FINALLY - 5 Underwood 10mm Ammo Disections

[Kwesi]

A buddy has the same gun and regularly shoots his loads of 165-175 grain that chrono 1500-1600.  The CA89-10 with the Hi impulse locking piece installed should handle the Underwood ammo.  My concern is that a round may have been loaded over spec causing dangerous pressure spike.

My 180 gr FMJ loads chrono'd @ 1232 with PP and 1262 with Longshot.  I also chrono'd some factory Georgia Arms Canned Heat 165's @ 1360.  All these were fired in the CA89-10.

I'll look closely at the other cases BUT I fired some of my loads that are mixed in.  All are Starline.

[REDLINE]

I wish we knew what we'll never know.  That is, what were the COL and powder charge weight in that one?

9 or 10 rounds were fired.  It wasn't till the last round was set off that an issue occured.  Coincidence?  Maybe, maybe not.

I agree with 4949shooter in that I also would especially like to have a look at the other fired cases.  This would allow for various other confirmations/insights.

The_Shadow, you mentioned indications toward an unsupported case head concern.  I think there is a possibility there, but not enough information yet to make judgement.

[REDLINE]

A buddy has the same gun and regularly shoots his loads of 165-175 grain that chrono 1500-1600.  The CA89-10 with the Hi impulse locking piece installed should handle the Underwood ammo.  My concern is that a round may have been loaded over spec causing dangerous pressure spike.

I wish we knew, but once they've been fired, there's little way to tell, outside of educated guesses.

I'll look closely at the other cases BUT I fired some of my loads that are mixed in.  All are Starline.

That would be awesome if you could tell which ones were from Underwood and post pics.  Maybe you can tell with some of them by a different residue being left behind inside the cases by the different powders used between UW using 800-X and you using what you did in the handloads?

[The_Shadow]

One other thing I have thought of would be during the extereme cycling di a fresh round suffer a set back issue as it was being chambered?  That would present why the issue occured like it did!

[Intercooler]

 Did you contact Kevin about shooting it in a rifle? He doesn't have any ammo in 10mm classified as rifle ammo. I couldn't do ammo. People are going to shoot it out of anything including home-made firearms.

[REDLINE]

That's a good point The_Shadow about setback during chambering.

I will say though, I had a hard time pulling the 200 grain XTP loads with the kinetic bullet puller.  I'm not sure if Kwesi was shooting those or a 200 grain FMJ load from UW.  But back to pulling the 200XTP bullets, a few times I thought for sure I was going to break the kinetic bullet puller trying to get those bullets pulled.  Multiple full force blows of the "hammer", over and over and over...

I could see a setback issue with a ligher bullet weight, but I'm not so sure with 200gr bullets.  Plus, he has shot lighter bullet loads that should allow for easier setback, though it seems safe to say they were not up to the same load level of the UW loads.

[Kwesi]

Did you contact Kevin about shooting it in a rifle? He doesn't have any ammo in 10mm classified as rifle ammo. I couldn't do ammo. People are going to shoot it out of anything including home-made firearms.

Yes.  I discussed it prior to ordering.  He thought it would be fine.

[Kwesi]

That's a good point The_Shadow about setback during chambering.

I will say though, I had a hard time pulling the 200 grain XTP loads with the kinetic bullet puller.  I'm not sure if Kwesi was shooting those or a 200 grain FMJ load from UW.  But back to pulling the 200XTP bullets, a few times I thought for sure I was going to break the kinetic bullet puller trying to get those bullets pulled.  Multiple full force blows of the "hammer", over and over and over...

I could see a setback issue with a ligher bullet weight, but I'm not so sure with 200gr bullets.  Plus, he has shot lighter bullet loads that should allow for easier setback, though it seems safe to say they were not up to the same load level of the UW loads.

I was shooting the UW 200 XTP's.

[Intercooler]

  You may want to talk to David Sneed he also had a carbine problem with an Underwood.

[gofastman]

I haven't test with the lighter bullets but in conversations with Mike Willard of SwampFox he mentioned the lighter bullets  achieved better results with LongShot than 800X.  However he used LongShot across all bullet weights in his ammo.

I think the 155gr and lighter Swampfox loads were stoked with Win. AutoComp, not Longshot

[The_Shadow]

I haven't test with the lighter bullets but in conversations with Mike Willard of SwampFox he mentioned the lighter bullets  achieved better results with LongShot than 800X.  However he used LongShot across all bullet weights in his ammo.

I think the 155gr and lighter Swampfox loads were stoked with Win. AutoComp, not Longshot

What information leads you to this assumption?

Here is some of what Mike shared on Glock Talk...
Post 07-26-2011, 09:05 #33
It depends on the burn rate. Slower powders burn over a longer period of time.

Comparing a shorter barrel to a longer barrel using, as an example, factory winchester silvertips. I can see that the pressure rises earlier and is topped out by the time the bulet moves about 3.5 inches.

In this case, a longer barrel will not affect the pressure but will achive a higher speed because it is continueing to act on the bullet for a longer time.

If you have a powder that is slower and the pressure is rising through practically the entire length of a 4.6 barrel if you add extra barrel length the prressure will rise higher. This is particularly true with the heavier bullets.

Using the silvertip bullet above as an example. I use a slower powder, one not optimized for a short barrel. If I look at it on a pressure barrel I can see it has not completely topped out at 4.6. My pressure barrel is 8 inches long.

This ammo is capable of 1350+ fps in a 4.6 barrel, but weel over 1400 in a 6 inch. The pressure rises to almost 37kpsi at teh 4.6 mark but is at 38kpsi+ at the 6 inch mark.

In the end, You have two choices when making ammo.

Make it for general use so that it will work pretty well in all firearms, but not great in any of them or you can be specific to the firearm/configuration and acheive greater results for that firearm but can have issues in others.

This was be seen in a recent case where a customer of mine was using my 200gr at 1325fps, that is optimized for a 4.6 barrel in a 6 inch barrel.

Post 08-05-2011, 13:18 #49
I would add that the lighter the bullet the faster the powder can and should be, or more powder compression is needed(speeds up the burn rate) = shorter COL, or a slower powder and a magnum primer to speed the burn for light bullets, typically 135 or lower.

I find that longshot has has a slight advantage over 800-x on bullets in the middle of the weight range for 10mm, and 800-x is slightly better on 200gr and higher.

[REDLINE]

I was shooting the UW 200 XTP's.

Thanks for clearing that up.  It helps a lot toward understanding the bigger picture.

[REDLINE]

Thanks for posting that information The_Shadow.

The only idea I'm not buying into in what you quoted was "pressure is rising through practically the entire length of a 4.6 barrel."  There is no way. 
I don't believe that's true or possible without going to some slow burning rifle powder that wouldn't even work for 10mm Auto.  For that to be the case I'ld expect any 4.6" platform (obviously a G20 in this case) to practially be a literal flame thrower immediately upon the bullet leaving the barrel, well beyond what anyone has ever seen from Blue Dot under virtually any circumstances.

So I also don't believe "The pressure rises to almost 37kpsi at the 4.6 mark but is at 38kpsi+ at the 6 inch mark."  Not with any shotshell/pistol powder anyway.  Not even H110 or 4227.  There would simply have to be waaaaaaaaaaaay too much powder still burning for the pressure to continue to rise from 4.6" - 6" like he said.

Maybe I'm wrong, but I don't think so.  Unless proof surfaces otherwise, I'm not buying it.

My understanding is that pressure spikes sometime in the bullet travel of within the first couple inches of barrel length and goes down from there.  This is the first time I've seen it suggested otherwise.  Like I said, without going to a much slower burning powder than any pistol powder, let alone 800-X or Longshot.

[Yondering]

Redline, I agree 100%. From what I can tell, it looks like Swampfox was doing his own pressure testing, and based on his numbers, I think he messed up the time calculations. Could be just a decimal point in the wrong place, or something more. Regardless, pressure in any 10mm load is not increasing all the way until the bullet leaves the barrel. It just doesn't happen.

We've had this discussion on the Glocktalk forum too, about Mike's claim that longer barrels cause higher pressure. How he arrived at that conclusion I'm not completely sure, but I'd bet it wasn't by testing a long barrel and then shortening it and retesting. I think he was comparing different barrels with different lengths, which also had different internal dimensions.

[REDLINE]

Yeah, it just doesn't add up. 

It's just plain outside of common sense, well, with some understanding of primer(s)/power(s) being lit up within a very small enclosed space acting upon a bullet then moving along some length of barrel, all the while not exploding the platform in the mean time.  In this case, fast burning powders in short barrels within the realm of common handgun cartridges using common bullet weights per cartridge.