CM40 breaking in

[aimtrue]

During the break-in of a Kahr CM40 does a heavier or lighter weight bullet foster an easier or faster result?

Or, that bullet weight has no impact on the break-in and it is solely the repetitive use of the springs that promotes reliability?

[hardluk1]

When I broke my 40 in I had some 165gr loads and 180gr. Those are the two I used. Not sure with the 40 if bullet weight makes any difference as the recoil spring is the same as the 9mm. Now there a 124gr seem to work better than 115gr.

Cleaner up well . soften any sharp edges and give her a good lube job and hang on tight !! You might find at around 100 rounds your hand is say'n its break time.

Maybe I am just getting old and weak but that's about all I can control really well during a shooting session in any more with a 40.

Carry a couple brands of ammo at least, don't mix ammo or mags till you know what works well. Some guys mix ammo and mags , have problem and have no idea where to start looking.

[aimtrue]

Thank you for your comments.

I have on hand 300 rounds of Winchester Q4238 180 FMJ ammo and will use this to break in my new CM40.

I have been able to handle up to about 400 rounds of this same ammo during a single session in a larger .40 S&W pistols but think that my limit with the small CM40 might be about 100 rounds or so.

[getsome]

Welcome to Kahrtalk there aimtrue...Bullet weight during break in doesn't matter but stay away from the cheap steel case stuff and stick with some Winchester or other decent American brand of FMJ range ammo and you should be fine...Keep an eye on your magazine followers as there has been some cases of cracked or broken followers in the CM40's and CM9 pistols due to a too long feed ramp but yours may be fine just look at them when you reload and if you suddenly start having feed problems take a peek at the followers....

Keep her clean and well lubed and it should run like a top....Do read the Proper prep of a new Kahr sticky thread in the new member section as there is much good info there as well as a lube chart showing all the places that need a drop of good lube....

Let us know how it goes and if you have any questions just ask away and the many nice and knowledgeable folks here will be glad to help you in any way we can....Good luck and shoot um up!!!

[aimtrue]

Thank you getsome

[otium]

In my defensive pistols, I tend to shoot the same bullet weight in my plinking rounds I plan to carry in defensive rounds.

My preference tends to lean towards the heavier end of bullets commonly available for the caliber in question, 147gr in 9mm, 158gr in 38spl, 180gr for 40sw and 230gr in 45.

For me this is more about trying to keep my POA close to the same. Different weights as well as significant velocities differences can shift things up or down on the target.

Enjoy your new piece.

[aimtrue]

I went to the range today for the first time with my CM40. My apprehension about a difficult breaking-in session proved to be unwarranted. From my reading I had expected tight tolerances and functional failures until at least 200 rounds had been expended.

The tolerances of the CM40 are extremely tight. However, I do not consider this to be a bad thing. To the contrary, I believe the tight slide to frame fit and exceptionally stiff recoil spring make for an accurate firearm.

In any event, I shot 80 rounds each of FMJ and JHP ammunition. A single round failed to load properly. I attribute this to my not properly seating it in the magazine.

The manual indicates that the pistol requires a 200 round break-in period. At first, hand racking the slide was difficult. However, repetitive shooting lessened the tightness of slide movement. By the end of my session, hand racking the slide was no longer difficult for me to do.

Recoil was not too sharp with either the FMJ or the JHP rounds that I used. To be specific, I shot Remington L40SW2B JHP .40 S&W 180gr with a muzzle velocity of 1015fps and Winchester Q4328 FMJ .40 S&W 180gr with a muzzle velocity of 1020fps.

Any thought that the CM40 could be a recreational target gun was soon disproved to me soon after shooting ten magazines. Shooting this pistol is not my idea of fun at the range. The CM40 is what it is, an easy to conceal protector for close quarter’s encounters.

Regarding how the gun functioned this first time at the range breaking it in, as stated, I experienced a single jam produced through my error.

I was accurate at seven yards and could probably print decent kill patterns at even further distances. But, my purpose today was simply to familiarize myself with the pistol and look for problem areas. Next time, I will focus on accuracy.

I used an identity flaw target for my first two 5-round magazines to see about the sights and my hand grip control:

http://i567.photobucket.com/albums/ss112/shepsan/Targets/110713KahrCM407-Yardtarget.jpg (http://s567.photobucket.com/user/shepsan/media/Targets/110713KahrCM407-Yardtarget.jpg.html)


I aimed one round high and one round low to check the front sight. My next eight rounds were scattered in the bullseye. My accuracy with this small pistol surprised me. I did not expect to shoot this well with it. So much for anticipation.

For its primary purpose, I think the small CM40 is a good choice for pocket conceal carry. The cost of the gun is modest and the value apparent.

I see no reason to try other grain weights of ammunition. The pistol handles the 180gr easily and does not give a harsh recoil.

In conclusion, I am well pleased with the design, components and performance of my new small carry gun. In time, I should be able to handle it as well as I have done with full size pistols.

[jocko]

damn ur good,nicepost and nice target

[otium]

Glad yours is up and running and off to a good start.

I'd agree it is probably not much of a target/range gun, but certainly does what it was built to do. I use the 180gr in my cw40 as well.

I like to use qwik grips for a grip covers, but have started using ones I fashion out of a 1.75" inner tube. It helps a bit in knocking down the "cheese grater" effect on my hand from the grip after shooting for a while. Makes it a tad more comfortable for me to shoot at the range.

[RRP]

Nicely written range report, aimtrue. Welcome aboard.

[scosgt]

I bought some Winchester Ranger Law Enforcement 135 JHP from Lucky Gunner. It has two benefits in the CM40.
1. Less recoil, faster back in target. Still makes high velocity .40 holes
And MORE IMPORTANTLY
2. The bullet is shorter, which should lead to less premature slide lock issues.

And on that note:

DEGREASE THE INSIDE OF ALL YOUR MAGAZINES.

I had PSL on my MK9 so often I got rid of it.
I had three in the first 200 rounds on the CM40
Then I got ALL the oil out of the inside of the mags. NO MORE PROBLEMS

The oil on the inside of the mags allows the rounds to push forward on recoil, causing the top round the hit the slide stop on the way up and lock the slide open.

Wish I had figured this out when I had the MK9. It was a sweet gun, but nothing cured the PSL. This would have done it, Kahrs are shipped very wet. Need to remove ALL the oil from the mags.

[muggsy]

If you read the words on the target Jocko is guilty of all of them. :) Welcome aboard aimtrue and enjoy your new toy.

[hardluk1]

Glad your cm40 turn out to work so well , At least till you got to 70 rounds. HA . Nasty little pistol as round count goes up. Good shooters tend to do well with them. Some just can't think thru any problems they may have. Welcome to the club. Now you gota find another one to own !!

[aimtrue]

I went out to the range again yesterday to finish the break-in of my CM40. By the time I sent 200 more 180gr rounds downrange I was quite tired. My hands, arms and shoulders took quite a pounding.

Interestingly, whereas I had only had one jam the first time out with this pistol, this second time I suffered four jams late in my session. It could have been a combination of things but I think that fatigue played a large part in my lack of firm grip during my final five magazines.

The pistol is pretty well broken-in now and I am confident enough to carry it concealed on a daily basis. The reliability factor with regard to my being fatigued after firing so many rounds in yesterday's session will not be a factor if I have to use the pistol to stop an attack in the future.

I am somewhat embarrassed that I have not mastered the take-down to clean and lube the pistol. It seems simple enough but my clumsy hands have not made the job easy. Practice, practice and more practice should resolve this matter for me.

[robert3409]

I hand cycled my CM40 a few hundred times then I went to the range with a mixture of 180gr ammo. I fired Winchester white box FMJ, Winchester Ranger T-Series JHP and even some Ultramax reloads with 180gr JHP. In the year I've had my CM40 I've experienced 0 malfunctions of any kind. It is my dedicated off duty carry weapon. It goes everywhere with me in a JP IWB holster.

[garyb]

I hand cycled my CM40 a few hundred times then I went to the range with a mixture of 180gr ammo. I fired Winchester white box FMJ, Winchester Ranger T-Series JHP and even some Ultramax reloads with 180gr JHP. In the year I've had my CM40 I've experienced 0 malfunctions of any kind. It is my dedicated off duty carry weapon. It goes everywhere with me in a JP IWB holster.

Good way to do part of the break in is to hand cycle it, many, many, many times. It helps to loosen things up a bit. Then wipe it down and relube it. Good point.

[hardluk1]

aimtrue 200 rounds of 40 at one setting?? You da man. I think fatigue does cause many problems. My first time out with my cm9 I managed to wear thru a couple layers of skin before I realized it and that stopped any shooting for a couple weeks before I healed up. I think the say'n , Stupid is as stupid does fits here.

Gota find a round count where you say Enough for today. For me after you know its broke in well and dependable my round count that I fire drops to a few mag fulls of practice ammo followed by shooting up what was in the pistol while carried but shot last if other handguns at taken. Shot the heck out of it when new , then back off to whats needed to keep me in tune with my pistol . I try to shoot a bit ever two weeks with my cc pistols.

[garyb]

I went out to the range again yesterday to finish the break-in of my CM40. By the time I sent 200 more 180gr rounds downrange I was quite tired. My hands, arms and shoulders took quite a pounding.

Interestingly, whereas I had only had one jam the first time out with this pistol, this second time I suffered four jams late in my session. It could have been a combination of things but I think that fatigue played a large part in my lack of firm grip during my final five magazines.

The pistol is pretty well broken-in now and I am confident enough to carry it concealed on a daily basis. The reliability factor with regard to my being fatigued after firing so many rounds in yesterday's session will not be a factor if I have to use the pistol to stop an attack in the future.

I am somewhat embarrassed that I have not mastered the take-down to clean and lube the pistol. It seems simple enough but my clumsy hands have not made the job easy. Practice, practice and more practice should resolve this matter for me.


200 rounds in a session is a lot to handle for anyone. Great cal but with factory loads it is a handful. So much that in a 200 round session... some of your failures may have been you as much as the gun. However, could be the break in too. Who knows. It will loosen up and work like a champ for you. I usually stick to 50-100 of my puffy reloads at a session and that is enjoyable. If you reload, you might try a nice soft load of 165's or 180's on top of a lighter powder charge. If you don't reload....start reloading (for a ton of reasons)....mainly so you can develop a nice custom load for your new gun and enjoy it FAR more on the range. You can develop a nice puffy load that just cycles and feels more like a 9. (Not bashing the 9...just saying that the 40 will be more pleasant on the range and still give you the extra whallop for SD). As for take down...you will very quickly get the hang of that too.. I don't know how much simpler a take down you can get than with the Kahr. I think it is easier to take down than my M&PPro.

Welcome to the Kahr family. Good cal choice.

[jocko]

my 21 cents: tired shooter. cm40 is a handful for 50 rounds let alone 200. Keep ur sessions short .. less costly to. Just sayin.

if alleslefaisl MAGNA PORT thatsucker and realy enjoy it more.

[muggsy]

With the tight tolerances of Kahr pistols it's a good idea to limit yourself to 100 rounds per range session during the break in. Dirty guns with tight tolerances tend to have more problems. Cleaning and lubing you gun between range sessions will help, too.

[garyb]

Good points Jocko and Muggsy. I hesitate to use both of your names in the same sentence by saying we are all in agreement, but it is what it is. Good points.