Jump to content
Brian Enos's Forums... Maku mozo!
Sign in to follow this  
racer-x

Correlation between 9 major and slide cracks?

Recommended Posts

Last week, I discovered a crack in the ejection port of one of my open guns (9 major). The crack originates in the top, front left corner of the ejection port and travels straight down the left side of slide about 9mm. I recently heard of another 9 major open gun that developed a crack in the exact same spot.  Neither of these 2 guns ever made it to a high round count.

This gun was running a new 9# recoil spring with an ejection distance of only 5-7' (low slide velocity). I've used mostly 124's with around 800 115's most recently this summer. I carefully worked up loads that never exceeded 174PF using True Blue in the beginning and switching to Winchester Auto Comp this summer. OAL's of all loads have been 1.165" and primers have minimal signs of high pressure. Never ran the gun much over 200 rounds without cleaning either and always kept very well lubed.

 

Has anyone noticed a correlation between slide cracks and 9major? As opposed to 38 super or SC? 

Anyone else ever see a crack develop in this location?

 

IMG_0626-3.jpg

Share this post


Link to post
Share on other sites
53 minutes ago, racer-x said:

Last week, I discovered a crack in the ejection port of one of my open guns (9 major). The crack originates in the top, front left corner of the ejection port and travels straight down the left side of slide about 9mm. I recently heard of another 9 major open gun that developed a crack in the exact same spot.  Neither of these 2 guns ever made it to a high round count.

This gun was running a new 9# recoil spring with an ejection distance of only 5-7' (low slide velocity). I've used mostly 124's with around 800 115's most recently this summer. I carefully worked up loads that never exceeded 174PF using True Blue in the beginning and switching to Winchester Auto Comp this summer. OAL's of all loads have been 1.165" and primers have minimal signs of high pressure. Never ran the gun much over 200 rounds without cleaning either and always kept very well lubed.

 

Has anyone noticed a correlation between slide cracks and 9major? As opposed to 38 super or SC? 

Anyone else ever see a crack develop in this location?

 

IMG_0626-3.jpg

Mine cracked. STI replaced the slide as far as I know.

Share this post


Link to post
Share on other sites

soemone told me that a 9mm major slide is like a D/Q. its not will it crack, just when.  some builders consider them consumables and won't warranty it .   

Share this post


Link to post
Share on other sites

STI replaced a friends trubor 38sc same spot and another on a Dvc 9 major on the top where the lightening holes are. 

Share this post


Link to post
Share on other sites

Yes, this is an STI slide.

Appreciate the feedback guys. I sent it back to STI today.

Share this post


Link to post
Share on other sites

Do you use recoil buffers? They help big time to keep cracks from happening by softening the slide slamming into the frame. I use the poly ones in my 9 major gun, it is also tri-topped with about 5k rounds after the tri-top and probably over 15k before. 

Share this post


Link to post
Share on other sites
29 minutes ago, MrPostman said:

Do you use recoil buffers? They help big time to keep cracks from happening by softening the slide slamming into the frame. I use the poly ones in my 9 major gun, it is also tri-topped with about 5k rounds after the tri-top and probably over 15k before. 

Any opinion on the poly vs say the dawson aluma buffs?

Share this post


Link to post
Share on other sites

In my opinion the poly is the better choice, the aluminum is softer than steel but it still allows quite a bit of force to be transferred since it is still solid. The poly ones compress which helps dissipate most of it. They may not last as long but a pack of 6 is like $5, which is very cheap insurance. Plus since they compress the recoil stroke is not shortened as much verses the aluminum buffs.

Share this post


Link to post
Share on other sites
On ‎10‎/‎4‎/‎2016 at 6:54 PM, js1130146 said:

Any opinion on the poly vs say the dawson aluma buffs?

I've run Poly for years, but decided to try the aluma buff from dawson.  Never had a problem with the poly ones in my open guns. After about 100 practice rounds there were numerous tiny aluminum shavings or chips inside the gun.  I've gone back to poly.

Share this post


Link to post
Share on other sites
On 10/4/2016 at 11:41 PM, MrPostman said:

In my opinion the poly is the better choice, the aluminum is softer than steel but it still allows quite a bit of force to be transferred since it is still solid. The poly ones compress which helps dissipate most of it. They may not last as long but a pack of 6 is like $5, which is very cheap insurance. Plus since they compress the recoil stroke is not shortened as much verses the aluminum buffs.

Brand? Source? How often do you swap them out to be safe?

Share this post


Link to post
Share on other sites

I use the Wilson brand buffs. 

http://www.shootersconnectionstore.com/Wilson-Shok-Buffs-P624.aspx

I have had the same one in my gun for the last 2K rounds and it is still in good shape, I will probably let it go one more K and then swap it out for a new one.

Some guns will chew them up faster than others depending on the condition of the steel parts that they are sandwiched between. I just check it everytime I clean the gun which is after every match.

Share this post


Link to post
Share on other sites

your mixing stuff guys

shockbuff, wont help high chamber pressure, if thats causing it. 

Proper load, powder, etc will massivly differntiate. my load is within regular 9mm pressure I load superduperlong with 3n38. 2 hybrid holes. 

174PF, hybrid, autocomp, 115gr.. now thats some pretty hefty shit on general basis, but without knowing the specifics, we cant really comment. 

Share this post


Link to post
Share on other sites
2 hours ago, ano said:

your mixing stuff guys

shockbuff, wont help high chamber pressure, if thats causing it. 

Proper load, powder, etc will massivly differntiate. my load is within regular 9mm pressure I load superduperlong with 3n38. 2 hybrid holes. 

174PF, hybrid, autocomp, 115gr.. now thats some pretty hefty shit on general basis, but without knowing the specifics, we cant really comment. 

I agree that the crack up there may well be caused by excessive pressure and/or an unlocking timing issue (likely unlocking too early). 

when the round is fired you want the gun to stay in battery and then slide and barrel to move together and not start to unlock (link down) until the pressure has dropped. if it's unlocking too early you get damaged top lugs from all that pressure, or possibly damage the slide.

but as mr postman suggests it could also be excessive slide speed causing a nasty hit at the end of the rear slide travel that then causes a crack to start where there is a stress riser.

It could also just be a faulty slide...

shockbuffs do seem like a reasonable idea. I run one on my 2011 major pf pistols. I've used the wilson ones, egw ones and some clear ones (I think perhaps older wilson?). I also tried the dawson alumabuff. I didn't mind it but it did get a couple of small burrs on it. when removing the top end off the gun if the guide rod head pops down off the lower lug (which often happens as you're sliding the slide forward) the alumabuff would kind of drag along the bottom of the dustcover making the slide harder to remove (and that caused the little burrs on it). I certainly didn't get any shavings or chunks but the removal issue was enough for me to just go back to the polymer wilson ones. 

Share this post


Link to post
Share on other sites

Slide velocity is very low, even with a 9# Wolff variable recoil spring (confirmed at slightly over 9lbs at full slide travel).

"This gun was running a new 9# recoil spring with an ejection distance of only 5-7' (low slide velocity). "

 

Regarding the load, I played with 3N38 and 124's for a while in 9, but it was so messy to load even with a powder ram. I ran that load at 1.195 until I had a bullet fall out of case in magazine while shooting... Dropped down to 1.185 with 124's and never had that happen again. 115's need to be loaded a little shorter since there is less bullet to mate with case. 1.165 seems to be a good compromise OAL for MG 115 JHP's in 9 major. Long as possible, but still enough in case to be reliable. 

The only way I have to gauge case pressure is by looking at primers after being fired. The primers after these WAC-115 load are slightly flattened, but not extreme at all.

My 38SC primers don't look much different with a similar PF load, 1.250 OAL and 115's.

Seems like either using primers to gauge pressures is an ineffective measure (probably) or there is another stress component of the firing cycle that accompanies the much smaller case volume. Maybe the frequency of the pressure spike is more destructive with the slightly faster burn rate powder and smaller case volume .

End wild speculation  :) 

 

 

Share this post


Link to post
Share on other sites

I had a used open gun crack the slide from the left rear corner of the ejection port. My gunsmith said that happens due to the stretching of the slide every time a round is fired. The highest energy event is when the gun fires, The case slams into the bolt trying to get the rear portion of the slide moving even though it is still in battery. The ejection port is the weakest part of the slide to have to withstand the rearward force. Once the slide is moving and dumping energy into the recoil spring, the forces are reduced. the buff probably helps some but the main event is firing.

This was a Caspian slide by the way. My smith said that he has seen no pattern of a particular brand slide cracking.

Later,

Chuck

 

Share this post


Link to post
Share on other sites

I run a 7lb recoil spring and 17lb hammer spring in my 2011 open gun, so the slide has plenty of velocity going back and less going forward so the muzzle doesn't dip, as verified by doing some slow motion video.

Now the notion of the slide stretching is possible and it would of course stretch in the weakest area which would be in the ejection port, but if you take into account where the forward frame rails are located, and then imagine the bottom of the slide hitting the inside of the frame, then that would cause stress at the top of the slide because the impact is at the bottom.  

The bottom impact would cause the top portion of the slide to bend downward ever slightly in the area between the frame rails, which in this case will be the ejection port area due to it being the weakest area structurally.

After enough cycles every slide will eventually crack, even using the buffers, but using a buffer in theory should prolong the life of the slide by absorbing most of the impact force. 

The Glock slide is no different than the 1911/2011 due to the frame rail locations, the only gun that I haven't seen this happen on is a Tanfoglio or CZ due to the frame rails being inside the frame and usually the same length as the slide. 

Just something to think about.....

Share this post


Link to post
Share on other sites

Ah well there you have it, thanks for sharing that. How many rounds on the gun before the crack?

Share this post


Link to post
Share on other sites

don't know this for fact... but.. someone told me that shooting 115's versus 124's is more damaging to a slide on a major gun... 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...