More powder = less velocity ( reloading is difficult).

bakerboy

bakerboy

New member
I've been working up (slightly increasing) two loads to achieve a certain velocity in order to match up the ballistics with my Burris ballistics plex scope reticles.
I'm pretty good mechanically, and have a lot of chemistry lab experience so I can measure small quantities or so I thought. Reloading is beginning to test my patience. I know about doing everything the same each time, but I'm getting some squirrely results. Case in point. 75g vmax with 62g H4831SC = 3554 FPS. 75g vmax with 62.3g H4831SC = 3480 FPS. 100g nosler bt with 54.3g = 3098 FPS. Same bullet with 54.5g = 3038. ( All are 6 shot averages). Same primers, same length, same everything. I zero the scale, RCBS 502,
and can tell the difference in 1 piece of powder. Somebody please give me an explanation that hopefully does not include buying another $ 200 item (digital scales).
 
what is the standard deviation? is this for a 25-06? do your headstamps match? cases from the same lot? a 6-shot sample is almost useless, unless your sd's are in the low-teens or better.

generally speaking, when you run into this, it is because the powder you are using is too slow for the cartridge. drop to a faster powder (rl-19, h-4350), or go to a heavier bullet.

the other thing... there is some debate about when to use a magnum primer. it is my personal opinion that magnum primers are called for once you get to around 55 grains of powder.

if your cases are matched lot and headstamp, and you are confident in your loading technique, then switching to a mag primer will likely cure your problem.

what is happening is that the extra powder you are putting in the case isn't burning as efficiently.

so... either go to a heavier bullet, faster powder, or hotter primer.
 
Burning rate relates to barrel length. My guess would be that all the powder isn't being burnt in the barrel. Go to a faster burning powder.
 
IN BALLISTICS THERE IS A TERM KNOWN AS "BREAK OVER POINT". THIS HAPPENS WHEN YOU REACH A TOP LOAD AND ADD MORE POWDER AND THE VELOCITY ACTUALLY DROPS.

GO BACK TO YOUR TOP LOAD AND STOP THERE. THAT IS ALL YOUR ARE GOING TO GET FROM THAT PARTICULAR POWDER.

NEXT OBVIOUS CHOICE, A FASTER POWDER AS ONE OF THE POSTERS RECOMMENDED.
 
Seems to be some pretty good advice here on your problem. I would say use the same type brass and work with another powder. I would think you have reached all this one will do as mentioned before.
 
Make SURE there is absolutely no wind/breeze at all in the room....It affects the beam scales a bit more than the digital ones...that may be just your problem. other than that switch to a mag primer and work back up
 
Just a thought. How far out do you have the bullets seated? If you can get them closer to the lands, back off on the powder, and work up again. This could give you some more velocity and consistency......But, work up the load! I have found this can make a difference. I also, seem to get the most speed out of the reloader powders and like them best. Although, IMR 4064 is great in my 220Swift.
 
You are talking about a difference in your loads of .481% and .367% respectively. I don't think you can expect much with such a little change in powder. There are so many other factors at work here that such a small increase in overall powder weight pales into insignificance compared to other things. There are so many variations from loaded round to loaded round that, in my opinion, they are more likely to be the explanation for the lower velocities you are seeing. I know you are keeping things the same, but variations in case weight, bullet weight (0.1-0.3 grains per bullet), etc.,etc. Just my $0.02
 
Carefully reloaded and shot both 75 and 100 gr bullets with the same results (i.e. less velocity). As was suggested, the powder is not being used, and I need to try some faster powders. Thanks for all the help.
 
Quote:
Carefully reloaded and shot both 75 and 100 gr bullets with the same results (i.e. less velocity). As was suggested, the powder is not being used, and I need to try some faster powders. Thanks for all the help.



thats why were here. were really not ballasticians but we do play like one when we reload. just some of the things you find out when you been playing the game 50+ years.

good luck in your quest.
 
These type of results are why I reload for accuracy and ignore velocity. Of course I have no use for trajectory scopes anyway!!LOL
the quest for speed is greatly overrated. if they group, shoot em.
Carl
 
Sometimes this can be caused by your chronograph being placed too close to the muzzle. Unburned powder granules blast across the sensors with the bullet and can trip up the chronograph.

Try moving the chronograph out to 15 feet from the muzzle and see how things look.

As has already been pointed out by another member above, it is certianly true that you'll reach a point with any load where the load density is such that the powder burn isn't as complete as it would be with a lighter charge. That could also cause what you're seeing.

One last thing. You'll probably like 4350 better with the 25-06 (presumably what you're shooting) than the 4831...

Best of luck.

Dan
 
With all of your help I have found the correct load to achieve the 3200 FPS objective. Picked a slightly faster powder IMR 4320 and after studying suggested loads I decided on 49g for my 75g vax in 25-06. Happily, I also found a very, very accurate load as well. Those two holes touching are 3 shots!

target2.jpg
 
Sorry about the confusion I created. The velocities were actually 3595, 3623 and 3612 which was what I was looking for. Those numbers shown on the target are from the 100g nosler bt which were (3200) also what I was looking for. However, the accuracy wasn't quite up to par on the 100g.
I may try Reloader 19 or live with 3100 with the H4831SC which shot very accurately.
 
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