Vel of 308 cal VS 380 cast PC bullet

[Dom]

I 'm trying to understand a difference in the accuracy between my 308 bolt rifle using a 215gr cast GC PC bullet & the 260gr GC PC bullet in my Marlin 38-55. I drive the 215gr 308 ( sized .311 ) to 1763 fps with about 1" groups at 100yd. In my Marlin ( Deep Grove Ballard rifling ) 38-55 with a LBT 260gr GC ( sized .380 ) I can't exceed 1485 fps without accuracy going to 3" to 4" at 100yds. Both bullets are using the same BHN 15 alloy. What am I not considering. I thought I would be able to easily get 1600 fps in the 38-55.

[RickinTN]

You don't say what powder you're using in the 38-55 round. Try a slower powder and see what you get. With cast bullets it's often the pressure which exceeds the alloy strength, not the velocity.
Good Luck,
Rick

[Goofy]

l suggest your alloy for the .38-55 is too hard. Knock it down to about BHN 11-12.

[Dom]

I'm using 2400 powder in both rounds. I started with a BHN of 10.5 to 11 in my38-55. 1400fps was the best I could do for acceptable accuracy at 100yds. This is why I went to a harder ( BHN 15 ) alloy in the 38-55 which allowed me to reach 1485 fps with good accuracy ( 1 1/2" @100 yds ) . I really wanted a softer alloy for hunting. Perplexed at this point.

[RickinTN]

Well. Best to only change one thing at a time. It's not your alloy limiting your velocity. You should be able to go faster with a +/- 12 alloy. My next step would be to try one of the 4227 powders if you can find it. One of the 4198's would be something to try. Re-7 or even 3031 on the slower side. 2400 is an excellent powder in the 38-55 within it's limitations, which you have discovered in your rifle.
You probably will be able to exceed the velocity where you are now with your softer alloy and one of the slower powders.
Good Luck,
Rick

[charlie b]

Factory ammo is something like 1300-1400fps at that bullet weight.

I understand you can probably go higher, .375Win type velocities. Don't know if rifling twist is changed for the higher velocity cartridge. Don't know if the 1-18 twist is your problem.

[Mk42gunner]

There is also the base accuracy of the two rifles to consider. I too have a bolt action .308 and a Marlin Model 336CB in .38-55. I have never directly compared the rifles, they are not in the same category.

With my .308, I can reliably hit 3/4" rocks at 150 yards; from a rest with M80 ball. I have never tried it with the iron sighted .38-55, it is beyond dreaming to think it can do the same as a scope sighted heavy barreled .308.

Both are fun to shoot, they are just designed for different things. If I had to make a shot at three hundred yards, .308. If I want to slip through the timber looking for Bambi's Grandpa? .38-55.

Robert

[sigep1764]

I think that twist rates and pressure are whats separating the two in the accuracy vs speed department. My suggestion would be to change powder in the 38-55. 3031 would seem the best bet but look at the loadings in the old Lyman manual. None are greater than 1100-1200fps.
http://marvinstuart.com/firearm/Manuals/Bullet%20Casting/Lyman%20Cast%20Bullet%20Handbook%20-%203rd%20Edition%20-%201980%20-%20Reduce.pdf

[Dom]

Success!! Accuracy with velocity. I changed my primer for the 38-55 from a Win LR to a CCI LR. Trying to think uniformity. Went to IMR-4198. Inserted a tuft of Dacron over the powder to firmly hold the powder in place. Three shot group at 100yds ( Burris compact 4x scope ) I'll be 77 next month & my eyes just don't focus the way they used to. Sorry to you purist. Was wanting 1600 fps, got 1615. Feel this is a viable 150yd load. Perhaps not for elk but deer for sure. With my 260gr LBT GC PC bullet .285409285410 Yes I use my targets over & over.

[sigep1764]

Nice work Dom! Whats the recoil like? Any issues with sticky cases?

[Dom]

Recoil is no big issue. Cases extract as easily as ever. Another point I failed to mention. I only size the case down about 1/3 to just below where the base of the bullet would be. The rest of the case gets no sizing. I'm loading with RCBS Cowboy dies. They come with a .376 & .379 inside neck ex pander. I'm using the .376. My cast 260gr PC bullet is right at .380. This is the bullet. Clear with OD green for a camo look. ATTACH=CONFIG]285415[/ATTACH]

[Texas by God]

My 38-55 likes 4198 too. I use it under the 379250F Lee for flatter trajectory for hunting loads; for practice loads I use Unique powder. My Winchester 94 is a JES rebore and I size to .377".
I've used 3031 as well, but I don't need the extra recoil of those loads.

Sent from my SM-A716U using Tapatalk

[Mk42gunner]

Success!! Accuracy with velocity. I changed my primer for the 38-55 from a Win LR to a CCI LR. Trying to think uniformity. Went to IMR-4198. Inserted a tuft of Dacron over the powder to firmly hold the powder in place. Three shot group at 100yds ( Burris compact 4x scope ) I'll be 77 next month & my eyes just don't focus the way they used to. Sorry to you purist. Was wanting 1600 fps, got 1615. Feel this is a viable 150yd load. Perhaps not for elk but deer for sure. With my 260gr LBT GC PC bullet .285409285410 Yes I use my targets over & over.
Wow. Great results there Dom. Please ignore my earlier post about how the .38-55 wasn't that accurate.

I am going to have to try mine with a scope, at least for load development.

Robert

[charlie b]

Congratulations!

I use 4198 in my .308 loads and it is position sensitive at lower load densities.

[Dom]

That was my thought on putting Dacron on top of the powder. Then the bullet on top of the Dacron . Snug on top of the powder. I think this is most likely the reason for my accuracy improvement. Powder in the exact same position every shot...

[35remington]

A partially filled case with 4198 will see 200+ fps velocity variation or more when powder shifts fore to aft. 2400 will not be quite so bad but some variation will still occur.

[MostlyLeverGuns]

Many lever actions shoot very well when scoped like the bolt guns. An open-sighted or peep-sighted lever gun vs a a rifle with a scope topping out at 9-14 power is not exactly a level playing field. I have scoped many lever actions with quality scopes that go to 14-20 power, tuning the rifle, stoning the trigger, and adding careful and DIFFERENT bench techniques can all get some pretty amazing accuracy out of the many lever guns. I have had excellent accuracy using Rldr 7, 4198 and Accurate 5744 in many different rifles using cast bullets. Like others have said, a slower powder may work better in the 38-55, equal sighting equipment will also help narrow the gap between lever guns and bolt guns. Sometimes a primer change may make a difference, a large pistol primer or a magnum pistol primer, some say a magnum rifle primer can help when powder position can vary. The neck of the 308 may be helping with uniform powder ignition while the 38-55 has little to help make the ignition and bullet movement as uniform. Sometimes a milder primer lets the powder ignite better before the bullet starts to move. A strong crimp on the 38-55 may also help ignite/burn the powder more uniformly.

[Dom]

Three items that appear to have improved the accuracy of my 38-55. Going from the Win LR primer to the CCI LR. A heavy crimp & most definitely the Dacron filler that holds the powder "snugly" in place. I see the Dacron filler as the most significant accuracy improvement of the three.

[GooseGestapo]

Marlins are notorious for oversized bore. You obviously found a workaround with the 4198 and filler.

You didn’t mention the use of a filler with the #2400. I find I get much better accuracy using a filler. Especially with non-gaschecked bullets such as the Lee 255gr .378”.
I occasionally shoot those through my .375Ruger over 16.0gr of Unique.