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Loss in velocity
#6439738
09/06/16 02:29 AM
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Joined: Nov 2010
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P & Y
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What can cause loss in velocity? Same loads and same power lot. Round count on the barrel is only 300 or so. Somehow I lost about 70-80 fps. I have never cleaned the rifle but it's still shooting amazing groups, just slowed down on me. Confused to say the least
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Re: Loss in velocity
[Re: P & Y]
#6439751
09/06/16 02:36 AM
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Joined: Nov 2007
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RiverRider
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Could be temperature related. Also, you don't mention the cartridge...but its possible you have just a bit of throat erosion causing a drop in starting pressure, and that will cause lower velocity. Another possibility is chronograph error. There could be more possibilities too.
"Arguing with you always makes me thirsty." -Augustus McRae
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Re: Loss in velocity
[Re: P & Y]
#6439768
09/06/16 02:43 AM
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P & Y
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7x300 win mag H1000 powder
I really don't think it's a chronograph error. I have a 4" steel target at 430 and couldn't get on target. Checked my 100yd zero and it was 3/4" low. Set up a larger target down range and was shooting 4" low at 430. Plugged that info into the GSeven calculator and it showed my velocity had dropped like 85fps. Then I shot it over a chrono and it was reading about 75fps slower that what these loads have been running.
Last edited by P & Y; 09/06/16 02:44 AM.
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Re: Loss in velocity
[Re: P & Y]
#6439776
09/06/16 02:45 AM
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Joined: Feb 2010
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watchale
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I was reading about one of the top PRS shooters and they were saying velocity loss is just gonna happen. So I guess it's pretty common.
Last edited by watchale; 09/06/16 02:46 AM.
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Re: Loss in velocity
[Re: P & Y]
#6439790
09/06/16 02:48 AM
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ChadTRG42
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What did you change in the ammo from the first batch to the second batch? Sometimes, when you size differently or have different neck smoothness on once fired brass vs virgin brass, it can change up the fps some.
Also, what bullet are you running? I am building a 7/300 Win Mag right now, and plan to shoot the 195 Berger's with either Retumbo or H1000.
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Re: Loss in velocity
[Re: P & Y]
#6439840
09/06/16 03:11 AM
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P & Y
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I didn't change anything as far as the brass. I loaded up 200pcs with Virgin Norma 300wm brass and necked it down. I was seeing consistent velocities through the first 125-150 and now this. I am running the 180gr hunting VLD
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Re: Loss in velocity
[Re: P & Y]
#6439846
09/06/16 03:14 AM
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J.G.
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Re: Loss in velocity
[Re: P & Y]
#6439849
09/06/16 03:17 AM
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P & Y
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What's odd is, my friend has the exact same rifle. Built by the same builder using all of the exact same components. They have always shot extremely similar. The load I have, shot great in both rifles and we have shot the drop data to verify velocity. He was shooting beside me with the same Ammo a week ago and had no issues. It's like it lost the speed out of nowhere. Round count on both rifles is probably within 75 rounds of each other
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Re: Loss in velocity
[Re: P & Y]
#6439851
09/06/16 03:18 AM
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J.G.
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You didn't push the shoulders back farther than you did for the faster ammo, did you?
I wonder if fouling can slow it down? Though I've never seen that happen.
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Re: Loss in velocity
[Re: J.G.]
#6439854
09/06/16 03:18 AM
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P & Y
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That's what I'm thinking
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Re: Loss in velocity
[Re: J.G.]
#6439860
09/06/16 03:20 AM
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P & Y
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You didn't push the shoulders back farther than you did for the faster ammo, did you?
I wonder if fouling can slow it down? Though I've never seen that happen. I typically take a base to datum every 15 rounds or so when sizing. I'll go back and double check but the brass was all prepped in the same batch
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Re: Loss in velocity
[Re: P & Y]
#6440003
09/06/16 10:50 AM
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Joined: Nov 2007
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RiverRider
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"Arguing with you always makes me thirsty." -Augustus McRae
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Re: Loss in velocity
[Re: P & Y]
#6440405
09/06/16 04:11 PM
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dee
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Could simply be difference in barrels. Measure your throat and see. Also run a patch or two down it and find out. Double check scope and chrono too. This is all if absolutely nothing in the load changed.
"A vote is like a rifle; it's usefulness depends on the character of the user" Theodore Roosevelt
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Re: Loss in velocity
[Re: dee]
#6440559
09/06/16 06:19 PM
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P & Y
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Yes sir, same powder Could simply be difference in barrels. Measure your throat and see. Also run a patch or two down it and find out. Double check scope and chrono too. This is all if absolutely nothing in the load changed I went ahead and did this last night. I really don't make a habit of cleaning my precision rifles but I broke down and cleaned it. I cleaned out all the copper and all. I'm taking it out today to see if cleaning it changed anything.
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Re: Loss in velocity
[Re: P & Y]
#6440582
09/06/16 06:38 PM
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Joined: May 2014
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TackDriver
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Was the outside ambient temperature the same as last time you shot it?
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Re: Loss in velocity
[Re: P & Y]
#6440797
09/06/16 09:15 PM
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Slow Drifter
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For how many rounds was velocity down? Did it stay down for the remainder of the rounds? Wonder if the bass changed lots right there at 150 and maybe case capacity changed, affecting pressures? Just spit-balling here.
"I have no idea what WW-III will be fought with, but WW-IV will be fought with sticks and stones." A. Einstein
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Re: Loss in velocity
[Re: P & Y]
#6440805
09/06/16 09:21 PM
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P & Y
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I have shot it in summer and winter without significant velocity swings
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Re: Loss in velocity
[Re: Slow Drifter]
#6440815
09/06/16 09:26 PM
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P & Y
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For how many rounds was velocity down? Did it stay down for the remainder of the rounds? Wonder if the bass changed lots right there at 150 and maybe case capacity changed, affecting pressures? Just spit-balling here. I probably ran 30 or 40 through it that Day. They all shot consistent and slow
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Re: Loss in velocity
[Re: P & Y]
#6446035
09/10/16 04:27 AM
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Joined: Jan 2016
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glocker17
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What chronograph are you using?
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Re: Loss in velocity
[Re: P & Y]
#6451943
09/14/16 06:26 PM
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Joined: Feb 2008
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cullbuck
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Did cleaning do anything to it?
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Re: Loss in velocity
[Re: cullbuck]
#6451962
09/14/16 06:37 PM
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P & Y
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Not a thing. I shot it the next day and after a couple foulers I took it to 450 and shot a 5shot 2" group. My buddy pulling Ammo from the same box shot equally well but still 80fps faster. My come up at 450 was 6min while his was 5.25. I quit trying to figure it out and just gonna roll with it. It does pizz me off I have a 7x300 running 7mag speeds
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Re: Loss in velocity
[Re: P & Y]
#6452043
09/14/16 07:22 PM
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Joined: Nov 2007
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RiverRider
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Do you know the round count on you friend's rifle?
"Arguing with you always makes me thirsty." -Augustus McRae
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Re: Loss in velocity
[Re: P & Y]
#6452804
09/15/16 03:23 AM
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Joined: Nov 2010
Posts: 971
P & Y
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Re: Loss in velocity
[Re: P & Y]
#6452920
09/15/16 10:43 AM
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Joined: Nov 2007
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RiverRider
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I think you're seeing the effects of a little throat wear, that's all. You might check your distance to the lands and see if it's changed just so you'll know, and if it has you could try seating a little further out to see what happens.
"Arguing with you always makes me thirsty." -Augustus McRae
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