Chambering issue: Reloads

[Osburnjd]

Hoping for some insight on a problem I experienced with some of my reloads in an ar308 and ar15 (300 BO) using a Redding Turret press with Redding dies. Both of the rifles are new builds with just a few rounds through them. The BCG fails to fully close as the reloads won't fully chamber. Factory ammo chambers and fires perfectly. In both instances on both rifles, after firing a couple of rounds of factory ammo, the reloads that failed to chamber in a "cold" rifle previously, now chamber and fire. I can't pick up a difference in cartridge width using my micrometer. Any feedback you may have is appreciated.


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[UclaPeon44]

compare cartridge headspace with hornday comparater. if headspacing is good, then check if your bullet is touch the rifling. bullet you are using might have different ojive than factory, causing the round to jam into rifiling, if this is the case slightly shorten the COAL.

[pacrat]

The BCG fails to fully close as the reloads won't fully chamber. Factory ammo chambers and fires perfectly

I would estimate that 90+% of the "fail to chamber" issues with bottleneck rifle cartridges. Such as yours, is caused by insufficient bumping of the case shoulder during sizing.

I suggest your first diagnostic step should be to use a black marking pen to coat a cartridge that fails to chamber. From the neck/shoulder junction. To down past the shoulder for 1/2" or so. Then try to chamber again.

If that case shows "rub marks" on the shoulder. Your shoulder needs to be bumped more.

Are your sizers set for a "hard bump" against the top of the shell holder? Most issues can be resolved by properly adjusting the die.

If you already have a hard bump on the shell holder. The issue may be "tolerance stacking". Which can usually be resolved by removing a bit of matl from the top of the shell holder. Or the bottom of the die.

NOTE........factory ammo is sized to fit "ALL" firearms. Which means it is typically "smaller" than standard SAAMI specs require. Whereas reloading dies are made to return cases to SAAMI specs. Add to that variance the normal +/- tolerances of manufacturing standards. And "tolerance stacking" raises its ugly little head and bites many reloaders on the butt.

[JackEllis]

I had this happen with once-fired cases and in one instance, factory ammo. Full length sizing the cases solved the problem with hand loads.

[zoner]

size an empty case and try it in your rifle. Put it in the chamber then let the bolt chamber it. If the bolt won't close or the bolt closes and it is VERY difficult to extract the empty case manually your case shoulder needs to be bumped back a bit

[edgerly779]

^^ Easiest way to check sizing.

[Dark Hunt]

Check the diameter of the case shoulder. If it's too wide, your seating die is probably screwed in to far and the case mouth is hitting the the step in the die and pushing the neck down causing the shoulder to buckle slightly.

[bsumoba]

for AR platforms, small base dies IMO is a must. It is not always the shoulder bump, but the base of the case expanded to the point where it will not chamber. A small base is the only way to fix this. If a small base does not work, chuck the brass.

[JagerDog]

There are cases where the sizing button being drawn back through will tug on the shoulder affecting headspace too. A little lube in the case mouth can help preclude this.

Yes to checking a resized case in the rifle before adding powder/bullet. Then check again with bullet. Find out where the process is failing.

[OpenSightsOnly]

for AR platforms, small base dies IMO is a must. It is not always the shoulder bump, but the base of the case expanded to the point where it will not chamber. A small base is the only way to fix this. If a small base does not work, chuck the brass.

For 223 gas gun, a properly adjusted FL die is all that is needed to size commercial or once-fired milspec brass (rifle or MG-fired).

First time reloaders don't know how to set-up the die to the press or even measure the length of the brass using a cartridge headspace tool

[Osburnjd]

Thanks for all of the great input. Certainly some suggestions for me to address. Still a little confused as to why a cartridge that would not chamber initially will chamber after running a couple factory rounds through it. I will proceed with the suggestions provided and thank you again for the feedback.


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[Sailormilan2]

I agree with all the comments here. But a question since I didn't see the issue addressed. Did you trim all the cases back to minumum recommended length? 2.005" for .308.

[Osburnjd]

I agree with all the comments here. But a question since I didn't see the issue addressed. Did you trim all the cases back to minumum recommended length? 2.005" for .308.

Sailorman, great question. I did trim all the cases back to Saami specs that were over sized. As I recall there were some I did not trim as they were under the spec. I don't remember the length off the top of my head but did follow the specs as published in the Hornady manual I purchased earlier this year.


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[Kmai24]

for AR platforms, small base dies IMO is a must. It is not always the shoulder bump, but the base of the case expanded to the point where it will not chamber. A small base is the only way to fix this. If a small base does not work, chuck the brass.

+1
Had the same issue when I first started reloading 223..had FL dies and I adjusted up and all the way down to where it bottomed out and for the life of me I still couldn’t get it to resize all the way. Ended up buying RCBS small base dies and bingo, problem solved and haven’t had any problems since. Wouldn’t definitely recommend SB dies for auto loafers.

** loaded 223 and 300bo using RCBS SB dies **

[MrElectric03]

Thanks for all of the great input. Certainly some suggestions for me to address. Still a little confused as to why a cartridge that would not chamber initially will chamber after running a couple factory rounds through it. I will proceed with the suggestions provided and thank you again for the feedback.


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Either your bolt has a bit more momentum after firing a case to chamber it or the chamber is hot now and expanded. Or a combo of the two. Either way it's not right. Get a case gauge so you can properly set your FL dies. Some dies don't size well. If the inlet of the die is very rounded, they don't size properly. You want a die to be more squared off on the bottom. I have had to file down some .223 dies on the bottom to get the shoulder bumped back enough. I have never needed small base dies, not to say that's not your problem but that won't always fix it.