300 BLK AR Optimized Subsonic Boolit

[Dr.Phil]

I got into casting my own boolits a few years ago specifically for use with Subsonic 300 BLK.
This forum was a priceless resource for helping me get up and running and enabled me to purchase my first NOE 247 FN WHISPER mould.
Most importantly, I had all the information required to safely make these boolits.

The issue that I have come across is reliable feeding in an AR platform.
I started a thread over at 300 BLK Talk trying to get the 247 NOE Boolit to feed reliably.
http://www.300blktalk.com/forum/view...?f=141&t=83966

This thread is not intended to continue the discussion regarding function of the 247 Grain NOE in the AR platform.
It is intended to discuss the feasibility of casting boolits with a long unsupported secant nose.
Several bullet manufactures have developed projectiles with a profile that is optimized so they will feed reliably in a 300 BLK AR.

Here are several examples:
125 Grain SMK:

110 Grain Barnes TAC-TX:

Lehigh Defense 194 Maximum Expansion:

Lehigh Defense 110 Controlled Chaos:

Remington UMC 220 Subsonic:


AAC / Robert Silvers realized early on that for the 300 BLK to perform at the same reliability level in an AR platform as 5.56 NATO, it needed to use projectiles that had the optimal dimensions.
Optimal dimensions being:
- A projectile that was long enough to be magazine length when loaded.
- A projectile that contacted the magazine rib in a manner that mimics the shoulder of 5.56 NATO brass.
- A projectile that is able to withstand the harsh environment of the Direct Impingement Action and Feed Ramps of an AR.
- A projectile that is of the appropriate weight for either Super Sonic or Sub Sonic use.

This leads me to the point of this thread.
Why can't a cast projectile / boolit be utilized to achieve the same results.?

Using the online tool over at Mountain Molds, I designed this boolit:

My intention was to design a boolit mould that would function the same as the Remington 220 OTM Subsonic.
It has the same nose length as the 247 Grain NOE (.875") and weighs in at 245 grains.

The Mountain Molds online application will not allow you to order this design since it violates the program's parameters regarding the Meplat.
I apologize if the question / idea I'm posing is "stupid", but if this design is working with solid and jacketed bullets, why wouldn't it work for cast boolits?

[Jupiter7]

It'll work fine and does. Very similar to the designs member dolomite supafly has done. I own the 31-240E.

http://accuratemolds.com/bullet_deta...=31-225B-D.png

This is a cut down version for supersonic
http://accuratemolds.com/bullet_deta...=31-180W-D.png

[Dr.Phil]

Thanks for the info.
I run into DS all the time over at 300 BLK Talk.
His boolit designs are pretty cool.
I know that he was hoping to get a smaller point on the 31-225B-D than what he ended up with.
If I remember correctly, he was limited by the size of the point that Accurate Molds could produce.

If you look at our two designs side by side, I think that my design might feed better.


The primary goal for me is to get as close to 100% subsonic reliability from a cast boolit in the AR Platform as possible.
If there is already a mould out there that does that, even better!

[popper]

DrPhil - I spent about a month working on my mags to get 150 gr. SPP factory to run in my 308 AR. I found the long pointy nose would get bent (jacketed already)! Actually, even the RD 180 gr. was not reliable. The nose runs into the flat below the M4 ramps. The BCG would move the case til the boolit got shoved back into the case (it would NOT feed). Short story, your meplat must be above the bottom of the feed ramps. Even then a long nosed weak alloy may bend. If you want to PC, get rid of the crimp & lube grooves, cut the non-sized nose down to ~0.298. That will add ~ 8 gr. I use a 31-165B that is very reliable. Loading to full mag length is only needed to get the weight up.

[Dr.Phil]

Thanks for the input!
Good to know about the Meplat having to be above the bottom of the feed ramps.

As far as not having to be at mag length, I've had problems in the past when 300 BLK loads aren't loaded long.
Even if the bullet is making perfect contact with the magazine ribs, it doesn't take much to get the cartridges to move forward.
That almost always results in a mess in the magazine that results in a stoppage.

My thoughts are to take the dimensions of the 5.56 NATO cartridge and create a 300 BLK specific boolit that matches them as closely as possible.
- From the case mouth, the boolit length would be .882"
- Width of the boolit where it contacts the magazine rib would be .25"
- The boolit would contact the magazine rib .161" out from the case mouth

[PalmettoShooter]

DrPhil - I spent about a month working on my mags to get 150 gr. SPP factory to run in my 308 AR. I found the long pointy nose would get bent (jacketed already)! Actually, even the RD 180 gr. was not reliable. The nose runs into the flat below the M4 ramps. The BCG would move the case til the boolit got shoved back into the case (it would NOT feed). Short story, your meplat must be above the bottom of the feed ramps. Even then a long nosed weak alloy may bend. If you want to PC, get rid of the crimp & lube grooves, cut the non-sized nose down to ~0.298. That will add ~ 8 gr. I use a 31-165B that is very reliable. Loading to full mag length is only needed to get the weight up.

+1 You're dead on about the meplat. That's a headache and a half for a lot of people and you never think about it until AFTER you get the mold. AR's feed ramps are funny with loading. And Dr.Phil, you'll have a good 300blk subsonic soon enough... The samples of my 200gr projectile are still on sched to go out mid-January.

Joel O.
Palmetto Projectiles

[wlc]

This is partially off topic, my apologies. With the M-4 feed ramps used in AR's being designed basically for the 5.56 round wouldn't it be beneficial to open them up in some way to accommodate the larger 30 cal bullets/boolits we want to shoot in the 300 blk?

Dr Phil, I like your design. Personally I would want it a bit lighter @+- 220-225 gr but that is just me. I think a lot of it will have to do with finding a mold maker that can accommodate making a "pointy" boolit mold or at least one with a smaller meplat.

[Frozone]

With the M-4 feed ramps used in AR's being designed basically for the 5.56 round wouldn't it be beneficial to open them up in some way to accommodate the larger 30 cal bullets/boolits we want to shoot in the 300 blk?

I open the ramps in My 300 blks. You don't need to for jacketed, but I have had jams from the sides of the ramps cutting into a cast boolit before I recontoured and polished them.

[wlc]

I open the ramps in My 300 blks. You don't need to for jacketed, but I have had jams from the sides of the ramps cutting into a cast boolit before I recontoured and polished them.

Dremel operation or by hand?? I've never done it so school me a bit.

[Frozone]

I used a dremel, but I use them a lot. If you aren't careful, you can do alot of damage in a hurry with one.
I used the small fine chain saw sharpener stone for the rough cut then eased it into smooth with a cylinder shaped cratex.

If you're nervous about the dremel ( and most should be) wrap a nail in emery for a similar effect.

[wlc]

I hate to keep hi-jacking Dr Phils thread, I'll PM you tomorrow with a couple more questions.

Sorry for the hi-jack. Back to your regularly scheduled forum thread.

[Dr.Phil]

+1 You're dead on about the meplat. That's a headache and a half for a lot of people and you never think about it until AFTER you get the mold. AR's feed ramps are funny with loading. And Dr.Phil, you'll have a good 300blk subsonic soon enough... The samples of my 200gr projectile are still on sched to go out mid-January.

Joel O.
Palmetto Projectiles

Thanks again for the samples Joel!
I can't wait to test them out.
Hopefully they are just what I'm looking for.

I feel fortunate that I was able to get on the list to receive your samples.
The anticipation is killing me...
I know that you are keeping the design under your hat, but seeing how close it comes to meeting "optimal 300 BLK" criteria will be very interesting!

I hate to keep hi-jacking Dr Phils thread, I'll PM you tomorrow with a couple more questions.

Sorry for the hi-jack. Back to your regularly scheduled forum thread.

No worries...
I have not cut on my feed ramps / barrel extension.
My goal is to try and avoid that if at all possible.
It is nice to hear all the techniques for doing so though.

[Dr.Phil]

This is partially off topic, my apologies. With the M-4 feed ramps used in AR's being designed basically for the 5.56 round wouldn't it be beneficial to open them up in some way to accommodate the larger 30 cal bullets/boolits we want to shoot in the 300 blk?

Dr Phil, I like your design. Personally I would want it a bit lighter @+- 220-225 gr but that is just me. I think a lot of it will have to do with finding a mold maker that can accommodate making a "pointy" boolit mold or at least one with a smaller meplat.

I agree on the weight, but going heavier allows it to mimic the jacketed bullet performance better.
Additionally, the heavier boolit allows one to use the Forster Hollow Pointing jig to make hunting boolits that are still around the 200 grain mark.

[wlc]

I agree on the weight, but going heavier allows it to mimic the jacketed bullet performance better.
Additionally, the heavier boolit allows one to use the Forster Hollow Pointing jig to make hunting boolits that are still around the 200 grain mark.

Bolded above: How so? Not trying to be a smart butt, but really would like to learn. My one question is would the additional length of the 250 gr boolit require the use of the 1:7 twist barrels where 220-225 still reliably stabilize in a 1:8? Or is that more an issue in jacketed rounds?

[Dr.Phil]

The twist rate required to stabilize a bullet is primarily dependent on the length of the bullet at a given velocity.
A cast boolit is more dense than a jacketed bullet and therefore will be shorter for the given weight.
245 - 250 grains is pretty much the cut off for a cast bullet running subsonic velocities in a 1:8 twist barrel.
220 grains is generally considered the cut off weight for a jacketed bullet.

So, with that said, a heavier cast boolit will be longer than a lighter jacketed bullet, but the heavier boolit will be similar in length.
This is what I meant when I made that statement.

Another example using different metals would be comparing solid copper bullets to jacketed ones.
The solids are much lighter than their FMJ counterparts due to this density difference.
And for one final example, the M4 Carbine called for a 1:7 twist barrel.
That was not done to accommodate the new 77 grain OTM projectiles.
It was done to accommodate the 63 grain M856 tracer rounds that accompanied the 62 grain M855.
They are extraordinarily long for their weight and require the 1:7 twist rate.

[wlc]

Thank you. Makes sense to me now.

[Dr.Phil]

Here is the latest versions of my "Dream Moulds" for 300 BLK.

Here are the subsonic and super sonic boolits that I would like to get moulds for.

230 Grain Subsonic


175 Grain Supersonic
(If these were powder coated, could them be run without a GC?)

Now if I could only find a manufacture that would be able to make them I'd be all set.
Apparently the big road block for Accurate or Mountain Moulds is Meplat size.
For right now, I think the closest that I can get to my goal is to hope that Joel @ Palmetto Projectiles comes up with the "Magic Boolit".

[gds]

Dr phil. I think you are on the right track. While my NOE boolits have fed fine in my ARs. I have really wanted a boolit like you describe. Especially one that once powder coated, i would not need to change the seeting depth so much like i have had to do with the NOE. Also like the idea of being able to hollow point it with the forster jig. Which is what i do with the NOE. Or maybe order it as a hollow point mold.

[Dr.Phil]

While getting this mould made would be awesome, the normal sources for one off moulds are not able to produce one with such a small Meplat.
I have not contacted Sweede @ NOE yet, but if he is able to make a mould similar to my specification, I wonder if there would be enough interest to start a group buy?
With casting for the 300 BLK being as popular as it is, and looking at the popularity of the NOE 247 FN mould, I suspect that there might be enough demand to warrant a group buy.

What say you?
If the interest is there, I will contact NOE and start a Group Buy thread. (If he can make this shape.)
I would focus on the 230 grain subsonic boolit first then look at the 175 supersonic.

[Artful]

Wonder if it would be possible to have someone create your design down to where their equipment couldn't make the nose any
smaller then create a end mill with the correct contours to continue in a plunge cut to get the last bit out of the cavity?