MV Decrease and Variation Questions

I am really struggling with my long range hunting/target gun and I would love some help. I am shooting a Rem 700 (Long Range Model) chambered in 7mm rem mag. My hand loads are 77.2 g of RL33, once fired and not resized Nosler brass, Winchester Large Rifle magnum primers, pushing a 180 grain Berger Hunting VLD. I have weighed and measured size and volume of every piece of brass. H20 weight 88.1g with a .5g ES, LTS of 2.141" with a .005" ES, OAL if 2.515" with .001" ES, and almost no differences in diameter at neck, shoulder and just above the belt. During load development I landed on 77.2 g with an average MV of 2975 at 75 degree air temp with groups about .5 to .75 MOA. All the brass, primers, powder and bullets are from the same lot. I use a RCBS digital scale, that I warm up for about a half hour before use, and Redding Competition Neck and Seating Dies. I have uniformed all the primer pockets with a K&M Pocket Correction Tool and seat the primers with the RCBS Universal Hand Priming Tool. My length to ogive is 2.804" which is .003" off the lands. I use a Magneto Sporter to measure MV. The stock barrel has 803 rounds through it, and 607 rounds since I last removed any copper.

With all the care and detail I have put into these hand loads, I am still getting a pretty high extreme spread in MV of 46 FPS. I have also started to get lover and lower average MV. Last time out the average MV was 2937 at 91 degree air temperature, 14 degrees hotter than my testing at 75 degrees.

So I have two questions: 1. what could be causing the lower MV and 2. What can I do to reduce my ES?

Cheers!

RL33 is more for things like 338 Lapua and 300 RUM etc. Sometimes a faster powder will give better ES. I would try something like H1000.

Also, have you been annealing your brass? Changing neck tension may be affecting the speed. Usually with a belted mag it can take about 3 firings before the case reaches it max capacity, lot of that increase is from the shoulder getting longer. I have seen speeds decrease when using the same amount of powder when the case volume is increasing.

I agree with checking your neck tension , also have you tried different primers? I've seen big changes in changing primers. I would try changes in stages though, that way you can see a direct effect of each component.

I developed the load with new brass so I did not do anything with the neck tension originally. Since then I have annealed the once fired brass and have been using the same neck bushing but slightly changing how deep I resize the necks. Do you you think that could cause this much of a fall off in MV?

On new brass besides full normal prep I always run a NT mandrel through all the necks that is .002 smaller than bullet OD. This does two things. It works out any dings, but more importantly sets a consistent neck tension. Also are u running bushing die with expander button installed? If so try running it with expander out of the die. I tried RL33 in a 7mm and could never get what I was looking for and switched to H1000. Also you said 600 something rounds since you have removed any copper? Is that you have cleaned your gun but not got any copper fouling or it has been 600 rounds since you have cleaned the copper?

Also if neck tenion is super tight which sometime it is with new brass depending on company I have seen higher muzzle velocity as compared to when I resize and set my neck tension at a consistent .002, however I don't know it I have ever seen that much. But also now that u have fired that brass assuming u are neck sizing only the shoulder will move forward slightly changing volume of case. There is no way around this if u properly size your brass whether FL or neck size as new brass is usually a good ways out from actual chamber actual head space dimension.

If your brass is actually fire formed now I wouldn't worry about what your MV was on new brass and just press on tweaking your load. Loosing that much velocity could have knocked u out of the node. Sometimes it takes time to get a good load, meaning good accuracy and low ES. U can have accuracy at them short ranges with horrible ES, have seen it a lot. I will take a 1/2 moa group with single digit ES over a 1/4 moa group with high ES any day of the week as that low ES load will hold that 1/2 moa out to distance. Just my two cents brother I am still a rookie myself in the reloading game. Good luck man and keep posting your results and findings.

Remmy700 said:

On new brass besides full normal prep I always run a NT mandrel through all the necks that is .002 smaller than bullet OD. This does two things. It works out any dings, but more importantly sets a consistent neck tension. Also are u running bushing die with expander button installed? If so try running it with expander out of the die. I tried RL33 in a 7mm and could never get what I was looking for and switched to H1000. Also you said 600 something rounds since you have removed any copper? Is that you have cleaned your gun but not got any copper fouling or it has been 600 rounds since you have cleaned the copper?

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Remmy700,

Thank you for your help! Here are the answers to your questions.

When I developed the load with new brass I did no case prep, except unfirming the primer pockets. With this one fired brass, I have annealed, cleaned and only neck sized with out the expander installed.

I have cleaned the barrel, but only with Hopes #9. The last time I used a Copper removing solvent was 600 rounds ago.

I would prolly start with a good full barrel cleaning brother.

Remmy700 said:

If your brass is actually fire formed now I wouldn't worry about what your MV was on new brass and just press on tweaking your load. Loosing that much velocity could have knocked u out of the node. Sometimes it takes time to get a good load, meaning good accuracy and low ES. U can have accuracy at them short ranges with horrible ES, have seen it a lot. I will take a 1/2 moa group with single digit ES over a 1/4 moa group with high ES any day of the week as that low ES load will hold that 1/2 moa out to distance. Just my two cents brother I am still a rookie myself in the reloading game. Good luck man and keep posting your results and findings.

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Remmy700,

Thank you for the information...very helpful. I agree that the larger case size and the lower neck tension are contributing to the lower MVs, but I was just surprised to see that much of a decrease and was wondering if cleaning or something else might be adding to the decrease.

As far as the MV ES, it sound like you are suggesting a change in powder to achieve the same precision and lower ES in MV. So a faster powder like H1000 might give me better MV ES. Is that correct?

Yes sir I got a 7mm and use h1000 and have loads for 180s. I can get u pointed in the right direction man.

Remmy700 said:

Yes sir I got a 7mm and use h1000 and have loads for 180s. I can get u pointed in the right direction man.

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Remmy700,

Thank you so much for the help. Here is my plan. Any other suggestions or changes?
1. Completely clean gun and remove all fouling and Copper
2. Purchase some H1000 and develop a load with that.
3. According to QuickLoad an Hodgson's Website I will start about 65g and work up from there.

That is what I would do brother. Someone else might chime in on RL33 but I had zero luck with it. And your load data is correct, start around 65. I am currently at 69.4 with 180 bergers and at around 70.2 with 180 eldm

Remmy700 said:

That is what I would do brother. Someone else might chime in on RL33 but I had zero luck with it. And your load data is correct, start around 65. I am currently at 69.4 with 180 bergers and at around 70.2 with 180 eldm

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Sounds good, I will get working on it an let you know how it goes.

Just a quick question, why will a faster powder result in a lower MV ES? Is it because the smaller grains of powder will sit more uniformly in the case?