Rifle Load Development

[Ganderite]

For the Primer Test I fired 12 groups at 100 yards. Average group was around 1.5”, which was not very impressive.

I have never had good performance from this rifle. It should be capable of steady sub 1.0” groups.

The Primer Test was shot in virgin cases, with 46.0 gr of N140 and the Sierra 155 at 2.790”. I want to do some tweaking to see if the groups can be shrunk. Same brass as the last test, but neck sized.

I will test 10 shot groups, so as to have a little more validity in the results. I have shot thousands of 10 shot groups and have noticed that the first 5 shots usually mean almost nothing.

So I have loaded 10 of the “standard” load (46 gr and 2.780”) and then 4 variations:
Same load with a tighter neck.
Same load with bullet seated longer (2.815”)
Standard load with 0.3 gr more powder (46.3gr)
Tight neck, bullet seated longer and 46.3 gr. (3 changes from standard load.)

I will also try the standard load with a muzzle brake and with a linear comp. I expect adding a muzzle device will increase group size.

 

[Lead hammer]

Interesting test, looking forward to the results, however to me you are just guessing with powder and seating depth in your increments.

 

[Mystic Precision]

Are the necks partially sized?

Jerry

 

[Grizzlypeg]

Which Sierra 155's are you using? I keep trying to get something good going with 2155C but I can never do any better than a good factory loading. But, I keep trying. Maybe its my powder selection, IMR 4895 and Varget.

 

[Ganderite]

Are the necks partially sized?

Jerry

Yes. That is how the neck sizer does it. Don't know why.

 

[Ganderite]

I am using the 2156C. No idea what the difference is. Varget and 4896 are excellent choices. I have used a lot of both. Also RL15, N140 and N150.

When I developed load for my target rifles, these powders would easily be sub 1 minute. Maybe this rifle is NG. I will keep tweaking. I can try some Lapua and Bergers, too.

 

[Grizzlypeg]

I am using the 2156C. No idea what the difference is. Varget and 4896 are excellent choices. I have used a lot of both. Also RL15, N140 and N150.

When I developed load for my target rifles, these powders would easily be sub 1 minute. Maybe this rifle is NG. I will keep tweaking. I can try some Lapua and Bergers, too.

I believe the 2156 is a newer, improved version. Like a dummy, because I won a pile of them at a Sierra sponsored competition, i bought even more. I chambered a palma spec barrel with a palma reamer and never got spectacular results. So I rebarreled it to 223 rem and didn't look back. But now I am working on shooting them in my 308 Bergara.

Projectiles aren't cheap anymore, and also hard to source.

 

[Grizzlypeg]

From Sierra's site:

The 155 grain #2155 was designed especially for PALMA® competition (800, 900, and 1000 yds.). First introduced at the 1992 PALMA® matches held in Raton, New Mexico, this bullet has earned high praise from long-range competitive shooters around the world.

Sierra created the 30 caliber 155 grain HPBT PALMA® to fill the long-range demands of the PALMA® and other long range shooters. The #2156 PALMA® bullet has a longer, more streamlined 9 caliber ogive, slightly longer OAL and a pointed meplat, which is a first for Sierra Bullets.

????

 

[Ganderite]

One would think the the 2155C would be a bit more forgiving.

 

[Mystic Precision]

How long has the throat become?

155's have a pretty short bearing surface.

Jerry

 

[Ganderite]

I spend an hour on the range, testing some ammo load changes, to see if I could tweak an improvement.

It was not a good day for shooting. High winds and blowing snow. At times I had to pause until I could see the target again.

Testing got off to a poor start. First shot clipped the chronograph.

Test results:

I have a "Standard" load for this rifle. It gets consistent fair results, grouping around 1.4". I shot it first. 1.35" Groups are 10 shots each, so they have some statistical validity.

The first tweak was the same load, but the bullet was seated 25 thou longer (2.815") This showed a definite improvement.

The next tweak was the standard load (46.0 gr and 2.790") but with a tighter neck. This made the group worse.

Next I tried the standard load, except slightly more powder 46.4gr N140. This made the group much worse.

Next I tried a tight neck, the extra powder and the longer bullet seating. When I made this ammo, I expected all three tweaks to improve the group size and the combination of all of them to be even better. Did not work. The rifle does not like the tight neck or extra powder.

So the day was a success. I learned what does not help and one factor that improves the group size. I suspect that throat erosion now requires a longer OAL. I will make some measurements.

In addition to blasting the chrony, there was one other incident. One round was hard to chamber, but I forced the bolt closed. The recoil was heavier and I had to pound the bolt open. The bullet hit 4" away from the others. I suspect that a 190 gr bullet got seated, instead of 155gr. I will keep an eye on the rest of the bullets from this box.

 

[Mystic Precision]

From the flyers in the groups, I would say your barrel either needs to be set back or replaced. If you are over 3k rds, I would get a new pipe... if the goal is to keep shooting the 155's

Plan B would be to get some older Hornady 178gr Amax... these had a really long bearing surface... Maybe the 175gr MK?

Jerry

 

[Ganderite]

This barrel had 5,000 and then got set back, Now has 1000 more.

I have lots of 168, 175 and 190MK. I guess I should try some of those.

 

[Mystic Precision]

That barrel owes you nothing and I think it doesn't want to play anymore.

If you can pull the barrel, just look at the throat and see if you still have rifling on all the lands. I suspect, a couple of them are getting a wee bit thin... or there is pretty extensive fire cracking.

New barrel time.

Jerry

 

[Grizzlypeg]

Thanks for the report. You are a tough one going out and testing ammo under those conditions. It was only minus 5 when I went out, but the wind had me so chilled, I was freezing after an hour. Ran out of patience to try all the variables I wanted to test.

 

[gewehr76]

Wow that's perseverance. I only come to plink at targets under those conditions

 

[Dogleg]

I've occasionally found myself going down the rabbit hole of trying to fix gun problems on the reloading bench. Too often, truth to be told. Compared to the price of components, barrels are cheap.

In a general sort of way, if accuracy is nowhere near where you want it there is little sense in a lot of tweaking. Go for big changes, starting with the bullet.

 

[old303]

Wow that's perseverance. I only come to plink at targets under those conditions

Winter is when the iron-sight guns come out and get shot from the shoulder. Between a scope and my safety glasses there are too many fog issues in the cold, and sitting really still with a bipod and rear bag is not how to stay warm!

Next thing I've been meaning to try is to buy more magazines and have them pre-charged in the warm and not have to fiddle with individual rounds on the line. But dropping singles in top works too.