Bullet tumble, etc.

[mjt]

I have read several threads here that addressed the issue of bullet instability, tumble, etc. and there is debate about how much this matters.  It seems that the main concern is whether the bullet penetrates and does the damage that a 9mm round should, or whether the instability compromises the effects the round has.  This seems like a question that could be addressed empirically.  It would be interesting to compare the penetration of these bullets against that from other bullets fired out of similar caliber guns or even smaller caliber guns (for example, what is the penetration of the standard 9mm out of the Rohrbaugh vs. the penetration of a .380 fired out of another pocket pistol, a +P .38, etc.).  

One way this might be settled is with some comparison gel or wetpack tests in which these rounds are compared.  Has anyone seen this kind of test anywhere?  

[R9SCarry]

All my tests (accessible thru some links on FAQ site) were short range wet pack.  Main interest was bullet performance thru different varieties.

I agree some longer range comparisons plus different cals would be well interesting.  Trouble is - well for me - the time it takes to set it all up.

Even on shorter range wetpack tests, there some examples of recovered bullets where ''peel back'' was either incomplete or asymmetrical - suggestive of tumble perhaps.  Forget details without checking.

However - let's think short range again here re defensive use .... the recovery depth of the poorer examples was IIRC very close to that produced by the near perfect examples like Gold Dots.  They DID DAMAGE!!

We may worry about penetration - maybe too even be concerned whether our std pressure 9mm's will in fact expand at all (clothing issues).  Then too - some folks worry about over penetration too with 9mm!.

So where does that leave us?

For me - it leaves me knowing that even if I have a slight tumble, the prejudicial effect on accuracy and/or damage production is gonna be small.  Remember as I keep stressing - CLOSE range - by which I'll place the limit at 7 yards.

If at a later time, there is some change in the gun's design that can eliminate this then great - but meanwhile I am not going to concern myself overly.  

I see some necessary compromize in design within the R9 - one reason as I see it, for the large freebore - the root of the problem.  Perhaps an advance in material spec's one day might just permit a reduction in said freebore - because of chamber pressure tolerance being higher - we'll see.  Meantime, I accept what I have.

Incidentally - at a shoot on Saturday - coupla folks tried the R9 - and with basic WWB FMJ - at about 7 to 10 yards - I saw no tumble evidence in approx 18 shots.  I think ammo OAL is a major factor - increasing or decreasing the ''jump''.

[dmobrien2001]

All my tests (accessible thru some links on FAQ site) were short range wet pack.  

Incidentally - at a shoot on Saturday - coupla folks tried the R9 - and with basic WWB FMJ - at about 7 to 10 yards - I saw no tumble evidence in approx 18 shots.  I think ammo OAL is a major factor - increasing or decreasing the ''jump''.

[R9SCarry]

No idea if any difference in factors - but Saturday was #2 R9 and - of course - a totally different batch of WWB.  Tests on FAQ are from #1 R9.

Not looking to explain difference but as I said out of 18 shots on paper - I could see none that showed other than clear round holes.!  That was fact!

[dmobrien2001]

Well, I'm calling Rohrbaugh tomorrow and register my concern.  I've got two 50 round boxes of Win 115 STHP ordered.  When I get it, I'm going to the range with some white paper plates and document every kind of ammo I have on hand and I have quite a few different types (unfortunately mostly 147 grain which is damn fine SD ammo in std pressure form!  Ya, that's a sore point with me!)

I'll send you some Gold Dot 147 and some more Win Ranger T 147 for your #2 gun to try if you are so inclined.  The heavier rounds seem to exhibit it more.

Oh, right, I forgot. I wasn't going to post on this anymore.  

[R9SCarry]

If I can - I will try and run another test - leaving out the wetpack aspect which is very time consuming but - just some shooting of paper to get some more data.  I have some 135 Hydrashocks left - just a very few, but nothing heavier.

Quite a few Blazer 115's I kept aside and some Gold Dots too - again 124 heaviest.  That's about it right now.

[dmobrien2001]

See my other thread where I didn't post, just made notes. http://www.rohrbaughforum.com/YaBB.cgi?board=R9S;action=display;num=1116641383;start=24#24

The tangle web woven is becoming unravelled.

The ammo with the lightest weight and longest OAL out to stablize the best. Longest OAL alone isn't enough.  Bullets under 115 grn are likely too short. 124 GD could very well be the sweet spot.

[Richard S]

I have found a 9mm pistol which I can almost absolutely, positively guarantee will not be likely to "tumble" its bullets.  It can be had for the paltry sum of $3,750.00, and even comes with a flap holster for those who do not prefer the option of pocket carry.  

Without further ado,   here it is:

http://www.collectorsfirearms.com/pr4551.htm

[R9SCarry]

Hehe Richard - that's a given, and with that length barrel, well - just the prob of concealment!  Oh and - financing!

[USGuns]

FYI - This is probably old news here, but;
I read a Gun-Tests review of the R9s vs. PM9 and they seem to think the tumbling is due to insufficient rifling twist rate:

http://www.kahr.com/review_gtc_0804.html
"Unfortunately, we had other problems with the Rohrbaugh. We noticed clear indications of bullets striking sideways at a range of 10 yards, with all three types of our main test ammo. There were two partially sideways strikes with Speer’s Lawman, one with PMC’s FMJ, and two with Winchester’s BEB ammo. In most cases the tipped bullet struck well away from the main group. We noticed the Rohrbaugh’s 3-inch barrel had, visibly, about half the twist rate of the Kahr’s barrel. This undoubtedly led to insufficient stabilization of the bullets, and resultant sideways bullet strikes. We guess the low twist rate was used to slightly diminish felt recoil or twist in the hand. But we’d rather have a bit more twist and kick to the gun and have all our bullets strike head-on, particularly those that are designed to open, which must at least strike head-on in order for that to happen. There are no guarantees a firefight will take place at ranges where accuracy just does not matter, so we always prefer all the accuracy we can get."

[dmobrien2001]

FYI - This is probably old news here, but;
I read a Gun-Tests review of the R9s vs. PM9 and they seem to think the tumbling is due to insufficient rifling twist rate:

Yup, old news. Rohrbaugh's "rebuttal" isn't very convincing.  I took some "measurements" and the "industry standard" for 9mm doesn't seem to be 1:16.

http://www.rohrbaughforum.com/YaBB.cgi?board=R9S;action=display;num=1116641383;start=24#24

PS: I called Maria today. She's going to have Karl call me back sometime today.  She mentioned something about me having an "early number" and "possible changes in production"... If it wasn't for Chris's second gun not keyholing WWB, I wouldn't give this much hope.

PPS: Maria called back. She talked with Karl (who is the main guy these days at the plant) and he said, "Early serial number gun, hmm, have him send it back, we made some tweaks since then."  I post again AFTER it gets back in a couple of weeks (I'm guessing).

[dmobrien2001]

Very interesting that the "earlier" models have this tumbling isssue...

What number is your Rohrbaugh? I have #531 and have also had problems w/ tumbling--i wonder how far back (or forward) this issue runs...?

R157

it was an early number (Feb '05), but a late delivery due to as Maria said "anodyzing problems".

[Richard S]

I am the proud owner of R9s No. 132.  It doesn't "tumble" its bullets.  It doesn't "keyhole" its bullets.  It has always made neat, clean, precise, round 9mm holes in its targets with the various ammunition types I have fed it -- Gold Dot (115 & 124), Golden Saber (147), and the ubiquitious Winchester "White Box" (115).  

I have not yet (thank God!) had to use my Rohrbaugh to shoot anything which was shooting back at me.  However, reflecting now upon my life from the vantage point of my seventh decade, there are at least two occasions -- both back in what Joseph Conrad once described as the "Heart of Darkness" -- when my survival might not have been so much the result of pure luck if I had been able to have a Rohrbaugh in my pocket.

RS

[dmobrien2001]

I am the proud owner of R9s No. 132.  It doesn't "tumble" its bullets.  It doesn't "keyhole" its bullets.  It has always made neat, clean, precise, round 9mm holes in its targets with the various ammunition types I have fed it -- Gold Dot (115 & 124), Golden Saber (147), and the ubiquitious Winchester "White Box" (115).  

Excellent. There is hope, then, that mine will also when it gets back from its little visit back home...  GS 147 are some of the best rounds I have tested in my old Kahr PM9, BTW. I use Win Ranger T 147 because I could get a case of them cheaper (but it is also a good SD round).

[dmobrien2001]

Excellent. There is hope, then, that mine will also when it gets back from its little visit back home...  GS 147 are some of the best rounds I have tested in my old Kahr PM9, BTW. I use Win Ranger T 147 because I could get a case of them cheaper (but it is also a good SD round).

Interim news.  Sent in via FEDEX Overnight to factory on 6/1.   Per Maria it was evaluated by Karl and others at an offsite range and the fix is to "run a new barrel on the machines when the current run is finished..."  It will likely be next week before I hear anything else.

Now that I type this I'm confused why they need to setup the machine different to run a new barrel for my pistol?  Thoughts?

Perhaps there is a later overall design change and my early serial number gun requires an early style barrel (with whatever magic they've done to straighten out the keyholes -- more twist? less freebore?).

Others?  I'll ask Maria next week.

Gee, I miss the little fellow.  I'm tired of running around with this BLOCK 26 IWB...