Blow back

[100yrdopenchamp]

I formed 30/06 brass to 7.65x53 Argentine formed then annealed loaded 167grn cast coated from 18-20 grns of imr 4198 and felt chucks hit my face cases are all full of soot accuracy 3-4" at 50yrds but I would get one 6" flyer. I have been loading since the 60s but never loaded cast bullets it sure is different just signed on last week hope I'm doing this right.

[EDG]

Review your load data to see if it can be boosted a grain or 2 to raise the pressure. Slightly higher pressure might make the case necks seal better.

Tilt your muzzle upward to make the powder settle back against the primer.

[Outer Rondacker]

100yrdopenchamp welcome to the addiction. Many here will jump in to help out with any issues you have. Might be a bit slow since the holiday weekend but shortly after the answers will come.

[Rcmaveric]

second double checking the load manual. Sounds like low pressures caused the cases not to full swell and seal the bore also resulting in a dirty burn. I have never been hit with anything in the face. But i have had soot leak into my chamber and dirty ignitions while experimenting with uncharted powders. Sometimes increasing the charge will cure it or try another listed powder. Looking at my Cast Bullet Handbook i don't have a 167 Gr listed, but it does have the 170 listed and you get several grains to go before ma.

[john.k]

A simple cure is to flare the case neck for the cast bullet,and leave the flare.It will size to neck dia as its loaded,and seal the gases while pressure builds up.Unless the chamber neck is hopelessly oversize,which can happen in old milsurps.Another simple cure is to make your reformed case slightly long in the shoulder,and it will seal there as the bolt closes and forces the metal contact.Even in a 91 Mauser,you shouldnt get gases in the face....some other rifles ,yes.

[shaggy357]

Which bullets? Shooting .308 bullets in a .312-314” bore can do that also.

[rbuck351]

I would think switching to a faster powder such as red dot or unique would fix this.

[RickinTN]

It is best to have your cases well fireformed in the rifle you intend to shoot them in before loading and shooting cast. Many of our loads won't form the cases to the chamber and If you reach high enough pressure to do so you most often have exceeded the strength of the lead bullet. Fireform them well with jacketed bullets and then only neck size for your cast loads. Your blow-back, or blow-by will probably go away.
Good Luck,
Rick

[EDG]

One important factor for getting a good case seal is the proper anneal of the case mouth and shoulder.
When you shoot a work hardened case it takes more pressure to expand the case to make it seal off the chamber. Annealing makes the yield point of the brass lower and it will expand and seal the chamber at a much lower pressure.

[Moleman-]

If you're using a 1891 mauser without the wings on the bolt sleeve there's nothing preventing gas from going down the left bolt race and dumping right in your face. If so try finding a winged type sleeve.

[GregLaROCHE]

I agree, next step should be trying with a jacked bullet with a good charge. Maybe even a second time on the same cases. If that doesn’t solve the problem, there are more things to consider.

[gumbo333]

When fireforming, don't put your cheek on the stock and face behind the bolt. If the brass fills out well, should be good to go. Even if a slight imperfection should finish fireforming on the next shot. Good time to practice your hip shot.

[gwpercle]

Which bullets? Shooting .308 bullets in a .312-314” bore can do that also.

Bingo !
Lyman Cast #4 calls for .311 sized boolits .
13.0 grains of Red Dot or 12.0 grains of Unique might work better .
IMR 4198 is on the slow side of the burn rate for cast boolits .
Gary

[fguffey]

I formed 30/06 brass to 7.65x53 Argentine formed then annealed loaded 167grn cast coated from 18-20 grns of imr 4198 and felt chucks hit my face cases are all full of soot accuracy 3-4" at 50yrds but I would get one 6" flyer. I have been loading since the 60s but never loaded cast bullets it sure is different just signed on last week hope I'm doing this right.

Why? I form 7.65B.BM/Argentine from 30/06 case, after forming the cases the cases are 7.65mm53 B.M, 7.65mm53 Argentine, fire forming is not necessary, same for 8mm57, 7mm57 and 7.7 Japanese 257 Roberts etc. etc. After forming I load, chamber and then shoot. I do not find it necessary to use cereal or any other filler.

F. Guffey

[gnostic]

I always seat the bullet into the lands and neck ream. It sounds like reaming isn't needed in your rifle. How large is the finished round? It Must be huge considering the bullet should be .001 over bore size and with the neck thickness from a case that hasn't been reamed. I'm surprised you can get a loaded round to chamber...

[rockrat]

Might also need to anneal the case necks

[AntiqueSledMan]

When I formed 7.65x53 for my 1891 Argentine, I used military 30-06 brass. I used a Redding Form & Trim Die, then trimmed to length, then finished forming with a Lyman sizing die before loading. I did load with a Hornady .312 diameter 150 grain jacketed spritzer, but I never fire formed. The case looked a little rounded at the shoulder but after firing they sharpened up. I did have to turn the necks with an RCBS Neck Turning Tool on my case trimmer as the cartridges were hard to chamber.
But now with correct head stamped brass available, why bother forming?

AntiqueSledMan.

[dogmower]

think your loads are just too light. i shoot a 210 grain over 22 grains imr 4198 and it's a pretty light load. probably just not enough pressure to seal the breech. also agree they may be undersized. i size mine to .314

[1hole]

When I formed 7.65x53 for my 1891 Argentine, I used military 30-06 brass. ... I did load with a Hornady .312 diameter 150 grain jacketed spritzer, but I never fire formed. The case looked a little rounded at the shoulder but after firing they sharpened up.

Ditto.

Don't know how the web guru practice of "fire forming" with a reduced load got started but it's obviously wrong. Pulling a trigger on a light load is for sure "fired" but the case is by no means "formed"; that demands a full power load.

I've made a good bit of Argentine brass from surplus .30-06 GI cases for my old '91 but I've never had to neck ream/turn any of it.

[fguffey]

I've made a good bit of Argentine brass from surplus .30-06 GI cases for my old '91 but I've never had to neck ream/turn any of it.

Consider the 7.65 BM chamber has a generous neck.

F. Guffey