flattens. Then load on each side to see how large it is It can also be that the brass has a different case volume or you missed you charge weight. Need to retest and confirm. Also expand it to see how large it is.
 
Your speed is not way out of standard deviations. You may have a small flat in velosity which if in your goal range would be worth investigating... overall I dont believe your test size is large enough to draw conclusions, but does perk up some interest.
 
.308 Norma said:
Curious AH64ID, where did you get the load data for H4831SC powder? A couple of my manuals list data for regular ol' H4831 (in fact I burn a lot of it in my 308 Norma Mag), but neither list H4831SC.
At any rate, there are quite a few sources that you can find with a Google search that claim when you get close to a maximum charge of powder for a particular cartridge, you might actually see a decrease in velocity as you increase your powder charge even more. I'm not saying for sure that's what's happening, but it looks like it could be according to what I read.:)
Click to expand...

According to most sources, to include Hodgon, H4831 and H4831SC are interchangeable for load data. H4831SC is just supposed to meter better and have a better load density at higher amounts. Variations in performance between the two is supposed to be similar to differences between Lots.

I've never tried H4831.

It's very possible I am close to max. This is my first time working up a load with a 180gr bullet in this caliber. Everything else has been 200gr bullets, most of them moly coated, and all with H4831SC. It's a pretty good combo, but I am wanting to change things up on this particular rifle. Most of the rifles shoot a 200gr bullet with 75gr of H4831SC very consistent and just under 3000fps. This particular rifle used to shoot a Swift A-Frame 200gr moly coated bullet at 3010fps with 75.5gr of H4831SC, but that wasn't even 90 rounds and now I'm done with moly, thou dad still uses it.

Blue68f100 said:
You may have found a node to work in. I always look for zones where the velocity flattens. Then load on each side to see how large it is It can also be that the brass has a different case volume or you missed you charge weight. Need to retest and confirm. Also expand it to see how large it is.
Click to expand...

That kinda what I am thinking, but will have to play with it some more and see.

I am also wondering if I can play with 74.4-75.7 grains and get a tighter velocity spread at the same velocity.

AJC1 said:
Your speed is not way out of standard deviations. You may have a small flat in velosity which if in your goal range would be worth investigating... overall I dont believe your test size is large enough to draw conclusions, but does perk up some interest.
Click to expand...

I am defiantly floating all around my fps goals. At this velocity the 180gr TTSX has more energy than the previous load starting at about 100 yards.

I do need to load up some more, oh darn, and see what it does. It did raise my eyebrows a little thou.
 
AH64ID said:
This is a new one for me.

I am working on a new hunting load for my R700 300H&H with a 26" Lilja bbl.

180gr Barnes TTSX, H4831SC, and Federal 215M primers

I was doing 1 shot tests the other day and got the following (42°). I cleaned the rifle and shot it 5 times before starting this.

71gr: 3044fps
72gr: 3063fps
73gr: 3069fps
75gr: 3155fps
75gr: 3162fps

So I loaded up 3ea at 74.7, 75, and 75.3. All loaded the same day, individually weighed, same scale calibration, same once fired brass from the same rifle, and seated to the same depth.

I went out shooting today and got the following (63°)

74.7gr: 3139,3149, 3136 (3141 avg, 13 fps spread, 5.5 std dev)
75.0gr: 3186, 3074, 3153 (3137 avg, 112 fps spread, 48 std dev)
If I throw out the 3074 as probable chrony error and add the 2 from last weekend
75.0gr: 3155, 3162, 3186, 3153 (3164 avg, 33 fps spread, 13 std dev)
75.3gr: 3136, 3130, 3130 (3132 avg, 6 fps spread, 2.8 std dev)

So as you can see the 75.3 gr has the best consistency, other than it's slower than 74.7 and 75... why?

Also, while I wasn't shooting for extreme accuracy and had a nasty sidewind at 60ish yard all 3 of the 75.3's were touching, none of the other test rounds were even remotely close....not putting a lot of stock in this thou as I was more concerned with velocity.

No pressure signs on the bolt opening or the brass, in fact the "plinker" Hornady 180gr BTSP's with 215Ms and 68gr of H4831SC show flatter primers but they also have more resistance in the bore than the TTSX's do, so they should run more pressure. They are all around 2850fps.
Click to expand...

I would get more data points before making any meaningful conclusions, especially since you're throwing out numbers you don't like, and adding others from the day before.
 
small statistical group size (number of shots) leads to inaccurate conclusions.

To really know what's going on, your group (number of shots) needs to increase if you get inconsistent data from 5 shot groups, increase to 10 (or better 20) shot groups.
 
drband said:
small statistical group size (number of shots) leads to inaccurate conclusions.

To really know what's going on, your group (number of shots) needs to increase if you get inconsistent data from 5 shot groups, increase to 10 (or better 20) shot groups.
Click to expand...
So he did combine groups over two days which in seeking day to day and different conditions consistancy is a desired path. For getting bulk 20 shot data I'm torn between 5 shot groups on 4 days and 2 10 shot groups. These bullets are sold an expensive. I may try and see if he has found a node first before settling into large group refignment. The process doesn't change but my desire to minimize testing goes up with the cost of shots.
 
Thought I would bring this back up.

I was able to replicate the velocities, so I backed the powder down a little to 74.5gr and am holding a steady 3130 fps. Why run more powder for nearly the same speed.

I have been playing with bullet seat depth now and have found a nice load that is giving me consistent sub 1/2 MOA groups at 100 yards.

Now that I have a good 100 yard load time to start shooting long range and see how it holds up.
 
If you’re compressed you might have an OAL that’s stretching. I would check it with a comparator.
 
At this power charge and seat depth I am not compressed. I do use a comparator on each round, as well as after loading to verify there isn't any OAL stretching.
 
The H4831 and H4831SC load data is interchangeable. I cannot comment on how each does with a compressed load as I have not compressed loads.
I think the 75.3 grain load has the best internal ballistics since the deviation is so low. Your barrel likes it the best so don’t worry about 20-25 ft/sec. Your consistency is the best thing you can have and that helps accuracy.
 
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