Increase in pressure?

[Ucsdryder]

7saum - load development done with 20-50 rounds of fired brass. Now at 200 plus I'm getting pressure. I saw a significant barrel speed up around 100. I dropped from 64.2 or h1000 to 63.8 and STILL seeing heavy bolt lift and ejector marks. Also getting a bolt click at the top. 180 eldm and ADG brass.

I also loaded some 145 CEB at a very mild load, about 1 grain under pressure at the same time I did my eldm load development and those are also showing a hard bolt lift and click now.

Carbon ring?

The brass has been run hard due to the increase in pressure and multiple reloads have had ejector marks as I try to figure it out. Could the brass be "blown out" at this point causing the pressure and click?

Something else? I cleaned the barrel and it has about 40 rounds after cleaning. The jump is around .120" so definitely not close to the lands.

 

[BoomFlop]

Just like the Sherman Wildcats (I have a 7 Sherman Short), the ADG brass is undersized to match Gunwerks chambers. They need to be fireformed with a mild load before running any pressure to prevent the head and primer pockets from going. My guess is that your brass is junk from running pressure on the first firing.

I shot my 210 pc of brass with 56 gr RL 26 with a 180 Hybrid before doing any load development per Rich's recommendation.

Hope this helps.
Steve

 

[Ucsdryder]

Just like the Sherman Wildcats (I have a 7 Sherman Short), the ADG brass is undersized to match Gunwerks chambers. They need to be fireformed with a mild load before running any pressure to prevent the head and primer pockets from going. My guess is that your brass is junk from running pressure on the first firing.

I shot my 210 pc of brass with 56 gr RL 26 with a 180 Hybrid before doing any load development per Rich's recommendation.

Hope this helps.
Steve

Thanks for the reply. I did a ladder and stopped when I hit pressure. The hot loads started when all of a sudden it decided to show pressure signs at previous "ok" loads. I am thinking the same though, toss the brass and start over with load development (after hunting season).

She's still killing like the plague!

 

[HSmithTX]

Could be a carbon ring. Could be long brass. Could be copper fouling. Could be barrel speed up simply has you at high pressures. I have seen all of these do what you are experiencing. Assuming you don't have a bore scope to tell you if there is a carbon ring? What does the chrono tell you? First thing I would do is chrono the reduced loads you are thinking have you at a more reasonable pressure, my best guess is you were running a pretty stout load all along and now it is simply overpressure and the speed will tell you that.

 

[Ucsdryder]

Could be a carbon ring. Could be long brass. Could be copper fouling. Could be barrel speed up simply has you at high pressures. I have seen all of these do what you are experiencing. Assuming you don't have a bore scope to tell you if there is a carbon ring? What does the chrono tell you? First thing I would do is chrono the reduced loads you are thinking have you at a more reasonable pressure, my best guess is you were running a pretty stout load all along and now it is simply overpressure and the speed will tell you that.

Gun cleaned up in 5 patches. I ordered a cheap bore scope, we'll see if it works. Brass is trimmed each firing.

I was curious if barrel speed up could cause increased pressure.

 

[Dmagna]

Didn't happen to change powder or bullet lots? I did that once, grabbed the wrong lot number and threw me for a loop

 

[HSmithTX]

Speed up is a direct result of pressure increase. As all the tiny imperfections in the bore are worn down or filled with copper and carbon the barrel seals the bullet better and friction becomes higher, as friction increases so does pressure and with the increased pressure you see the speed increase. With your barrel cleaning so easy and brass trimmed I'd double down on my guess that the chrono will tell you why you are seeing pressure increase. Never owned a SAUM but H1000 isn't known for carbon ring being a huge deal, I would guess that it could be a contributor but I don't think that is the primary cause. You could dope check at 700-1000 and it would tell you the same thing without 'wasting' bullets if you're a magneto user like I am......

EDIT: the lot # is a good point too, I have seen 3% charge weight changes with Hodgdon Extreme powders lot to lot. It's usually 1% or less but good point all the same.

 

[RegionRat]

It is perfectly normal for a good quality barrel to speed up for the first 50 - 150 rounds. This by itself isn't a warning sign.

The borescope is a good idea. Take a look at the edges of the chamber where the case mouth ends and into the freebore and land ramps. If you see a stubborn build up there, do not pass go and clean it up before you re-test.

Ejector marks are one thing, clickers are another. If your brass continues to make ejector marks on the brass, my advice would be to plan to rework the load after you verify nothing else is wrong first.

Also, chambers, brass, and dies need to run coordinated to avoid clickers and functional issues. If your chamber and dies are not coordinated, it doesn't take long to get clickers. My advice would be to get the prints out and study your virgin and cycled brass in detail. Pay particular attention to the diameters. The 200 line should stay at or below 0.5500" and up near the shoulder junction, you can either study the line at 1.450" up which is supposed to be at or below 0.5357" or the shoulder junction itself which should stay at or below 0.5347".

If your brass meets those numbers after sizing, and give you trouble on the next cycle, you may want to consider having the chamber cast to see if your pressure ruined your brass or if the chamber and dies don't like each other. YMMV

 

[Predator 22]

Gun cleaned up in 5 patches. I ordered a cheap bore scope, we'll see if it works. Brass is trimmed each firing.

I was curious if barrel speed up could cause increased pressure.

What are you using to clean your barrel?

 

[Ucsdryder]

What are you using to clean your barrel?

Boretech eliminator.

 

[Predator 22]

I had the same thing happen with my short mag. I ended up having to clean with a good carbon cleaner and a bronze brush. It happens in about 60 rounds on my barrel with h1000. I don't get any copper but have to specifically go after the carbon.

 

[KsKevin]

Chamber dirty and / or brass have any residual lube on it maybe???

 

[7mmTikkaShooter]

I'm thinking carbon ring. I've had similar issues and was able to alleviate with a good cleaning. I'm not sure what everyone here will think of it but I used regular old carb cleaner from an auto parts store and an old brush on a drill. Just gave a good squirt into the end of the chamber and then a quick spin with the brush. Repeated it a couple of times and gave the bore a typical cleaning afterward. Didn't let anything set very long as it was kind of an experiment but seemed to work really good. I don't have access to a bore scope so it's just a guess that carbon ring was my issue and can't speak to how it looked before and after. Gun shoots really good still so I don't think I screwed anything up too bad. Something to think about though is your trim length. I have started to limit how much I trim the brass. I try to stay about 0.005" (was 0.010") under book length for brass now and I'm not seeing any new issues. Pretty sure I was creating the perfect scenario for a carbon ring to start. I should really get a chamber cast done and find a friggin bore scope so I'm not guessing anymore but for now this seems to work.

 

[Blangcfr]

Wow I am going through the same thing with my 6.5 saum right now. My Brux barrel sped up about 100 fps at around 300 rounds.
One thing me and friend thinks is my 8 lb jug of H1000 may have absorbed some moister through humidity that may have made it hotter. Also my cleaning must not have been great, I discovered I had a lot of copper in my barrel, I mostly only clean carbon during cleanings.
My charge of 60.5 running 3080 went close to and over a couple time to 3200.
I have dropped my charge to 59 and am running a 140 berger at 3100 now.
Gun shoots great now with no more pressure signs and same speed I was shooting before, but with a lower charge.
Good luck.