Author Topic: Double Groups??? (Read 1225 times)

Rob45 · « **on:** April 03, 2004, 07:06:49 AM »

Veral,

I am getting double groups with my 458-400-M. Before I go changing or tweaking my load I figured I'd get your opinion. What I'm getting at 100 yards is two very tight groups about 2.5" apart from each other. Today I put my first shot low, my next three into an outside to outside group not over .5"!!!!. Then the next shot went beside the low one. I didn't clean the gun so I could see if what was happening last week was still happening. I don't think it's my bench technique...I'm fairly experienced at this and the scope is fine, I checked it with some other loads and they do as they always did. These bullets are air cooled straight WW metal. I'm willing to try the water quenching if that may be part of the problem. I'm getting no leading at all, I'm using 50/50 Beeswax/Staylube Moly-Graph grease which has always worked well. I did bump my load up 1 grain of RL-7 from 45 to 46 since your bullet doesn't seat as deep in the case. I'm tempted to go more but I want your opinion first. Thanks,
rob

Rob45 · « **Reply #1 on:** April 03, 2004, 07:10:49 AM »

I guess I should add this is a Marlin Guide Gun and the three shots in one hole are the high shots about 2.5" above the first and fith shots. Barrel cooling doesn't affect it. Five in a row and one shot every 5 minutes, it still seems to do the same thing and it's only with this bullet. I'm wondering if bumping the powder charge up a bit and water quenching might help.

rob

Jim L. · « **Reply #2 on:** April 03, 2004, 12:46:46 PM »

Not Veral, Rob you may be getting some purging from the lube? This would be my first choice. Since leading is non existent try filling one less groove and see what happens. Sounds like you are having some fun. Hows the shoulder look?

Jim

Rob45 · « **Reply #3 on:** April 03, 2004, 04:12:16 PM »

You may have a point there Jim. I'll try that and see what happens. The shoulder is OK as long as you only run about 10-12 of them through it a week from the bench. I can go a lot more rounds as long as I'm not on the bench:)

rob

dave375hh · « **Reply #4 on:** April 04, 2004, 03:06:22 AM »

Rob45,
If you have a scope on the rifle, loosen the rings and turn the scope 90deg. Tighten the rings down a see if it shoots double groups R & L instead of up and down. This can and dose happen even in new scopes. It is particulary prevelent in hard kicking rifles. Make sure it's not bouncing off the frt bag unrestrained because you can't set it back the same each time no matter how careful you are. When benchresting the thumpers I hold the forend and rest the back of my hand on the frt bag.

Veral · « **Reply #5 on:** April 11, 2004, 07:05:32 PM »

You have a problem I've never experianced, so don't have an answer.

Since both writers above have some experiance, it seems wise for me to leave their answers in place and zip my own mouth!

Rob45 · « **Reply #6 on:** April 19, 2004, 04:49:22 PM »

Quote from: dave375hh

Rob45,
If you have a scope on the rifle, loosen the rings and turn the scope 90deg. Tighten the rings down a see if it shoots double groups R & L instead of up and down. This can and dose happen even in new scopes. It is particulary prevelent in hard kicking rifles. Make sure it's not bouncing off the frt bag unrestrained because you can't set it back the same each time no matter how careful you are. When benchresting the thumpers I hold the forend and rest the back of my hand on the frt bag.

I forgot I posted this...glad I checked in today. The gun doesn't do this with another load using the same weight bullet (but RCBS, not Veral's) and same powder. Switching to the LBT bullet it will and then the to the RCBS it won't. I haven't had a chance to shoot it again since I posted this but I'm going to bump the powder charge up one more grain just in case it's a matter of the base of the case barely touching the powder column on some and not on others. I may even try leaving a lube groove empty and see if that works. I bench test my big bore rifles and all leverguns exactly as you describe with my hand in the same place on the foreend witht he same tension each time...or it makes huge monumentous changes in POI.

rob

Veral · « **Reply #7 on:** May 02, 2004, 05:25:20 PM »

I think you have your nose in the right set of tracks.
Lbt bullets tend to slip through the gun easier, by design, so changing the powder charge will perhaps stress the bullet the same as the RCBS, as perhaps will leaving one lube groove dry, prooving whether lube purging is the problem.