266 grain cast bullet, the Dolomite special

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Smurky
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Re: 266 grain cast bullet, the Dolomite special

Post by Smurky »

Dolomite_Supafly wrote:
Smurky wrote:
Dolomite_Supafly wrote:Load them at 2.12" or a little shorter.

Magazine?
I am having difficulty getting a load worked up that will work in my rifle. As near as I can figure the free bore is too short to allow the blunt nose of this bullet to seat at a reasonable length, certainly not 2.12.

Comparing a 208 Hornady bthp which I often use and trying to replace with a more economical subsonic bullet for plinking. With a Forster Datum dial for 308 caliber bullets the 208 Hornady is .8055 from base to ogive. On the Acme 265 I measure 1.1960 base to Ogive.

If I seat these so the bullet is just in the lans I end up with a extremely compressed load.

I have a PWS mk109 mod 1, which has been working very well with other loads and factory ammo.

Dolomite is the bullet your referencing on the right with a Hornady 208 bthp on the left

Image
Can you measure the bullet at the beginning of the bore rider,ogive, and at the base of the bore rider please. Just curious.
  • Not sure exactly what measurement you're asking for?
Are they preventing the bolt from locking up? Or are you concerned that they are getting engraved by the lands? They are designed to be engraved by the rifling. This helps center the bullet in the bore and that helps accuracy.

At 2.12 feeds OK, prevents the bolt locking up. I used a dummy round and here is the measurement I came up with Image.

I've seated some at deeper at about 2.000 OAL the bolt closes and locks, here is the Ogive measurement Image.


Depending on the OAL how heavy they will be engraved by the rifling, they were designed to do that. Rather than having a gun with a tight, match chamber this bullet fills the chamber instead, giving better performance. It is a very forgiving bullet accuracy wise. Most are surprised at how well they shoot without any serious load development but they definitely take more work than a traditional jacketed bullet to find what works best in your gun.

These were designed around a SAAMI spec Blackout chamber. Some chambers are tighter than spec so they require the bullet to be loaded to a shorter OAL to work.

ACME is also getting ready to release my version of a 245 grain bullet. It uses a more traditional nose and will likely work better in guns with a tighter chamber. It is a true 245 grains not a 247 that actually weighs a lot less like a lot of other bullet makers sell.

I will be really interested when they're released. I've liked the ACME for some time I use them in pistols for USPSA
Thanks for coming up with these bullets, info and replys.
Last edited by Smurky on Mon Dec 18, 2017 8:54 am, edited 1 time in total.
Smurky
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Re: 266 grain cast bullet, the Dolomite special

Post by Smurky »

dellet wrote:
Smurky wrote:10 grains CFE Black is the load I'm trying to use with these.

For instance,

208 Gr Hornday seated at 2.250 COL is 1.571 long to ogive

265 Acme seated to 2.007 COL is 1.825 long to ogive. Nose of the bullet jams pretty hard into the lans.

Wondering if anyone else has had the issue with these bullets? I've previously read how the majority of 300blk rifles have a lot of freebore with considerable jump to the rifling.
The bullet design is a bore rider. The nose will ride on the lands of the rifling. If the coating is a little thick it can be tight, same if your bore is a bit tight. The portion that will actually cause a jam is where the taper from the bearing surface to nose occurs. Loaded at 2.120" should put that taper right at the top of the neck.

CFE sucks until it's compressed, so it's a good choice for this bullet. Try 12.5-13 grains at 2.100"-2.120". That will get you in the ball park for velocity in a 16" barrel and will be very light compression.

I use a fired case that has the neck expanded and drop a charge in. Then set whatever bullet I am going to use on top and measure length. Thats my starting point.

When using CFE I generally shorten that number by .025", I want at least that much compression.
The bolt won't close at 2.12, I had to take it down to 2.000 to get the bolt to close and lock up consistently and it's still in tight. Using a dummy load the measurement I got from case head to ogive and is 1.7475. The same measurement for the 2.000 OAL cartridge is 1.8305 so I'm about .083 into the lands by my figures.

My rifle has a 9.5 barrel and with a Saker 7.62.

Thanks and appreciate any additional comments or suggestions.
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dellet
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Re: 266 grain cast bullet, the Dolomite special

Post by dellet »

Smurky wrote:
dellet wrote:
Smurky wrote:10 grains CFE Black is the load I'm trying to use with these.

For instance,

208 Gr Hornday seated at 2.250 COL is 1.571 long to ogive

265 Acme seated to 2.007 COL is 1.825 long to ogive. Nose of the bullet jams pretty hard into the lans.

Wondering if anyone else has had the issue with these bullets? I've previously read how the majority of 300blk rifles have a lot of freebore with considerable jump to the rifling.
The bullet design is a bore rider. The nose will ride on the lands of the rifling. If the coating is a little thick it can be tight, same if your bore is a bit tight. The portion that will actually cause a jam is where the taper from the bearing surface to nose occurs. Loaded at 2.120" should put that taper right at the top of the neck.

CFE sucks until it's compressed, so it's a good choice for this bullet. Try 12.5-13 grains at 2.100"-2.120". That will get you in the ball park for velocity in a 16" barrel and will be very light compression.

I use a fired case that has the neck expanded and drop a charge in. Then set whatever bullet I am going to use on top and measure length. Thats my starting point.

When using CFE I generally shorten that number by .025", I want at least that much compression.
The bolt won't close at 2.12, I had to take it down to 2.000 to get the bolt to close and lock up consistently and it's still in tight. Using a dummy load the measurement I got from case head to ogive and is 1.7475. The same measurement for the 2.000 OAL cartridge is 1.8305 so I'm about .083 into the lands by my figures.

My rifle has a 9.5 barrel and with a Saker 7.62.

Thanks and appreciate any additional comments or suggestions.
Can you measure the diameter a couple of places on the nose. Everything I have is either pre-production or first run.

The problem with coating is that no matter how hard you try, I don't think you can ever get it perfect. It's possible it's too thick or just not well applied. I don't know what the spec is for that portion of the bullet, but Dolomite can tell you by that measurement.

I won't volunteer him but if you shoot him a PM with a phone number he might just give you a call and will get it worked out. If I had to venture a guess it could be a max bullet in a minimum bore like a .301 bullet or a .2995 bore.

If this is a new barrel or low round count, that is nitride treated, a good cleaning and 100 rounds could be the solution. A slight imperfection or edge on a land could be the hang up. This type of imperfection is why barrels generally produce better groups after break in.
300 Blackout, not just for sub-sonics.
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Dolomite_Supafly
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Re: 266 grain cast bullet, the Dolomite special

Post by Dolomite_Supafly »

Can you measure the diameter at the beginning of the nose right after the ogive. Measure back where it ramps up to meet the bearing surface. Measure between those two.

I am needing the diameter, not the OAL of the cartridge to the ogive.

I will gladly talk to anyone via text. FB message or over the phone. Send me a message and I will give you my number.

When you say 2.00" is the the ogive length or the overall length.

Might be time for V2.0 with a lot more clearance for those who have tighter barrels and chambers.
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Re: 266 grain cast bullet, the Dolomite special

Post by Dolomite_Supafly »

I have ordered another set of molds. We will have a newer, more forgiving version, being sold the beginning of the year.

If anyone would like to buy a mold the casts the current version PM me. They are Magma machine molds but handles should be available.
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Smurky
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Re: 266 grain cast bullet, the Dolomite special

Post by Smurky »

Dolomite_Supafly wrote:Can you measure the diameter at the beginning of the nose right after the ogive. Measure back where it ramps up to meet the bearing surface. Measure between those two.

I am needing the diameter, not the OAL of the cartridge to the ogive.

I will gladly talk to anyone via text. FB message or over the phone. Send me a message and I will give you my number.

When you say 2.00" is the the ogive length or the overall length.

Might be time for V2.0 with a lot more clearance for those who have tighter barrels and chambers.
Thanks again for the response,

I’ll get the measurements to you.

2.00 is the OAL
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Re: 266 grain cast bullet, the Dolomite special

Post by Dolomite_Supafly »

He said the nose measures .303” at the ogive. I believe the nose is mushrooming because the case neck is not a expanddd enough causing excessive resistance while seating the bullet. The excessive resistance is causing the nose to mushroom while being seated.

Cast bullets are not like jacketed and the case MUST have a case neck sized larger for the larger OD cast bullets generally have.
Last edited by Dolomite_Supafly on Fri Dec 22, 2017 4:33 pm, edited 1 time in total.
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Re: 266 grain cast bullet, the Dolomite special

Post by 2manyToys »

I'm using an NOE .309 x .313 expander ( there's some spring-back). What a difference this type of expander maskes when working with cast bullets no shaving, no bulges.
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Re: 266 grain cast bullet, the Dolomite special

Post by Smurky »

I've been shooting this rifle for awhile, had it a year and a half. It has about 1K rounds through it. 110, 150 and 208 jacketed bullets. As of late I've used the Palmetto Projectiles but not satisfied with them. I use the ACME coated bullets for pistol, loaded a lot of .40 as I shoot USPSA and have been very satisfied with them.

I use the Lyman 30 carbine M die. Bullets seem to slide in pretty easily, then lightly crimp with LEE FCD. I've measured about a dozen bullets out of the bag, one was .301, most are .302 and had a couple at .303. The step up of the bullet that seats inside the case seems to be a consistent .310.

Come to think of it the bullets may have mushroomed a bit when 3.12 didn't work I just seated them deeper so that may have caused the mushroom when I did that.

What size are the bullets supposed to be? I plan on getting NOE expanders, what size would you suggest, 312/308 or 313/309?

Thanks for the assistance
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Re: 266 grain cast bullet, the Dolomite special

Post by Smurky »

Now that it’s finally getting warmer I’m trying to find a load that will work with these bullets. I Sized them on a Redding full size die, used a NOE .312 x 308 expander in a Lee Universal and crimped with a Lee FCD. I didn’t change the crimp from working my previous loads. Worked up some dummy rounds and they’ll cycle out of the mag but unless I shorten them to about 2.050 OAL the bolt won’t close. At 2.050 without powder the cartridge was at 2.0270 with a few marks on the nose of the bullet.

I don’t think I can get these to work any longer in my rifle. The rifle is Mod 1 mk109 upper. 9.5 inch piston Operated upper that I run with a Silencer Co Saker suppressor.

I also checked powder capacity and 8 grains of N105 would be compressed with this OAL.

Looking for opinions, is this just a no go because the cartridge has to be so short? I have N105, N120 IMR 4227 and H110, SW blackout and have a little CFE blackout left. My thoughts here are that a faster powder may be the way so I was thinking N105 or H110 and would appreciate any opinions.
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