What to check for pressure signs in 610 - Pistolsmith
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Old 05-28-2008, 06:37 PM   #1
 
Join Date: May 2008
Posts: 3
What to check for pressure signs in 610

In my recent run to the range to check aa7 loads behind a 180 fmj, I was reminded of a problem I've seen before....

How the heck do you check pressure in a 610?

My 610 had flattened primers from the starting load of 9.9 gr on. I assume this is because the cases are always thrown back into the receiver.

Well, at 11.1, still had flattened primers, and rounds ejected fine. at 11.4, cylinder wouldn't open. I could see that the last fired round didn't want to leave the face of the firing pin area.

I let it sit for a few minutes, and then poked at the rim a bit and rocked the cylinder. It opened.

Primers were now flattened clean to the brass.

Gun functioned fine after this.

Now, I know I'd call 11.1 gr load max on this gun, and I don't think the 11.4 harmed it (mainly because same load didn't show excessive pressure signs in my glock).


From what I've seen, factory hornady 200 grain loads flatten primers this way, as do corbon and doubletap loads.

So what the heck can i measure to watch for signs? Or do I shoot until I've got primer flow?
 
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Old 06-01-2008, 01:54 PM   #2
 
Join Date: Jun 2003
Posts: 260
The only way I know is to believe the manual -

The only way I know is to believe the manual.

Notice there are some reasons to think pressures run higher in a 610 than in a semi-automatic because the bullet goes barrel shaped in the cylinder gap and the bullet is the squeezed - swaged - back down into the forcing cone and some say the extra resistance into the forcing cone will spike pressure nicely.
 
Old 06-01-2008, 05:17 PM   #3
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Quote:
Notice there are some reasons to think pressures run higher in a 610 than in a semi-automatic because the bullet goes barrel shaped in the cylinder gap and the bullet is the squeezed - swaged - back down into the forcing cone and some say the extra resistance into the forcing cone will spike pressure nicely.
This may be the case, but I haven't been convinced.

Its a long way to the forcing cone, and I would think maximum pressure would have been reached and passed before the bullet even gets there.

Maybe I am wrong. With my 610, I have worked up to the maximum loads listed a couple of times. With my Delta Elite, I can not go quite that high, as cases will start to bulge before I get there.

It doesn't take much to size a bulet down. You could do it yourself with a small hammer just tapping on it.

Individual tolerances between guns could easily differ enough to account for some differences seen.
 
 
Old 08-08-2008, 07:04 AM   #4
 
Join Date: May 2008
Posts: 3
Re: What to check for pressure signs in 610

I'm still looking at this. Just did a #9 load, and had similar results.

Figured out that when the loads start getting warm, the cylinder may not want to open easily... but it's not cases or moon clip binding. It appears to be the ratchet in the center of the cylinder binds. It will spin easily, but when you try to swing the cylinder out, it sticks or binds. I wondered too if this isn't because this is near the end of the test session, and there is some crap on the face of the receiver at that point.
 
Old 10-07-2008, 11:58 AM   #5
 
Join Date: Apr 2002
Posts: 248
Re: What to check for pressure signs in 610

What primers are you using? Mag primers tend to be a bit thicker and don't flow as easily as std primers. Fouling at the end of the shooting session might be part of the equation. I would presume that excessive flattening/cratering are good signs that you are at or over max for that gun. Carefully inspect the primers under a good magnifier to see if maybe the primer flowed into the hammer nose bushing, locking up the action. You should be able to see evidence of cratering and then shearing off of the craters.
If that is the case, back off the the safe level. If you REALLY think you want to go that hot, Back off and substitute a mag primer and work up a new load.
 
Old 10-07-2008, 12:04 PM   #6
 
Join Date: May 2008
Posts: 3
Re: What to check for pressure signs in 610

I do use mag primers.

Factory ammo flattens all primers too... so it's not really a way to judge loads at all.

Like others have said, you won't know it's too hot until it's too late
 
Old 10-07-2008, 12:57 PM   #7
 
Join Date: Apr 2002
Posts: 248
Re: What to check for pressure signs in 610

Somewhat true about being too late on the pressures. I like to look at the primer under a strong magnifying head set. Look for cratering around the FP indent. A raised ring around the FP indent indicates primer flow. If the flow runs into the FP bushing around the hammer nose (Firing Pin) it can lock up the action. When you forcibly open the cylinder it can shave off a bit of metal leaving tell tale signs. If you are already using Mag Primers, I would back down to the load that works. Chrono it and compare it to the velocity of factory ammo.
 
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