Author Topic: verticle stringing (Read 840 times)

Doctor Sam · « **on:** August 15, 2005, 06:18:48 PM »

Probably been discussed many times but I am new to lever actions. Anyone know about vertical stringing with these machines? My first few shots with my Rossi M92 in .45 Colt with a 250g cast bullet seemed to walk up and to the right. Later the groups appeared rounded.

Is this normal until the bbl heats up?
Many thanks.

John Traveler1 · « **Reply #1 on:** August 15, 2005, 06:43:42 PM »

Hi Doc!

Vertical stringing is usually caused by extreme velocity variations in the ammunition.

Several shooters have reported that the Rossi M92 in .45 Colt gives "breech blowback" problems with standard loads, with the breech failing to seal. Blowback of course, means incomplete combustion and extreme velocity variations.

The solution is to (carefully) increase your powder charges in 0.01 grain increments until complete obturation is obtained. I use 8.0-8.5 grains Unique under a 250 grain Keith SWC for most of my revolvers, and find that this combo often does not shoot well in Rossi 92 Carbines unless the powder charge is increased to 9.0 grains.

HTH
John

Doctor Sam · « **Reply #2 on:** August 18, 2005, 07:26:29 PM »

Thanks, John. I'll take a look at that. Easy enough solution if that is what it is.
I have several pounds of Herco obtained on a deal and am trying to find a suitable load with a 250g RNFP hard cast bullets that I bought. Too darn hot to cast anything now. Started with 8.0g and worked thru 9.5g without much luck. Still some cases coming out with powder blackening. No signs of high pressure and I plan to move on up gradually from there.
Perhaps somewhere the load will "round out".
Appreciate your suggestion.

WD45 · « **Reply #3 on:** August 19, 2005, 02:58:28 AM »

Hey Doc,
How much walkin ya talkin here.. several inches , an inch ??

Doctor Sam · « **Reply #4 on:** August 19, 2005, 09:16:20 AM »

Anywhere from 5 - 7 inches with a cold barrel.

jd45 · « **Reply #5 on:** August 19, 2005, 04:04:52 PM »

John, just curious, but didn't you mean a tenth of a grain increments, because .01 is a hundredth & I know there's no powder scale capable of that small a measure. jd45

WD45 · « **Reply #6 on:** August 24, 2005, 04:01:17 AM »

5 to 7 inches is way to much especially with a cold barrel.. Does it settle down any with a hot barrel ?
Also how many are you stuffing in the tube. Try loading and shooting one round at a time if you havent yet and see if that makes a difference.
what powder / powders are you using ?

Tycer · « **Reply #7 on:** August 24, 2005, 04:21:52 PM »

It also helps mine to rest on the front bag in exactly the same spot each shot. If I let my rifle back up a little each shot, it will raise the POI.

John Traveler1 · « **Reply #8 on:** August 25, 2005, 12:09:19 PM »

jd45, you are RIGHT of course! That should have been 0.1 grain (one tenth of a grain) increments.

John

Lloyd Smale · « **Reply #9 on:** August 25, 2005, 01:02:52 PM »

make sure your resting the frame of the gun right in front of the lever on the bag and not the forearm.

Doctor Sam · « **Reply #10 on:** August 26, 2005, 06:15:57 PM »

Many thanks for all of the replies, Gentlemen.
I switched to HS5 powder. Old, never opened cans that I inherited. Went from 9.0g to 12.5 in 1/2g increments with a Bonus Bullet 250g RFNBB, Alcan LR primer. 11.0g gave the best groups with greater amounts opening up. Still getting vertical stringing with these loads. Would a hot bbl account for this? I would blame it on my shooting but at the same range sessions my 1909 Argy engineer's carbine made nice round groups with cast bullets.
I will try again with the forearm off the sandbags but that alone will probably open the groups.
I am using a Williams 5D and a Firesight.
These groups still are all minute of deer or hog.

WD45 · « **Reply #11 on:** August 31, 2005, 06:10:40 AM »

a hot barrel will make a difference, especially starting with a cold barrel and running about 10 or 15 shots in a fairly quick string. The most I have had is about 2 inches. I would try some different powders/ primers as that will make a difference aslo. Maybe not 7 inches of stringing but it will change things. My 92 shoots 250 grn SWC's very well with plain ole unique and CCI primers.