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tophatjones
January 29, 2009, 00:50
Hi all,

I was planning on mating a Brit barrel to a DSA inch (if I can get one from this batch). That is until I came across this:

"Note: You can't use a British barrel on a DSA Inch or Century Inch receiver without modifying the threads on the Brit barrel near the shoulder.

On Brit barrels, the threads don't go all the way the shoulder.

Don't ask me how I know."

-arashi

What exactly do I need to do to get the barrel on the DSA inch receiver? Also, if I can't get an inch receiver, what modifications do I need to make to fit a metric DSA receiver? What are the drawbacks of fitting an inch barrel to a metric receiver? Thanks for the advice!

garandguy10
January 29, 2009, 01:08
Inch barrels aways require a "Breeching washer" They are available in different sizes to adjust your barrel breeching torque[Barrel timing]

dirtyrice
January 29, 2009, 04:16
This is all bollocks I have more than one dsa inch receiver with a British barrel. Yes you must use a breeching washer as with any inch pattern build as the guy above me said.

If you were to use a metric receiver I believe you WOULD NOT use a breeching washer. As far as I know the threads on the barrel are the same but I believe the flash hider threads are different. Tons of people have l1a1s built on metric receivers especially imbels because they were cheap at one time.

Abominog
January 29, 2009, 04:44
Just to be clear, you will need a breaching washer on the DSA L1A1 (yes, I am being repetitive) but probably not on the Century L1A1.

That is because the Century is not a proper L1A1 receiver, but a transmogrified (sp) metric receiver.


Is transmogrified a word?

ce
January 29, 2009, 13:40
You need to use a breeching washer with all inch barrels in all receivers.

arashi
January 29, 2009, 19:34
Originally posted by tophatjones
Hi all,

I was planning on mating a Brit barrel to a DSA inch (if I can get one from this batch). That is until I came across this:

"Note: You can't use a British barrel on a DSA Inch or Century Inch receiver without modifying the threads on the Brit barrel near the shoulder.

On Brit barrels, the threads don't go all the way the shoulder.

Don't ask me how I know."

-arashi

What exactly do I need to do to get the barrel on the DSA inch receiver? Also, if I can't get an inch receiver, what modifications do I need to make to fit a metric DSA receiver? What are the drawbacks of fitting an inch barrel to a metric receiver? Thanks for the advice!

On British barrels, the threads aren't cut close enough to the shoulder of the barrel or the diameter is larger.

The DSA Inch receivers, at least mine from a year or so ago, have threads that that start at the face of the reciever. They are setup for Aussie barrels. Aussie barrels have the threads cut further up towards the barrel shoulder or a reduced diameter at the shoulder.

It is not a big deal to use a Brit barrel, you just need to cut the threads a half turn more or reduce the diameter of the area near the shoulder a hair.

Additionally, the Century MADE, cast, unibrow receiver I have, also has threads that go to the face of the receiver.

You can just "muscle" a Brit barrel on an Aussie cut receiver, but when you take it off, you find that the threads are hosed at the receiver face. I now need a tap to fix the threads. I can't even get a barrel started on it now...

I built 4 DSA inch guns with Aussie barreles and have at least 3 or 4 extra Brit barrels. I was hoping to use my like new 80's dated Brit barrels, but I am too lazy and just hope Enterprise comes through with the Brit receivers.

I will not help to chase the barrel threads with a standard die either as the threads that need cutting are too close to the shoulder for the die to get too... AMHIK


It is not that big of deal, but it is no bullocks either...

ETA: Yes, I am aware that a breaching washer is required and have washers 1-8...

arashi
January 29, 2009, 19:39
Originally posted by dirtyrice
This is all bollocks I have more than one dsa inch receiver with a British barrel. Yes you must use a breeching washer as with any inch pattern build as the guy above me said.

If you were to use a metric receiver I believe you WOULD NOT use a breeching washer. As far as I know the threads on the barrel are the same but I believe the flash hider threads are different. Tons of people have l1a1s built on metric receivers especially imbels because they were cheap at one time.

What are you talking about? If you an inch barrel, you need a breaching washer. Metric or Inch receiver...

Have you ever even built an Inch gun???????? :rolleyes:

I would refrain from calling something "bollocks" when you obviously have no idea what you are advisingl...

Biotech
January 29, 2009, 20:58
Inch barrels require breeching washers in either an inch receiver or a metric receiver. The reason you need a breeching washer is because the barrels are not threaded all the way to the facing of the barrel. Metric barrels don't require breeching washers because they are threaded all the way to the facing. This is one of the major differences between an Inch and metric barrel. the other being that the gas port in at an angle on inch and 90 dedgrees under the front sight for a metric one.

tophatjones
February 01, 2009, 01:55
Hi and thanks to all the replies.

Just to get the terminology squared away, the shoulder of the barrel is the aft face at the end of the barrel taper; the shoulder being perpendicular to the bore? I measured about 0.050" of unthreaded barrel between the shoulder and the threads.

Since DSA will not be making any inch receivers until 2010, I'm planning on building this to a metric receiver and perhaps change over to a proper inch pattern in the future. Will I need to make any serious mods to the metric receiver?

dirtyrice
February 01, 2009, 04:38
Yes Ive built 3 inch patterns but never on metric receivers. SORRY. I thought on a metric receiver you didn't need one. I was wrong. I never said I was 100% right definitely and everyone else is wrong.


arashi: You could've just provided some info like biotech did nicely but instead you wanna be a jackass.

Biotech
February 01, 2009, 10:20
If you will be using all Inch parts on the metric receiver you maight have to make a few cuts or reliefs. The tabs at the back end of the top cover will need to have relief cuts made in the receiver channel ( the other option is to remove the tabs from the top cover or use a metric one). The front channel for the folding charging handle will need to have either a relief cut on the front section to allow the handle to fold down completely or the back side of the handle ground off( if you are planing on chaging to an inch recveiver in future you need to decide which part is more important to you). The mag well cut is more difficult and it is better to just use metric mags in mean time. There should be a detailed instructions one of the stickies or history files with pictures.

elbo
February 01, 2009, 12:48
Originally posted by Biotech
Inch barrels require breeching washers in either an inch receiver or a metric receiver. The reason you need a breeching washer is because the barrels are not threaded all the way to the facing of the barrel. Metric barrels don't require breeching washers because they are threaded all the way to the facing. This is one of the major differences between an Inch and metric barrel. the other being that the gas port in at an angle on inch and 90 dedgrees under the front sight for a metric one.

On inch barrels the shoulder is deliberately further from the breech face. The threads aren't cut all the way because there is no need to have threads under the washer.

Vagabond
February 01, 2009, 19:53
Originally posted by Abominog
Is transmogrified a word?

It is now! :beer: :biggrin:

North Texas Ed
February 21, 2009, 16:04
I'm about to put an L1A1 barrel (and the rest of the kit) on a Coonan Metric receiver. The kit's breeching washer is too big to get to 15 degrees before top dead center hand tight, so I'll probably just stone it down with the diamond stones until the fit is right.

The only other things I need to do to get this put together are:

1. Put a Metric bolt hold open on, instead of the Inch hold open. Easier than trying to fit the Inch hold open to the Metric receiver.

2. Stone the back of the Inch charging handle slide to fit in the Metric slot. Choices then include do nothing more, leaving the folding part permanently folded out, cut the back of the folder, or cut the receiver to allow the handle to fold flat.

3. Use enough US parts content.

Obviously I also need to use Metric Mags, but that's OK because they are lots cheaper than the Inch mags. I already have them from my Century "Sporter" which (according to Century) was built on a metric receiver Imbel built for Century (early 90s gun). That one will also be getting rebuilt with US parts content to be able to change the stock and, probably, thread the barrel and add a "recoil reducer".

North Texas Ed
February 22, 2009, 09:34
Before anyone points out that I left off getting the right sized locking shoulder (if the one with the kit isn't the right size), I'll do it myself.

Concentrating on the Inch-Metric difference, I left out the really obvious part. But everyone knew that.

arashi
February 23, 2009, 03:21
Originally posted by North Texas Ed
Before anyone points out that I left off getting the right sized locking shoulder (if the one with the kit isn't the right size), I'll do it myself.

Concentrating on the Inch-Metric difference, I left out the really obvious part. But everyone knew that.


Take the breeching washer off and see if the barrel will hand time without it. If it is a brit barrel, I bet it won't completely hand time even without the breeching washer in place.

ETA - I saw in another thread that it times to 2 o'clock without the washer.

Is the barrel Brit or Aussie?

Thanks

North Texas Ed
February 23, 2009, 07:28
Without the breeching washer the barrel runs to (using the hour hand of a clock simile) about 2PM. Way past top dead center.

North Texas Ed
February 23, 2009, 07:33
Missed the second part of that. It is a Brit barrel, or should be. It was in a kit sold as a Brit kit, with pebble grain furniture and bought before the Aussie kits were on the market.

arashi
February 24, 2009, 01:53
Originally posted by North Texas Ed
It is a Brit barrel, or should be.

What markings are there on the barrel and gasblock?

I've been sold "Brit" kits before with Aussie barrels.

Dunk RD
February 24, 2009, 02:12
Don't mean to be repedative but just to make it clear
The distance from the shoulder to the breach face of a inch barrel is longer
than a metric by 1 full turn pluss about .015. When you hand time a inch barrel into a receiver with out the breaching washer it times a little past 12:00. you need to back it out one full turn then to 11:00 with a breaching washer before you start to time.
To find the proper size breaching washer, back it off 1 full turn then to 11:00 and measure the gap with a feeler gage. Make sure the barrel shoulder is tight on the gage . Breaching washers can be ordered from SLR 5000 in the thickness you need or you can sand one down useing a figure 8 motion on emery paper . That is if you have one that is to thick.
Inch and metric receivers are the same length so this same method must be used on both. It is the barrel that is different.
This is also why inch gas pistons are a little longer than metric. To make up for the thickness of the breaching washer.
Hope this helps
Dunk RD

arashi
February 24, 2009, 02:37
Originally posted by Dunk RD
Don't mean to be repedative

I only ask these questions because of my problems attempting to install British barrels on Aussie or Metric type receivers.

They will go on once, then mess up the receiver threads...

I would have never known if I hadn't removed Brit barrels and come to the rude awakening.

I have had the issue with DSA Inch, Century Inch, and DSA Metric.

It has nothing to do with breaching washers.

North Texas Ed
February 24, 2009, 09:44
I can't say I'm any expert in Brit barrel markings vs. Aussie. The barrel has
multiple "broad arrows" stamped into the barrel. I don't think (but certainly don't know if) the Australians used the "broad arrow" mark for their military equipment. If there is some other marking which clearly designates a Brit (or Aussie) barrel, let me know what it is and I'll look for it. As I said elsewhere, I bought this kit back in the early 90s and, IIRC, Aussie parts kits weren't yet on the market when I bought it. That certainly doesn't mean Aussie parts weren't in the country, I don't know when they were imported.

Since I have to either thin the washer I have, or use feeler gauges and buy the correct size breeching washer, I can't say whether there would be any problem once the barrel is torqued onto the receiver. But I don't have any intention (beyond Murphy being alive and well) of removing the barrel once it is installed (I'll be sure to remember to put the rear handguard retaining ring on the barrel before I screw it on the receiver).

Dwalton
February 24, 2009, 17:01
Originally posted by Dunk RD
you need to back it out one full turn then to 11:00 with a breaching washer before you start to time.



Incorrect . You just back it out till 11.00/11.30 . If you back it out ONE FULL TURN ,you will have to make up that difference ('0.062") in the locking shoulder .
Because the threaded shank is longer than a metric , there will be a gap even fully threaded in . Because the barrel bottoms out at the breach end .

I just would hate to have someone buy /make , a too thick breaching washer , and then have to get a too thick locking shoulder to headspace .

DJW

Dunk RD
February 24, 2009, 23:52
NOT INCORRECT
Yes, one full turn is 1/16 th .0625 and that is in the range of all the locking shoulders in my drawer. Some times a lttle bigger. If you don't use a standard breaching washer on a british barrel you will need a LS of about .200
Dunk RD

Dwalton
February 25, 2009, 09:54
Originally posted by Dunk RD
NOT INCORRECT
Yes, one full turn is 1/16 th .0625 and that is in the range of all the locking shoulders in my drawer. Some times a lttle bigger. If you don't use a standard breaching washer on a british barrel you will need a LS of about .200
Dunk RD

Bear with me .
Are your inch rifles set up with a 0.062" + gap from the end of the feed ramp to the end of the barrel at the breech ?

When you screw an inch barrel all the way into a receiver , metric or inch , it bottoms out at the breech end inside the receiver . Overtiming to 1-2 o'clock . But because the inch barrels threaded shank is longer than a metric , there will be a gap from the receiver face , to the barrel shoulder . A little less than 1/16 " .

A metric barrel should bottom out on the barrel shoulder , before the breech end , leaving a small (a couple of thousandths ) gap at the breech side . When you torque the barrel home , the gap at the breech end becomes smaller , so it almost or does contact the receiver at the breech .

If , on the inch barrel you back off one complete turn , as you suggest , the breech end gap will grow 0.062 " , and the breeching washer size will almost double . And since you are moving the barrel forward an extra 0.062 , with the already cut chamber , are you not increasing headspace by the same amount ?



DJW

Dunk RD
February 25, 2009, 21:31
DJW
Well you are right Bud
I would have swore the last Brit barrel I checked bottomed out on the shoulder.
But today I wanted to make sure so I tried six different barrels. None would bottom out and were all one revelution short and just past 12:00.
So You are correct My Mistake.
Dunk RD