Action type

R

rudedog

Guest
I've noticed that all the main benchrest actions are front lugged actions.
Why doesn't anyone make a rear lug actions,is it manufacturing cost,more weight,longer length or design problems.
Thanks Rudy Manuel
 
It seems to me that the strongest part of the action is the solid ring up front, it only makes sense to put the recoil lug up there. If it were in the rear wouldn't there be more flex due to the ejection port?
 
Rear locking actions with bolt bodies manufactured to the "traditional" diameters (no more than .7") have been shown to suffer case stretch at peak pressures. The Remington 788 is the best known example. However, when larger diameter bolts & actions are involved, this might not be an issue.

For benchrest use, the challenge would be whether a rear locking action could be manufactured that would be of equal or less weight than existing custom Remington clones that would accept the range of aftermarket accessories, particularly triggers, that the market wants, be of sufficient stiffness to hold a benchrest level load without the case stretching & have the simplicity of bedding that we expect of the current range of actions.

In other disciplines - target rilfe & F class - this possibility is being explored by Robert Chombart who is best known for his association with the RPA & Millennium actions. His Inch design is currently under production & about to be released. See http://www.topcorp1.com/swing/inchdeltabis.html. While that action is lighter than state of the art front locking actions, it can't handle a Jewell 2 ounce trigger, for example.
 
John

Thanks John thats what I was thinking.
Rudy Manuel
 
rudedog said:
I've noticed that all the main benchrest actions are front lugged actions.
Why doesn't anyone make a rear lug actions,is it manufacturing cost,more weight,longer length or design problems.
Thanks Rudy Manuel
Click to expand...

My view on it...

The cartridge case is simply a removable gasket to keep the high gas pressures where they belong...

It makes sense that you would contain this gasket the strongest, simplest way...

Front locking lugs do this... and with simple heat treating of the front of the action and of the front of the bolt...

Rear locking lugs add more material that can stretch or fail... and the heat treat of the action needs to be throughout the whole action and of the bolt...

Even the big old heavy rear lug Shultz and Larsen actions had case stretch with hot loads...
 
Rear lugs

My first action I built was a massive 3 lug rear lock up, single shot, bolt diameter was .750. I still had severe case stretch problems even with moderate loads. Not a good design. Gun sits in the cabinet a leeson on what not to do. Oh by the way caliber was 7.82 Warbird, built it in 1998. Wow 10 years ago already, where has the time gone.
 
I'm not an engineer, but my understanding is this: at 60 kpsi steel compresses. Most BR loads are at least 60 kpsi, and if the lugs are at the rear of the action there's more steel to compress. The compression is expressed in inch/inch and although it's only maybe 0.0005" or less compression per inch if there's five inches of steel between the bolt face and locking lugs there can be 0.0025" compression, which allows the case to stretch that amount. Makes getting the bolt open a bit difficult and it's harder on brass too.
 
thanks everyone

Good information here thank you.
Rudy Manuel:D
 
I'm of an opinion

John Kielly said:
Rear locking actions with bolt bodies manufactured to the "traditional" diameters (no more than .7") have been shown to suffer case stretch at peak pressures. The Remington 788 is the best known example. However, when larger diameter bolts & actions are involved, this might not be an issue.

.
Click to expand...
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Regardless of weight if there was a one "rear locking action" that would be 3" of diameter and have a bolt of 1.5" diameter and won every single Benchrest competition it still wouldn't be accepted by the shooting public as a good action.

There still would be plenty all those imbeciles saying exactly the same as what they'r saying now.

As soon as one says it's a "rear locking action" 99% of people say; it's a rubbish.

Shoot better
Peter
 
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Rear Lug Actions

The only experiece I have had with a rear lug action was a 788 that I helped a friend build. It was in 308 Winchester.
He had a custom that we had built on a short ADL 700. Both Rifles had 1-12 Krieger barrels, and a minimum spec chamber.
At the range, we soon learned one of the problems with the 788. With the 700 actioned Rifle, we could easilly push a 168 grn Match King to 2850 with a big dose of N140, with no ill affects at all.
The 788 was another story. Anything over 2650 produced a very tight bolt.
We did a little inspecting, and found that out of all of those rear locking luggs, only about 4 were actually touching.
We went to work with a lapping compound, (no easy task with that round bolt), and finally got about 6 of them making contact with Prussian Blue.
It didn't help much. Anything that we considered a medium upper end load in that 700 would produce a tight bolt in the 788.
I know all of that is anecdodal. And while I do not consider myself an "imbecil", I will admitt that this is the only rear lug action I have ever personally messed with........jackie
 
It's all been done before

I went for an o-l-d read last night & pulled out Townsend Whelan's "The Ultimate in Rifle Precision". Would you believe that back then one of the benchrest rifles pictured had a rear locker action - an old Schultz & Larsen.

And Peter, you'd jump with joy. It also pictures a 98 Mauser action fitted with a Bellows reinforcing sleeve.
 
Donovan-Something like that

dmoran65 said:
Peter: aka PPP MMM --

Much like you regard the China made lathes...........
Plenty of those imbeciles too...... knocking what so many have and use successfully.

Happy Shooting
Donovan Moran
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Donovan

Some time ago I've bought a REM.788 chambered in .308W for $150, that had about 150 rounds throught the barrel from a "knowledgeable" bloke who was saying everything what always goes on with when the "rear locking actions" are mentioned. The stretch, compression, this and that,,,,,,,,what every parrot repeates over and over again. In his own words of hatred he was getting rid off all of his junk and rubbish rifles.

When I've shot the rifle as it was it was shooting 30MM/100M

When I glass bedded the action it was shooting 15-20MM/100M

The other day I've lapped the barrel in my 15Year old lapping jig and also carefully lapped the locking lugs by using a "soft" Arma Grout to center the bolt. The same rifle now shoots 7.5-12MM/100M (.3-.4")/109Yards. 178A-Max /2625fps from a 22" barrel.

Keep in mind, that the action wasn't trued in any other way, as I wasn't going to waist my time or money on a $150 rifle. Also keep in mind that I don't load for a super accuracy and I don't use any of the "accuracy super sorting techniques".

I have yet to pick up the difference with brass stretching.

Shoot better
Peter
 
A size is what matters

The problem if there is any with the "rear locking actions" is the size. It's a parrot problem again. A .700" bolt for a front locking action is not problem. For the rear locking action the bolt has to be considerably larger and also the receiver has to be larger as well.

It's pity that Paul Mauser didn't made the M 98 with a .800" bolt and 1.6" receiver. Because all other actions made ever since would have been made in these sizes, as the engineers parrots would copy it, just as they did with the .700" bolt size alike.

A Russian II World War made Antitank rifle was shooting 14.5MM 1000gr. projectile at 3450fps and the action had rear locking lugs. The lugs would be some 7-8" from the bolt face.

I wouldn't climb over a front locking action to get a rear locking action, but if a such action is engineered proportionally there shouldn't be a problem with neither of them.

The rear locking action wouldn't be my action of choice for a benchrest, but I wouldn't mind it for a reliable hunting rifle.

Shoot better
Peter
 
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