Shot first .40 S&W reloads... Need advice...

[Idaho45guy]

Was not an ideal range session since I drove 15 miles in a blizzard to get to my dad's range, then realized I had forgot a barrel that I was going to test.

Cast my own 175gr Lee boolits, checked everything out, made sure the OAL was good, crimp was good, used 6 grains of Unique in one load and 4.5 grains of Tite Group in the other.

Pistol was my S&W M&P40 compact. I had read where other folks had bought a factory M&P40 fullsize barrel and dropped it in for an extra 3/4" of barrel and increased velocity. Sounded like a neat idea, so that's what I did. This was the first time shooting the pistol with the longer barrel dropped in, so I brought some FMJ plinking rounds to break it in. I also intended to bring the stock barrel with me which gives me incredibly tight 1.5" groups at 25yds. But, I left it sitting on the kitchen counter...

Got to the range and loaded up a magazine of the plinking rounds and fired away. Barrel locked up. Tapped it forward and fired again. Locked up again. Disassembled and ran break-free on everything. Started running good and I continued shooting until it had broken in. Fired some groups and was not impressed; 3" or so.

Then I loaded up five rounds of the 6.0 grains of Unique. Cycled the slide and it went into battery as normal. Fired the first shot and hit close to where I was aiming, but the slide didn't return to battery. It was maybe 1/8th of an inch to the rear. Tapped on the back of the slide and it went forward. Fired the next four rounds and each one I had to hit the back of the slide to get it to go forward. And the group was awful; didn't even bother measuring it...

Attachment 187071

Then I tried the 4.5 grains of Tite Group loads and had the exact same results with the slide not going all the way into battery and awful group sizes...

Attachment 187072

Since I also got poor accuracy from the factory loads, I'm chalking that up to the failed barrel experiment. But the factory loads had no issues with going into battery, so that is something going wrong with my reloads.

What should I be checking first? My OAL is the proper 1.115 for a 175gr cast boolit...

[plainsman456]

Be sure to do the plunk test with your loaded ammo.

Might be need to be seated a tad deeper.

[rodsvet]

Sounds like the brass was previously fired in a Glock or other poorly supported chamber. I had that problem and bought a Redding bulge buster and de-bulge before sizing and all my rounds plunk now. Don't roll crimp and check your OAL. Good luck with your new barrel! Rod

[reddog81]

No mention of OAL in the post but that is probably the culprit. Your bullets are getting lodged into the rifling. Smacking the slide is fully chambering the round and seating the bullet into the lands. Not an ideal situation for accuracy.

even if you did the plunk test at home you can run into this problem at the range once the gun is dirty or the barrel starts to lead. Bullets that previously can now cause problems.

Sometimes un-sized bullets or too large bullets can cause this problem if you have a tight throat but I'd guess slightly too long OAL.

[Idaho45guy]

Be sure to do the plunk test with your loaded ammo.

Might be need to be seated a tad deeper.

Doh! Rookie mistake... Checked and the factory stuff fully seats but the reloads do not. It seems that the cast boolits are not going to work with my chamber. They are at the perfect OAL and seating them in another 1/16th of an inch is going to increase pressures??

Do I need to go with another design that doesn't have that straight-walled rim for the first 1/16th of an inch?

Attachment 187079

Attachment 187080

Attachment 187081

[Idaho45guy]

Sounds like the brass was previously fired in a Glock or other poorly supported chamber. I had that problem and bought a Redding bulge buster and de-bulge before sizing and all my rounds plunk now. Don't roll crimp and check your OAL. Good luck with your new barrel! Rod

Brand new unfired Starline brass...

[gnostic]

Sounds like a job for 'the bulge buster.' Measure your loaded round in the web area, it may be too large. Can you see where the sizing die stops on a sized case?

[Dusty Bannister]

Did you powder coat those bullets? What is the groove diameter and what is the bullet diameter? When powder coated, the diameter of the bullet is larger as is the nose of the bullet, so a plain lead bullet will still be OK, but powder coated will engage the lands a little sooner. If you know how to use the dowel or cleaning rod method to determine the cartridge OAL, give that a try and see what the cartridge OAL actually is for that bullet in that barrel. The published cartridge OAL is for their bullet in their barrel. If you do need to seat a little deeper, start with the suggested starting load and slowly work up until you get reliable cycling or pressure signs, or the max charge.

If the cartridge is not fully and easily chambering, it will shoot high because it is not going completely into battery. See if the firing pin is centered in the primer cup.

New unfired Starline? Did you full length size when starting?

[MT Gianni]

I have a Kahr that has to have bullets sized .401 and a Smith and Walther that prefers .402. I suspect you may be a little too wide to seat in the barrels throat. I would try an impact slug and set oal and diameter off of that. Both my guns prefer power pistol by a wide margin.

[Idaho45guy]

Boolits are .403 and it slugged at .401...

Easy fix for future boolits...

[308Jeff]

The couple of 40's I've reloaded for have been very finicky about what they like.

What's the weight of that cast bullet? I'd be a little nervous about seating them any deeper. 40 pressures go up REAL quick. Just looked at my load log and all of my 40's have been seated between 1.125 and 1.135.

It looks like you've got a pretty healthy crimp on those bullets. Enough so that if bullets are not oversized (which you've already said they're .401), I'm inclined to think that you are getting hung up on that bullet shoulder, and it's not a conducive design for your barrel.

I could be wrong. I learn something new on this site every day.

[DougGuy]

With that much shoulder sitting proud of the case, it would help IMMENSELY if it had enough freebore to plunk those.. Your barrel would benefit greatly from being throated, this is what throating does, allows you to load to whatever COA you want to, without the boolit interfering in the throat because the throat is too tight when it goes into battery.

ALSO.. And I will mention this, the 40 is already a fairly high pressure round, and if any of your boolits suffer setback into the case when you "tap the slide home" you could be in for a KB and it has happened in exactly this scenario. Boolit gets pushed back into the case, pressure goes through the ROOF, blows the case out and then ignites the top 2-3 rds in the mag and blows it all out the bottom if you are lucky, out the sides and into the palms of your hands if you are not. This ctg and the 9mm are both critical that no setback occurs, in the 9mm, if it is loaded to the max of 35kpsi, just .010" worth of setback can run pressures upwards of 60kpsi.. Not fun.

Pic of Glock 19 barrel after throating, this might be a KKM or LW barrel it is not the factory Glock barrel:



These are LW barrels, on the left is a 10mm barrel after throating, on the right is a 40 S&W barrel for the same pistol that the owner wanted throated long enough that he can load to 10mm COA and use 40 brass:



Next is a Kahr P-45 barrel with polygonal rifling. Kahr is notorious for tight barrels with zero throat, I carry a CW45 that would only chamber .451" and nothing else. It's fixed now too..



I am sure these pics will give you a good idea of what works really well for cast in an autoloader, seating deeper than what load data calls for is just a poor workaround for the real problem, too tight a throat and either zero freebore or freebore slightly too small to function well with cast.

[Love Life]

Doh! Rookie mistake... Checked and the factory stuff fully seats but the reloads do not. It seems that the cast boolits are not going to work with my chamber. They are at the perfect OAL and seating them in another 1/16th of an inch is going to increase pressures??

Do I need to go with another design that doesn't have that straight-walled rim for the first 1/16th of an inch?

Two choices:
1) Seat deeper and do a full load work up
2) Get the barrel throated

I would choose option number 1.

[Idaho45guy]

Awesome advice and knowledge here as always... Thanks guys!

[Idaho45guy]

Going to pull all of the boolits (only have 40 left) and salvage the cases and start from scratch with properly sized boolits this time. I'd hate to mess with my factory barrel since it gives me such awesome accuracy. Might try a different style of boolit mold as well. The new XDS arrives next week, so I'll have to see how tight it's chamber is as well and go from there...

[KYCaster]

So you install a new barrel and the gun malfunctions. You get it to function, but accuracy is lousy with factory ammo.

You try your reloads, gun malfunctions and accuracy is lousy.....

I'd start by looking at the barrel fit. It may not be a true "drop in"....not all that unusual.

Next, I'd take DougGuy's advice and get the barrel properly throated.

Next, I'd take Love Life's advice and determine the proper OAL for your cast boolit, start low and work up a load that works.

Or, do the last two steps in reverse order...load your boolit like you want it then send the barrel (with some dummy rounds) to DougGuy and have the throat reamed to fit your load.

Jerry

[Chihuahua Floyd]

My Kahr likes my Lee 175g TC seated just a tad deeper than a factory ammo OAL. Don't have data as I am out of town, but only had to seat 0.01 deeper.

[runfiverun]

If you have any full diameter sticking out of the case that's probably what's hitting.
seat deeper, drop the load.

I'm running a full grain lower with the T-group in the SIL's 40 using a 180gr boolit.
I had to work the oal down to 100% chambering then work the load up to 100% function.

[Love Life]

If you have any full diameter sticking out of the case that's probably what's hitting.
seat deeper, drop the load.

I'm running a full grain lower with the T-group in the SIL's 40 using a 180gr boolit.
I had to work the oal down to 100% chambering then work the load up to 100% function.

Perzactly, lol.

[Bzcraig]

Two choices:
1) Seat deeper and do a full load work up
2) Get the barrel throated

I would choose option number 1.

This...... Though I chose option 2 because I wanted to be able to try different boolits without having to do the full work up.....Lazy