308 Load Variance Advice

E

ESBVader

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Mar 12, 2018
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#1
I am in the process of trying to identify a node for a LRI trued Remington action with 26" Criterion 1/10 twist barrel. I am shooting suppressed as well. I have also been gathering velocity data with a Magnetospeed V3.

The components I am using are, Lapua Brass (once fired), Federal GMM 210 primers, Sierra 175 TMKs, and IMR 4064 powder.

I started out with 15 rounds in .2 grain increments to try and identify a node and thought I found a few, the faster being 43.9 grains of powder at about 2790 FPS and producing a SD of 4.9 on one 5 round string and 6.2 on another.

I load the exact same load to test another 15 rounds to verify and I get a flyer or two at about 2765 fps then they all drop to 2735 fps. My SD wasn't as good, but not terrible at around 10-11. Without the flyers though they were well within single digits. I thought it might be an issue with the chronograph but the Magnetospeed was securely fastened to the suppressor.

I just do no understand the significant drop in velocity. 60 fps average for the same load under almost identical environmental conditions and while being super cautious to make sure I was loading accurately is nerve wracking.

Anyone have any ideas on what issues I may be experiencing?
 
#2
If you were shooting your 15 round string fairly quickly, it is not unusual for barrels to drop velocity as the barrel heats up and expands. I have two barrels that consistently and predictably fall off on velocity for the last three rounds if I am shooting a rapid fire 10 round string. This may not be your problem, but is a possibility.
 
#3
Without knowing your reloading methods this is a hard question to answer. I’ve reloaded for 20 years and I swear I did not really learn the finer points till about 3 years ago. So I would start by evaluating your powder measure accuracy. This is where I picked up the most improvement. Went from beam scales to a charge master then to an auto Trickler. Auto trickler cut my SD and ED with the same load way down in a 25 round test. So best advise give the information is check accuracy of charge weight. Good luck, happy shooting.
 
#4
If you are not at the optimum oal for the powder charge/velocity you’ll see this. Some of the shots will fly faster some slower. The overall ES will be 30 FPS or so but the spread will not be evenly distributed. Btw, your 43.9 gr load is too hot. That might also have something to do with it.
 
#5
Great advice. Thanks!

I am pretty particular about not rushing the powder dispensing to final measurement stage. I am using a Chargemaster thought I know they can be off by as much as. 1 from charge to charge. I'll keep an eye on that too.

I think there is a node around 43.5 or so as well. I think the logic of optimal OAL and potentially having too hot of a load is another place I can start. I was not seeing a lot of consistent pressure signs in the brass, though occasionally there was some. (Ejector marks)
I'll try to work up some with the next node down, assuming I have identified that correctly.
 
#6
918v said:
If you are not at the optimum oal for the powder charge/velocity you’ll see this. Some of the shots will fly faster some slower. The overall ES will be 30 FPS or so but the spread will not be evenly distributed. Btw, your 43.9 gr load is too hot. That might also have something to do with it.
Click to expand...
What source says this is a hot load?
 
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#7
ESBVader said:
Great advice. Thanks!

I am pretty particular about not rushing the powder dispensing to final measurement stage. I am using a Chargemaster thought I know they can be off by as much as. 1 from charge to charge. I'll keep an eye on that too.

I think there is a node around 43.5 or so as well. I think the logic of optimal OAL and potentially having too hot of a load is another place I can start. I was not seeing a lot of consistent pressure signs in the brass, though occasionally there was some. (Ejector marks)
I'll try to work up some with the next node down, assuming I have identified that correctly.
Click to expand...
i wouldnt expect two nodes at 43.9 and 43.5, that's awfully close. you may be looking at 1 node at 43.7

don't worry about the dude who said it's a hot load. unless he's used that load in your gun he doesn't have a clue and just likes to spout info from manufacturer books or his uncles third cousin
 
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#8
ESBVader said:
Great advice. Thanks!

I am pretty particular about not rushing the powder dispensing to final measurement stage. I am using a Chargemaster thought I know they can be off by as much as. 1 from charge to charge. I'll keep an eye on that too.

I think there is a node around 43.5 or so as well. I think the logic of optimal OAL and potentially having too hot of a load is another place I can start. I was not seeing a lot of consistent pressure signs in the brass, though occasionally there was some. (Ejector marks)
I'll try to work up some with the next node down, assuming I have identified that correctly.
Click to expand...
None of us of course, can tell you where the node is for your combo, but past experience tells me that you are in the right area. Varget, IMR 4064 & IMR 4320 are all so close in burn rate, that nodes often show up within 0.2 grains of each other. With a 308, 175 bullet, and Lapua brass, 43.5 - 43.7 grains is a recurring theme.
 
#9
Chargemasters swing way more than.1
You can’t go off that junk scale they use.
With that said, I shoot for years with one and my scores never suffered because of it. When chasing absolute perfection, it just won’t do. Is my preformance improved greatly since switching? No. But my ammo loading is faster and better quality.
As stated above hot loads differ from rifle to rifle. All my 308s love lower velocity. Fastest I have is just under 2700 in a 24” barrel with 175 SMK. All the others are 2620 or less.
Wise man once told me that is it impossible for a person and their rifle at distance to shoot better than 10 SD and 20 ED. He was a bench rest shooter i shot with back in my Quantico days. Just food for though. Good luck
 
#14
In lapua brass that is hot load. In lighter brass maybe not. What was trued on your action by LRI, it sounds like you may have used a Remage barrel on an action with the threads opened up. Node info for the .308 and 6.5 creedmoor especially H4350 and 4064 and Varget are widely known and shared.
 
#15
Correct. I had the Tier 2 service for a Remage barrel performed as well as the barrel install while they had it. Lugs and action face were trued as part of the service.
 
#19
918v said:
No lol?
Click to expand...
There is no need to start a pissing contest over this. Normally, heavy cases such as Lapua, Lake City and Federal require a 0.4g - 0.5g reduction, that is common practice. To say it requires a 2 grain reduction is definitely outside of what is commonly observed.

But so what? You are giving the benefit of your individual experience, and it isn't like you are telling him to go 2 grains heavy (like posts in other threads I've seen), so no harm right?
 
#23
Skookum said:
Nope, you said 43.9 grains was too hot. That is already 1.7 grains under book maximum.
Click to expand...

Do you understand the relationship between bullet length, seating depth, and case volume as they relate to pressure? A max load developed in the most voluminous case on the market with a short bullet is excessive in a heavy case with a long bullet.

A 1.7 grain reduction is reasonable, but the load is still hot. No it won’t explode the gun or blow primers but it’s still hot, max, whatever you wanna call it.
 
#24
What I understand is that this discussion threatens to go sideways, and I have no desire to contribute to that, so I'll just concede the point.

You win.
 
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