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Neck Sizing, groupings, and chambering issues

 
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  #1  
Old 07-19-2011, 10:47 AM
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Neck Sizing, groupings, and chambering issues

Okay so I have been working up a load for my .308 and have only fully sized the brass I have been shooting. (I have only been reloading a few weeks). I have shot a good .38 MOA group at 100 yards using 43 gr of rl-15 with 168 btips seated .02 off the lands. Since this is a hunting load and I am using a 20 inch tube, I am trying to get all the velocity I can within reason as long as it I am not sacrificing accuracy. My loads over 43 gr have had 1 moa to 1 1/2 moa accuracy till I hit 45.5 gr and it came back to just under 1 moa. My book is showing 44.8 as the max, but I inched up and have yet to see any pressure signs. This leads me to the questions I have.

*Note - I am shooting off a bipod with bags to eliminate my shooting as a factor as much as possible. All my groupings are very consistent. So my groupings don't have much to do with my shooting.

Have any of you guys experienced your groupings opening up as you increase the powder and then start to shrink as you find a higher powder amount your rifle likes?

So instead of using anymore powder to see if the group would shrink anymore ( I understand I most likely don't want to go much farther if any) I decided to to just neck size some Remington cases I had (was using winchester) and see if some fireformed brass would help close the groups. I sized them by just backing off my full length size die about 3/4 of a turn. So I backed off to 45.2 gr and loaded up some rounds exactly the same as I have been using. These rounds wont even chamber? If I don't add any powder and seat a bullet the round chambers fine? Whats the deal? Is this just to much powder for the Remington case and after seating the bullet its(powder) pushing the shoulder of the case enough to not chamber the round? I can't think of any other reason why. I ran out of time to try a lower powder amount or a neck sized Winchester round and wont get a chance for a few days.

Thanks in advance
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Old 07-19-2011, 05:13 PM
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Join Date: Jul 2011
Location: Near Napoleon,MI
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Re: Neck Sizing, groupings, and chambering issues

I recently ran into trouble with inconsistent case lengths on my 7.62x38 reloads. Since the brass was once fired, I didn't check its overall length or trim any of it. When it came to seating the bullets, I noticed a distinct difference in the "feel" of the bullet seating operation between different shells. I later discovered that the case neck had been distorted (bulged outwards slightly in diameter) due to the variation in case length. The thin neck will only remain stable up to a certain force in the bullet seating operation. If that is exceeded I have seen 2 different things happen: 1) The neck expands (seen on my 7.62x39) or 2) The junction of the shoulder to the main cartridge diameter is distorted (bulges outward) which I saw on some of my 8mm mauser cartridges.

In both cases the cartridges would not chamber and in neither case did it have anything to do with the amount of powder in the case. I would say that if my 7.62x39 was a bolt action, I would probably get the bolt closed on it, but my ar15 is too wimpy and the camming action too weak.

So be sure that your case lengths are identical. Backing off the full length die 3/4 turn may be a bit much. You should lower it until you can tell that it starts touching the shoulder and stop right there. Moving the shoulder back takes more force for sure...
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Old 07-19-2011, 06:24 PM
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Re: Neck Sizing, groupings, and chambering issues

I definitely thought maybe I should bring the die down a little bit more after thinking about it today, however the cases chamber great by themselves and I did trim them all to 1.985 (2.005 SAMMI) so they aren't to long.
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Old 07-20-2011, 08:17 PM
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Re: Neck Sizing, groupings, and chambering issues

trust me its not the powder at all.the powder would crush before the case would buldge.

now that I have just typed up something and then removeing it after I just read your post again this is what I think is happening to you.

you are useing alot of powder in your loads. ( I think )will have to look at Quick load to really find out for ya.but if I am right the bullet is being pushed out after you seat the bullet on TOP of the powder.this will sometimes happen on a compressed load.but you can tell by measureing the load again after you have loaded a few.and with you seatting the bullet just .002 of the lands its then pushed out fare enough to give you a hard time chambering the bullet.

you may want to look into getting a neck sizeing die say a Lee collet.they really work great when you get the hang of it.

now to your other question.yes adding or takeing powder from a load will cause that to happen.thats why we or alot of use use the ladder test.this will help you out to find two different accuacy loads for that rifel your loading for.you end up with a low and high accuacy load.you have come up with a high load for your load.but useing the ladder test by loading in steps say .3 or .5 grains at a time. ( 42.0-42.3-43.6-42.9 and so on )this helps out alot.for me I do the three of each when test a powder.and use a long seated bullet say .010 off the lands for all the three lot powder loads.after that shoot at 300 and find out what shot the best.then load it up in a lot of five useing different lengths ( long and small )

will look at Quickload to see if am right.or maybe someone with a better idea can chime in to help.

OK just took a looksee for ya.you are at the high end but still safe by Quickload.but it still may be the case of the bullel being pushed out by the load.are you cleaning all of the sizeing lub out of the necks?or your seatting die isn't adjusted right.maybe you are seatting the die up different from the other times.

just seems to me that the seatting die is not adjusted like before and touching the case when you are seatting a bullet to just push the neck in to keep it from chambering.but keep going back and reading your post.and you say it will chamber with a seatted bullet with no powder.so I keep thinking on the pressure of the powder in the case is pushing the bullet out.for me too I will just have to keep a eye on your post or think a little more on it.hope things work out for ya.

Last edited by Johnboy; 07-20-2011 at 08:38 PM.
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Old 07-21-2011, 07:46 AM
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Re: Neck Sizing, groupings, and chambering issues

I measured the rounds right after I seated the bullet and as far as everything being clean, there is definitely no issue there. I have been double checking everything i do and they measured correctly however, who is to say that the pressure didn't slowly push the bullet back out I didn't think of that. I can't check till later tonight but that could be the issue.

Yesterday I did FL size some of the Remington cases and had no issue. I also did a neck size with the die back off like 1/6th this time and the cartridge chambers fits tight, but there is no issue chambering. I have yet to shoot any of these rounds and wont get to till Saturday.

As far as the ladder testing that is exactly what I am doing. Once I am satisfied with the powder charge, I will focus on the seating depth. My only issue is I can only shoot to 100 yards as of right now because I live in northern va. So I am just gonna hope whatever is best at 100 will be the best at 500. I plan on making a drive once I have the round I think I want to use.

Last edited by twiedenh; 07-21-2011 at 08:06 AM.
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  #6  
Old 07-21-2011, 10:09 AM
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Join Date: Sep 2009
Location: Cheraw S.C.
Posts: 285
Re: Neck Sizing, groupings, and chambering issues

good to hear that you are load testing with a ladder test.but said to hear you are still haveing a problem.in fact I am going to my reloading room to see for myself what might be your problem.I have remmy brass and will put your load of 45.2gn's of R15 in a case.then seat a bullet to see what happens.

keep going back to what you said.it chambers without powder in it.so the case is OK when you seat a bullet without powder.so I keep thinking about the pressure in the case after you charge it then seat a bullet.I haven't had this to happen to me but have heard of it to happen.

the only other thing that keeps me thijking on this is that your not resizeing the case all the way down to the head enough but pulling the away to neck size. BUT you can chamber an uncharged case with bullet seated to you specs.and with you just .002 off the lands it just make since to me that the pressure in the case after chargeing it is the reason.

well out to my reloading room I go.
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