Best breach seal for BSA Challenger & MK1 Mercury S

[I. J.]

I find the Weihrauch breach seal gives a better seal than the grooved BSA seal.

In the early editions of Airgun Shooter where Steve Pope wrote the workshop section he found that the Weihrauch seal gave 1/2 ftlb more power than the BSA seal.

All the best Mick

Why has the standard BSA seal got a nick/groove in it?

The HW77 breech seal has a grooves all the way round its circumference. I use a '80/35/85/95 ...... non grooved seal and have had no problems.

ATB
Ian

[look no hands]

As already said above, I have HW seals on my Merc and challenger, seem to seal a lot better and all the BSA seals I've had to dig out after they've gone brown, hard and crumbly.

Pete

[kennp]

Looks like the Weihrauch Breach seal may be the way to go but has anyone had any experiance of the T.R.Robb breach seal?
Thank you for your replies.
Pete.

[T 20]

Looks like the Weihrauch Breach seal may be the way to go but has anyone had any experiance of the T.R.Robb breach seal?
Thank you for your replies.
Pete.

Hi Ken

I have a feeling the red seals that John Knibbs sells are made by T.R Robb --- if so the breach seals are very good but I'm not too keen on the red piston seals.



All the best Mick

[T 20]

That explains why there is a BSA breech seal in my Venon HW.

Why has the standard BSA seal got a nick/groove in it?

The HW77 breech seal has a grooves all the way round its circumference. I use a '80/35/85/95 ...... non grooved seal and have had no problems.

ATB
Ian

I've no idea why BSA put the groove in Ian --- it could be something to do with how they're formed.

The 77/97 seal has the groove round the middle so that it can deform when compressed, the break barrel seal doesn't need this groove.

I find the break barrel seal works well in 77s and 97s if there is a bit of play in the cocking linkage and makes up for the wear.



All the best Mick

[maximus]

I've no idea why BSA put the groove in Ian --- it could be something to do with how they're formed.

The 77/97 seal has the groove round the middle so that it can deform when compressed, the break barrel seal doesn't need this groove.

I find the break barrel seal works well in 77s and 97s if there is a bit of play in the cocking linkage and makes up for the wear.



All the best Mick

I reckon the nick in the BSA seal is to allow air to escape when inserting it into the recess on the barrel.

atb

Max

[I. J.]

I reckon the nick in the BSA seal is to allow air to escape when inserting it into the recess on the barrel.

atb

Max

Could be - but why then doesn't the HW ones have that 'air release' nick?

[maximus]

Could be - but why then doesn't the HW ones have that 'air release' nick?

Ahh well, them Germans dont think of everything y'know! British Engineering!
Also, Theoben breech seals are just an o ring but have a small nick in for what I believe to be the same purpose.

I think the std seal is fine for the BSA. I take with a pinch of salt the 1/2 ft lb increases. My recently refurbed mercury challenger gives single figure consistency over the chrono, many
readings being the same or within a couple of fps of one another so the new BSA seal cant be that bad!

[martin bingham]

on my lightning se i fitted a hw seal as id been advised it could help cure the slightly wobbly breech,it did and its now spot on with no play,

[oliver13]

The nick in the BSA seal is supposed to allow it to expand hard against the side of it's recess under the influence of the HPA when it's fired, & thus provide a better seal - at least that's the theory.

I tried an HW seal once, it's a bit deep & needs trimming so I cunningly put about a mm shim in the recess, put the seal in backwards & sliced it off nice & square - then found it was in so tight I damaged it trying to take it out, so they are a bit deep & maybe a touch wide, they are noticeably good quality though.

[gary_c_ham]

There is a cut out so that when closing the barrel it doesnt catch on the transfer port and cut the seal. I had this ans had to dress the sharp edge to stop the seal being nicked.

Why has the standard BSA seal got a nick/groove in it?

The HW77 breech seal has a grooves all the way round its circumference. I use a '80/35/85/95 ...... non grooved seal and have had no problems.

ATB
Ian

[I. J.]

There is a cut out so that when closing the barrel it doesnt catch on the transfer port and cut the seal. I had this ans had to dress the sharp edge to stop the seal being nicked.

The seal doesn't stay in the same position and why doesn't other break barrel manufacturers have this problem?