buckbrush
Well-Known Member
- Joined
- Nov 26, 2008
- Messages
- 711
- Reaction score
- 926
- City & State/Province
- Eastern Montana - Almost North Dakota
What do you think the cause of the velocity loss is?
muzzle velocity - brass brand
- Thread starter JMack
- Start date
lancetkenyon
Well-Known Member
Neck tension (interference) caused by lack of annealing (brass hardness and springback) can cause some of this. But unless the brass is so hard/tight and causing bullet deformation during seating, I highly doubt this would cause 100fps difference. But not LESS velocity unless you are going the opposite way and not getting the necks sized down enough, so neck tension has lessened by a large amount.
How many rounds down the barrel? Carbon ring could cause velocity issues, but again, they increase. Unless you had one before, and you cleaned it out.
Hornady brass. If this is the exact same 10 pieces, then nevermind. But if they are from a different lot of factory ammo, weigh them. You might not see a big difference of POI @ 100 yds when you shot before, but it would show up at 500.
Have you been chronographing every round prior? Of just a couple?
How many rounds down the barrel? Carbon ring could cause velocity issues, but again, they increase. Unless you had one before, and you cleaned it out.
Hornady brass. If this is the exact same 10 pieces, then nevermind. But if they are from a different lot of factory ammo, weigh them. You might not see a big difference of POI @ 100 yds when you shot before, but it would show up at 500.
Have you been chronographing every round prior? Of just a couple?
stinkyduck13
Well-Known Member
Soo what were the actual velocity's that you were seeing? And what powder charge of H4831? And bullet weight.
It's a new rifle less than 50 down the pipe.
Hornady brass. I shot the factory 180 eldms and am using the brass to reload from that box.
Ya basically my buddy set up his Garmin and just left it on as we shot.
stinkyduck13
Well-Known Member
I sometimes get 75 fps variations with a new gun not broken in
Mikecr
Well-Known Member
MV will change as the brass changes, and brand won't mean much to that.
The worse your brass-chamber fit, the worse this will be.
That's why it's important to get your brass to a stable condition, whatever that amounts to, directly.
The worse your brass-chamber fit, the worse this will be.
That's why it's important to get your brass to a stable condition, whatever that amounts to, directly.
Have to get some rounds down the pipe to get it settled out
Hogdon 4831sc? Is rifle new?
Yes. Yes.
HSmithTX
Well-Known Member
Super weird, the powder you are using is one of the best for stability. It's maybe a touch fast for PRC but should work fine. With carbon rings I have seen pressure go up but I don't recall a marked velocity loss. Bullets are good. Seating depth variation to make 100 FPS change I don't think is possible, not even from hard jammed into the rifling to .100" off the lands. Just noodling on this, I have seen velocity drop and excess pressure start showing in 80 rounds before from fouling. Sewer pipe savage factory barrel, it coppers so badly it's crazy but it is a fairly linear change for 60-70 rounds and then gets much worse quickly. It won't do it overnight unless you shot a LOT yesterday and don't see the pressure signs starting and go out again and shoot a lot today. How many rounds since cleaning? Did you do a barrel break in at all and if so how many rounds did it take before you started not seeing copper in the bore? Are the two boxes of factory ammo the same lot number? If not see Lance's advice to weigh the brass, I've seen some pretty sizeable changes in brass weight with Hornady brass in 6.5 manbun but I simply sorted and used the middle of the range so what will happen from lightest to heaviest I can't say.
lancetkenyon
Well-Known Member
What is your barrel length? 18-20"?
Per Hodgdon data, you are WAY over max charge weight (55.0-60.6 for similar bullets since the 180 Hyb is not in their list).
However, the 180 ELD-M is showing 2881 for 60.6gr, and 195 is showing 2774 for 60.3gr from a 24" barrel.
H4831SC might work, but I would not use it for the heavier bullets. Pretty fast burning. I would try H1000, N565, Retumbo, or N568.
