A few weeks ago i bought a new Glock 40 for a trip to Idaho to visit family and do some hiking. I've been loading 200gr hard cast Montana bullets for it and have been getting a few fliers. I'm not a great pistol shot so I decided to shoot it off a bag on the bench, still had a few fliers so I decided to slug the barrel. What I found is that the barrel is tight in the middle, in a rifle this is undesirable, but a pistol I don't know.

Anyone here experienced anything similar in a pistol?


Thanks, Justin

Hello Justin and welcome to the forum.

This is not desirable in handguns either.  I have seen this mostly in revolvers (mainly 45 caliber) just under the barrel threads where they screw into the frame but I have seen it in a few 1911 barrels as well.

While I have had moderate success fire lapping the choke point out of revolvers, with pistol barrels, the few times I've tried it, the improvements were slight at best.

I've gotten the best results with fitting a new match grade barrel.  Now, if you don't have the skills to properly fit an oversized match barrel, this can quickly get cost prohibitive as a new barrel alone can easily exceed 300 male deer.

There are several "drop in" replacement barrels.  I only have experience with KKM precision and can say nothing negative about them nor have I heard any from people I know and trust. If you wish to go this route, KKM is what I can recommend.

Hope this helps.

Jeff

Thanks Jeff.

Time is too short for my upcoming trip to get a new barrel. It may be something I may consider later. The Montana's I've been shooting are .401", and that's the major diameter in the tight spot in the barrel. I'll order some .402's Monday and see how they shoot.

I'm going to load some Berrys hollow base copper washed 165's to practice with and work on my skills, particularly my trigger skills.

Justin

My personal cast bullet are sized to 0.4015" and have done well in all of my 10mm firearms to include the Glock factory barrels in the G-20 and G-29

I don't own any Glock pistols but I thought the type of rifling they use is not recommended for cast bullets?

Quote from: 38_Super on June 24 2023 10:32:28 AM MDT
I don't own any Glock pistols but I thought the type of rifling they use is not recommended for cast bullets?

It may be in the notes from Glock, maybe CYA,  but just requires knowledge of what your doing... proper size of bullet, hardness, maybe gas check.

have fired many lead only rounds in my G20... no more leading than any other gun .

Me too, but with more care taken when cleaning. Ultimately my KKM barrel is used most of the time anymore for lead

I cleaned my 40 yesterday after just over 100 rounds, nothing but Montana hardcast lead bullets. There was virtually no lead in the barrel, first I ran a dry patch through, then a patch soaked with Bore Tech Eliminator and let it soak for 30 minutes or so. When I wiped the barrel out there was virtually nothing on the patch. The Montana hard cast do have a brass base so that may have something to do with it.

Quote from: tommac919 on June 25 2023 07:12:03 AM MDT

Quote from: 38_Super on June 24 2023 10:32:28 AM MDT
I don't own any Glock pistols but I thought the type of rifling they use is not recommended for cast bullets?

It may be in the notes from Glock, maybe CYA,  but just requires knowledge of what your doing... proper size of bullet, hardness, maybe gas check.

have fired many lead only rounds in my G20... no more leading than any other gun .

I did a little more research and the issue with lead bullets mentioned was related to the type of rifling used in the barrels causing lead bullets to not engage the rifling well.  Sounds like the latest generation Glocks use a more traditional rifling.

one thing that may help keep leading down is softer bullets.  Not pure lead, but something in the 8-10 bhn range.  They hopefully be soft enough to obturate up after they pass the narrow section.

I'd think a softer bullet would lead the barrel more. The bullets I'm shooting are 22 BHN.

Quote from: 38_Super on June 25 2023 04:44:35 PM MDT
I did a little more research and the issue with lead bullets mentioned was related to the type of rifling used in the barrels causing lead bullets to not engage the rifling well.  Sounds like the latest generation Glocks use a more traditional rifling.

Yes, the rifling is different... polygonal rifling in glocks vs conventional. TMK all glocks use it with some variation of hills/valleys.
The polygonal is supposed to seal better ( smoother barrel cuts ) .

I think the use of reloads and lead were more of a CYA on glock's part to ensure the guns would function all the time..

Either way, it doesn't really lead up more if the right bullets as prev mentioned are used.

Quote from: 1BadDart on June 25 2023 08:28:20 PM MDT
I'd think a softer bullet would lead the barrel more. The bullets I'm shooting are 22 BHN.

Yeah. Bullet hardness is not usually the solution to leading.  More often it is the cause since the bullet can't seal the bore.  The primary cause of leading is the bullet not sealing the bore.  This allows the hot combustion gases (plasma) to escape between the bullet side and the barrel, resulting in leading from melted lead.  Harder bullets don't increase the melting point of lead and if the hardness is the result of a eutectic allow like linotype, it will actually lower it a significant amount.

Back in the day everyone knew that until the bore was sealed, don't even look to the next step.  If the bore is sealed and you still have leading, the next most likely issue is the bullet is skidding in the rifling.  A harder bullet may help here.  As a result, the most common solution was a harder bullet.  But as time went on and common knowledge became less common, all people remembered was dad or grandpa needing a harder bullet to fix leading.  And pretty soon hard bullet became the panacea.

The unique challenge in sealing a barrel that varies in diameter is having a bullet that can also vary in diameter.  To do this you have to have a bullet soft enough to swell back up at the base once it has passed the narrowest part of the barrel.  This would mean you need the pressure to be above the elastic deformation pressure of the alloy, but below the plastic deformation pressure.  Softer allows are more able to vary in diameter and also have a larger "sweet spot" between elastic and plastic deformation pressures.

All that said, this is a very challenging condition and you are unlikely to have great results without a gas checked bullet design.