loss of velocity with proven load

[greyghostnw]

recently the load i developed has dropped 45 fps or so and i am trouble shooting why. 673 is load count on barrel, all components are same, same brass prep, same tools, same barrel maintenance. original max cbto has not changed and have a bore scope to see whats going on with fouling, erosion, fire cracking etc. 300 rum, CA barrel, 88.3 gr h1000, fed 215 m, norma brass, 212 eldx, 20 off touch, 3058 avg single dig es, sd's, near same hole at 100 yrds, validated 1760 yards... now 3015 avg, still single es, sd's. lab radar ive had since came out, the dope from kestrel 5700. change in velocity dosnt amount to much when dialing but still would like to trouble shoot. with lack of available components any heads up from knowlegable loaders woulld be appreciative. figure i will add .02 gr of h1000 and seat out .001 for a try. still within both seating and powder nodes. thanks in advance

 

[Lawnboi]

Powder humidity?

 

[Keith Stone]

It’s a stretch to have any single one of the following variables result in that much drop but will throw out thoughts for review. Relative temp during testing
Change in lot numbers of powder or primers
Firings on brass before and after
Type of chrono
How many shots to verify mv
How you are shooting ex. Free recoil will give you different numbers than loading into a secure bipod
How often are you cleaning your barrel and how are you cleaning the barrel

Curious side note when you say the dope doesn’t change much. If your shooting to a mile a 45fps drop should give you quite a bit of change so would like to hear more around this.

 

[WeiserBucks]

How many rounds down the barrel?

 

[Brado16]

Measure distance from lands. With that round count your going to have throat erosion and might need to load them out further to chase the lands.

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[rifletuner]

How many rounds down the barrel?

"673 is load count on barrel"

 

[rifletuner]

Has the temperature that the data was shot in changed? I could see that amount of variation if you shot in hot weather, than again in much cooler temperatures. Though I guess thats unlikely given current weather in the USA?

Have all the shots been from the same lot of H1000?

 

[WeiserBucks]

673 rounds on a RUM you absolutely have throat erosion and need to re-tune the load. Depending on the firing schedule the barrel might be simply worn or completely smoked if it's been abused.

 

[greyghostnw]

It’s a stretch to have any single one of the following variables result in that much drop but will throw out thoughts for review. Relative temp during testing
Change in lot numbers of powder or primers
Firings on brass before and after
Type of chrono
How many shots to verify mv
How you are shooting ex. Free recoil will give you different numbers than loading into a secure bipod
How often are you cleaning your barrel and how are you cleaning the barrel

Curious side note when you say the dope doesn’t change much. If your shooting to a mile a 45fps drop should give you quite a bit of change so would like to hear more around this.

The mile validation was prior before change. The change in dope at 870 yards that ive tested isnt a hole lot considering the amount in change, think was 16.5 min to 17 roughly… At one mile without calc it’s obviously more dramatic than 870. Its same lab radar ive had sice came out. One thing is new lot of h1000 ive switched to.

 

[greyghostnw]

How many rounds down the barrel?

673

 

[greyghostnw]

Has the temperature that the data was shot in changed? I could see that amount of variation if you shot in hot weather, than again in much cooler temperatures. Though I guess thats unlikely given current weather in the USA?

Have all the shots been from the same lot of H1000?

I just changed lots of h1000. In past there is a slight change on velocity but seems like way more than what ive seen befor.

 

[WeiserBucks]

I just changed lots of h1000.

You changed lots of powder and your barrel is two thirds of the way through its life span, sounds like you've answered your own question. 3058 to 3015 is a 1.47% difference in velocity that is easily attributed to either a change in powder lot or barrel wear much less both.

 

[Novahunter]

You changed lots of powder and your barrel is two thirds of the way through its life span, sounds like you've answered your own question. 3058 to 3015 is a 1.47% difference in velocity that is easily attributed to either a change in powder lot or barrel wear much less both.

Agree with this assessment. I have about 80 rounds down the current Krieger barrel for my 300 RUM. I figure 1000 round count is about max I'll get out of the barrel.

Change in powder lot, and nearly 700 rounds on the barrel and only a 45 fps change in velocity sounds pretty reasonable.

 

[greyghostnw]

Measure distance from lands. With that round count your going to have throat erosion and might need to load them out further to chase the lands.

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Ill re measure today but did so not long ago and was hard to see any change. My brass now

Agree with this assessment. I have about 80 rounds down the current Krieger barrel for my 300 RUM. I figure 1000 round count is about max I'll get out of the barrel.

Change in powder lot, and nearly 700 rounds on the barrel and only a 45 fps change in velocity sounds pretty reasonable.

i just checked and new on 4/30/2017 max cbto was 3.104, on 2/13/19 was 3.117 with 523 rounds so .013 longer and today was 3.137 so .033 total in 673 rounds. i thought for sure in 2019 it hadnt changed. and havnt shot it much since due to my high country rifle. i originally decided on .020 off touch because it was a laser beam with my tests for nodes with. so ill try 20 off the new touch and hope everything goes well again. it still shoots well with near same hole zero at 100 and must have a seating node around 30 off as well since still shoots be it 100, 400, 800 yars etc. will still be testing longer to address erosion. much appreciate the help. sometimes another set of eyes can help problem solve. on another note do i test with the ti pro 3 brake i just received or stick with th CA ti side baffle to keep it simple?! thanks...................

 

[WeiserBucks]

Keep it simple, one thing at a time until you get it sorted out.

 

[35WhelenAI]

As per your first post, I must disagree. All components are not the same. You changed powder lots. If (picking a number out of the air for the sake of discussion) at round 625 you averaged the higher number and from round 626 on with the new powder lot your velocity changed, you have your answer.

Changing powder lots is one of the most common causes for velocity variation and should be fairly well known within the reloading community.

 

[greyghostnw]

As per your first post, I must disagree. All components are not the same. You changed powder lots. If (picking a number out of the air for the sake of discussion) at round 625 you averaged the higher number and from round 626 on with the new powder lot your velocity changed, you have your answer.

Changing powder lots is one of the most common causes for velocity variation in should be fairly well known within the reloadin

 

[greyghostnw]

fair enough...i have had to change lots of h1000 a couple times on this and there had been minimal change in velocity in testing in past. this new lot i was lucky to score 10 one pounders same lot so whatever it produces is what it is. thanks for response.

 

[PA Hunter]

I load for 5 different. 300 Rums and i always shoot through a chrony at the range. My same rounds from same box always shoot a little different from summer to winter close to 50 fps.

If im practicing in Summer for hunting i usually put my shells on ice in a cooler shoot one at a time very slowly. What your describing is not unusual & i wouldn't worry.

 

[MTtrout]

@WeiserBucks, or someone else elaborate on barrel abuse? I’m guessing it’s too many consecutive rounds fired while the barrel not having a chance to cool back down. If so, is that based on temp hand feel of the barrel? When shooting a string of 5 during the summer I usually stretch it out over 7-10 minutes. The barrels certainly hot but won’t burn you. I then wait ten minutes before firing again and the barrel feels fine that point. Is it as simple as if the barrel will burn you skin then you have gone too far? Thanks