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#6439738 - 09/05/16 09:29 PM Loss in velocity
P & Y Offline
Tracker

Registered: 11/28/10
Posts: 948
Loc: North East Texas
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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#6439751 - 09/05/16 09:36 PM Re: Loss in velocity [Re: P & Y]
RiverRider Offline
THF Trophy Hunter

Registered: 11/11/07
Posts: 6226
Loc: Wise Co.
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.
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Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6439768 - 09/05/16 09:43 PM Re: Loss in velocity [Re: P & Y]
P & Y Offline
Tracker

Registered: 11/28/10
Posts: 948
Loc: North East Texas
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.


Edited by P & Y (09/05/16 09:44 PM)
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#6439776 - 09/05/16 09:45 PM Re: Loss in velocity [Re: P & Y]
watchale Online   content
Pro Tracker

Registered: 02/18/10
Posts: 1804
Loc: Tx
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.


Edited by watchale (09/05/16 09:46 PM)
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#6439790 - 09/05/16 09:48 PM Re: Loss in velocity [Re: P & Y]
ChadTRG42 Offline
THF Trophy Hunter

Registered: 09/16/09
Posts: 9433
Loc: Lewisville, TX
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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#6439840 - 09/05/16 10:11 PM Re: Loss in velocity [Re: P & Y]
P & Y Offline
Tracker

Registered: 11/28/10
Posts: 948
Loc: North East Texas
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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#6439846 - 09/05/16 10:14 PM Re: Loss in velocity [Re: P & Y]
FiremanJG Offline
THF Celebrity

Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
Rifle gremlins.
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#6439849 - 09/05/16 10:17 PM Re: Loss in velocity [Re: P & Y]
P & Y Offline
Tracker

Registered: 11/28/10
Posts: 948
Loc: North East Texas
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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#6439851 - 09/05/16 10:18 PM Re: Loss in velocity [Re: P & Y]
FiremanJG Offline
THF Celebrity

Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
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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#6439854 - 09/05/16 10:18 PM Re: Loss in velocity [Re: FiremanJG]
P & Y Offline
Tracker

Registered: 11/28/10
Posts: 948
Loc: North East Texas
Originally Posted By: FiremanJG
Rifle gremlins.


That's what I'm thinking peep
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#6439860 - 09/05/16 10:20 PM Re: Loss in velocity [Re: FiremanJG]
P & Y Offline
Tracker

Registered: 11/28/10
Posts: 948
Loc: North East Texas
Originally Posted By: FiremanJG
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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#6440003 - 09/06/16 05:50 AM Re: Loss in velocity [Re: P & Y]
RiverRider Offline
THF Trophy Hunter

Registered: 11/11/07
Posts: 6226
Loc: Wise Co.
Same powder lot number?
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Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6440405 - 09/06/16 11:11 AM Re: Loss in velocity [Re: P & Y]
dee Offline
Extreme Tracker

Registered: 04/10/10
Posts: 4665
Loc: Red River way
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.
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#6440559 - 09/06/16 01:19 PM Re: Loss in velocity [Re: dee]
P & Y Offline
Tracker

Registered: 11/28/10
Posts: 948
Loc: North East Texas
Originally Posted By: RiverRider
Same powder lot number?

Yes sir, same powder

Originally Posted By: dee
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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#6440582 - 09/06/16 01:38 PM Re: Loss in velocity [Re: P & Y]
Big Stan Offline
Bird Dog

Registered: 05/02/14
Posts: 272
Was the outside ambient temperature the same as last time you shot it?

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