.300 AAC blk reloads won't chamber & sticking?

[ol' poke]

Hello reloading experts.

I've been trying to work up a load for my .300blk AR, and am stuck (figuratively & literally)

168 gn Sierra HPBT; 11.6 gn H4198; 1xfired S&B 300blk brass cases - fully sized

It seems that 2-3 rounds in each mag of my reloads fail to fully chamber and get stuck in the chamber. Stuck to the point where the forward assist won't budge it (actually makes it worse) and I have to either bang the stock butt on the bench while simultaneously pulling the charging handle back, or even prying the bolt back with a tool. (i.e. they get jammed in TIGHT!) It behaves as if a grain of sand is getting jammed between the case and the chamber wall. I've checked the measurements with a micrometer, and they seem to be the same as factory ammo. I've have S&B factory subsonics which run flawlessly, mag after mag.

I originally thought my crimp was not tight enough and the mouth of the case was catching somewhere in the chamber, but my last batch was "very" crimped and it made little, if any, difference.

I use Lee dies and have followed their setup instructions. Someone has suggested I adjust/tighten my sizing die to insure I get a better sizing - possibly even shaving the top of the shell holder down to allow the brass to get further up into the die? I have not tried this suggestion yet.

Any other suggestions? What might be going wrong, and how can I correct it?

 

[guardman7]

take one of the rounds that won’t chamber, try to remove it as carefully as you can to avoid more damage, then take a sharpie marker (dykem layout fluid works perfect if you happen to have it) and cover every part of the cartridge… then let it chamber fast from the magazine…. This time when you remove it, check the cartridge to see where the marker rubbed off, this will show you where your issues are.

My suspicion is your trim length which can be a dangerous situation. seating depth could be an issue, possibly the need for small base dies.

 

[efd1295]

Factory brass or resized 223 brass?
What’s your current col?

I tried to keep my original BLK loads at max mag length but found out that’s too long. I noticed when they are too long they can chamber kitty whompas and nick the bullet, creating a burr.

Shorter seems to be better for me in gas guns.

 

[turnerdye1]

Yup I’d double check your trim length. Too long will cause chambering issues like you’re seeing.

COAL also may be affecting it if you’re pushing the round into the lands. Anything 2.25 or shorter should be fine in most cases and with most ogives.

I use Lee FL dies on new 300, once fired 300, and converted 5.56 lake city to 300 without any issues at all in both a gas gun and bolt gun

 

[Squid556]

+1 for coloring the round and re loading it.

Sounds like trim length or OAL to me.

Hope ya figure it out.

 

[ol' poke]

I'm using 1x fired S&B 300 blk. brass and load to a COL of 2.180.

I'll dbl check my case trim length (again ).

I like the marker suggestion, as that should at least show me where things are going bonkers. I just now ordered some Dykem blue. Looks like that stuff can be handy to have.

Thanks for these suggestions.

 

[gcoop]

I have had good results resizing blackout brass using RCBS Small Base Sizer dies. Double check trim and check brass with a Case Gauge before reloading. Just a suggestion....

 

[bwframe]

I have had good results resizing blackout brass using RCBS Small Base Sizer dies....

I have read this before. Years back the RCBS SB die was a problem solver.

Ended up buying one of these for myself after having the exact same problem as the OP. I was using cut/reformed .223 brass though. Me and Hawkeye7br had to pound out a loaded round with a chunk of wood to the charging handle.

I cannot speak to shooting enough rounds after the RCBS die to say it is a for sure cure all though.


.

 

[Hawkeye7br]

I have read this before. Years back the RCBS SB die was a problem solver.

Ended up buying one of these for myself after having the exact same problem as the OP. I was using cut/reformed .223 brass though. Me and Hawkeye7br had to pound out a loaded round with a chunk of wood to the charging handle.

I cannot speak to shooting enough rounds after the RCBS die to say it is a for sure cure all though.


.

I had totally forgot about that! Aaahh, the good old days...

 

[Elcardo]

Had this problem when I started doing 300blk for me the cases just weren't forming correctly, some cases like LC went fine , others like hornady didn't
Now days if I run one through the sizing die and it feels harder to pull the handle I just give it a couple more pulls then drop the case in the sizing Guage for a check
I also check all my rounds after I load them in the size Guage before I toss them in the ammo can and haven't had a single one bind up since

 

[bgcatty]

Two words: Case Guages.

 

[DadSmith]

Hello reloading experts.

I've been trying to work up a load for my .300blk AR, and am stuck (figuratively & literally)

168 gn Sierra HPBT; 11.6 gn H4198; 1xfired S&B 300blk brass cases - fully sized

It seems that 2-3 rounds in each mag of my reloads fail to fully chamber and get stuck in the chamber. Stuck to the point where the forward assist won't budge it (actually makes it worse) and I have to either bang the stock butt on the bench while simultaneously pulling the charging handle back, or even prying the bolt back with a tool. (i.e. they get jammed in TIGHT!) It behaves as if a grain of sand is getting jammed between the case and the chamber wall. I've checked the measurements with a micrometer, and they seem to be the same as factory ammo. I've have S&B factory subsonics which run flawlessly, mag after mag.

I originally thought my crimp was not tight enough and the mouth of the case was catching somewhere in the chamber, but my last batch was "very" crimped and it made little, if any, difference.

I use Lee dies and have followed their setup instructions. Someone has suggested I adjust/tighten my sizing die to insure I get a better sizing - possibly even shaving the top of the shell holder down to allow the brass to get further up into the die? I have not tried this suggestion yet.

Any other suggestions? What might be going wrong, and how can I correct it?

Did you do a plunk test to make sure it fit the chamber properly?
If not I suggest you try that next. If the bullet is seated to long seat it deeper by .001" at a time until it chambers properly. Then seat it .002 deeper and you have your COL for that bullet.
You may have to reduce powder charge depending on how much deeper you seat the bullet. I'd start low and work your load up to find out how much if any extra pressure it might have.

 

[Chance]

Two words: Case Guages.

THIS! Also, if you get into case forming you will need to use cases like Lake City that have a thinner wall thickness. Even when sized correctly, a case with a thicker wall will be large enough to stick once you seat the bullet. You will also need to anneal cases that have been converted from .223/5.56. Lots of good articles out there on this process.

 

[dieselrealtor]

I have a slotted Sheridan case gauge, if you are local I could meet you.

 

[ol' poke]

I have a slotted Sheridan case gauge, if you are local I could meet you.

Thanks for the offer DR, but I'm having one delivered this week.

 

[WhiskE TangO]

Possible that the base of the case near the rim is to wide and/or not sized correctly. You may want to try Lee's carbide factory crimp die in 300blk. I had one..... worked great reloading thousands of 150gr. This will obviously go on the very last station of your press.

Lee Precision, Inc.. Collet Style Crimp Die

Collet Style Crimp Die. Incorporates a collet to apply a rifle type crimp to the case. Makes these very difficult to crimp cartridges a delight to reload. Bullets do not need a crimp groove, as the collet is so powerful it will form one. NOTE: This die is not carbide.

leeprecision.com

 

[BiscuitsandGravy]

Just a fyi... I always would put a slight chamfer on the case mouth outside. It would seemed to help feed/chambering issues.

+1 on the Sharpie/Dykem test. Another diy method is to use a candle to 'soot' the case.

 

[STFU]

Two words: Case Guages.

This one:

300 Blackout Ammunition Gauge

Choose between SLOTTED or NON-SLOTTED. AMMUNITION GAUGES are uniquely designed to check loaded ammunition, giving you the ability to check your factory ammunition or reloads against a spec chamber. The gauge is machined to the SAAMI minimum chamber spec for the 300BLK caliber. This allows…

sheridanengineering.com

Trust me...you'll be glad you did.

 

[DadSmith]

Thanks for the offer DR, but I'm having one delivered this week.

Please let us know what the problem was once you figure it out.

 

[ol' poke]

Possible that the base of the case near the rim is to wide and/or not sized correctly. You may want to try Lee's carbide factory crimp die in 300blk. I had one..... worked great reloading thousands of 150gr. This will obviously go on the very last station of your press.

Lee Precision, Inc.. Collet Style Crimp Die

Collet Style Crimp Die. Incorporates a collet to apply a rifle type crimp to the case. Makes these very difficult to crimp cartridges a delight to reload. Bullets do not need a crimp groove, as the collet is so powerful it will form one. NOTE: This die is not carbide.

leeprecision.com

Just curious....How can Lee's carbide FCD change the case base if it "is too wide and/or not sized correctly"? Or are we taking 2 separate issues.

I currrently using Lee dies in a Classic Turret press.


This dang rain has not let me get to the range lately, but frees up time for trying and learning new things.