GM IBS 40 cal owners

For those of you who own a 40 caliber Green Mountain barrel for a TC Hawken, what is the lightest charge of 3F Goex you have gotten to shoot very well? I've been using 40 grains, but I think that is going to be a bit hot for squirrels unless they are hit in the head and that is not always possible.

30 has been my standard load and is speedy. have shot 20 with no great loss of accuracy out to 70yds and shot 15gr last weekend on a trail walk hitting 2-3 inch targets out to 25yds.

How is the accuracy out to 100 yards?

28" and 38" GM barrels: They don't seem picky except the 38" does better with hollow bases, perhaps because the extra acceleration time helps. 48" twist is great for .50, .54 and .58 but too bad GM didn't make the .40's just a wee tad quicker to give the barrels a little more flexibility. Oh well, glad to have them just the same even if they are percussion.
Never tried less than 30 grains with round ball. How much is the minimum for the little breech space?

The only load I have shot in my 40 is 40 grains of 3F Goex. It shoots very well and from reading here it seemed that's what most of the 40 caliber guys were using. No I want to hunt squirrels with it and am looking for a lighter load. Need to get out back and shoot some if it ever warms up and the wind stops.

about 3 inches on a good day from sticks using the same load of 30gr.

Brett SR,

Is it a one hole grouper at 25 & 50 yards? What are you using for patch lube? What are you using for a patch?

Anyone else have 2 cents worth to add?

I have shot my 40 with down to 20 grains using prb. Accuracy was just fine at 25 yds. But I'll bet the squirrel isn't going to know the difference and if you hit them in the body :nono: , it will be a big nasty hole either way. I'd just go with what I was most accurate with and aim for the head.

Thanks for the replys. I have been thinking about getting rid of my 32 Cherokee and just using the 40 for small game hunting. Got more rifles currently than I can use. What I was looking for was post on where someone had down loaded a GM 40 barrel and shot a squirrel in a place other than the head. Wanted to know if the critter was blown in half or if the damage was acceptable? Yes I know some of you computer hunters will quickly post to aim at the head. Well all shots taken in the field don't always land in the head. There are times when you can't see the head. So I was looking at a report on how acceptable the damage was.

There will be some meat damage,but that is soaked in salt water and put in the stew.
Don't know as I would get read of a rifle as much as use it less!!!!!!!!!!!!
Like you pointed out,,head shot are good,,just not always there or as in my case,they just don't happen. :idunno:

Lots of good input from everyone, thanks. Anyone else have two cents they wish to add?

My .40 GM 32 inch is a true one hole shooter at 25 yards with 25 grains FFFG. :grin:

selvinman said:

My .40 GM 32 inch is a true one hole shooter at 25 yards with 25 grains FFFG. :grin:

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Will try that this morning nice to see the sun agin rained all week end.

When I shot offhand, I used 40 gr 3f, ticking and a .400 ball
at 25 and 50 ygs. Lube was spit.
At 100 yds I used 60 grains 3f - best there was 39X.

Now I'm old and shoot of a bench and shoot mostly at 50 yds
and use , usually ticking, 50 grains 3f and a .400 ball.
Lube is usually Fantastic, Birchwood-Casey 77 or penetrating oil.

I guess I'm the odd one or got an odd GM IBS .40 barrel. Mine takes 80 grains 3f to shoot ACCURATELY.

gl1200a said:

I guess I'm the odd one or got an odd GM IBS .40 barrel. Mine takes 80 grains 3f to shoot ACCURATELY.

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My rifle shoots well at half that amount. Nothing would be left of any squirrel hit with an 80 grain load. I plan to shoot my rifle a bit this morning. Will try some of the loads posted here and see what happens.

I have got to ask, what load (patch, ball, lube)
ya'll that are shooting 15,20,30 grains are using?

This barrel has driven me crazy developing an accurate load.
Probably have 6lbs of powder invested in it.

It can shoot 3" groups with about anything at 50yds.
I'm talking

What's the smallest ball any yall tried?

I tried some .375 that I shoot in my .36 revolvers.
Used a thick denim patch. I could shoot a couple that would touch then a few that would fly off 4" or so.
I gave up on it.