I'm finally here ..... Sorry Shadow "Wade" for taking so long after the invite.

[drsjr1969]

So, I get referenced a lot here about my findings chronographing 10mm and 44 mag, but mostly 10mm. My spreadsheet and video's were important to me that they remained uncomprimised with keeping everything exactly the same.
I chose to keep it real world as I call it because most people never modify their handgun at it remains stock in its lifetime so my results would match theirs.

I will soon be starting a new thread based on a new adventure of finding a recipe for loading 10mm carbine/rifle ammo.

Glad to finally be here.

[The_Shadow]

drsjr1969, Glad you decided to join in on the fun here as well.  Your work with the various commercial loads has been a real world look into the window of commercial load offerings.  I have enjoyed your Youtube Vids and spread sheets you shared in the psat.  Therefore I'd like to say thanks to you for your work and dedication to document your findings! 

[Intercooler]

   You were instrumental in me buying my first Chronograph (R.I.P) in search of real 10mm. I knew early on some of the ammo out there just wasn't up to snuff. Your original data sheet has gotten me rolling on testing several different calibers since then. I'm still always searching 

     Hope to see a new video soon!

[MCQUADE]

Very happy to see you here drsjr1969!

[drsjr1969]

In November 2012 I took my carbine deer hunting only to have it Kaboom when I had a deer in my scope. From researching here It looks like the Underwood 200 gr I was using had 800X powder in it. I'm on a quest to find a new powder that will safely give me the same performance.

[The_Shadow]

David, Did the carbine suffer any damage?  If yes...What was needed to repair it?

I was in discussion with Mike Willard (gone but not forgotten) of SwampFox ammo and he mentioned that in the longer barreled guns (6" & longer) that the loads started to show pressure issues on his LongShot loadings using the 200 grain bullets.  We haven't heard of anyone blasting the Underwood 200 grain or 220 grain stuff from the 9" LWD barrels from their G-20's.  This may show issues if the timing and lockup are not in sync.

What I think was happening was the pressure although dropping, the impulse was such that the timing of the cycle changed enough to allow early unlocking but the pressures remained too high as the bullets were still in the barrel.  This caused the brass to be unsupported, thus excessive cases swelling or even to the point of case rupture.

This is why I talk about gun setup, lockup and load impulse.  These semiauto guns are very dynamic, each can be very different in their dwell timing vs. cycling.  With longer barrels the bullet's extra time in barrel has an effect on the timing.

For some machine guns, there could be multiple bullets in the barrel, their action cycling and load choice has to account for this.  The expression "it runs like a sewing machine" comes from, meaning it never misses a stitch!

[drsjr1969]

Wade, yes both the upper ccu from mech tech and the lower glock 20 frame had to be repaired. The case ruptured where the unsupported ramp area is in the chamber. design very similar to a stock glock barrel.

So, my thinking is maybe a slower burning powder would be safer? like maybe No.9 or 2400 or 296 even. I just sent a email to Anthony over at PBR ammo to confirm that they use NO.9 in their 200gr ammo.

[The_Shadow]

The slower powder may help out, but the dwell time for the slide or in the case of the CCU, they need to stay locked and closed just a few more micro seconds to allow the pressure to drop with the higher impulse ammo.  Some guns benefit from stronger recoil spring setups, others not so much.

I have noticed the heavier recoil spring in my G-29 21 was about right for most everything I was loading, however as I pushed the same potential as the SwampFox and UW loads, this increased the slide speeds which showed as brass took off beyond 10'.
Switching to the 23 lb spring (too tough/stout for defensive work) it curtailed the slide speeds back on ejection.

I am not too familiar with how the recoiling/lockup of the bolt in the CCU is handled, and what may help to change the dwell time, other than adding mass to the bolt.  The recoil spring may be of some help...But! This is what MechTech states in their info...

Selecting ammunition for your CCU

There are certain factors to consider when selecting ammunition for use in the CCU's. The CCU is a 'blow back' type action. The main design element in a blow back is the weight (mass) of the bolt. This must be chosen to anticipate the 'hottest' loads encountered. The physics of a blow back action is such that the bolt mass and the bullet weight (mass) work together to limit the amount of the case which is allowed to move out of the chamber while the bullet is still in the bore. When the round is fired two things happen immediately:

1) the bullet begins to move out of the case mouth and up the bore
2) the case begins to move to the rear pressing against the breech face.

To elaborate, the case acts like a piston pushing out of the chamber to the rear and the only thing limiting the amount of movement of the case is the mass of the bolt - contrary to popular belief the recoil spring plays a negligible role in the initial case movement. The real design issue is to limit to a safe value the distance over which the case moves to the rear out of the chamber over the time that the bullet is still in the bore. As long as the bullet is in the bore the gas pressures are high and the case must have sufficient support to prevent case head blow-out or other pressure signs. The bolt weight in the CCU is enough for a good safety margin and as such the ammunition needs to be powerful enough for reliable ejection. 'Target' loads generally are not 'hot' enough. One should use the hotter factory loadings especially in 9mm where a +P loadings are best.