Powder in my action

[Cort]

I am trying to seat my bullets into the lands. In my .308 AR, I have had to pry the bolt back because the cartridge was stuck in the chamber. Upon removing the cartridge, I noted strong scuff marks on the bullet. Fortunately, the bullets stayed in the case. I wasn't so lucky with my 6BR. I didn't get a lot of powder in the action but still had a stuck bullet in the barrel. Some of my 6 BR cartridges load and unload with no problem and others load but stick in the chamber.

How do I get consistent seating depth? I measured all of the cartridges OAL for both my .308 and my 6BR. I get a variance from 2.141 to 2.151 in my 6BR and a similar result in my .308. I am using 70 grain Sierra Match Kings in the 6 BR and 168 grain Sierra Match Kings in the .308. I am using a Redding competition seating die in my 6BR and a Dillon standard seating die in my .308.

For now, I have seated everything such that the longest OAL is short enough to load and unload easily. Powder in the action makes for a short range visit ;-)

Cort

 

[fdshuster]

Cort: I know it's after the fact, but I've been there, done that, the main reason I will not seat any bullets to jam.

Recently was fireforming some 6BRX brass with the bullet(s) jammed into the lands, had a primer mis-fire (Rem 7 1/2), had to extract the loaded round. Held the rifle with the barrel pointing up, carefully opened the bolt, and most of the powder remained in the case, but enough spilled out that firing that rifle, that day, was out of the question.

Fortunately it's one of my switch-barrels & it was easy to remove the barrel, giving complete access to the receiver lug area for a complete cleanup.

Is there some reason you feel you must jam the bullets into the lands?

My 6BR's do an excellent job with the bullets just touching & the 308 does very well with as much as .030" of jump.
I've always used the Stoney Point Chamber O.A.L. gauge to establish bullet seating depths, have the max lengths recorded with the bullets just touching & will not exceed that length.

 

[jo191145]

First off I'd refrain from loading into the lands on any semi-auto. Thats a No No.

OAL is not the way to get any accurate measurements. You need a comparator to measure off the ogive.
While your at it buy a Hornady case guage tool with both 308 and 6BR case guages so you'll know exactly where your lands are.

Back up, slow down, buy some tools and gain the knowledge they provide.

 

[Glenn Powell]

I believe you are measuring the wrong part of the bullet, the tip. When seating into or close to the lands you have to measure to the ogive of the billet. The ogive is where the bullet actually contacts the lands. Stony point makes a tool specifically made to measure such. Match kings will vary from the ogive to the tip, just the nature of the beast. Stony point comparator gage is what ya need, with out it you are just guessing.

 

[Cort]

Thanks for your insight. I have been thinking about the problem and had come to some of the points on my own but it helps to be pushed a little.

I am not sure what is going on with my AR. I was loading the 168 SMK's to an OAL of 2.800 as indicated in the Sierra book and confirmed by measuring some factory fresh Federal Gold Medal Match cartridges. I am loading them shorter now. I agree that I don't want to jam a bullet in an AR but it was happening and it wasn't intentional. I guess the throat on my AR is a bit short.

I am ordering some tools to help me with the 6BR and the .308 Winchester bolt rifle that is in the works. Maybe I will figure this out.

Thanks again,

Cort

 

[KevinThomas]

Cort,

It may well be a bit of a lost cause on the AR, if you'll follow along for a moment. I seriously doubt that a 168 gr bullet seated to 2.800" would be jamming into the rifling as it is loaded. What happens after the bolt is closed is another matter entirely. Have you tripped the bolt, extracted the unfired round and measured it after being chmabered? That's a real eye opener for many. What you're dealing with there is a very large, heavy and expensive kinetic bullet puller, every time you close the bolt. Unless there's pretty firm neck tension, that bullet will move forward when the case finds the end of that chamber, usually stopping about the time the impact the rifling. In essence, you're probably "soft seating" the rounds upon chambering. A chamber cast will tell you everything you need to know about the chamber, as will one of the old Stoney Point gages used with some discretion. Just a little something to take a closer look at when you get a chance.

 

[Cort]

Kevin,

Thanks, that is excellent food for thought. I just ordered a Stoney Point gauge. I will check my AR when it comes in.

The problem with measuring OAL after slamming the bolt home is I have to pry the bolt open. I suspect the bullet is pulled out a bit as a result. I am not crimping my loads since bullet movement is very likely.

Cort

 

[KevinThomas]

Cort,

Never seen an AR that wouldn't produce some bullet movement when the bolt was closed, and it can be rather pronounced in some. Never tried this in an AR-10 (though I'm in the process of building one right now for 1,000 yard Service Rifle), but I've gotta assume that it'd be even worse, given the heavier bolt, stronger springs and more violent cycling. We'll see, but I'm betting on there being some movement. Hope that helps!

 

[Cort]

Focusing on my 6 BR only, how do I seat bullets so that they are consistent in depth of seating relative to the ogive? I don't really care what the OAL is since my rifle is a single shot bolt action.

I like Frank's advice; no more than just touch. But I still want the jam, jump or touch to be consistent.

On my AR-10, I don't want to crimp the bullets because I don't want to deform them. I guess any deformation would be consistent so accuracy would not suffer (too much).

Cort

 

[fdshuster]

Cort: When you start measuring from the case head to a datum point on the bullet ogive, you will get consistant length dimensions.

Unless I'm loading for the AR, and want to magazine feed, I could care less what the length is to the bullet tip. They all vary by as much as .020" right out of the box. Hollowpoints are especially bad with the jagged tips. The plastic tipped V-Max, A-Max, etc. will have less variation.

 

[jo191145]

cort

Kevin is probably spot on correct.
Its very rare for me to see an autoloader at the BR comps I attend. Not of my realm
The one time I was next to an AR-10 that very problem occured causing a jam. (eggshoot not BR but who cares)
The shooter was able to eject the cartridge and the bullet remained in the case.
It landed near my feet so I returned it. Was easy to see the engraving of the lands and the amount the bullet had moved forward in the case.

After the relay was over we got to talking.
Seems the shooter and his brand new 308 AR had developed loads single loading.
At the match he decided to utilize the magazine and thats where the trouble started.

I've read where the AR is likely to throw the first shot out of a group using a mag simply because the force of letting the bolt slam shut is not equal to fully cycling under fire.
If theres any truth to that could it be a change in DTL caused by force doing that? Still out of my realm but an interesting question.

As you've already surmised neck tension is critical. You may need to go .003"-.004" neck tension to hold them buggers in.
Standard dies may not give you that. A bushing die may be needed.
If using a bushing I'd strongly suggest ditching the expander ball. Not so much for accuracy as some might think but to negate the need for any lube inside the necks.

Another consideration. Tumbling brass in walnut/corncob imparts its own lubriscocity to the neck ID.
Might want to refrain from tumbling in this scenario. Theres no awards for shiny brass.

FWIW I've done quite a bit of dabbling in crimped loads years ago. Started by accident. Theres no doubt they can actually increase accuracy in some circumstances.
The deformation in the bullet is pretty much ironed out as it enters the throat.
The deformation that steered me away from ever crimping again is the deformation in the brass.
Makes no difference if you leave em in the mud but for a reloader to deal with the severe changes in brass ductility from load to next loading can leave you pulling out hair.
That was my expierience anyway.

 

[Bradley Walker]

Cort,

It may well be a bit of a lost cause on the AR, if you'll follow along for a moment. I seriously doubt that a 168 gr bullet seated to 2.800" would be jamming into the rifling as it is loaded. What happens after the bolt is closed is another matter entirely. Have you tripped the bolt, extracted the unfired round and measured it after being chambered? That's a real eye opener for many.

Word. Good advise here...

 

[22BRGUY]

Hi all...Just checked on ebay and there are 12 volt small vacuum cleaners that might come in real handy on these occasions...also for those who walk or ride your bike to the range, there are the cordless type too.

 

[Ronb]

Cort, If you jam, always keep canned air, cleaning rod, bullet drop tubes, chamber swabs handy. Just be careful to not get any powder in the trigger when you pull the bolt out. These will clear the stuck bullet and clear all the powder to get you going. Ron

 

[Cort]

I received my Hornady OAL gauge today. The maximum OAL for my AR-10 with 168 grain SMK is 2.752. Consequently, the Sierra maual recommended length of 2.8 is too long. I have seated my new loads at 2.732. It will be interesting to see if I still get the stuck bolt syndrome.

My 6BR is short throated too. Its OAL with the 70 grain SMK is 2.109. The Sierra manual lists the SMK at an OAL of 2.150. I knew the reamer was "special" for my 6 BR but did not realize what I had.

Now I understand my problem.

Thanks for all the good advice.

Cort

 

[quartermaster]

Good topic and good posts. I am subscribing to it so I can throw in my 2 cents when I'm not so tired.