Thread: Has anyone had this problem?

I worked up a load with AR 2217 powder and ELDX 162 gr bullets, I was using 171.5 gr of powder and it had a velocity of 2940 with nice groups some even tack drivers. I ran low on powder so got some more yesterday, I replicated the load and headed back to the range and to my surprise they were traveling at 3050 fps instead of the 2940 that I was getting the last time I went out and the groupings were terrible.
I went home and broke the remaining loads down to double check I had put 171.5 gr's of powder which I had so now I am wondering if someone has slapped the wrong label on the new batch of powder as I have no other explanation for it.
The only thing I can think of doing now is lighten off the load with the new powder to reduce it back to around 2940 fps and hope it comes back into tune. And I had 2 cony graphs going and they were both reading the same so it isn't a faulty machine.
Thoughts please?

Its 71.5 not 171.5 is my first thought.

2nd thought is look at the powder batches and report back. What chronograph did you use in both instances?

Originally Posted by PerazziSC3

Its 71.5 not 171.5 is my first thought.

2nd thought is look at the powder batches and report back. What chronograph did you use in both instances?

Sorry, correct 71.5 gr I'll have to get back to you on the chronograph's 2 different types but not mine and I'll have to get back to you on the batches as they are not at my place. Can get that info tomorrow. Thanks for the reply.

Did you clean the barrel between outings?
If not I'd say you could have a copper issue.
Was there any real difference in temperature as that could effect all sorts including the chronographs.


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Not thoroughly so I am in the process of doing that right now, thank you for that idea though as it gives me a glimmer of hope that it could be the problem but not sure why it would increase in velocity by 110 fps

Originally Posted by 7mm Rem Mag

Not thoroughly so I am in the process of doing that right now, thank you for that idea though as it gives me a glimmer of hope that it could be the problem but not sure why it would increase in velocity by 110 fps

Copper can/will increase pressure. But I would say coupled with different conditions on different days including light. How fast you fired your strings how warm or cold your barrel was reliability of said chronographs etc will account for the velocity and possibly accuracy issues.

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A velocity difference when you get a new tin of powder is common. Some powders are worse than others.

Originally Posted by R93

Copper can/will increase pressure. But I would say coupled with different conditions on different days including light. How fast you fired your strings how warm or cold your barrel was reliability of said chronographs etc will account for the velocity and possibly accuracy issues.

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Ok thank you, I hope to give it another go tomorrow so fingers crossed

Originally Posted by stug

A velocity difference when you get a new tin of powder is common. Some powders are worse than others.

Thanks @stug that's a bugger when you are chasing accuracy but good to know, would you recommend going down a grain or 2 to get back to 2940 fps to try to get it grouping well again?

Different batches of powder can have slightly different burning rates even if its the same powder. I try to buy enough of the same lot to not run out
Other wise its a few grains out or in using a chrony to get the velocity "just right" like the batch before

Originally Posted by PerazziSC3

Its 71.5 not 171.5 is my first thought.

2nd thought is look at the powder batches and report back. What chronograph did you use in both instances?

Chrony gamma master chrony plus an Oehler 35 T one in front of the other 3 meters from the muzzle

Originally Posted by mikee

Different batches of powder can have slightly different burning rates even if its the same powder. I try to buy enough of the same lot to not run out
Other wise its a few grains out or in using a chrony to get the velocity "just right" like the batch before

OK thanks for that, I may have to buy 2 or 3 at a time

Sounds like different batches of powder to me.

Other thing to consider is if there were major differences in atmospherics between when you shot last and this test.

What you want to record for a barrel is the muzzle velocity for a particular powder batch / weight combo.

When you get a new batch, load some test rounds to make sure you are still in the velocity band that worked previously (called a node).

Depending on how much you shoot, buying powder in bulk is well worth it for consistent results. For fullbore I tend to buy powder in 4kg bottles, and that is not exactly a busy season...

Ive had the same thing at times, ammo was in the back of the truck for the day, and was warmer than the last time. Now I usually bury my ammo in the coldest part of the truck and dont leave it in the sun as Im using it.

Originally Posted by ebf

Sounds like different batches of powder to me.

Other thing to consider is if there were major differences in atmospherics between when you shot last and this test.

What you want to record for a barrel is the muzzle velocity for a particular powder batch / weight combo.

When you get a new batch, load some test rounds to make sure you are still in the velocity band that worked previously (called a node).

Depending on how much you shoot, buying powder in bulk is well worth it for consistent results. For fullbore I tend to buy powder in 4kg bottles, and that is not exactly a busy season...

OK thank you, I had never heard of that before