Sticking cases when shooting suppressed?

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MJF1911
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Sticking cases when shooting suppressed?

Post by MJF1911 » Wed Jun 01, 2016 12:14 am

I've been shooting my Rem 700 300 Win Mag and I have only shot hand loads but the cases are sticking pretty tight in the chamber. I have to beat the bolt open. I've tried reducing the charge with no improvement and today I took the can off and none of them stuck. Can is a AAC 300TM. I've shot numerous other rifles with this can and none of them have stuck cases. I don't want to shoot this gun without the suppressor. I'm going to try my Specwar and see if it does it with that can.
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Re: Sticking cases when shooting suppressed?

Post by johndoe3 » Wed Jun 01, 2016 1:02 am

What I would do is try shooting a few rounds of new factory ammo with the can on, and see if they stick too. If they don't, then maybe it's a small issue of sizing the brass and/or needing to set back the shoulder, back within spec, when you resize the brass.

Factory new brass in cartridges is deliberately slightly undersized to function well in any gun of that caliber. So if they function OK, then you can measure where your reloaded brass is larger than the factory new stuff and causing a problem.

I would also carefully examine the stuck brass to try and determine where the sticking is mainly occurring.

My thought was that if you are neck-sizing your brass and not full-sizing it, that the brass has grown and is at the marginal limit. The little extra pressure and heat with the silencer on is pushing the brass slightly over the shoulder length limit. Full-sizing with a shoulder bump might fix your problem.
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Re: Sticking cases when shooting suppressed?

Post by MJF1911 » Wed Jun 01, 2016 1:52 am

I was using new brass, running it in my sizer die only rounds out the neck.

Before I polished the chamber there were scratches just ahead of the belt, after polishing I noticed the brass was shiny in the same area without scratches.
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Re: Sticking cases when shooting suppressed?

Post by T-Rex » Wed Jun 01, 2016 7:38 am

I've experienced this as well.
My thought was that the reduced charge does not fully expand the brass. The suppressor increases back pressure and forces powder residue between the case and chamber.
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Re: Sticking cases when shooting suppressed?

Post by Fulliautomatix » Wed Jun 01, 2016 10:44 am

T-Rex wrote:I've experienced this as well.
My thought was that the reduced charge does not fully expand the brass. The suppressor increases back pressure and forces powder residue between the case and chamber.
I've noticed that as well. Not stuck cases, but dirty brass due to neck sealing not occurring due to reduced loads.
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Re: Sticking cases when shooting suppressed?

Post by T-Rex » Wed Jun 01, 2016 11:55 am

Yeah, I wouldn't call them stuck, just a noticeably stiffer bolt to unlock.

Maybe in this case the added back pressure is expanding the case a bit further? Increasing the tension on the chamber wall?
Try to polish the chamber and see if it helps.
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Re: Sticking cases when shooting suppressed?

Post by kyk » Wed Jun 01, 2016 4:45 pm

MJF1911 wrote:I've been shooting my Rem 700 300 Win Mag and I have only shot hand loads but the cases are sticking pretty tight in the chamber. I have to beat the bolt open. I've tried reducing the charge with no improvement and today I took the can off and none of them stuck. Can is a AAC 300TM. I've shot numerous other rifles with this can and none of them have stuck cases. I don't want to shoot this gun without the suppressor. I'm going to try my Specwar and see if it does it with that can.
Polished chamber can cause slipping, coarse surface have less contacting surface and reduce friction.
Also it's not a good idea to neck size a new brass, at first they should be fire formed in your chamber.

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Re: Sticking cases when shooting suppressed?

Post by MJF1911 » Wed Jun 01, 2016 6:27 pm

I tried some factory ammo today and it stuck with both cans.

I full length sized the new brass, although my sizer die didn't even touch the cases, just rounded out the necks.

My hand loads still stuck with the Specwar, but noticeably less.

New brass measures .506 just ahead of the belt, resized measures .511 and fired measures .513 SAAMI is .513 so I would say the chamber is in spec.
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Re: Sticking cases when shooting suppressed?

Post by whiterussian1974 » Wed Jun 01, 2016 6:34 pm

This is just my theory with nothing to back it up. But, maybe it's the added time before the pressure curve lowers that allows the brass to cool. This means that instead of relaxing and contracting to midway in dia, the neck remains flared until the soft, plastic character of the brass rehardens in it's less maleable state.

Just a thought. :)
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Re: Sticking cases when shooting suppressed?

Post by MJF1911 » Wed Jun 01, 2016 10:28 pm

If there was some kind of mark on the neck it could be possible, the only mark I see is just ahead of the belt.

I ran these over the chronograph today and got an average of 3050 FPS, which is the top end of 190 grain bullets in the 300 Win Mag. I loaded some more this afternoon and backed off three more grains. I won't get to shoot again until Friday afternoon.
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Re: Sticking cases when shooting suppressed?

Post by kyk » Thu Jun 02, 2016 5:26 am

If you are using maximum loads you can have problems with low cost brass.
Just try to reduce the load. And measure the rim of the new brass and compare it with fired.

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Re: Sticking cases when shooting suppressed?

Post by MJF1911 » Thu Jun 02, 2016 10:10 am

This isn't low cost brass and I wasn't using max loads, however it appears they are pretty warm according to the chronograph. I reduced by 3 more grains to see if that improves anything.
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Re: Sticking cases when shooting suppressed?

Post by CanOfWhooppass » Thu Jun 02, 2016 10:56 am

MJF1911 wrote:This isn't low cost brass and I wasn't using max loads, however it appears they are pretty warm according to the chronograph. I reduced by 3 more grains to see if that improves anything.
It is also posible your chamber isn't as perfect as it should be. A single high pressure round could have stretched the area in front of the belt creating a slightly larger diamater than the area behind it. If this is the case, you are fire forming the brass and the back of the chamber has to act like a sizing die as you pull it out. I'd do some measurements on spent brass to see if it's round and the same diamater in the shiny area. Polishing can also remove metal and make it worse.

Depending on how tight your chamber was to start with, a chamber reamer might be a fix.

I'm new to the suppressor field, but have run across bulged chambers before and the shiny area in front of the belt seems suspect.
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Re: Sticking cases when shooting suppressed?

Post by MJF1911 » Thu Jun 02, 2016 11:23 pm

That is my thought as well, somehow there is a slightly larger diameter ahead of the belt. I'm out of town for work but I'll get in touch with a gunsmith and see if he can do a chamber cast.
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Re: Sticking cases when shooting suppressed?

Post by savagetactical » Wed Jun 08, 2016 4:16 pm

Only time I've had issues like this is when my Case OAL is longer than spec. I know it doesn't jibe with your results with factory ammo, but I'd measure the OAL of the cases to be sure. Who knows, the factory rounds you used might be longer than spec as well. You might have a tight throat, or your rifle could just make brass grow OAL really fast. Just a thought.

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Re: Sticking cases when shooting suppressed?

Post by whiterussian1974 » Sat Jun 11, 2016 5:55 pm

MJF1911 wrote:That is my thought as well, somehow there is a slightly larger diameter ahead of the belt. I'm out of town for work but I'll get in touch with a gunsmith and see if he can do a chamber cast.
Before you go through the trouble of a cast, have you mic'd the section w calipers?

A change in tension/rubbing b/t unfired and fired could indicate the expansion forward of the belt.
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Re: Sticking cases when shooting suppressed?

Post by Fulmen » Sun Jun 12, 2016 3:59 am

What I can't understand is why this would happen only with a silencer fitted. Have you confirmed this or was it just a coincidence.

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Re: Sticking cases when shooting suppressed?

Post by T-Rex » Mon Jun 13, 2016 8:48 am

The following is all conjecture so please take it as such.

If your chamber is even slightly rough, it will increase the total surface area the brass will need to stretch over. A rougher chamber finish will also increase the amount of time the brass is stretching. This increase in time is carried through the different stages brass will undergo during a heat cycle. A suppressor will increase the amount of dwell time available for the pressures it has contained, further increasing the stress factors on the brass casing.

My first suggestion would be to have (2) lots of between 3-5 rounds each. Use, new, unfired rounds.
Fire the first lot, unsuppressed, from a clean rifle. Save the brass.
Fire the second lot from a, clean, suppressed rifle. Save the brass.

Measure the: OAL, neck dia, body dia (in 2 or more areas), Head and Rim dia's.
Compare these between the 2 firing conditions.
Also, take note of the brass condition. Do both conditions show firing marks? In the same locations? Are there any additional scratches, marks or powder residue? Is the shoulder formed identically, between the 2 conditions?

You might also try to coat some cases in layout fluid (dykem) and fire. This might highlight some areas your naked eyes couldn't catch.
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Re: Sticking cases when shooting suppressed?

Post by Historian » Mon Jun 13, 2016 9:24 am

T-Rex wrote:The following is all conjecture so please take it as such.

If your chamber is even slightly rough, it will increase the total surface area the brass will need to stretch over. A rougher chamber finish will also increase the amount of time the brass is stretching. This increase in time is carried through the different stages brass will undergo during a heat cycle. A suppressor will increase the amount of dwell time available for the pressures it has contained, further increasing the stress factors on the brass casing.

My first suggestion would be to have (2) lots of between 3-5 rounds each. Use, new, unfired rounds.
Fire the first lot, unsuppressed, from a clean rifle. Save the brass.
Fire the second lot from a, clean, suppressed rifle. Save the brass.

Measure the: OAL, neck dia, body dia (in 2 or more areas), Head and Rim dia's.
Compare these between the 2 firing conditions.
Also, take note of the brass condition. Do both conditions show firing marks? In the same locations? Are there any additional scratches, marks or powder residue? Is the shoulder formed identically, between the 2 conditions?

You might also try to coat some cases in layout fluid (dykem) and fire. This might highlight some areas your naked eyes couldn't catch.
Following on T-Rex's great analysis a technique I used long ago to ensure
that a chamber is smooth is to make a burnishing tool from spent brass.

Drilled out spent primer, screwed from inside the case a long machine screw and
anchored with a nut on the outside. Now could grab with a pin-vise.
Rubbed some Kroil on the case, sprinkled jeweler' rouge over it, and
then lapped the chamber with the coated case by spinning it
while moving unit up and down. Those ancients who actually rebored hot-rod
iron engines know the action.

Did this for a target piece that whose extraction was hinkey. Eliminated problem.
Felt like a mini-Bob Chow.

Commercially produced barrels do have varying degree of roughness and diameter
vacations.

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Re: Sticking cases when shooting suppressed?

Post by MJF1911 » Sat Jun 18, 2016 8:23 pm

Sorry I haven't gotten back to you guys, work has been hectic lately.

I reduced the load further than I had before, down to 70 grains, and no more sticking. As I've had a few days to process this, I'm using a new powder that hasn't received a lot of testing. Alliant's data for RL23 called for 75.5 grains to deliver 3005 FPS with 190 grain SMK. I averaged 3050 with 73. I didn't run the 70 grain loads over the chronograph but I will eventually.
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