Blowby

Status
Not open for further replies.

jval

Member
Joined
Mar 25, 2004
Messages
83
Location
Florida
I recently started reloading 45 LC and am getting a lot of blowby. I started with 8.0 gr of Universal pushing 200 gr RN lead (med to heavy crimp), then upped it to 8.5 grs. I still get about the same among of blowby. I get the same blowby with 200 gr Jacketed bullet. 8.8 is the max for this combo. Any ideas?
 
What exactly do you mean by blowby? Is gas blowing around and past the bullet and coming out the muzzle? Or do you mean the cases are really dirty on one side? The details matter.
 
If you mean blow back, it's pretty common with the .45 Colt, especially if your firearm has a generous chamber, which a lot of them do. The case is large and thick, and it takes quite a bit of pressure to get it to fully expand and seal the chamber, in particular with lighter bullets. I have several .45 Colt Ruger Blackhawks, and three Marlin 1894CB rifles in that caliber. Unless I load them near maximum, they all exhibit blow back.

Hope this helps.

Fred
 
Your oal is part of the problem. A cut-a-way of a cylinder. Same bullets loaded with different oal's.If you look closely at the top bullet you can see a gap between the nose of the bullet and the throat of the cylinder. The bottom bullet has a longer oal & the nose of the bullet sits in the throat of the cylinder.
cXoGpNh.jpg
The difference is the top bullet/load has to have the case expand to seal the cylinder and the bullet has to move forward to seal the cylinder. The bottom load will seal the cylinder faster which ='s less blow by.
 
A fellow cowboy action shooter struggled for years with blowing in .45 Colt rifles. Using a heavier bullet helped but did not always solve the problem. He tried annealing the brass, too, but some rifles continued to have a problem. He eventually bought a .44-40 rifle. Problem went away.
 
  • Like
Reactions: tcj
Thanks guys, yes I meant blowback, dirty/sooty cases on one side. Sounds like I might have to live with it.
 
I think part of my problem might be that the heavy crimp for my 45 Rossi lever might be too heavy for my 45 SA Uberti pistol since I use the same reloads for both guns. The photo in the cut away above shows no crimp in the bottom round. I typically shoot both the lever and the SA when I go to the range. Next time, I will observe exactly which gun is producing the most blow back.
 
An issue that has forever plagued the .45Colt is oversized chambers. Rifles are particularly bad. Couple that with light loads that don't produce enough pressure to expand the brass and you're going to get blow-by. Seating depth has nothing to do with it.
 
Hmmm. Several different suggestions. Blow-back, blow-by, is from gas escaping around the case mouth/chamber gap. Light loads will not have enough pressure to seal the case/chamber gap and allows gas/soot to flow back on the OD of the case. There are other considerations, but most are rare (doubtful if case length and OAL have anything to do with the sooty case problem). I have a fairly new SAA clone in 45 Colt and have a favorite, lighter load that deposits soot on the case OD, but is a good, fun shooter. I can live with a bit of soot...
 
Status
Not open for further replies.
Back
Top