Magnum Forcing Cone Erosion. A Better Way?

[tmanbuckhunter]

It's no mystery to any of us that enjoy shooting magnum handguns that forcing cone erosion is a very real reality. It is most commonly seen with double base spherical powders like W296/H110, 2400, or the most infamous, Lil'Gun. Here recently I've been doing some load development with H-Lil'Gun out of my BFR 44 Magnum trying to get a load I'm happy with for deer hunting. Now, knowing me, I'm still going to settle with my 270gr bullet over Unique moving about 1200fps, but the Lil'Gun is fun to play with, but I'm finally starting to see very early signs of forcing cone erosion. It's just discoloration for now, nothing serious, but it had me thinking.

Accurate has a powder known as 5744. Many are familiar with it, as am I. There was a time where I was burning 8 or more pounds of it in a year. I have load data for this powder for the 44 Magnum and 45 Colt (Ruger/TC/FA only). 5744 is a double base, extruded powder that sits on the burn rate chart not far from W296, on the slower end. Now I reckon, it would probably work better in a longer barreled rifle, but it is not position sensitive and most certainly doesn't require a magnum primer.

What are the odds that forcing cone erosion would be reduced, or eliminated altogether by using a double base, extruded powder to reach magnum velocity and pressure, vs sand blasting it each time with a double base spherical powder. Has anyone tested this? I'll be trying it next time I hit the range out of my BFR. I will try to get my hands on thermal imager to measure barrel temp and compare it to lil'gun.

[MT Gianni]

I think heat figures in as well. It is easy to see erosion happening in a hot barrel, and LG is notorious for heating things up. I have seen erosion with 296/110 but not nearly as much with 2400. No idea how AA9 or others fit in. It is easier to see in revolvers because of the cylinder swing out or being removed than it is in rifles or single shot pistols. I would stick to fining one round every 5 minutes if I were concerned.

[Outpost75]

Surface finish of forcing cone is important because circumferential tool marks provide crevices for powder gases to impact, having lower heat capacity, and thus causing heat checking and erosion. Best is to have smooth, lapped forcing cone in which surface finish is 16 microinch root mean square (RMS) or better.

[wilecoyote]

I wonder if avoiding double base powders by default and adopting single-base powders with a similar burning rate can reduce, if not eliminate, the problem_

[tmanbuckhunter]

I think heat figures in as well. It is easy to see erosion happening in a hot barrel, and LG is notorious for heating things up. I have seen erosion with 296/110 but not nearly as much with 2400. No idea how AA9 or others fit in. It is easier to see in revolvers because of the cylinder swing out or being removed than it is in rifles or single shot pistols. I would stick to fining one round every 5 minutes if I were concerned.

Pressure is more of a killer of a barrel than heat. It takes an awful lot of shooting to get a barrel hot enough to do any serious damage. I think one of the reasons we see so much forcing cone erosion is pressure. For example, 454 Casull operates at what, 55-65,000psi or somewhere there abouts? That's a lot, and that's pushing those granules up against the metal bits very fast, and very hard.

I wonder if avoiding double base powders by default and adopting single-base powders with a similar burning rate can reduce, if not eliminate, the problem_

I also wonder as well. What powders fit that description?

[TurnipEaterDown]

I recut the cannelure on 300 gr Noslers to load at 1.73 inch in the 44 Rem Mag at one time, and crunched in up to 24 gr of XMR 5744.
Performance in my 7.5" Ruger SBH was rather dismal, and recoil was not aggressive (didn't chrono, I doubt it was over 1100 fps).
I gave up on that quick - same as using WC680 stuffed under 300 XTPs at 1.73". Complete lack of performance.

[wilecoyote]

Pressure is more of a killer of a barrel than heat. It takes an awful lot of shooting to get a barrel hot enough to do any serious damage. I think one of the reasons we see so much forcing cone erosion is pressure. For example, 454 Casull operates at what, 55-65,000psi or somewhere there abouts? That's a lot, and that's pushing those granules up against the metal bits very fast, and very hard.


I also wonder as well. What powders fit that description?

I know I'm quite monotonous, not due to lack of imagination but due to difficulty in continuous supply_ double-base 296 was my .44 mag. powder: today it is unavailable, here, but I don't miss it since I've tried the single-base Vihtavuori N110, around 20 yrs. ago_ just saying...

[DougGuy]

LilGun is only really harmful in full house loads like the Casull, but for those of us who use it to hunt with in 44m and 45C where we are concerned with accuracy much more than power, it won't harm the gun at all.

I am using the Lee 310 in 44 magnum, seated long, over 17.0gr of LilGun with WLP primers for 1180-1200 fps. After a cylinder full goes downrange, yeah the gun is markedly warmer than with 2400 or H110 but it groups very well and I don't need any more range time with this load in this gun. I am sure the gun suffered absolutely no damage in the forcing cone or barrel just going 5 rounds getting sighted in.

LilGun earned the reputation it has from much more aggressive loads than your typical 30kpsi Ruger Only loads for a BH or SBH. In these applications, LilGun shines!

[tmanbuckhunter]

LilGun is only really harmful in full house loads like the Casull, but for those of us who use it to hunt with in 44m and 45C where we are concerned with accuracy much more than power, it won't harm the gun at all.

I am using the Lee 310 in 44 magnum, seated long, over 17.0gr of LilGun with WLP primers for 1180-1200 fps. After a cylinder full goes downrange, yeah the gun is markedly warmer than with 2400 or H110 but it groups very well and I don't need any more range time with this load in this gun. I am sure the gun suffered absolutely no damage in the forcing cone or barrel just going 5 rounds getting sighted in.

LilGun earned the reputation it has from much more aggressive loads than your typical 30kpsi Ruger Only loads for a BH or SBH. In these applications, LilGun shines!

Agreed, I really like it. My load for my 44 Magnum BFR IS over book max, depending on the source you look at... two sources its a full grain under max, some it's over. 270gr cast boolit, works well. Velocity out of a 7.5" BFR is about 1460. Whitetail medicine? I think so.

[lawdog941]

I switched over to Enforcer (AA4100) and I4227 for 454. Only problem is little granules of 4227 leftover until I put a heavy crimp and near max load. I really like LG, but the shooting session gets a little hot quickly. W296/H110 is always a good standby.

[243winxb]

Mostly use 296/110 powder. Just lately Unique, 10 grs . All with 250 gr cast swc. Shoot, then replace? Should take many years.

New 44 barrels $275 + fitting. Barrel setback, even less. My 29-2 barrel was set back 2 years ago, instead of replacement, mag-na -ported.

Still looks bad, shoots ok.

[tmanbuckhunter]

Mostly use 296/110 powder. Just lately Unique, 10 grs . All with 250 gr cast swc. Shoot, then replace? Should take many years.

New 44 barrels $275 + fitting. Barrel setback, even less. My 29-2 barrel was set back 2 years ago, instead of replacement, mag-na -ported.

Still looks bad, shoots ok.

And that's half the battle, getting over how it looks. I bet a reamer would clean that right up and avoid setting back for a couple more thousand.