Modern Sporting Rifle Evolution
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JohnOD

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2/23/20 Update

I backed off the powder charge 1/2 a grain and also changed out the cam pin & buffer spring and she digested 16 rounds without a hiccup

Ordered 100 pieces of Hornady 6GT brass this morning and will be retiring the 6.5x47 Lapua I've been using

Thanks to all the members that offered advice

End of update

I have a 20” 7VAR upper I purchased used in March of 2017. I had put something like 4/500 trouble free rounds down range without a hiccup. Recently I changed out the upper to a Young Mfg. side charger, and put a new bolt pin and handguard on at the same time.  The bolt, barrel, adj gas block & gas tube all remained unchanged. I did put new gas rings on the bolt while I had things apart.

The carrier moves  freely in the upper and charges normally when cycling the charging handle with the gun empty. Sized, unloaded cases camber easily with light fingertip pressure on the back of the carrier with the ejector removed. Same with loaded rounds where I use a firing pin with the tip ground off and no ejector. 
IMG_2790.jpg
A few weeks ago I made it out to the range with my rebuilt upper and had problems with fired rounds only extracting about ¼” and locking up.

IMG_2779.jpg 
I had to mortar the gun while pulling on the side charge handle to get it cleared. Sometimes it took about all I had to get it open. My assumption was it’s under gassed so I started turning the adj gas up and things didn’t improve.

Once I had the gun home I tore it down & checked the barrel nut for tightness and gas block alignment. The Syrac Gen ll gas block might have been off a degree or so but it was close.  Anyway I reset it and torqued it to spec.

Fast forward to today and I started with two different magazines, each loaded with one round and the gas block open two clicks. Ran into the same issue of the bolt not cycling back more than ¼” and needing to mortar the gun to get the bolt open. I opened the gas up to five clicks and the case wouldn’t eject but I could work the charging handle without mortaring the gun.  At 10 clicks the case ejects and the hammer cocks but the bolt is in the closed position…. not locking back on both empty magazines. 12 Clicks and no change. 14 Clicks and I’m back to needing to mortar the gun.

So next I take another lower that runs perfectly on my 6.5 Grendel and put the 7mm upper on it. No change.  I tried multiple gas settings with the second lower and it’s more of the same problem.

I’m using the same load that functioned perfectly before I changed out the upper and bolt carrier.
IMG_2780.jpg
IMG_2787.jpg   


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BIGGDAWG

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if it ran fine before and not now something you did is probably causing the issue.  though benchmark at that load is at or slightly over max sticking cases can be high pressure. 

also benchmark almost always takes a wide open gas port to cycle, cfe and some of the slower ball powders are a little over gassed and i normally turn down my slr gas blocks for them 6-8 clicks from full open

as a test load a few rounds at 34.5 benchmark and see what happens then go over everything you changed the secret is there somewhere.

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JohnOD

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Thanks BD, I'll give that  a try
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Rifter

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I don't remember exactly, but back when the Wolverine was new, and the Valkyrie as well, some of the powders we tried didn't generate enough gas at safe pressures to properly cycle things.  Do you remember which of the ones we tried were lean on gas?  
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BIGGDAWG

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Originally Posted by Rifter
I don't remember exactly, but back when the Wolverine was new, and the Valkyrie as well, some of the powders we tried didn't generate enough gas at safe pressures to properly cycle things.  Do you remember which of the ones we tried were lean on gas?  


to answer i changed the port early on so it would run the benchmark and h322. but if you read everything he said it was running fine until he changed the upper. he shot the same loads now he is having issues so something happend.

i just thought too that check the gas tube for a restriction i have heard of that happening and it is possible with taking it off a chunk of carbon or copper or something may be restricting it. 

the other thing i would do is take off the adjustable and put a standard gas block on to test it if you don't find anything else.  as i stated h322 and benchmark will take a full open port or dang close cause that is what i tuned the port to..

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JohnOD

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Don't necessarily think this is contributing to my cycling issue but I did find some rough machining on the carrier that was grinding away on the cam pin (in my photos look inside the cam pin raceway in the carrier at the vertical marks in the dark section). The carrier is on the way back to Young's for them to look it over. 
This cam pin has somewhere around 60 rounds on it and has had .0015" ground off of it so far.
IMG_2799.jpg  IMG_2794.jpg

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BIGGDAWG

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Quote:
Originally Posted by JohnOD
Don't necessarily think this is contributing to my cycling issue but I did find some rough machining on the carrier that was grinding away on the cam pin (in my photos look inside the cam pin raceway in the carrier at the vertical marks in the dark section). The carrier is on the way back to Young's for them to look it over. This cam pin has somewhere around 60 rounds on it and has had .0015" ground off of it so far.

i would bet it is adding to the issue, we talk about it all the time stacking of tolerances. one end of spec on one and the other end on the other and then it don't work.  so that little thing combined with another as in new lot of powder or something causing pressures to increase slightly and it could be issue. 

so clean and polish that up. make sure gas block is wide open check gas tube for obstruction and drop a half grain on your charge and see what it does. also maybe load one of the pet loads with cfe223 to double check everything too.

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RangerJoe

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i would bet it is adding to the issue...

Agreed!  Several "little" things can quickly add up to a big thing.  It was working before, now it's not... the things changed between then and now caused the problem.  Finding and fixing whether that was one BIG thing or several SMALL things is a blend of art, science, and experience.

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JohnOD

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Thanks for the input guys. I spoke with Young's earlier in the week and the carrier is on its way back to them. I'll dial my powder charge back and reassess things from there.
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lapriester

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Take a close look at the cases you had to morter the rifle to extract. I had some of the same problems with my 27GPC and 22 Nosler. Even though I could close on the sized cases, after firing and having to pound them out while destroying a perfectly good charging handle, I did some close inspection of the fired cases and found a ring on the shoulder right at the transition from the shoulder to the neck. The ring was being caused by insufficient set back causing the case to seize on the chamber shoulder when the bolt slammed closed.

I actually had different causes between the two rifles. On the GPC I simply very slightly didn't set back the shoulder enough, my fault actually. It didn't take much. I had to take apart about 50 rounds, set back the shoulder with 1/8 turn on the die and all was good. On the 22 Nosler I was getting the typical case head extractor damage common to the crap Nosler brass and even though it would fit in my shell holder the damage on the case head was such it changed the set back enough when the flat surface of the bolt loaded the worse rounds they were jamming on the chamber shoulder. I ended up using a Dremel on the case heads to smooth out the extractor galling and they fed and extracted just fine. Now, I just cull all the worse Nosler brass and size the brass at max set back. No problems since. God I hate that 22 Nosler. The worse brass eating, but one of the most accurate uppers I own.

Just for shits and giggles you might try setting back the shoulders on a few rounds more and see if it resolves the problem. Worth a try anyway. What about factory ammo? It always has the shoulders set back to maximum.
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JohnOD

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Thanks for the input LAPRIESTER

The fired cased have all been reloaded so its too late for me to check for the ring on the shoulder. According to my records the shoulders were set back .003/4" so they should have been good.
No factory ammo available for the 7VAR so I'm starting back from ground zero with some lighter loads... now I just need to get back to the range and give em a try.
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Rifter

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Quote:
Originally Posted by JohnOD
Thanks for the input LAPRIESTER

The fired cased have all been reloaded so its too late for me to check for the ring on the shoulder. According to my records the shoulders were set back .003/4" so they should have been good.
No factory ammo available for the 7VAR so I'm starting back from ground zero with some lighter loads... now I just need to get back to the range and give em a try.

Did you make your own brass, and from which case?  When I got mine (one of the first barrels) Bruce made the cases for me from Lapua brass, and the first load was perfect.  Subsequent loads however, I snuck up on the headspace like a cat burglar at 2am.  It was tight, at a nominal .003".  But I've never had issues like what you're describing.  I haven't tried any cases made from the Dasher brass yet.

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JohnOD

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Rifter thanks for the input. I've been loading 6.5x47 Lapua brass that came with the used upper I purchased. No idea how many times it was loaded before it came into my hands. I've loaded mine 7 or 8 times and even though the primer pockets are still tight and I haven't had any split necks or other issues I plan on retiring it after the next firing. I 'm on the waiting list for some 6MM GT brass from Alpha but will order some Hornady it it doesn't come in soon.
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Rifter

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Quote:
Originally Posted by JohnOD
Rifter thanks for the input. I've been loading 6.5x47 Lapua brass that came with the used upper I purchased. No idea how many times it was loaded before it came into my hands. I've loaded mine 7 or 8 times and even though the primer pockets are still tight and I haven't had any split necks or other issues I plan on retiring it after the next firing. I 'm on the waiting list for some 6MM GT brass from Alpha but will order some Hornady it it doesn't come in soon.

Check to see if you have a doughnut at the base of the neck inside.  With longer bullets that will cause the neck/shoulder junction to be 'fat'.  You can get that if the case has stretched due to a bit of excess headspace from too much sizing.  That was a problem with the Lapua case and why it had to be reamed inside the neck and turned down to the neck/shoulder junction outside.  Try seating a flat based bullet down past the base of the neck.  If you get more resistance at the base then the doughnut is likely the reason.  I would double check how far you're setting the shoulder back as well.

Lapua is super tough brass, and if you anneal it and have the headspace right, and no doughnut, there is no reason you shouldn't get at least 10 reloads if not more.

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