Author Topic: Blowback (Read 532 times)

tripper · « **on:** September 17, 2003, 11:02:34 AM »

I test fired some rounds today and had some powder blowback around the neck. Is this to be expected ?
Gun- 14 in. 7-30 waters contender
load-cci 200 primer, 35.5 gr. 748, 120 gr.seirra psp
The load was very accurate. I could cover a 10 round groupe at sixty yds. with the base of a 12 ga. shell.

WD45 · « **Reply #1 on:** September 18, 2003, 01:54:57 AM »

With groups like that I dont think I'd care about a little blowback :grin:
There are several factors that can cause blowback. I am not familair with that particular caliber or load so I'll let some one who is give you a real answer :wink:

Mikey · « **Reply #2 on:** September 18, 2003, 04:43:41 AM »

tripper: did the cases that gave you blowback have a half-moon shaped powder burn on them running from the case mouth to about half-way down the neck - if so, although the load is very accurate, your load may be a bit on the light side so that the brass does not expand to completely seal the chamber upon firing and the result is some blowback. If you did not feel any gases or particles blow back at you, but only saw the markings of powder burns on your case necks then I would say not to worry, you will find this with some cartridges and loads but I think you are safe. Let's hear from some of the others on this but I think you're ok. HTH. Mikey.

jhalcott · « **Reply #3 on:** September 18, 2003, 08:00:02 AM »

Tripp, try magnum primers with 748.Some lots are a bit hard to light and the mag primer helps. The Hornady book shows a MAX load of 38.5 grains with 120's.If the velocity you are getting is enough, maybe a change of powder will give better results! just my $.02, jh

Iowegan · « **Reply #4 on:** September 18, 2003, 11:15:02 AM »

Annealing your cases helps a lot. This makes the brass soft so it will puff up in the chamber and get a good gas seal. It usually improves accuracy too but with a group like you're getting, I wouldn't complain nor would I change the powder charge.

To anneal: place sized cases upright in a pan (cake pan works good) of cold water about an inch deep. Use a propane torch to heat the case from shoulder to mouth. When the case is hot, tip it over in the water. A schhh sound should be heard. Do one case at a time. A pink hue will be noted. Dry the cases throughly before reloading. Repeat annealing every 3 shots. Cases work harden from being fired and resized.

tripper · « **Reply #5 on:** September 18, 2003, 03:56:33 PM »

Thanks for the responses guys. The powder marks on the neck were pretty uniform and almost all the way back on the neck. None of the rounds had been loaded more then 2 times, some were being fire formed at the time. As fare as a hotter load gos, i also fired some 36 grainers and they showed the some results and the groupe got slightly bigger. I plan on trying some a little hotter but my TC book showes max at 36.9. I don't have a crono but the book shows 100 ft. differnce between 35.6 gr. and 36.9grs. If i can hold the accurcey I'll take the extra 100 fps.
thanks again