Velocity Increase Issue

BryanF

BryanF

Active member
Having an issue with a new .223rem. Each round increases velocity on 3 round groups. For example:

#1 - 3,117fps
#2 - 3,129fps
#3 - 3,173fps

Waited about 10min then shot the next group.

#1 - 3,110fps
#2 - 3,140fps
#3 - 3,172fps

24.5gr Benchmark, GM205M, 53gr vmax, New RAR 700 varmint in a chassis. Never experienced this before especially with the numbered shots being close in fps. Shot 12 rounds that measured .850moa total. Any thoughts?
 
My guess is either...
A coincidence, if you had fired round #3 first then your velocity would be decreasing or mixed.
If not, then maybe the powder is temp sensitive.

Also, if the rifle is brand new it may be settling in and you may get higher velocity spreads for a while. Would be good to clean the bore thoroughly. What Hammer are you using?
 
Koda said:
My guess is either...
A coincidence, if you had fired round #3 first then your velocity would be decreasing or mixed.
If not, then maybe the powder is temp sensitive.

Also, if the rifle is brand new it may be settling in and you may get higher velocity spreads for a while. Would be good to clean the bore thoroughly. What Hammer are you using?
Click to expand...
It's a 53gr v max for pdpogs. I haven't had any issues with the hammers in my other guns. The rifle is brand new with about 30 ish rounds through it. But again I just never had that issue with new rifles before. Is just interesting that the shot strings are consistently increasing like there is a heat issue.
 
Koda said:
My guess is either...
A coincidence, if you had fired round #3 first then your velocity would be decreasing or mixed.
If not, then maybe the powder is temp sensitive.

Also, if the rifle is brand new it may be settling in and you may get higher velocity spreads for a while. Would be good to clean the bore thoroughly. What Hammer are you using?
Click to expand...
Koda is spot on! My last three new guns were filthy! They do test fire them at the factory and don't clean them.
 
.223 is not gonna heat up in 3 shots. Both strings are essentially identical. Whatever is the cause, it's consistent.

I would ignore 3 shot groups and go to at least 10 round string to see if things stabilize. The barrel is way too new for meaningful data IMO. Everything is going to keep changing close to 100 rounds.
 
BryanF said:
The rifle is brand new with about 30 ish rounds through it. But again I just never had that issue with new rifles before.
Click to expand...
I suspect it can vary by different barrel makers and quality. Heres an article I bookmarked on the subject, I like the way it explains why new barrels speed up after a few rounds are spent.
Since 223 factory ammo is typically the most affordable Id run a couple boxes of the cheapest I could find thru it then go back to load development.

www.outdoorlife.com

Do You Really Need to Break in a New Rifle Barrel?

The old process of breaking in a barrel is unnecessary. But there are some things you need to know about "barrel break-in" and rifle accuracy.
www.outdoorlife.com www.outdoorlife.com
 
You aren't sitting in a bad spot at all, but I understand the want for better ES/SD. Lower ones sooth the OCD brain!
The CMV factory barrel steel, likely 4150/4160, isn't as finicky with break in and velocity increase as brand spanking new 416R stainless barrels that have had no rounds shot through them. 416R is softer than the CMV steels which makes them more susceptible to velocity increases till about the 125rnd count. 416R is easier on the tooling and easier to hand lap, it isn't all about 416R being superior for precision. Manufacturers could bring 4150 CMV to precision levels of 416R easily, but their tooling would be worn out twice as fast because of the harder steel and they ain't gonna increase their overhead and dip into profits.

Anyway, I would increase your powder charge 1/10th grain and see if that settles the ES/SD a bit better.
 
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