Barrel Tester, Looking For Ideas

N

NezRongero

Member
With sponsorship support from Shilen for the last 2 years, I have been cranking out AR barrels for TX Juniors high power team, totalling 24 active participants in the program this year, and we are still actively recruiting. At the rate they are going with our training sessions and shooting in matches, our best guess they will go through a barrel a season. Though I am not in the business, just providing free barreling work for the kids is enough to keep me busy in the garage at the start of the season.

The skill level of our kids varies from Marksman to High Master. There are but a couple at the HMs, mostly are Sharpshooter and Expert level shooters, we are expecting some to move to Master classification this year.

Having gone through the lengthy intro, I am looking for ideas how to test the AR barrels to determine precision. I read about barrel blocks in some rail guns, don't really know how effective would that be if I were just going to clamp the barrel past the receiver. I could drill a hole through the block for the gas tube. Or would it be better just to install a free float tube and clamp on the tube?

On the platform, my thoughts would just something adjustable bolted to linear bearing. Where I need some suggestion is what material to mount assembly to for a base that is stable enough to minimize warping. Would glued 2 layers of 3/4 MDF suffice? Or steel plate be the preferred material?

Another crossed that my mind is to find a small lathe bed with carriage that I can mount the adjustable platform.

A used return to battery would probably be a good option, I don't think I can sell the going price to the team for funding.

One of the reasons I want to test the barrels so we issue the best barrels to our top shooters who are in contention for winning matches
A lot of matches these days are determined by Xs or 1 or 2 points since CMP and NRA allowed up to 4.5X scopes for service rifles. Right now we just issue barrels and tested in a completed up by the shooter.
As the example an upper was returned to team management as not shooting well enough at 600 yards. We issued the upper to our top junior shooter to shoot at the mid range match. With no zeroes for her on the upper, she lost 2 points initially, but end up with 198-12Xs at 600 in a switching wind.

The SS ratchet barrels we get for free from Shilen shoot, but most likely some may shoot better than others. The high power scoring rings are very generous with 1 MOA X ring, a really good shooting one would mean higher X count at 600, and cleans with high X count at short range, 200 and 300, even considering shooting the rifle on your elbow and sling.

Again, I am looking for opinion on what would be a good system to test AR barrels grouping capability


Thank you all



Nez
 
Put the bbl in a flat top upper with a decent scope.
Add a flat to the front bottom, egw butt stock flat.
Use this to test bbls, then re-install in a match upper/lower.
 
Nez,

I can't help you on the barrel tester, but I just wanted to give you a tip of the cap for donating your time and expertise in chambering barrels for the junior shooters. Well done.

Justin
 
retired said:
Put the bbl in a flat top upper with a decent scope.
Add a flat to the front bottom, egw butt stock flat.
Use this to test bbls, then re-install in a match upper/lower.
Click to expand...

Thank you for the response.

Almost all the kids now shoot flattop uppers, and quad rails, installing a scope would be easy. As you suggested is how we pretty much test the uppers. Before the scopes were allowed, I assembled the uppers, adjusted the front sight base with rear sight on mechanical zero. I did the testing and the adjusted for no wind zero at 200. Bench techniques vary widely among people, I am looking for a better way to test barrels to somewhat minimize the human factor.

Here is how the typical upper shoots with irons at 200, about a minute and a half with this 65 year old retiree as the trigger monkey. Maybe the real grouping capability is better with minimal human factor using a machine rest.
 

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AMU uses a rail with a block that clamps around the float tube just in front of the upper. Block is high enough for the lower to fit. Pictures here.
 

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MilGunsmith said:
AMU uses a rail with a block that clamps around the float tube just in front of the upper. Block is high enough for the lower to fit. Pictures here.
Click to expand...

Thank you.

Is this the one in the building right behind Easley range? When I was one of the civilians helping AMU and CMP in their SDM program training we got to see their loading room, the machine shop, and the testing room. I remember their machine rest device is quite elaborate. Did not get to play with it, we were busy most of the times in the 4 times I augmented at program.
 
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Zebra13 said:
Nez,

I can't help you on the barrel tester, but I just wanted to give you a tip of the cap for donating your time and expertise in chambering barrels for the junior shooters. Well done.

Justin
Click to expand...

Justin,

Thank you.

Nez
 
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Nez, , I take it to mean you want to test the barrels, with no other variables to skew the results.

What would be great is you had Shillen build you a regular bolt action with the 13/16 16tpi that is standard for the AR barrel extension. Since their actions have a flat bolt face, it would work fine with the AR Barrel.

Mount the action on a simple Rail Platform by just bolting it to the top.
 
jackie schmidt said:
Nez, , I take it to mean you want to test the barrels, with no other variables to skew the results.

What would be great is you had Shillen build you a regular bolt action with the 13/16 16tpi that is standard for the AR barrel extension. Since their actions have a flat bolt face, it would work fine with the AR Barrel.

Mount the action on a simple Rail Platform by just bolting it to the top.
Click to expand...

Exactly, Jackie, test barrels with minimum interference.

Great idea on a special action from Shilen, never thought of that. Building on your idea of 13/16 x 16 thread in a bolt gun action, I wonder if it is feasible or safe to machine off the thread and press a sleeve in the 700 action, then re-thread it for the AR tenon?

Nez
 
NezRongero said:
Exactly, Jackie, test barrels with minimum interference.

Great idea on a special action from Shilen, never thought of that. Building on your idea of 13/16 x 16 thread in a bolt gun action, I wonder if it is feasible or safe to machine off the thread and press a sleeve in the 700 action, then re-thread it for the AR tenon?

Nez
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Nez, the action thread takes the full pressure of ignition, just like the bolt lugs and their abutments.

Perhaps one could take a regular action, thread it to 1.125 18 tpi, then make a sleeve with a corresponding thread on the OD and the AR thread in the ID. I have a little Shillen action, let me take a look at it.
 
jackie schmidt said:
Nez, the action thread takes the full pressure of ignition, just like the bolt lugs and their abutments.

Perhaps one could take a regular action, thread it to 1.125 18 tpi, then make a sleeve with a corresponding thread on the OD and the AR thread in the ID. I have a little Shillen action, let me take a look at it.
Click to expand...

Jackie,

I don't know if the tenon for this new barrel extension from Whiteoak would facilitate a better choice for conversion. It is 13/16 x 20 and .300 longer. We've used these on some barrels already.

https://www.whiteoakarmament.com/sh...el-group/competition-barrel-extension-m4.html
 
Wouldn't one need to assume

that some platforms are going to be better than others, speaking of the AR actions now. I think I would want that part taken into consideration when testing barrels. Pick a rifle that shoot exceptional and use it's platform to test for great barrels, then find out why that platform is better than the others.

Pete

P.S.
I guess the platforms could be tested any time as long as one has one great barrel so you might disregard what I have said.
 
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Pete Wass said:
that some platforms are going to be better than others, speaking of the AR actions now. I think I would want that part taken into consideration when testing barrels. Pick a rifle that shoot exceptional and use it's platform to test for great barrels, then find out why that platform is better than the others.

Pete
Click to expand...

Pete,

I don't know if anyone has ever done a real test what receiver is better. Most of our experiences, the barrel is the determinant in the ARs. Some people have claimed billet are better than forged, but I have not read any controlled experiment to substantiate the claim. Assuming there is a difference, but isn't barrel testing using the same modified action as Jackie suggested definitive enough to determine which barrel is the real shooter? Then when assembled into an upper if it did not shoot, then we can do exploration as to why, at least we all know the barrel itself shoots.

Nez
 
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I, i i i

NezRongero said:
Pete,

I don't know if anyone has ever done a real test what receiver is better. Most of our experiences, the barrel is the determinant in the ARs. Some people have claimed bullet are better than forged, but I have not read any controlled experiment to substantiate the claim. Assuming there is a difference, but isn't barrel testing using the same modified action as Jackie suggested definitive enough to determine which barrel is the real shooter? Then when assembled into an upper if it did not shoot, then we can do exploration as to why, at least we all know the barrel itself shoots.

Nez
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Well, even with bolt guns,some platforms shoot better than others and often the minor glitches are findable and fixable. I know some of the other service rifles are better than others so it would make sense to me that would be true with no matter what one was shooting. Likely easier to test with a bolt gun but it means building another rifle or fixture.

What is the life cycle of an AR platform? Same with barrels, how many rounds before they are toast?

Pete
 
Pete Wass said:
Well, even with bolt guns,some platforms shoot better than others and often the minor glitches are findable and fixable. I know some of the other service rifles are better than others so it would make sense to me that would be true with no matter what one was shooting. Likely easier to test with a bolt gun but it means building another rifle or fixture.

What is the life cycle of an AR platform? Same with barrels, how many rounds before they are toast?

Pete
Click to expand...

AR15 barrels run about 3000 to 3500 rounds then they start losing Xs at 600. Most top shooters I know replace them at that point. The uppers and bolts longevity are all over the place based on what people claim. Within the circle of shooters I know, some have over 20K rounds on them on the upper and bolt carrier. Some people change bolts on barreling, I personally just change gas rings and gas tube on barrel change. My number 1 gun has seen way over a dozen barrels since 96, and it still shoots. Back in my early days I was shooting 10K rounds a year, one of the reasons why I went through so many barrels.

On the last barrel change I just bore sighted it with 24 power scope (I shoot 4.5X March in competition) and fired the first 5 rounds through the barrel at 200, plenty good for high power.
 

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NezRongero said:
Some people change bolts on barreling.
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Good advice - IIRC, the US Army has taken this route due to bolt fractures after 3,000 to 10,000 rounds. Why? Cyclic motion + corrosion pits = fatigue tester. See https://www.sciencedirect.com/science/article/pii/S1350630705000221 for a report on this. Note the failure pattern of the bolt is typical for ARs - failure is normally at the lugs on either side of the extractor due to the "missing" lug. There have been instances where the bolt failed at the cam pin hole as well - again, corrosion and cyclic loading are generally the cause, with heat treatment being a factor as well.

AR-15 bolts are relatively cheap, and available. (About $50 to $75 for a "normal" bolt assembly.) Surgery (i.e., fixing eyes, hands, and face) is not.

NezRongero said:
Here is how the typical upper shoots with irons at 200, about a minute and a half with this 65 year old retiree as the trigger monkey. Maybe the real grouping capability is better with minimal human factor using a machine rest.
Click to expand...
Clean with 16? Think you're slipping. ;)

P.S. Think the AMU's rig is the direction you want to go.
 
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jackie schmidt said:
Nez, this is what I have in mind.

http://benchrest.com/attachment.php?attachmentid=20783&stc=1&d=1521140241
Click to expand...

That would be pretty simple to make. I'd bore and thread a piece for the inside thread. Then cut a thread on a barrel stub in the lathe to fit the inside thread, Turn the insert around and screw the insert onto the threaded barrel stub and then cut the external thread to fit the receiver with whatever shoulders you need to make it work. Doing everything like that, all your threads and shoulders would be concentric and at right angles. The hardest thing about making the insert would be to get the headspace correct and that would take some measurement to get it correct.
 
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