I recently purchased and installed an SR9-T "Match Barrel" from RCM on my target rifle nicknamed the GHG1 (ground hog gun 1). RCM's spiel on the site touts the Schneider P5 rifling, SR9 length and profile and a "Match Nato Chamber". To be honest, I completely missed the word "NATO" between "match" and "chamber" not knowing that it was going to be a bad mistake.

I took the rifle to the range and couldn't get anything I had with me (various factory ammo and my target reloads) to shoot better than 3.5"~4" at 100 yards. In comparison the bulllpup was shooting the same group sizes with my reloads using a 4X scope.

By definition a "Match Chamber" calls for a minimum spec. neck diameter and short freebore to ensure that the bullet touches the lands of the rifling. Typical .308 "Match" chambers have a freebore of .04"~.05" for a 168gr SMK, arguably the most popular bullet for 30 caliber target shooting in the USA.

I needed to measure the chamber to get to the bottom of the problem and made a longer copy of a Hornaday style OAL gauge so it would reach through the back of the receiver.





The point of the gauge is to determine the seating depth of the bullet to get the length needed for it to touch the lands of the rifling. Each brand of bullet will require a different seating depth due to the shape of it's ogive. I measured 3 different barrels (3x each) and averaged the measurements for each one using a 168 gr SMK bullet.

First up was an original Santa Barbara produced Cetme barrel with a NATO stamp. I will call it "zero" because it had the shortest freebore depth of the three.
Next was a McGowen barrel I chamber reamed using a Clymer 7.62x51 Nato chamber reamer. The freebore (distance to the lands) was .057" longer than the original barrel.
Last was the SR9 barrel that has a freebore depth .138" longer than the original barrel.

Here's where the problem starts. In the McGowen barrel the SMK bullet is still able to touch the lands and stay in the case mouth securely. In the RCM barrel the bullet is extended so far to touch the rifling that it literally falls out of the case and would be too long to fit in to a magazine.

I traded several emails with Mike Szabo last night, someone said he was the owner of RCM, I don't know. He claims the chambers of the SR9 and PSG1 barrels were purposely cut with extra long chambers and has coined the term "Match NATO Chamber" to cover himself. He has repeatedly said it was the buyers responsibility to work up an accurate load and suggested I start with Berger VLD bullets because they are better suited for jumping long freebores. He was completely aware of the extra long freebore distance.

It boggles my mind to think that anyone would purposely cut the worst chamber possible into one of the best match grade barrels available. In his last communication he said:

So buyer beware, the SR9 and PSG1 barrels will only shoot acceptably accurate with a special load you'll need to develop because of excessive freebore causing bullet jump to the lands. I have spent hours on the net trying to find any reason that someone would want bullet jump in a match barrel and came up dry.

I ordered some Berger 175gr VLD bullets and they came in today so I made some side by side comparisons.  Using dimensions from my bullet seat gauge I loaded both the Berger 175 and the SMK 168 to the depth they'd need to be loaded to in order to touch the lands in the rifling.  Then I pushed the bullets into the case until they were at the book length for a .308 at 2.8" OAL and remeasured them with the caliper and attachment used with the OAL gauge.

The Sierra Match King has to jump .180" to the lands and the Berger has to jump .265" due to the bullet ogive.

Here's a visual of how far off the rifling is from the Ogive of the bullet. The bullets are seated where they would have to be in order for the ogive to touch the rifling.

SMK:


Berger:

That is amazing.  Anybody from that company post here?

I've been building and reloading for target rifles for the last 9 years and have never run into a chamber like this ever.  I got two more emails similar to the above telling me his barrel is perfect and I don't know anything about match chambers and obviously don't know how to reload since I'm so concerned.

If anyone knows any tricks to get a bullet to jump that far and shoot accurately, please teach me.  No point in trying to discover what's already known. Otherwise, I either have to figure out the jump or pull the barrel off and use it for a tomato stake.

http://www.bergerbullets.com/setting-loads-optimum-accuracy/

http://www.bergerbullets.com/vld-making-shoot/

Out of curiosity what did Federal Gold Medal Match do?

I haven't got that far yet, going to try to get chamber casts today and load up some Berger 175's at maximum mag length.  I did notice that the FGMM Berger is loaded with 185's. If I see any improvement at all with 175's I'll order some 185's.  I read the links to Berger's jump info, they stopped at .120".

yes they stopped at .120, but you could keep going, its actually not as uncommon as you think to jump bullets a LOOOONG ways and still have them shoot well. right now the VLD you have is .265, the sierra .180. as Berger stated in the article, there is a window where they will shoot, you have to try to find it in your range, not necessarily that the window ends at .120, thats just as far as they usually have to, again, the super long linda lovelace throat they gae you, you hae to go past that. The point of the article was that you can jump them successfully. The only way to know is try. Yes you got a raw deal on that chamber, it is excessively long throated, but since you can't change it, you are forced to adapt to it. I a saying, there is hope, and a possibility you can get it shooting where you want despite the long jump.

fwiw in a factory 5R M700 I have, the 175 sierra will fall out of the case before it touches the lands, but with a 2.815 COAL they shoot 1/3 moa and fit in the AI mag. The HK mag doesen't give you the length an AI mag will, but it will give you some leeway. Since RIM won't help you out, its going to take some outside the norm work on your end to make it work, and I think its possible that you can find something that will work. Also you may need to adjust your locking piece if you start getting into some of the heavy bullets for optimum results in an HK.

might also want to reach out to the techs at Berger or Sierra and see what their thoughts or recommendations are. Good luck, and if there is anything I can do to help, let me know.

This morning I decided to start with loads of varying lengths as was mentioned in the linked Berger document. I loaded 175gr Bergers to 4 lengths (2.8", 2.813, 2.837, and 2.85") all using 42.5gr of Varget and CCI#43 primers.  I just wanted to see how the COAL affected group sizes.

2.8" COAL = 4.8" 5 shot group
2.813" COAL = 6.034" 5 shot group
2.837" COAL = 4.612" 5 shot group
2.85" COAL = 5.86" 6 shot group, however the last 3 shots were in a nicer .994" group by themselves. I fired one extra round just to see if number 4 and 5 being close was a fluke.

All shots were singly loaded (no magazine). The longest COAL my steel mag can handle is 2.85" but I haven't tried any aluminum mags. I'd already switched to a 37 degree locking piece so that part was taken care of.

I'll load some more to the 2.85" length for testing, this time with different weights of powder.  I might order some 185gr VLDs too.  I'm finding it difficult to get the chamber cast done well, it's hard to get the material into the chamber.

Thanks for the encouragement, but if it wasn't for the last 3 shots of the day I'd have already pulled this barrel off.

I almost purchased one of their barrels as a backup for my SR9. Now I’m glad I didn’t. Makes me wonder how accurate their other HK replacement barrels are.

The stuff I have been using for chamber casts (Densply Reprosil) is just too old to flow anymore, looks like I need to break down and get some cerrosafe.  Densply is the stuff the dentists used to use to take impressions of teeth. There is no shrinkage and it is flexible. This was the best I could do tonight.

Dentsply is a company/brand, not a product. There are many variants as well as alternatives to that material and probably dozens of companies that make it. Also, it is only truly dimensionally stable for a few weeks.

With that said, it’s interesting to see the differences there and that’s a unique way of using something that I have multiple cartridges of just lying around my home.

The product is Reprosil I believe.  It's a two part system I used it at a machine shop I worked at until 1998 that made the press dies for flip top beverage cans. All of the fine contour work on the dies that had radii on top was held to extremely high tolerances.  We would make a mold if the coutour work and then section it for measurement on an optical comparitor.

My old tubes were still working well when I was chamber fluting HK barrels 5 years ago, not so much yesterday. I've also used it for making molds of antique sockets of chisels I needed to make new handles for.

Great post.  I had been contemplating that barrel just because I thought it might be a tighter chamber than an HK barrel.  Now I know.  You saved me.  Thanks

Yeah downside is that it’s expensive. Think one cartridge is like $30-40

The diameter of the freebore on the cerrosafe slug measured .320" just ahead of the chamber flutes.

Wow. It's like Todd Bailey all over again!  I was going to buy some RCM parts for my Mp5 clone but after seeing this I think I'll pass.

If they can screw up a barrel this badly you have to wonder what else have they screwed up?

This barrel fiasco forced me to drag my chamber fluting setup out of retirement one last time to make a barrel that can shoot better than 4MOA.  Hopefully the information will give other home machine shop guys ideas to come up with a better system.



OK, I forgot that I can't post a video.  Here's the link:  https://www.youtube.com/watch?v=4hoBsSrvDjA

Tag for later, Im curious as to the process. Really cool

Hopefully this will put out the wild fire Holescreek ignited. Building a rifle to shoot this good requires experience and high quality parts. RCM has always supplied the parts. If your a home builder I recommend seeking out the advice of professionals prior to doing it yourself. Forums are just for that. Being respectful and courteous go a long way in this industry. Some companies strive to build the best to stay current with the new generation of HK enthusiasts. We don't need those people that bash part of it. At least RCM doesn't.

My post is just what the title says. It's a warning to fellow builders that your chamber has an extremely long freebore that measures out to also be cone shaped from the cartridge mouth to the lands. And I also pointed out that because of same the bullet cannot be seated to the lands.  I have dedicated a lot of time and money to provide data, photos, targets and measurements and presented the information as professionally as I'm capable of.  I sent you the same photos above and you've never denied they were from the chamber you cut.  You listed this as a "match" chamber and I  think it's important that builders be made aware of  what they are purchasing.  I certainly wouldn't have bought the barrel if I'd known.  The power of the internet is the free sharing of information. You consider it bashing because you cut the chamber.

From what has been displayed here, you are the one that is bashing the customer with the assumption that they do not know what they are doing and not taking to time to do any investigation into whether or not the claims are valid. The most precise companies in the industry all make a bad part from time to time. The best companies in the industry are sympathetic to the customer when the mistake is that of the company and humble when the mistake is that of the customer. You sir are doing neither.

A very inaccurate statement sir. The chamber molds shown are accurate and are that of a 7.62 NATO reamer. We call it our NATO Match reamer. If you can invision a case in that picture you would realize were our freebore starts. Compared to the G3 mold.
I would state it's a perfect chamber and exactly what we were striving for. I would bet money only from past history that the rifle was not built to the required standards to shoot sub MOA. Hopefully you opened up my previous post showing a proper built rifle from beginning to end. No short cuts at all. It was built to achieve the results that are pictured.

Why would you want the freebore to be that long?
How did HK ream it in their PSG1 and MSG90 barrels, as compared to the G3?

Subscribed for an answer to this.

As someone that shoots precision rifles twice a week, and handloads, I really want the explanation for a long freebore  in a match rifle.

I know whom I won't be doing any business with - based on the arrogance of your posts and lack of standing behind the product.

That's a shame, it's not arrogance. It's called standing up for your product. As far as having more freebore in a match barrel. IT WORKS better with the polyform and roller lock design. Less cycling issues.

Yep, a lot of factory chambers are long throated for the bullet to be out of the case or to the boat tail.  Sucks but not uncommon at all.  To the factory it’s a safety thing.  90% of the shooters will never measure that.

Correct, but its not normal in a semi auto with mag length restrictions.

Might try another bullet.  I struggled with the 6.5 124 SMK with numerous changes of seating length, powders, and primers to no avail.  Switch to the older 140 SMK or the 139 Lapuas and the gun shot well with almost anything.

Had the same problems with the accubond in my other .260.   Don’t get stuck on a road to nowhere.

The 168 Match Kings right out of the box shot dots with this barrel. I do not give the credit to just the barrel but to the guy who built the gun. He took all the extra steps in the build to insure accuracy. If you don't bother to do that then you might as well press a G3 barrel in it and save yourself some money.

What other sort of steps do you mean? Can you elaborate?

Strengthening the receiver?

This statement really piqued my interest from the standpoint that I've built more than a few roller lock rifles using original military barrels, cheap Bravo5 barrels, $100 Apex barrels and my own home chamber fluted barrels from McGowen blanks (and salvaged RPK barrels).  I've never heard of or seen anyone talk about cycling issues that weren't related to bad chamber flutes.

Are you saying that the Schneider polyform rifing in itself caused cycling issues in tests without the long freebore?

Since build construction has been brought up here are a couple of photos of the rifle with the RCM SR9 barrel currently installed.





The original build was done in 2010 using a Bravo5 "Designated Marksman" 20" barrel. The receiver is the standard ORF flat with stiffening rails applied and the HK shell deflector.  I made an AR15 grip adapter for the lower housing and the stock is a 4 piece design with the aluminum segments adjustable by an acme worm screw. The cocking tube is modified to let the cocking handle lock downward for scope clearance.  The front of the receiver has an extension welded to it which holds an aluminum hand guard rigidly to the receiver and leaves the barrel untouched (free floated) from the trunnion forward.

I found an old pic taken while the build was in process:



I haven't done any more with the rifle since before I made the chamber fluting video, too much going on to dedicate the time for it.  I am looking for a barrel blank suitable to make a replacement for the RCM barrel, it would be perfect if I could get a Schneider P5 blank for a reasonable price.

Just an update.  I kept the RCM barrel in the rifle for about 250 more rounds including Federal GMM 168's and various reloads in an attempt to get it to group at an acceptable level and at the end was shooting the same loads between two rifles and getting drastically different group sizes. Occasionally I could get 4 shots in a nice cluster but there was always one shot in a 5 shot group 2" or more away from the RCM.  More often than not all five shots went their own separate ways as happened the very last time I took it out to shoot.

I sent an email to Schneider about getting a blank but got no response so I ordered an unchambered Douglas 1:10 barrel from Red Hawk Rifles (cheaper shipping than Douglas direct) and turned it down to 20" OAL  and .825" at the muzzle. I finished the chamber with a brand new 7.62x51 NATO chamber reamer from Brownells black Friday sale and chamber fluted it yesterday morning.   I took it to the range this morning to start the break-in (miserable cold rain turned into snow) using some Malaysian surplus and some of my standard 44.5gr Varget/168 SMK loads (nothing tuned to this barrel).  Out of 9  five shot groups, four of them were .933", 1.123", 1.283" and 1.284".  It's amazing what a properly cut chamber does for a barrel.  I'll get it back out in the spring and work up a proper load, these were just a little faster than I expected with the mean FPS measuring at 2679. Not sure how much the temperature played into it, it was 34 degrees when I quit.  About 20 minutes before I was done shooting I started using the fired cases out of the rifle to warm my hands! (I'm too old for that stuff).

Here's how it looked last night after mounting the barrel:

That's pretty cool you can flute the chamber on your own

What do you mean work up a load? That's just unheard of?

Yeah, how'd you do that?

That's funny coming from you. You won't understand this but the home made Douglas barrel shot the same with Malaysian surplus on a bad day as your "match" barrel shot with FGMM on a good day.

It became painfully obvious in your emails that you aren't a builder, precision shooter, or reloader but were quick to say that the problems I pointed out to you were entirely my fault without knowing anything about me.

I still can't figure out why you thought it was smart (or cost effective) to use anything but a standard factory NATO chamber reamer made by any of the established reamer companies.  It would take the responsibility for chamber issues off your shoulders and buyers would be getting a good chamber to start with.  You can go to the CMP website and get the real dimensions for a "match" chamber if you weren't aware.

Edited to add:  Some have speculated that the chamber wasn't actually reamed at all, but lathe turned on the same machine you're fluting on.  I wasn't able to tell from the casts I made so if they are turned it's leaving a great finish. Care to elaborate?

Barrels were chambered with a NATO reamer as stated on the website. If that was not to your liking you shouldn't of bought it and installed it. You could of simply returned it for a refund. Many of these barrels have been used in different builds with great results. Sorry yours didn't. We do not single point our rifle chambers, Rough Ream and Finish Ream, Polish, Nitride and then Polish again.

Who makes that reamer, or did you make it yourself?

Pacific Tool and Gauge. Reamers are very complex. Especially 5 Fluted Carbide with a Helix on them. They are the only company we use. Dave Kiff is a walking encyclopedia when it comes to reamers weather they are standard or custom.