My 300 blackout doesn't like cast

[thumbs]

I started loading my powder coated lee mold 155gr (actually dropped at 165) only loaded five and tried to cycle the in the rifle. Nope got one or two to function but that was it. Checked the brass with my case checker it worked out fine. I then measured length and the neck diameter of the brass and again to spec or a touch under. After quite a bit of fiddling around trying to figure it out I decided to load a few dummy 135gr Hornady SP bullets. Loaded them to spec and they ran fine. The I put the two bullets together and of course the ogive on the cast it a bit longer. The Hornady tapers pretty fast while the cast is more or a pencil kinda thing. Of course its longer being 35grains heavier. Anyway I checked and rechecked everything I can figure and can't seem to figure it out. The cast won't go into battery but when I check the bullets I don't see any rifling marks on the bullet. Any ideas??

thanks

[turtlezx]

try sizing them down as cast dia runs about .312-.314 vs 308 or 310 dia Js

[geslayton]

I haven't had time to do any accuracy testing yet but did work up a load over the chrono of Lee 230 grain cast and coated. I sized to .309 and they have ran in several different guns

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[sukivel]

I’ve always read that Lee 155’s run in everything. I just got a .300 bo so I don’t know first hand yet...


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[thumbs]

turtles

Thanks. They are sized to .309. Long story but the short of it is "chamber length" LOL Who would have thunk it. Anyway I was taking my lead from Elvis Ammo. Nothing wrong with him but his chamber is a bit longer than mine apparently. My chamber runs 1.975. He set his OACL to around 2.335? I think. I was using his numbers and it wouldn't work. Anyway made up a case for my chamber gauge and found the problem. For my chamber I was way to long. I made up some dummy rounds with my cast and set the OACL to 1.965 and they ran perfectly. Even in my mags. I only dummy loaded 5 but they ran smooth. Didn't do that last time with the cast.

Thanks for the help its been a long day LOL

[John McCorkle]

So I had an issue with the neck/throat junction on one of my barrels...the brass was inside spec but still short enough that the pressure was causing the lead to "flow" into the tiny space between the case mouth and the chamber throat causing little lead rings that...after a round or two would cause the rounds to not go into battery. Give that throat a good scrub with a bronze brush and see if you find lead inside the throat.

It caused the rounds to not go into battery and leading until I trimmed up a batch of brass a bit longer that bridged that gap and no longer allowed lead to flow into that area just ahead of the case mouth. If you have some casting flux or cerrosafe , making a chamber cast will help you know where that neck/throat junction is on your rifle. Be careful not to leave brass too long or you get some issues with pressure or not going into battery for other reasons

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[thumbs]

One more question. I never loaded cast for rifle before so I know not of what I speak. For these bullets to function in the action of my upper I have to set the bullet about .0100 below the bottom of the neck for the case. In other words the base of the bullet is about .0100 below the neck into the case. Is this safe? Is there any reason the bullet cant extend into the case a bit. That is the only way I can get the proper COAL.

John this is a brand new upper not one round through her. When I put the case on the chamber gauge I can hear a metallic tap when I use the gauge up and down with only the case on the gauge not bullet. The case appears to be sitting the same way as the brass in my 5.56 chamber. The action seems to function properly, just manually running the action. Before the round would not go into battery. That problem may rear it ugly head once I get to the range and run some rounds through her. LOl

thanks

[Boolit_Head]

If it's brand new don't even worry about function until you get at least 100 rounds through it. The parts have to get a bit of function to them to loosen up a tad and work right.

[thumbs]

That was the problem I couldn't get it to go into battery from the get go. I couldn't fire one round if my life depended on it. I was checking to make sure it would at least cycle the rounds when I got a chance to take it to the range. The way it was I would have turned around an gone home with no rounds fires. LOL

[Boolit_Head]

Check it with factory rounds for a sanity check for the first time. Cuts out the errors you could have made on the reloads.

[thumbs]

Actually I was going to buy a box this afternoon but none to be found. Didn't have time to look very hard. I'll probably get to the range before I can find factory ammo. Always good to have around though.

[tomme boy]

Load them to 2.25" OAL and see if it works. That is a standard ar15 mag length to feed from the mag. You are limited by what the inside of the mag allows.

If it does not chamber then start seating deeper till it does.

[mattw]

I suspect the nose diameter, in front of the driving bands is to big to go into the rifling. Had that problem with mine, the barrel had very little leade. I switched to a 152 SP cast and it works like a dream!

[thumbs]

Load them to 2.25" OAL and see if it works. That is a standard ar15 mag length to feed from the mag. You are limited by what the inside of the mag allows.

If it does not chamber then start seating deeper till it does.

When I measured the chamber with the chamber gauge it was 1.975" now that was as far as I could get the 165gn Lee cast into the chamber. I cant get 2.25" COAL to even come close to going into the chamber with those bullets. Unless I am doing something wrong and I really don't know what it is. The 130 gn Hornady's will seat deeper but they aren't as long.

[thumbs]

I suspect the nose diameter, in front of the driving bands is to big to go into the rifling. Had that problem with mine, the barrel had very little leade. I switched to a 152 SP cast and it works like a dream!

Actually that is exactly the problem. I can get it to cycle but I have to seat the boolit so about .0100 of the boolit base is below the neck. Is that a problem??

[popper]

Neck on bo isn't really a neck. No problem.

[thumbs]

Neck on bo isn't really a neck. No problem.

Popper are you saying the boolit extending into the powder area below the, "neck"or whatever it is, isn't a problem?

[mattw]

Actually that is exactly the problem. I can get it to cycle but I have to seat the boolit so about .0100 of the boolit base is below the neck. Is that a problem??

With the 300BO, I have not seen an issue with the base of the bullet below the minimal neck. I am using the NOE 152 (on the left) the others are a light Lyman designed for the 30 M1 carbine. I really suspect that the diameter of the nose, just ahead of the case mouth is where your problem is. The NOE design has a reduced neck starting at the end of the top driving band, memory may be wrong but I think the diameter of the nose is .301 or .302. The Lyman 311414 would also work well, same nose design.

245408

[thumbs]

Yes the Lee 155gn is a bit cylendricial and has a rounded nose rather than a pointed one. I think this doesn't allow the bullet to push as far forward as a pointed bullet may. In other words the ogive is very much forward. In my case I have to seat the bullet back far enough for the round to cycle in the rifle but because of the oal for the bullet it necessitates the base to extend into the powder chamber. My factory bought bullets, although lighter, chamber fine using publish load data. The 155 Lee because of its shape extends into the powder chamber. I hope I am making myself clear. thanks My bullets are .313 sized at .309

[tomme boy]

It is not ideal that the base is in the case body. But, it will not hurt anything. Load some up and go shoot them.

[Petander]

So I had an issue with the neck/throat junction on one of my barrels...the brass was inside spec but still short enough that the pressure was causing the lead to "flow" into the tiny space between the case mouth and the chamber throat causing little lead rings that...after a round or two would cause the rounds to not go into battery.

I've been here,too. I was able to shoot quite a lot but there was this strange lead buildup. Took a while to figure it out. It was 458 Socom but the idea is the same. I was sizing too much.

[Sig556r]

If I can cycle PC'd TL-309-230-5R in any of my 300BLK ARs sub or super, you should be able to with 155g CBs. Just like J's, its unconventional seating, you have to determine the optimal seating that'll reliably feed in a semi-auto. No need to limit seating within the neck like regular 30cals, but crimping is necessary to avoid setback.

[John McCorkle]

I've been here,too. I was able to shoot quite a lot but there was this strange lead buildup. Took a while to figure it out. It was 458 Socom but the idea is the same. I was sizing too much.So sizing your brass made it too short or were you trimming too?

It was the strangest thing....I started casting for 38 spc (which is super friendly for casting)...then moved to 300 blk and had zero experience or knowledge on what was causing the issue....I just had these little silver rings of lead that kept showing up. It was this forum that helped identify what the source of the prob was. So big thank you to all for sharing the knowledge here.

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[cwlongshot]

I have five different 300 bo rifles and NONE of them reall shoot cast very well!!

Even my H&R SS I had with powder puffs or super
Sonics. Best i was ever able to do was about 2” @ fifty yards thats from
Barrels that will shoot moa or LESS with super jacketed bullets.

I pretty much gave up. I feel its the 1:7 rifling thats made for subs and just not cast friendly.

My 32/20 with 1:14 shoots quarters at 100yards same bullets...

CW

[Lloyd Smale]

but yourself a rcbs 130 gas check spitzer mold. Once I got the seating dept down they never missed a beat in my ars and shoot 1.5 inch at a 100 yards out of the 16 inch gun. Ill measure one later and let you know seating dept. I tried the 155 lyman and no matter what I did I couldn't get it to run a 100 percent in either of my bos. This is the only cast mold ive bought that really works. Im sure maybe some of the group buy designs do too but I came to the party to late for most of them.

[Buck Butcher]

Lloyd, that particular mold is on clearance at midway. Awful tempting, and free shipping to boot!

https://www.midwayusa.com/product/1010267198/rcbs-2-cavity-bullet-mold-762mm-130-spl-762mm-30-caliber-309-diameter-130-grain-spitzer-point-gas-check

I’ve used the lee 155 with great results, so I don’t need the mold. I am a sucker for free shipping though!

[sundog]

but yourself a rcbs 130 gas check spitzer mold. Once I got the seating dept down they never missed a beat in my ars and shoot 1.5 inch at a 100 yards out of the 16 inch gun. Ill measure one later and let you know seating dept. I tried the 155 lyman and no matter what I did I couldn't get it to run a 100 percent in either of my bos. This is the only cast mold ive bought that really works. Im sure maybe some of the group buy designs do too but I came to the party to late for most of them.

RCBS 7.62-130-SPL, GC'd and PC'd (Smoke's clear) works very well in 300 BO, 7.62x40WT and 7.62x39. Although I have not tried it, I would bet that it would also work in 300 Ham'r.

[Lloyd Smale]

ya I saw that and wouldn't mind a back up in case rcbs is discontinuing it. ive casted more then 5k out of that mold and a new one would make me feel secure.
Lloyd, that particular mold is on clearance at midway. Awful tempting, and free shipping to boot!

https://www.midwayusa.com/product/1010267198/rcbs-2-cavity-bullet-mold-762mm-130-spl-762mm-30-caliber-309-diameter-130-grain-spitzer-point-gas-check

I’ve used the lee 155 with great results, so I don’t need the mold. I am a sucker for free shipping though!

[Lloyd Smale]

well buck butcher midway has one less. I went and looked again and just cant pass up an rcbs mold at 53 bucks. Especially one that works and shoots as well as that one. Should be set till I die now.

[Petander]

So sizing your brass made it too short or were you trimming too?



Just sizing,bumping the shoulder too much. That creates excessive headspace and leaves room in the chamber for the lead to flow.

That was my first AR / cast attempt.

OP doesn't have this problem though.

[Lloyd Smale]

I would have thought that when the powder ignited the case would blow out to chamber size before the bullet even moved and surely quick enough that the bullet wouldn't have melted and left lead that close to the case neck. Bullet would about have to be melting before it clearned the case neck. I would guess more likely is your bullets were being shaved but seating without flaring and piece of lead were being left in the chamber.
Just sizing,bumping the shoulder too much. That creates excessive headspace and leaves room in the chamber for the lead to flow.

That was my first AR / cast attempt.

OP doesn't have this problem though.

[snuffer61]

I read somewhere on this forum how to get 300 BO cast bullets to feed in AR magazines. Set your calipers to .250" and lock them. Slide the calipers down over your bullet nose until they stop. Mark this spot. Now look at your magazine from the top. You will see a ridge inside on both sides. Seat the bullet into the case until the mark you made on the nose lines up with these ridges. From there you can play with OAL to fine tune it but this should get you a close starting point.
Hope this helps.
Snuffer

[thumbs]

With the 300BO, I have not seen an issue with the base of the bullet below the minimal neck. I am using the NOE 152 (on the left) the others are a light Lyman designed for the 30 M1 carbine. I really suspect that the diameter of the nose, just ahead of the case mouth is where your problem is. The NOE design has a reduced neck starting at the end of the top driving band, memory may be wrong but I think the diameter of the nose is .301 or .302. The Lyman 311414 would also work well, same nose design.

245408

I noticed your have a couple of different weight bullets your loading. I am trying to figure out how to get my Lee cast 155gn actually drop at 165gn to cycle in my 10.5" pistol. I have done all I can think out in checking the rounds for spec and drop each round into a case checker to be sure there is no problem there. At first I used a normal pmag for 556 and didn't have very good luck with reliablity . Then I filed down the top of the ribs to allow extra room for the larger bullets. It was much better but still have problems. Seems the cartridge being loaded doesn't get to the ramp and hangs up. Another cartridge behind the first jams under the first. When I take both out and reload them the function fine. My COAL is 1.955 because of the design of the bullet it isn't allowed to go deep into the chamber resulting in the shorter COAL. Any ideas? I have a couple of lancer mags on order but I would like to get the pmags to work if it is possible. Haven't tried my Hornady 130SP bullets yet. I see all the guys on youtube and few mention mag problems or what they did other than filing the rails down a bit. Maybe I still need to file more but they are pretty much even not all the way down the mag.

[thumbs]

I read somewhere on this forum how to get 300 BO cast bullets to feed in AR magazines. Set your calipers to .250" and lock them. Slide the calipers down over your bullet nose until they stop. Mark this spot. Now look at your magazine from the top. You will see a ridge inside on both sides. Seat the bullet into the case until the mark you made on the nose lines up with these ridges. From there you can play with OAL to fine tune it but this should get you a close starting point.
Hope this helps.
Snuffer

Now that sounds reasonable. I'll give it a try but I do have a limitation on my seating depth. I checked my chamber length using the Lee cast. I have to seat about 1.955". Part of the base of the bullet already in the shoulder of the case. The powder is very close to touching the boolit. I am loading today so I'll give it a try anyway and see if different powders gives me enough room in the case and the chamber will allow for the COAL to do your suggestion. I may have to go with a different profile bullet but I hear this one is supposed to run well. Not so much for me right now. LOL

[tomme boy]

Buy a 300 mag and skip the 556 ones. The 300 mags do not have the ribs on the inside that mess with the loading of the rounds.

[jmort]

Any of the Lancer Warfighter mags will work

[thumbs]

Thanks I have a couple of the Lancer Warfighter mags on the way. I did a little more work on the pmag I think it may be better but it really isn't right. Only way to tell is to take it out and see what happens.

[Petander]

I would have thought that when the powder ignited the case would blow out to chamber size before the bullet even moved and surely quick enough that the bullet wouldn't have melted and left lead that close to the case neck. Bullet would about have to be melting before it clearned the case neck. I would guess more likely is your bullets were being shaved but seating without flaring and piece of lead were being left in the chamber.

I used proper NOE expanders. No shaving.

Might have been a combination of things like too slow powder but bumping the shoulder less was the main solution. And a case gauge helps a lot.

Sorry for thread hijack... sizing for AR:s can be interesting, I shoot 300RSAUM too. J only.

[mattw]

I noticed your have a couple of different weight bullets your loading. I am trying to figure out how to get my Lee cast 155gn actually drop at 165gn to cycle in my 10.5" pistol. I have done all I can think out in checking the rounds for spec and drop each round into a case checker to be sure there is no problem there. At first I used a normal pmag for 556 and didn't have very good luck with reliablity . Then I filed down the top of the ribs to allow extra room for the larger bullets. It was much better but still have problems. Seems the cartridge being loaded doesn't get to the ramp and hangs up. Another cartridge behind the first jams under the first. When I take both out and reload them the function fine. My COAL is 1.955 because of the design of the bullet it isn't allowed to go deep into the chamber resulting in the shorter COAL. Any ideas? I have a couple of lancer mags on order but I would like to get the pmags to work if it is possible. Haven't tried my Hornady 130SP bullets yet. I see all the guys on youtube and few mention mag problems or what they did other than filing the rails down a bit. Maybe I still need to file more but they are pretty much even not all the way down the mag.

Wait for the new mags... I have not had any trouble with PMAGs using the cast SP bullets, a lot of folks have though. My rifles have pistol gas systems in them, I like them that way but it is key to use the proper burn rate powders. Does your bolt fully lock open if only 1 round is fired? My pistol gassed 16" rifles really like 4227. No if you have the curly wrap around gas tube that makes the action think it has carbine or rifle length gas, I would not know what powder it might like. The smaller bullet is a Lyman 311359, does not feed as well as the larger bullet. Do not get hung up on the base of the bullet being below the shoulder, many of the loads for the 300BO will be that way.

[Lloyd Smale]

have to agree. I have 300 bo specific p mags and lancers and there defineately better feeders then the 556 mags.
Buy a 300 mag and skip the 556 ones. The 300 mags do not have the ribs on the inside that mess with the loading of the rounds.

[thumbs]

Thanks guys. I am loading 4227 15.8 grains. Its a pistol gas system. Not sure about holding open with only one round. I do know at least once the bolt did not hold open on the last round. That being said that was with a 20 round pmag with the ribs filed. So may not be a good indicator. This Lee mold is round nose.

[jmort]

Lancer Warfighters never had problematic ribs
Lancer Warfighters never had feed problems with ACC 300 Blackout

[thumbs]

Good, the Pmags I have are just the 556 mags not the 300 blk. I only sacrificed one to try it. There are two places that may nave the Lancers reasonably local. If so I may pick one up to hold me till the other come in.

[Texas by God]

I read somewhere on this forum how to get 300 BO cast bullets to feed in AR magazines. Set your calipers to .250" and lock them. Slide the calipers down over your bullet nose until they stop. Mark this spot. Now look at your magazine from the top. You will see a ridge inside on both sides. Seat the bullet into the case until the mark you made on the nose lines up with these ridges. From there you can play with OAL to fine tune it but this should get you a close starting point.
Hope this helps.
SnufferI read this also and have used that formula in all of my 300 Blackout loading. I have yet to have a malfunction. After I got my 7.62 by 39 mm, I quit messing with the 300 Blackout and cast bullets. The accuracy is not there for me.

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[skeet1]

I had nothing but trouble with metal GI type magazines, they will not work in my rifle! I was in a gun store and saw some 20 rd. P-Mags and bought one and have been shooting ever since. I prefer 20 rd. mags but have tried the 30 rd. P-Mags and they work just as well. I shoot the Lee 312-155 and the 309-230 and both work equally well. I size the 312-155 at .311 with Carnuba Red and shoot the 309-230 as cast with LLA.

Ken

[thumbs]

Ok let me ask ya this. The Lancer mags. I see Midway says the Lancer mags are compatible with a bunch of calibers including 556 and 300 bo. Does Lancer make a specific mag just for the 300bo. Been looking but can't seem to find the answer. On the Lancer site I cant even fine 300bo specifically noted. Just 556. I have a couple from Gunmag warehouse I though the were 300bo specific unless they just said 300bo but really were the 556 and the others comparable including the 300bo

https://lancer-systems.com/awc/product/l5awm/?attribute_pa_rounds=20&attribute_color-options=Smoke

[popper]

https://lancer-systems.com/awc/product/l5awm-300blk/

[jmort]

The regular .223 family of cases mags are still specified by Lancer for supersonic
The 300 BO mags are for specified for subsonic heavies
Regardless, lancer has always been the ne plus ultra


"The L5AWM 300BLK has been specifically engineered for use with subsonic 300 Blackout ammunition, particularly 200+ grain cartridges. The updated internal geometry allows these longer heavier bullets to stack properly, which increases reliability when compared to a traditional .223/5.56 magazine. The outside of the magazine body is molded with 300 Blackout markings and the magazine ships with a contrasting flat dark earth base plate for easy visual identification.

NOTE: These magazines have been specifically designed and optimized to alleviate the stacking and feeding issues commonly experienced when running 200+ grain subsonic 300BLK cartridges in standard .223/5.56 magazines. If you are shooting lightweight supersonic 300BLK ammunition (<150gr), we recommend using a standard .223/5.56 magazine."

[thumbs]

https://lancer-systems.com/awc/product/l5awm-300blk/

Thanks you I did not find that one.

[thumbs]

Interesting day today. Got out to try a couple of mags with my son in law. Three different pistols two different magazines. Two different calibers.

I took the, what I think is a, gen1 pmag out to try the 300bo. This is the magazine I modified by filing down the ribs to allow more room for the larger cast bullets. We ran the mod gen 1 several times it two different 300 bo uppers. This is the same mag the unmodified had some major issues. Well today it ran fine with not only the 300bo but also .223. The second mag is a gen3 pmag with no mods. It ran both the 300bo and the 223 without any issues. The gen! mag was a straight mag. The gen3 mag had a curve to it like 30 rounder. We ran the two mags in the two 300bo and both mags loaded with the 223 in my 223 pistol

I hope this helps someone. At least my gen1 mag was able to be modified to shoot both the 300bo and the 223. The gen3 mag ran both calibers with no modifications at all.

I was using the Lee cast 155 gn 312 mold that actually dropped at 165gn and were powder coated.
The 223 ran the Hornady 55gn sp.

Both mags ran flawlessly today.

[Lloyd Smale]

must have been some concern because they now make 300 bo specific mags too. mine have "300 blackout" molded right on the magazine. Don't know what all they changed but defineately have a different follower on my bo lancers then my 556 lancers. They are great mags though, maybe even the best. problem to me is they cost substantialy more (50 percent more most places) then pmags and pmags work just fine.
Lancer Warfighters never had problematic ribs
Lancer Warfighters never had feed problems with ACC 300 Blackout

[Lloyd Smale]

by the way I have a couple of the D&H steel 300 bo mags too and they work just fine. All three of them run better then any 556 mag.