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Old January 23, 2013, 05:48 PM   #1
FiveInADime
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Primer switch ruined my pet load!

I recently switched from Fed. match LR primers to CCI BR-2 and it looks as if i may need to do some retesting to find my 7MM-08 accuracy load again. The original load was 45.2gr of RL17, RP brass, 150GR. Sierra MKs. It was producing ~1/2-3/4" groups with the Feds. and through 20 rounds today the best I could get was 1.75"-2.5"! I knew there might be a difference, but I wasn't anticipating that big of a change. Anyone else experienced swings in accuracy like this when switching primers?
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Old January 23, 2013, 06:15 PM   #2
Jerry45
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I went from Hornady 65 gr. SPFB to a Hornady 65 gr. SPBT in my 3006. I ran out of the FB and had BT on the shelf. Everyone was/is out of FB. One (without reloading experience) would think... there both 65 gr. so the same power and charge would produce the same accuracy right? I cannot get the BT to shot as well as the FB using the same powder. Close but no cigar. Still working on a load for the BT though. Rifles are funny animals.
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Old January 23, 2013, 06:54 PM   #3
Ifishsum
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That seems to be a bigger difference than I've ever experienced, but I bet you can find it again within a grain or so up or down from your original load. CCI primers have been the most consistently available primers for me so I've developed almost all of my loads with them, luckily haven't been forced to switch brands more than a time or two.

Jerry - I've had a number of rifles that just wouldn't shoot BT bullets as well as flat base. I think the BT design is just not as forgiving of small inconsistencies in the barrel, crown, etc as flat base. Usually I just give up and feed it what it likes, of course when available supply isn't an issue.

Last edited by Ifishsum; January 23, 2013 at 08:14 PM.
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Old January 23, 2013, 09:22 PM   #4
reynolds357
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You got any Federal primers left?
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Old January 23, 2013, 09:33 PM   #5
FiveInADime
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No Feds left. I bought a brick of the CCI, so I will try to make those work first. If not, I will just buy the Feds when I find them.
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Old January 23, 2013, 09:39 PM   #6
reynolds357
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I was just wondering if you had enough Federals left to load up a few for a test group just to verify nothing else is wrong.
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Old January 23, 2013, 09:48 PM   #7
FiveInADime
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Good point. Before i waste the bullets and powder i should verify that.
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Old January 24, 2013, 05:18 PM   #8
Slamfire
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Primers make a difference. Change them out and sometimes you have to re develop the load.
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Old January 24, 2013, 07:45 PM   #9
m&p45acp10+1
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This may sound a bit strange. I feel the need to ask becasue I have had what was a similar problem when I swithced primers.



How long ago did you clean the rifle?

I do not clean my varmint rifle that often. It shoots great till it seems that all of a sudden accuracy starts to drop off greatly. I clean it very well after that and accuracy goes right back to out of the box accuate again.

I ran it dirty, and I switched primers. Accuracy was not there. When I got home I had a few of my preferred brand of primers left. I loaded a few rounds and the next day tried them. They shot poorly. Then I figgured out that I had not cleaned my rifle in a while. I cleaned it well, and my groups tightened up with both loads.

I will admit there are one brand of primers that I have to run a hotter load with to get the accuracy out of my loads with. I do not use them if I do not have to.
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Old January 25, 2013, 05:05 PM   #10
Mike / Tx
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I normally run Winchesters, and CCI's they groups REAL close with most of my loads. That said with the Federals I HAVE used they have for he most part been in my magnums and YES i have seen just as dramatic a difference as you mention with everything else being the same. I don't know what it is, but I have shot a 1/2" group with Feds followed right up with a 1 3/4 - 2" group switching primers. Just throws the whole load off kilter.

Just as a for instance, here is a work up I did with a .243.


The bottom two left hand groups are the final load, with five shot groups fired one round every 30 seconds, one with Win WLR and the other with CCI BR2. The two outer shots are form the stock rubbing the barrel as it heated up, it's been fixed since and will groups stay together now.
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Old January 25, 2013, 08:27 PM   #11
Hummer70
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I ran a series of tests about ten years ago using Federal, Winchester and CCI primers.

I loaded up 33 rounds of ammo and a given propellant charge, went out and fired three rounds off target then shot 30 continious rounds for group and through the chronograph screens at same time.

Came and loaded same cases with same propellant and same bullets changing only the primers and ran test again same way.

The test was completed yet again with third primer top.

The differences the primers gave was amazing.

To make things worse I changed propellants and did the series again with the same cases etc and the velocities were different again.

For instance lets say primer 2 was fastest on first test, no 1 was in the middle and No 3 was the slowest. In the next series primer 3 may have been the fastest and primer 1 the slowest and primer 2 in mid range.

Thus it was quickly determined that the primer giving the lowest SD with the propellant was the one to work the load up with.

It quickly became apparent that just because I had good shooting with one primer did not indicate it would behave the same with another propellant.
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