Weird and interesting 9mm phenomenon

[bcp477]

I thought I'd open this up to the group, as I've pretty much exhausted my ideas on this , at this point.

I purchased a Kahr CM9 several weeks ago. This model, unlike the more expensive Kahrs, has conventional rifling. (The more expensive models, such as the very similar PM9 model, all have polygonal rifling.) As of today, I have put about 360 rounds through the gun.

I hand load all of my ammo, virtually all of it with cast boolits. I've been loading/ shooting cast in my other 9mm's for some time now, so I've worked through most all of the bugs. So, I tried my normal cast loads in the CM9, the first time at the range.

I found that the CM9 is very accurate. In fact, almost scary accurate. For such a tiny pistol, it is ridiculously easy to shoot well, at least for me. Shooting it well required no adjustment or getting used to the trigger for me at all.

However, I noticed from the first time out (with cast loads), that the barrel leaded pretty badly. OK, I thought, either the boolits don't fit (I was using 0.356" diameter, 125 grain, because they work perfectly in my other 9mm's)....or, the loads are too hot... or the boolit alloy is too soft.....or the lube is failing, etc. etc. Curiously, though, the accuracy did NOT decrease, after the barrel began leading. I began by shooting groups as small as about 2" at 12 yards.....and ended the same way (after the barrel had a lot of leading). Hard to believe, but true.

So, since that first range session, I've tried several things. First of all, the load I was using (the FIRST time out) consisted of 3.7 grains of Bullseye (or alternately, 3.5 grains of WST), under a 125 grain, 0.356" dia. boolit. The BHN of the boolits is 12 - 15. That load is by no means hot - rather mild, in fact. I have now tried boolits (also of BHN 12-15) of 0.357" and 0.358" diameter (still 125 grain). I have also backed the load down to 3.2 grains of WST. Further, I have experimented with lubes, trying straight LLA and a mixture of LLA and Johnson's Paste Wax, applied by tumble lubing, over the lube already on the boolits (the boolits are already lubed by the maker when I get them).

As for the results.....
Accuracy is the same as before. Excellent, in a word, especially for such a small gun. As before, the accuracy does not seem to degrade at all, even after the barrel is leaded.

The barrel still leads, although this has decreased somewhat.

Accuracy and leading are essentially the same, whether I am using 0.356", 0.357" or 0.358" diameter boolits. As I said, all three are the same alloy and rated by the boolit maker as BHN 12-15.

Going from relatively light loads (3.7 grains of Bullseye/ 3.5 grains of WST) to really light loads (3.2 grains of either powder) has made no difference.


So, what are the conclusions that can be drawn ?

I have not slugged the barrel, but it seems to me it is unlikely that the barrel is oversized, as it is just as accurate with 0.356" dia. as with 0.358" dia. boolits (in fact, groups may be a touch tighter with the smaller pills).

I have shot the pistol, with the loads mentioned, in both hot conditions (outdoors in 90 degree plus temps)....and indoors, in 70-75 degree temps. No differences were noted. So, I think lube failure is not likely.

As I mentioned, lightening the loads did not get rid of the leading.... so I have difficulty believing that they were too hot in the first place.


What am I missing here ? Anyone have any ideas ? I am not at all unhappy with the CM9, because it seems well made and it does shoot so well, even given the leading problem. I have j-word HP boolits as well, loaded with hotter loads for SD (124 grain HP over 4.8 grains of HP-38), and the pistol loves them. I am starting to believe that the leading MAY be due to a rough barrel (even when spotless, the interior of the barrel has apparent streaks, that appear as if they might be roughness...but I am not sure).

Of course, I will continue shooting the pistol and trying different variations. But, I am at a loss. At least the CM9 is accurate and reliable - so I can't complain too much.

Anyone have any ideas ?

[aspangler]

You may not be pushing them fast enough. If they don't expand to the rifling there may be gas cutting taking place. Try some faster loads and also som softer boolits. I don't know that this is the trouble but it might be. JMHO

[williamwaco]

My thoughts,

Moderate leading has very little effect on accuracy.

Most leading is caused by bullets being too small and or too hard.
Most lube used by most commercial casters fails miserably in light loaded 9mms,
You have re-lubed them and I am sure that lube is not the problem.

I strongly suspect fit and that they are too small.

Pull a loaded bullet and mike it.
You may find that, after loading, it is much smaller than you thought.

[retread]

I think williamwaco is on to it. My SR9 gave me the same fits. I started powder coating to avoid the leading. That worked well but it didn't tell the whole story. I did as williamwaco suggested and pulled some boolits from loaded cartridges, both powder coat and lube and sized. Both were sized to .358. The powder coat miced out at .356 and the lubed measured .354! I modified the powder funnel from a 38 special to work on the Dillon with 9mm which sized the case mouth larger while flaring to mouth. That ended the problem for me. Also turned a bushing for the modified powder funnel so it will still work in the 38 special mode. No out of pocket expense. :smile:

[retread]

One added note: Alloy for the above was 3 to 2 (COWW to Pb)

Jay

[Larry Gibson]

Many times antimonal wash is mistaken for leading. Usually there is no degradation of accuracy with antimonal wash. I suggest you add 2% tin to the COWWs before adding the extra lead. The tin will put the antimony in solution with the lead and alleviate the wash, if that's what the problem is.

Larry Gibson

[Fishman]

I have slugged two Kahr CW9's and they both came in at a hair over .356. I suggest you slug yours as well, as it only takes a few minutes.

[bobthenailer]

I really like Kahrs ! i have 3, a PM9 , CW45 and a TP45 and i shoot cast almost exclusviley for pratice , but before i shot cast i shot around 50+ rounds of jacketed ammo through each before i shot cast .I personaly have nothing negative to say about my Kahrs, there accurate , reliable , have excellent trigger & sights easy to carry and mild recoil for such a small & light weight handgun.
I also have 3 friends who also like the Kahrs and 2 of them have more than one.

[Skipper]

Fishman

I have slugged two Kahr CW9's and they both came in at a hair over .356. I suggest you slug yours as well, as it only takes a few minutes.


+1..............Until you have slugged your barrel, it's all just speculation.

[bcp477]

Interesting ideas. Many thanks to all for the effort.
Of course, I DO need to slug the barrel - everyone is quite right about that. I will get on with that this week.

As for the idea that the load(s) are not hot enough.....I have difficulty believing that. However, maybe that is so - I certainly don't know. I intend to try a bit different tack. One load that my other 9mm's LOVE is 4.0 grains of HP-38, with the same 125 grain boolits as I am using now. That is a bit hotter, but not hot enough to lead those pistols. When working up that load (using my other 9mm pistols), leading started at 4.2 grains. So, I will probably start at 3.6....and work up to 4.0 grains. Maybe the little Kahr will "like" HP-38 better. (A slower powder for a shorter barrel - that IS counterintuitive !) I will also try pushing my Bullseye/ WST loads a bit. What the heck - it couldn't hurt.

As for antimony wash - never heard of it (before). Again, Larry Gibson has demonstrated that he has forgotten more about cast boolits than I will ever know. However, I don't cast my own boolits, I buy them. So, altering the alloy is not doable for me.

I wonder though. IF the boolits ARE too small, then how could I be getting such terrific accuracy from this pistol ? I'm not kidding, the darn thing is like a laser. And, accuracy is terrific, whether the barrel is spotless (as it is at the beginning of each range session).....or dirty and leaded. It really doesn't seem to change. With my other 9mm's, even a little bit of leading destroyed the accuracy. Conventional wisdom (not that I have any of that myself), would seem to indicate that undersized boolits won't produce tight groups. As well, I've tried 0.356", 0.357" and 0.358" diameter versions of the same boolit. No significant difference in accuracy, no change in the "leading" situation. If the barrel is "oversize" (that is, larger than 0.355"), shouldn't the larger boolits produce better results ? Yesterday, after quite a few rounds were sent down the pipe (and I checked the barrel - it looked pretty badly leaded)....I stepped over to a fresh target and proceeded to put 6 out of 10 rounds inside a 2" diameter circle, at 8 yards. I had one "flyer", which I know was my doing. Excluding the flyer, the TOTAL group size was just about 3.5". This was standing/ offhand, NOT benched. The load was 0.356" dia./ 125 grainers, over 3.2 grains of WST.

I just can't see how I could get those results with an oversized barrel and undersized boolits. So, I confess, I am scratching my head until it bleeds (so to speak).

Nevertheless, Skipper is right. Until I've slugged the barrel, it's all guesswork.

To the fishing tackle store (for some soft lead sinkers), Batman !

Thanks again, everyone. I'll let you know what happens.

[Grump]

There's no arguing with accuracy, AFIAC. There's a saying floating about concerning "Believe the bullet."

IF cleanup is not too nasty, I'd be tempted to just live with it for a while, and the search for a less-leading or almost-no-leading or no-leading load would be a lesser priority.

Not to rain on your parade that much, but if you really want to know the accuracy effects, you really need to bench the pistol--at least until you can shoot a 2-inch CTC 5-round group at 25 yards with your best load and handgun standing on your hind legs. I'd be much more confident in your positive accuracy report if it was a 1-inch group at 10 yards--20% farther out than you tested. BUT if that's exactly the same accuracy you got before leading up the barrel, those two data points are indeed useful.

Based on my own experiences with a polygon barrel with a nitrided inside finish (well, the whole darned thing was nitrided), I have a very, very strong suspicion that something about them makes lead want to stick to them almost without regard to alloy or lube. Commercial cast bullets left it looking like a sewer pipe in 50 rounds. They were hard, too. My own cast bullets with ordinary RCBS lube were barely leaving lead after 100 rounds, and gave groups 1/2 to 2/3 smaller than the commercial cast loads and the worst factory loads.

Those Kahr polygon barrels are nitrided, right???

Lemme know, AND please post your slugging results.

Aggravating to have ONE firearm that doesn't behave like the rest, ain't it?

Best wishes on this quest.

[popper]

I didn't have much luck with Recluse or LLA in 40 so just use hi-trek coating for the XDS9 subcompact. 4 HP38 sizes 360 leaded & accuracy @ 7yds wasn't good. Sized 357 was like yours, scary accurate for a 3" SC. Mine slugged @ 355. Leading was hair like at the muzzle, no solder blobs. It was gone when I used proper sized CBs. No lead when I cleaned it, just a couple patches. Look for shaving at the throat. I got a pound of the WST to try, guess I'll be looking at a 3 1/2 - 4 gr.

[bcp477]

" BUT if that's exactly the same accuracy you got before leading up the barrel, those two data points are indeed useful."

I get what you are saying - benching a gun is the only true way to tell. I didn't get that formal, though I probably will make a point of it, in future, to see what the CM9 will really do.
Yes, the accuracy was/is the same. I shot 2" or smaller groups, 5 or 6 rounds (1 magazine), with a clean barrel (spotless, in fact) - at the beginning of the session. Then, as I stated above, 6 out of 10 (2 5-rd magazines) in the 2" circle - with a fouled barrel. Same type of target, same distance, same shooter, same technique. So, yes, those data points are fairly reliable. I wouldn't post them otherwise.

" Those Kahr polygon barrels are nitrided, right???"

I have no idea - but I do NOT have a polygonal rifled barrel. Not all Kahrs have polygon rifling - the cheaper models have conventional rifling. In 9mm, that means the CM9 (the pistol I have) and the CW9. 6 groove, right-hand twist, 1 in 10"....to be exact. Frankly, I was glad to find that the CM9 didn't have the polygonal rifling - I didn't want it anyway, as I wanted to shoot cast in it (and I didn't wish to have any issues with cast related to that).


Lastly, here are my barrel slugging results. I had some time this evening and I found in my stuff a 3/8" oak dowel and a couple of soft lead sinkers. Leftovers from slugging one of my other pistols, almost a year ago. So, I cut down (a portion of) the dowel sufficiently to just fit through the barrel cleanly....and away I went. Lots of oil and a little pounding later, I have a nice imprinted slug.

The dimension, corresponding to groove diameter, based on taking 6 measurements x 2 areas of the slug (toward the front and about 1/3 of the way from the back end), then averaging them....

is just LESS than 0.355". Call it about 0.3547"....near as I can make it out. Yes, that's right - I'm not kidding. Geez - no wonder the darn thing is so accurate. I couldn't quite believe it, so I've done the measurements 3 times. No mistake - the groove diameter is definitely smaller than 0.355". The slug came out without much base deformation at all, but I stayed away from the base and the nose (for the measurements).

So, as I believed, I do NOT have an oversized barrel after all. That both helps - and deepens the mystery. With a barrel tighter than 0.355", 0.356" boolits should be OK. Even 0.357" should work (and I've tried them too). My loads can't be too hot. Obturation can't be the problem, since the barrel is so tight, so hotter loads are probably not the answer. Lube failure is likely not the culprit.

Hmmm.....so what's left ? All I can figure is that the barrel simply doesn't "like" some aspect of my loads. So, I'll try some (more) different loads, different powder, etc. I did notice that the surface of the slug and the grooves corresponding to the rifling lands are a bit rough (on the slug). So, perhaps the leading has mainly to do with that. Putting lots of rounds through the gun should smooth out the barrel, as well. I'll pull some loaded boolits and check them, too. Hard to believe that they might be too small (to work well) - especially the 0.357" and 0.358" ones.

I'm not upset about this matter, really not at all. If the pistol was inaccurate, that would be different. But, as it is, I can definitely live with the issue, even if I never solve it. Heck, I can always just shoot j-word or plated boolits through this CM9.....blasphemous as that may be.

Again, thanks to all. If anyone has any further ideas, I'd love to hear them.

[popper]

groups may be a touch tighter with the smaller pills Same thing I found. If the throat is shaving off the LLA, no lube on the boolit. Now you just have factory lube in the groove, that stuff usually isn't any good. Remove the factory lube, use yours. Try 0.356. I never could get rid of leading in the 40 with LLA or Recluse, no matter what the load. I used MBC lubed, then added LLA, removed the factory and added LLA, still no good. Same problem when I used my cast. Went to PC, then hi_tek - problem solved using either. Never could get the PX4 to shoot anything other than plated well till I changed. The XD almost worked, but I'm not looking back. The hi-tek is easy to use, is inexpensive and works. I don't mind tinkering but I'd rather shoot.
I did notice that when using coated, accuracy didn't get worse when leading did occur (shaved coating when loading, etc.)

[bcp477]

Popper,

I'm not sure that I'm in a position to begin epoxy coating boolits (no facilities for that). However, I might be able to work something out with a friend (who has a nice shop building). Nevertheless, thanks for the input and the ideas. I will certainly put in some more effort with lubes.

As I just said in another thread, the Kahr is the first 9mm in which I've had ANY problems with cast. Up to now, it's been easy (I've been very lucky, I guess). Oh well, it's all a learning experience and at least it's not boring, right ?

[BD]

Brand new gun? I'd put 500 rounds of jacketed through it, then clean it really well, before even starting into the cast boolits. I'm not that familiar with Kahrs, but unless they are polishing the bore after rifling it, it may just need a touch of wearing in.
BD

[bcp477]

Brand new gun? I'd put 500 rounds of jacketed through it, then clean it really well, before even starting into the cast boolits. I'm not that familiar with Kahrs, but unless they are polishing the bore after rifling it, it may just need a touch of wearing in.
BD


You may have hit the nail square on the head. The rough bore (as a cause of the leading) is my current theory, too. The bore of the Kahr IS rather rough - no way that they lapped it after rifling. That is in contrast with the bores of my other 9mm's (a Beretta and an S&W), which are smooth as glass.

The gun is very accurate, the boolits are the right size (and the barrel is NOT oversized), the loads I'm using can't be too hot, the same boolits work beautifully in my other pistols, no real evidence of lube failure...... yet, the Kahr barrel leads.

The rough bore is almost the only possible cause, at this point. Fortunately, this sort of problem will generally work itself out, in time. I have 1000 FMJ j-words on the way . Time will tell.

[Bzcraig]

Tell us what reloading equipment you are using. I'm thinking your rounds are being swaged down in the seating and/or crimping step. I have a Kahr CW9. The barrel slugged at .355, plinking boolits are Lee TL356-124, 3.8gr of Acc #2, with LLA. Excellent accuracy and no leading with ACWW. YMMV

[bcp477]

Tell us what reloading equipment you are using. I'm thinking your rounds are being swaged down in the seating and/or crimping step. I have a Kahr CW9. The barrel slugged at .355, plinking boolits are Lee TL356-124, 3.8gr of Acc #2, with LLA. Excellent accuracy and no leading with ACWW. YMMV



My equipment is mostly Lee stuff, that I've been using for years. I haven't pulled any boolits to check them, as I don't have the right collet for my bullet puller (yet). However, when I measured the outside diameter of the flaring plug from my flare die, I get a smallest dim. of about 0.352" (at the bottom end).....increasing to about 0.366" (at the top). Mid-way up the flare is about 0.355". Trying to measure the inside dia. of a flared case is problematic, but it's the best I can do for now - I get between 0.353 and 0.354 (average).

There has to be some tension on the boolit in the case, of course, when seated. However, I don't know for sure that these dims are correct. But, I can say that, when seated to full depth, I get a VERY minor case bulge (on the outside of the cases), where the bottom of the boolit stops. The boolits I am using are 0.356"/ 125 grain - (and I always mike at least 30 of them, chosen at random, out of each new order I receive). They seem to be very consistent.

I am also crimping as lightly as possible - just enough to straighten the case mouth.

All in all, I have a feeling that the boolits being swaged down is not the problem - but only a feeling. I could easily be wrong. Regardless, thanks very much for the help (actually, someone else suggested the same thing - but I did not do any checking for this until now).

I am certainly NOT dismissing the idea. I will order a 9mm collet for my boolit puller. I may try to pull a few with pliers - carefully - but I'm not sure how that will work out. In any case, thanks for the help ! Sooner or later, the problem will get isolated - and fixed - I believe.

[Jailer]

The diameter of the expander in the Lee dies is only part of the problem. Then length is the biggest trouble when it comes to cast bullets. The short expander plug along with the case taper of the 9mm causes your bullets to swage at the base and the result is gas cutting and leading.

Get a 38 S&W expander plug for your powder through die and your leading problems will likely go away.

http://leeprecision.com/pm-expan-plg-38-s-w.html

[41 mag fan]

Got a picture of the patches you used to clean the with? Or the barrel after shooting?
Never heard of any gun that leaded where accuracy was not affected.
I'd have to agree with Larry on this, antimony wash

[bcp477]

No, I have no such photos....and no good camera with which to take them. Larry could be right - I can't be sure. I always apply a little bore cleaner to a brass brush and scrub out the barrel, while it's still hot, at the range after shooting. I get little flecks of "silver metal" coming out of the muzzle, when scrubbing it at the range. Also, the deposits in the barrel, certainly appear to have some thickness to them. They are not shiny, but rather rough looking and silvery in colour. As for the patches used for cleaning, the deposits come out as (again) little flecks of silvery metal.
Whatever is left in the barrel, when giving it a good cleaning at home....is hard to remove.

So, I don't know. The fouling may be just "antimony wash". Whether that or actual leading, it doesn't seem to affect accuracy - so my concern with this problem is not overwhelming. I would like to find the cause and control it, if possible though.

On the theory that the rough bore might be the cause, I intend to put several hundred j-word boolits through the barrel in the near future....and suspend shooting cast in it for now.


Jailer,

Very interesting. I have to say that your theory (or assertion as the case may be), makes a lot of sense. Gas cutting at the boolit bases.....hmm. Certainly would be well worth a try (the 38 S&W flare plug). Thanks for the idea !



Finally, a few words about today's range trip (I just got back a short time ago). I shot two loads this time out : 3.7 grains of HP-38 with the same 125 gr. TC (BHN 12-15)/ 0.356" boolits as before......and 3.9 grains of HP-38, with the same boolits. I reduced the crimp I used to the barest minimum. The pistol "likes" the 3.7 grain load very much - excellent accuracy. It was slightly less so with the 3.9 grain load. As for leading/ antimony wash, it was substantially less than before.

The different powder may just be incidental. If the bore roughness is causing the deposits, then it may be getting smoothed a bit (as I now have almost 500 rounds through the gun - mostly cast). HP-38, being slower than Bullseye and WST, might be giving the boolits a bit more sedate launch (leading to fewer deposits). I don't know. But, accuracy is still terrific, the pistol is absolutely reliable (so far) and I can't say that I am anything but pleased with it.

I'll see what happens after I put the j-words through it.

Many thanks for all the good ideas and everyone's effort on this matter ! I really appreciate it.

[bcp477]

A small follow-on update. I just finished cleaning up the CM9 a few minutes ago, after today's trip to the range. The deposits (lead or antimony - whichever they are) were much less than last time out. They were also quite a lot easier to remove. After the normal routine with Hoppe's, to remove the non-metal deposits, I ran a couple of tight patches through the barrel, with bore paste smeared on them. The deposits came out without much trouble. They still appear (on the patches) as little flecks of silvery metal.

After completing the normal cleaning routine, I ran several clean, tight patches, smeared with bore paste, back and forth through the bore - 50 passes each. Then, cleaned up after. The interior of the barrel now appears smoother and quite shiny, even before oiling. I can't be absolutely sure, but the striations in the barrel may be getting smoothed out already. That might be misleading, though. If the leading/ antimony problem continues to decrease with each range trip (as well as the ease of cleanup continuing)....then I think that will prove that I'm on the right track.

I inventoried my unfired ammo, brought back from the range.....and it looks as if I shot over 200 rounds today (I didn't think it was quite that many). So, in actuality, I now have nearly 600 rounds through the CM9, albeit almost all of them cast.

The range will be open tomorrow....and I'm free. So, I may go again.

[kweidner]

My guess is there might be a slight bbl restriction. Does this appear the full lengthnof the barrel or after a certain point?

[41 mag fan]

Thats where slugging the barrel would help to feel if theres any restrictions.

[bcp477]

The "leading" appears just ahead of the chamber and does not extend to the muzzle. It is irregular and never uniformly covers the whole bore. It usually inhabits the grooves between the rifling lands, for the most part. The grooves, by coincidence, seem to be the roughest areas in a pretty rough bore.

As for slugging the bore - we're way past that. There is no detectable barrel restriction.

As I stated in my previous post, the leading has decreased in amount - and is easier to remove than before. Further, the rough bore appears to be smoothing out. So, I am fairly confident that the problem is really due to roughness in the barrel - and will therefore go away (or mostly go away) on it's own. In furtherance of that, I intend to shoot only j-words through this pistol for at least the next few hundred rounds. Then, I'll try the cast again.

[bcp477]

OK, one last follow up. I stopped shooting cast in the CM9, for the time being. I've now put around 300 rounds of j-words through it, using a generic load (3.5 grains of Bullseye). The formerly rough barrel now looks smooth as glass.

So, last trip to the range, I brought out the cast again. Shot several loads - 4.0 gr. HP38/ 125 grain TC.....3.5 gr. Bullseye/ same boolit.....3.5 gr. WST/ same boolit.....3.7 gr. Bullseye/ same boolit. No leading whatsoever. Accuracy is as was before.... truly excellent !

I also took a look, during the interim, at my setting, with my Lee FCD die, on the theory that I might be over-crimping. In short, I believe that I was. So, I reset the die for the lightest possible crimp - really just straightening the case mouth, more or less.

So, in the final sum-up..... I believe that the problem with the Kahr was two-fold. Namely, a rough barrel combined with my over-crimping the loads. Nothing else made any sense, as the barrel is nice and tight (smaller that 0.355") and the 0.356" dia. boolits worked beautifully in my other 9mm's (both with 0.355" barrels), as well as in the pistol in question. Accuracy was never an issue, only the leading problem.

As the leading problem has now vanished, with the same loads as before (and the same boolits as before)..... and accuracy and function are still spot-on..... I consider the problem solved.

Many thanks to all that made the effort to help ! I am a happy man today !

[Rainier]

Congrats! bcp nothing like the feeling of finally sorting out a "problem" shooter. A rough bore can drive you crazy looking for a half dozen other variables - Rainier

[ironhead7544]

On a new barrel, I have been using J-B first for many years. There is generally a lot of gunk left in the barrel after the manufacturing process and firing over that can rough up a bore.