Long string load development

[Bc'z]

Shooting a club match yesterday I noticed a sharper recoil ,and ejector mark on round 7 of 20 not counting sighters.
Agian in the 2nd relay I started getting ejector Mark's halfway through the string. Temps were high 90's.
When doing load work temps were in mid to high 80's letting barrel cool between every 6 shots.

So my question is.
Should I be shooting continuous when doing initial charge weight to simulate heat generated during long strings of fire to find preasure caused by heat?
Cartridge and load..
6.5 Creedmoor
Peterson brass, cci200,
37.3gr IMR4166, 123gr scenar

 

[Jager]

Rounds 8 through 20 of the first relay were normal?

If elevated temps were the cause of your pressure excursions, I'd expect to see some pattern of intermittent, increasing, or regular occurrence after round 7. If round 7 was the only hot round in that relay, with 13 shots registering normally afterwards, I'd be inclined to look elsewhere.

Interesting problem. Your load should have given you lots of headroom unless that Peterson brass was unusually tight on volume.

 

[mikecr]

It doesn't make sense to prep for a match differently than you need.
But then 20 shots makes no sense to me either.
If you couldn't prove enough in 5 or 10 shots, then 20 won't help. Just burning out barrels...

So obviously I'm not a competitor.
I develop loads for hunting shooting (which is proven with EACH shot).
For ammo, I hold shots intended in my front pants pockets. This, even during load development.
The barrel is a different matter. I use cut rifled, and I would never mangle it with 20 shot group shooting.
If I had to, I would test for incremental loading to level a MV trend across a string.
This info could be useful and used for prediction with QuickLoad.

 

[Walt Krafft]

I am a fan of doing final testing as you will compete. I had a 22-250AI. Shot fantastic for 10 shots and I never shot more when testing for fear of burning it up. In the first match, I was clean with 8xs in the first 10 shots, 11 was off call but a 10, 12 was an 8, the rest of the 20 never made it to the target.

 

[Bc'z]

Rounds 8 through 20 of the first relay were normal?

If elevated temps were the cause of your pressure excursions, I'd expect to see some pattern of intermittent, increasing, or regular occurrence after round 7. If round 7 was the only hot round in that relay, with 13 shots registering normally afterwards, I'd be inclined to look elsewhere.

Interesting problem. Your load should have given you lots of headroom unless that Peterson brass was unusually tight on volume.

I was seeing ejector marks on 7 through 20.
Bolt lift was normal.

It doesn't make sense to prep for a match differently than you need.
But then 20 shots makes no sense to me either.
If you couldn't prove enough in 5 or 10 shots, then 20 won't help. Just burning out barrels...

So obviously I'm not a competitor.
I develop loads for hunting shooting (which is proven with EACH shot).
For ammo, I hold shots intended in my front pants pockets. This, even during load development.
The barrel is a different matter. I use cut rifled, and I would never mangle it with 20 shot group shooting.
If I had to, I would test for incremental loading to level a MV trend across a string.
This info could be useful and used for prediction with QuickLoad.

I'm just getting into this Fclass game.
20 shots for record.
I've always loaded for hunting and have no problems there with 3 shot groups for testing, and 5 shot groups for conformation.
It's the long sustained string of fire that is generating excessive barrel heat.
Wondering if the heat is causing a spike in preasure by cooking the ammo, something not seen in testing shooting 3-5 shots with cool down periods.
Rounds are not chambered until target is up.

 

[jr600yd]

Barrels getting warmer/hot as the string goes on and the temperature is increasing as the day goes on.

 

[MattPeetz]

Test like your gonna shoot

When testing, shoot round robin. This will give you a better idea of what the load will do.

say, have 20 charges to test. Three shot groups.
shoot 1-20 one each,, then go back 20-1 then 1-20. I usually leave 30seconds to a minute between each shot.
No, you don’t need 20 different charges. Just picked that number.

Benchrest would test different as your not shooting as much as f class

 

[CharlieNC]

In order to develop a load which could cause the problems you describe, I suggest doing the development in as extreme heat as you will experience and shoot the strings at the pace which you would in competition. The acid test so to speak. Then at a match, keep your ammo in the shade (cover with a rag if necessary) and don't chamber until you are ready to shoot to minimize problems. I know it is not always possible to do this, so I will shift to the lower end of the powder charge node in the summer if the load was developed in cool conditions.

 

[wkdickinson]

Here are a couple of suggestions from my High-Power and Long-Range days, which you may already know, but if you are just starting to compete, maybe not:

1. Keep your ammo out of the sun. Cover it with a white towel or something.
2. Lay your next round in the action while you scope your last shot, but don't close the bolt until you are actually ready to fire.

Simple, but often effective.

 

[Fuj]

Shooting a club match yesterday I noticed a sharper recoil ,and ejector mark on round 7 of 20

I would tend to say it's in the loading process. How were the intial ES
and SD's on the work ups ??

 

[Keith Glasscock]

Even with the best temp stable powders, pressure/velocity changes with barrel temperature. When I test for powder, I warm the barrel with several rounds to simulate the conditions expected during a match.

My typical load development string is 25 rounds, and I'm doing it effectively round robin. I try to shoot at string fire pace while doing it.

 

[Bc'z]

Test like your gonna shoot

When testing, shoot round robin. This will give you a better idea of what the load will do.

say, have 20 charges to test. Three shot groups.
shoot 1-20 one each,, then go back 20-1 then 1-20. I usually leave 30seconds to a minute between each shot.
No, you don’t need 20 different charges. Just picked that number.

Benchrest would test different as your not shooting as much as f class

I normally cover 6-7 charges in .3 increments plus sighters/foulers for roughly 25 rounds.
I'm thinking/agreeing if I didn't allow cool down I would have seen the preasure indicators.
Conditions yesterday were hot/humid/smokey. 98-99°.
We don't start our club match until noon, military match shoots ahead of us. This is also telling me to test after lunch instead of after coffee. Lol
In all honesty this was also new brass for all record rounds. I had contemplated using 1x fired, but chose to keep brass in rotation versus finding time to test 1x brass.
Lesson learned.

 

[Bc'z]

I would tend to say it's in the loading process. How were the intial ES
and SD's on the work ups ??

I never use a chronograph for load work up. Was thinking about running the magneto speed this morning while re-shooting charge weight.

 

[MattPeetz]

I normally cover 6-7 charges in .3 increments plus sighters/foulers for roughly 25 rounds.
I'm thinking/agreeing if I didn't allow cool down I would have seen the preasure indicators.
Conditions yesterday were hot/humid/smokey. 98-99°.
We don't start our club match until noon, military match shoots ahead of us. This is also telling me to test after lunch instead of after coffee. Lol
In all honesty this was also new brass for all record rounds. I had contemplated using 1x fired, but chose to keep brass in rotation versus finding time to test 1x brass.
Lesson learned.

i have tested in 20-30 degree weather like this and never had any issues when the temps got up in the 90’s with the same load.
but you need to pick the correct node though

 

[miningshawn]

I'm not your best source, but here goes!

I shoot PRS and FPR - so I shoot for load development just like I shoot competition. That means:
1.) I load from the magazine
2.) I shoot from prone using a bipod and bag
3.) I shoot groups as strings of five or ten
4.) All shots in a group go in about a minute
5.) Time between groups is less than 5 minutes (keep the barrel warm)

I realize this goes against pretty much all of the rules for Benchrest - but I don't shoot Benchrest. This also means that I am pretty much stuck with temperature insensitive powders.

I often do my load development in the late winter or spring, when A/D is around 6000. When I am competing the A/D is often 9000 or greater because of temperature alone. I am very much interested in "windows" of stability versus exact loads. Let's use .308 as an example - if I see a node that has good ES\SD and a good window of 0.3 to 0.4 grains I will load to the bottom of the window. For my rifle that is a stout load of Varget (44.5gr) in the best of conditions. pressure signs in this rifle show up at 45.2gr. The "window" of good stability is 44.5-44.8 and I see the best groups at 44.7. As A/D rises I should be good as long as I keep the sun off of my ammo.

I also tend to seat bullets in increasing depth. The initial seating for stages 1,2 and 3 would be 2.890 COAL, for stages 4,5, and 6 I seat at 2.891, and so forth. If the load is still great at the end of the match the final COAL becomes my initial seating depth for the next match, (I measure CBTO, but used COAL for this example for simplicity). I load all of my bullets long and bring an arbor or Lee hand press to the match and do final seating that day. A .308 barrel usually starts going south for me around 3000 rounds. I will typically see .003 to .005 of lands erosion in a match. Don't ask about my 6mm's......

The reason I do all of this? I don't have time to load before matches in the summer. I will load and seat long in the winter projecting how many rounds I will need for the season for each rifle. For .308 this means I load 1500 rounds in February and they typically last me the year - About 1000 for my wildcat and 6mm. .223 I typically shoot 7K-9K per year.

I very seldom load in the summer. Clear as mud?

 

[Texas10]

I would take a careful look at the throat for carbon build up. I've experienced this same pattern, shoots fine for 5 or 10 rounds then the ejector swipes or primer flow start showing, even with cool down time. The issue for me was I was not getting all the carbon out of the throat/leade, and as the round count went up on match day, carbon was building to the point that I was starting to lock up the bullet. Shot good, but still, no bueno!

I figured this out when I ejected a live round that I KNEW was seated .010 off the lands, but the bolt stuck as I ejected it. A close look at the bullet revealed scrape marks confirming the bullet was tight in the throat.

A wire brush and some Ed's Red fixed the problem. A borescope camera was an essential ingredient.

I hope this helps, Bret.

 

[Webster]

Shooting a club match yesterday I noticed a sharper recoil ,and ejector mark on round 7 of 20 not counting sighters.
Agian in the 2nd relay I started getting ejector Mark's halfway through the string. Temps were high 90's.
When doing load work temps were in mid to high 80's letting barrel cool between every 6 shots.

So my question is.
Should I be shooting continuous when doing initial charge weight to simulate heat generated during long strings of fire to find preasure caused by heat?
Cartridge and load..
6.5 Creedmoor
Peterson brass, cci200,
37.3gr IMR4166, 123gr scenar

I don't shoot competition but I assume that if you have an ES of 20 it means that each shot would have a different pressure. That would account for some of the cases having ejector marks. Even if you have a low ES each shot will not have the same exact time/pressure curve or peak pressure. You need to reduce your load a little bit. Extractor marks can only be caused by high pressure is my understanding. The high pressure forces a small amount of brass into the ejector hole and rotating the bolts tries to shear the high spot off. It cannot shear it off so it smears due to high contact pressure. I have been shooting off a bench for 50 years and never saw an ejector smear until I starting increasing the powder charge to find maximum.

 

[Bc'z]

I would take a careful look at the throat for carbon build up. I've experienced this same pattern, shoots fine for 5 or 10 rounds then the ejector swipes or primer flow start showing, even with cool down time. The issue for me was I was not getting all the carbon out of the throat/leade, and as the round count went up on match day, carbon was building to the point that I was starting to lock up the bullet. Shot good, but still, no bueno!

I figured this out when I ejected a live round that I KNEW was seated .010 off the lands, but the bolt stuck as I ejected it. A close look at the bullet revealed scrape marks confirming the bullet was tight in the throat.

A wire brush and some Ed's Red fixed the problem. A borescope camera was an essential ingredient.

I hope this helps, Bret.

Carbon has crossed my mind.
Barrel has 296 rounds on it.
I always spin bronze brush with Mpro-7 in the throat followed with good soaks and patches of
Wype Out.
I'm planning on a good scrubbing with JB'S blue label this afternoon.

 

[MattPeetz]

I don't shoot competition but I assume that if you have an ES of 20 it means that each shot would have a different pressure. That would account for some of the cases having ejector marks. Even if you have a low ES each shot will not have the same exact time/pressure curve or peak pressure. You need to reduce your load a little bit. Extractor marks can only be caused by high pressure is my understanding. The high pressure forces a small amount of brass into the ejector hole and rotating the bolts tries to shear the high spot off. It cannot shear it off so it smears due to high contact pressure. I have been shooting off a bench for 50 years and never saw an ejector smear until I starting increasing the powder charge to find maximum.

Extractor marks are not only caused by high pressure.
So much can cause that. To much headspace, oily chamber etc…..

 

[Webster]

Extractor marks are not only caused by high pressure.
So much can cause that. To much headspace, oily chamber etc…..

I don't understand why oil or headspace would cause it. It takes pressure to make the brass flow into the ejector hole. Seems easy to understand to me. Head space and oil don't increase the pressure. Every rifle and reloading manual is a little different. I would still bet that backing off .3 to .5 gr of powder would make the problem go away.

From the Hogden website:
6.5 Credmor 123 Gr bullet
34.2 gr IMR 4166 2624 fps 49200 psi
38.0 gr IMR 4166 2855 fps 61,000 psi. (your using 37.3 gr IMR 4166)