Need help w pressure problem

[HighUintas]

I've got a 22" 243 Tikka factory barrel that I throated out to seat the 108eldm and 112 match burner w the boat tail above the neck/shoulder. It's been shooting awesome but I just found some pressure today and not sure what to do.

125 rounds on it, through a scythe to suppressor, no cleaning of barrel or suppressor.

Starline brass, cci200 primers

About 35 of those rounds are with h1000. Other than that, it's been h4350 and mostly a 41gr charge of pushing 108eldm. The 108 shoot awesomely with h4350. Haven't checked the accuracy with higher charges.

The 112 match burner was to be shot with h1000. I did some pressure finding loads (with virgin brass). See below. The only one I saw an ejector mark on was the 43.5gr h4350 and eldm.



I then annealed and resized and trimmed 50 pieces. 0.003 bump. Did a test with 48.5gr h1000, 112mb, and cci200 vs gmm215. 12 rounds each primer. Bullet seated 0.030 off lands at about 2.960 coal.

The cci200 combo gave avg 3030fps. No pressure signs at all. Good accuracy. The very last shot measured 3100.... Not sure if that was real or just my Caldwell chrony.

The gmm215 avg around 3075, but accuracy and speed was erratic. I only shot 7 and pulled bullets on the other 5. A single very slight ejector mark.

I decided to back the charge down to 48.0gr h1000 with cci200 and seated to be 0.020 deeper. Checked the pressure on GRT and it was at 63k. Loaded the remaining 1x fired starline and went to the range today.

First 5 shots were ones I had pulled bullets from. First 3 were fine. #4 &5 had ejector marks though not horrible. Shots #6&7 had huge ejector swiped with #7 leaking around the primer and had heavy bolt lift. Speed avg was 3000fps.


So.... What does it sound like? Did seating 0.020 deeper really make that much difference in pressure even though I backed off 0.5gr? GRT has been very accurate after calibrating the powder from measured velocities.

I think that maybe I've got some bad carbon buildup from the suppressor and shooting a large load of h1000, but it's only been about 35 shots...

Not sure what to do. I do not want to clean the barrel and and monkey around with shit and multiple range trips to troubleshoot, etc etc. I don't have a solid load yet for hunting Oct 4th, unless I just shoot the 41gr h4350 with the eldm and hope that I don't magically have pressure issues with that too.

Should I shoot the h4350 and eldm?

Should I back the h1000 and 112mb down to 47gr?

 

[ResearchinStuff]

When I've had pressure build up during a string, it's been because of lube on the cases and building up in the chamber

 

[HighUintas]

When I've had pressure build up during a string, it's been because of lube on the cases and building up in the chamber

Definitely not a lube issue. I've used Lee lube for forever and have used the same process forever and never had a lube pressure problem. I always wipe them clean w a wet cloth after sizing.

 

[Shortschaf]

In no particular order

1. What do you lose by just loading and chronoing 40gr h4350 and sending it for hunting season?
2. Finding pressure with virgin brass is a waste of time--will give misleading results
3. 0.5gr is nothing to back a charge off of. It's 1% of the load
4. 100+ shots on a suppressor with loads close to the lands can cause pressure issues that only cleaning will resolve (assuming no change in load)
5. You probably won't have pressure with 41gr h4350 and the eldm.
6. I dont really see what accuracy you are trying to obtain/preserve with hotter loads
7. Nothing anyone on the internet can tell you will be as useful as troubleshooting yourself

 

[HighUintas]

In no particular order

1. What do you lose by just loading and chronoing 40gr h4350 and sending it for hunting season?

Not sure if this load will give me pressure signs or not

1. Finding pressure with virgin brass is a waste of time--will give misleading results

Not completely. It will give you a ballpark idea

1. 0.5gr is nothing to back a charge off of. It's 1% of the load

I didn't really need to back off 0.5gr based on my 12 shots with 48.5gr and 1x fired brass. No pressure signs. I just wanted to drop the speed a bit.

1. 100+ shots on a suppressor with loads close to the lands can cause pressure issues that only cleaning will resolve (assuming no change in load)

125 shots 0.020-0.030 off. Then today the 7 I shot were 0.050 off. 0.050 off should not cause pressure issues.

1. You probably won't have pressure with 41gr h4350 and the eldm.

1. I dont really see what accuracy you are trying to obtain/preserve with hotter loads

I had about 1" accuracy with the 112mb. I was targeting 3000fps. I was not seeing any pressure at all until suddenly today I did and would not think that I would since I dropped the charge and backed off the lands a bit more. I'm now just wondering if I can shoot any load with the 112s without high pressure.

It could be the h1000.... I've read it tends to be very dirty in the 243

1. Nothing anyone on the internet can tell you will be as useful as troubleshooting yourself

Probably true. Just looking for ideas on most likely root causes. The 22cm thread comes to mind.

 

[pbroski]

Sometimes pressure has a way of just creeping up as you shoot more shots. Doesn't always happen, but I've see it before where there has been zero change to the load and pressure has climbed. Don't know the cause. The only real solution is to reduce the powder charge, then the pressure should stabilize.

I don't know anything about suppressors though. Maybe pressure increases when they need cleaning?

 

[Shortschaf]

Not sure if this load will give me pressure signs or not

If 40gr has pressure, your setup is beyond internet-stranger-help and requires more troubleshooting than you posted you were willing to do.

Not completely. It will give you a ballpark idea

No. It is not always even ballpark. Put the initial pressure tests with virgin brass out of your mind and look at your most recent set of data--you have pressure

I didn't really need to back off 0.5gr based on my 12 shots with 48.5gr and 1x fired brass. No pressure signs. I just wanted to drop the speed a bit.

I was giving perspective on the 1%. You have pressure signs. Quick and easy fix is to drop charge

125 shots 0.020-0.030 off. Then today the 7 I shot were 0.050 off. 0.050 off should not cause pressure issues.

That's plenty close to cause problems. Cleaning isn't going to cause problems. But it can alleviate them

I had about 1" accuracy with the 112mb. I was targeting 3000fps. I was not seeing any pressure at all until suddenly today I did and would not think that I would since I dropped the charge and backed off the lands a bit more. I'm now just wondering if I can shoot any load with the 112s without high pressure.

You probably have 1" accuracy with a wide variety of ammo. Drop the speed if you're married to the 112's and forget about it. You asked for a quick fix

It could be the h1000.... I've read it tends to be very dirty in the 243

Could be. Use H4530 then if you're convinced its the problem

Probably true. Just looking for ideas on most likely root causes. The 22cm thread comes to mind.

You got it. Just trying to help